stb_voxel_render.h

// stb_voxel_render.h - v0.88 - Sean Barrett, 2015 - public domain
//
// This library helps render large-scale "voxel" worlds for games,
// in this case, one with blocks that can have textures and that
// can also be a few shapes other than cubes.
//
//    Video introduction:
//       http://www.youtube.com/watch?v=2vnTtiLrV1w
//
//    Minecraft-viewer sample app (not very simple though):
//       http://github.com/nothings/stb/tree/master/tests/caveview
//
// It works by creating triangle meshes. The library includes
//
//    - converter from dense 3D arrays of block info to vertex mesh
//    - vertex & fragment shaders for the vertex mesh
//    - assistance in setting up shader state
//
// For portability, none of the library code actually accesses
// the 3D graphics API. (At the moment, it's not actually portable
// since the shaders are GLSL only, but patches are welcome.)
//
// You have to do all the caching and tracking of vertex buffers
// yourself. However, you could also try making a game with
// a small enough world that it's fully loaded rather than
// streaming. Currently the preferred vertex format is 20 bytes
// per quad. There are designs to allow much more compact formats
// with a slight reduction in shader features, but no roadmap
// for actually implementing them.
//
//
// USAGE
//
//   #define the symbol STB_VOXEL_RENDER_IMPLEMENTATION in *one*
//   C/C++ file before the #include of this file; the implementation
//   will be generated in that file.
//
//   If you define the symbols STB_VOXEL_RENDER_STATIC, then the
//   implementation will be private to that file.
//
//
// FEATURES
//
//   - you can choose textured blocks with the features below,
//     or colored voxels with 2^24 colors and no textures.
//
//   - voxels are mostly just cubes, but there's support for
//     half-height cubes and diagonal slopes, half-height
//     diagonals, and even odder shapes especially for doing
//     more-continuous "ground".
//
//   - texture coordinates are projections along one of the major
//     axes, with the per-texture scaling.
//
//   - a number of aspects of the shader and the vertex format
//     are configurable; the library generally takes care of
//     coordinating the vertex format with the mesh for you.
//
//
// FEATURES (SHADER PERSPECTIVE)
//
//   - vertices aligned on integer lattice, z on multiples of 0.5
//   - per-vertex "lighting" or "ambient occlusion" value (6 bits)
//   - per-vertex texture crossfade (3 bits)
//
//   - per-face texture #1 id (8-bit index into array texture)
//   - per-face texture #2 id (8-bit index into second array texture)
//   - per-face color (6-bit palette index, 2 bits of per-texture boolean enable)
//   - per-face 5-bit normal for lighting calculations & texture coord computation
//   - per-face 2-bit texture matrix rotation to rotate faces
//
//   - indexed-by-texture-id scale factor (separate for texture #1 and texture #2)
//   - indexed-by-texture-#2-id blend mode (alpha composite or modulate/multiply);
//     the first is good for decals, the second for detail textures, "light maps",
//     etc; both modes are controlled by texture #2's alpha, scaled by the
//     per-vertex texture crossfade and the per-face color (if enabled on texture #2);
//     modulate/multiply multiplies by an extra factor of 2.0 so that if you
//     make detail maps whose average brightness is 0.5 everything works nicely.
//
//   - ambient lighting: half-lambert directional plus constant, all scaled by vertex ao
//   - face can be fullbright (emissive), controlled by per-face color
//   - installable lighting, with default single-point-light
//   - installable fog, with default hacked smoothstep
//
//  Note that all the variations of lighting selection and texture
//  blending are run-time conditions in the shader, so they can be
//  intermixed in a single mesh.
//
//
// INTEGRATION ARC
//
//   The way to get this library to work from scratch is to do the following:
//
//      Step 1. define STBVOX_CONFIG_MODE to 0
//
//        This mode uses only vertex attributes and uniforms, and is easiest
//        to get working. It requires 32 bytes per quad and limits the
//        size of some tables to avoid hitting uniform limits.
//
//      Step 2. define STBVOX_CONFIG_MODE to 1
//
//        This requires using a texture buffer to store the quad data,
//        reducing the size to 20 bytes per quad.
//
//      Step 3: define STBVOX_CONFIG_PREFER_TEXBUFFER
//
//        This causes some uniforms to be stored as texture buffers
//        instead. This increases the size of some of those tables,
//        and avoids a potential slow path (gathering non-uniform
//        data from uniforms) on some hardware.
//
//   In the future I might add additional modes that have significantly
//   smaller meshes but reduce features, down as small as 6 bytes per quad.
//   See elsewhere in this file for a table of candidate modes. Switching
//   to a mode will require changing some of your mesh creation code, but
//   everything else should be seamless. (And I'd like to change the API
//   so that mesh creation is data-driven the way the uniforms are, and
//   then you wouldn't even have to change anything but the mode number.)
//
//
// IMPROVEMENTS FOR SHIP-WORTHY PROGRAMS USING THIS LIBRARY
//
//   I currently tolerate a certain level of "bugginess" in this library.
//
//   I'm referring to things which look a little wrong (as long as they
//   don't cause holes or cracks in the output meshes), or things which
//   do not produce as optimal a mesh as possible. Notable examples:
//
//        -  incorrect lighting on slopes
//        -  inefficient meshes for vheight blocks
//
//   I am willing to do the work to improve these things if someone is
//   going to ship a substantial program that would be improved by them.
//   (It need not be commercial, nor need it be a game.) I just didn't
//   want to do the work up front if it might never be leveraged. So just
//   submit a bug report as usual (github is preferred), but add a note
//   that this is for a thing that is really going to ship. (That means
//   you need to be far enough into the project that it's clear you're
//   committed to it; not during early exploratory development.)
//
//
// VOXEL MESH API
//
//   Context
//
//     To understand the API, make sure you first understand the feature set
//     listed above.
//
//     Because the vertices are compact, they have very limited spatial
//     precision. Thus a single mesh can only contain the data for a limited
//     area. To make very large voxel maps, you'll need to build multiple
//     vertex buffers. (But you want this anyway for frustum culling.)
//
//     Each generated mesh has three components:
//             - vertex data (vertex buffer)
//             - face data (optional, stored in texture buffer)
//             - mesh transform (uniforms)
//
//     Once you've generated the mesh with this library, it's up to you
//     to upload it to the GPU, to keep track of the state, and to render
//     it.
//
//   Concept
//
//     The basic design is that you pass in one or more 3D arrays; each array
//     is (typically) one-byte-per-voxel and contains information about one
//     or more properties of some particular voxel property.
//
//     Because there is so much per-vertex and per-face data possible
//     in the output, and each voxel can have 6 faces and 8 vertices, it
//     would require an very large data structure to describe all
//     of the possibilities, and this would cause the mesh-creation
//     process to be slow. Instead, the API provides multiple ways
//     to express each property, some more compact, others less so;
//     each such way has some limitations on what it can express.
//
//     Note that there are so many paths and combinations, not all of them
//     have been tested. Just report bugs and I'll fix 'em.
//
//   Details
//
//     See the API documentation in the header-file section.
//
//
// CONTRIBUTORS
//
//   Features             Porting            Bugfixes & Warnings
//  Sean Barrett                          github:r-leyh   Jesus Fernandez
//                                        Miguel Lechon   github:Arbeiterunfallversicherungsgesetz
//                                        Thomas Frase    James Hofmann
//                                        Stephen Olsen   github:guitarfreak
//
// VERSION HISTORY
//
//   0.88   (2019-03-04)  fix warnings
//   0.87   (2019-02-25)  fix warning
//   0.86   (2019-02-07)  fix typos in comments
//   0.85   (2017-03-03)  add block_selector (by guitarfreak)
//   0.84   (2016-04-02)  fix GLSL syntax error on glModelView path
//   0.83   (2015-09-13)  remove non-constant struct initializers to support more compilers
//   0.82   (2015-08-01)  added input.packed_compact to store rot, vheight & texlerp efficiently
//                        fix broken tex_overlay2
//   0.81   (2015-05-28)  fix broken STBVOX_CONFIG_OPTIMIZED_VHEIGHT
//   0.80   (2015-04-11)  fix broken STBVOX_CONFIG_ROTATION_IN_LIGHTING refactoring
//                        change STBVOX_MAKE_LIGHTING to STBVOX_MAKE_LIGHTING_EXT so
//                                    that header defs don't need to see config vars
//                        add STBVOX_CONFIG_VHEIGHT_IN_LIGHTING and other vheight fixes
//                        added documentation for vheight ("weird slopes")
//   0.79   (2015-04-01)  fix the missing types from 0.78; fix string constants being const
//   0.78   (2015-04-02)  bad "#else", compile as C++
//   0.77   (2015-04-01)  documentation tweaks, rename config var to STB_VOXEL_RENDER_STATIC
//   0.76   (2015-04-01)  typos, signed/unsigned shader issue, more documentation
//   0.75   (2015-04-01)  initial release
//
//
// HISTORICAL FOUNDATION
//
//   stb_voxel_render   20-byte quads   2015/01
//   zmc engine         32-byte quads   2013/12
//   zmc engine         96-byte quads   2011/10
//
//
// LICENSE
//
//   See end of file for license information.

#ifndef INCLUDE_STB_VOXEL_RENDER_H
#define INCLUDE_STB_VOXEL_RENDER_H

#include <stdlib.h>

typedef struct stbvox_mesh_maker stbvox_mesh_maker;
typedef struct stbvox_input_description stbvox_input_description;

#ifdef STB_VOXEL_RENDER_STATIC
#define STBVXDEC static
#else
#define STBVXDEC extern
#endif

#ifdef __cplusplus
extern "C" {
#endif

//////////////////////////////////////////////////////////////////////////////
//
// CONFIGURATION MACROS
//
//  #define STBVOX_CONFIG_MODE <integer>           // REQUIRED
//     Configures the overall behavior of stb_voxel_render. This
//     can affect the shaders, the uniform info, and other things.
//     (If you need more than one mode in the same app, you can
//     use STB_VOXEL_RENDER_STATIC to create multiple versions
//     in separate files, and then wrap them.)
//
//         Mode value       Meaning
//             0               Textured blocks, 32-byte quads
//             1               Textured blocks, 20-byte quads
//            20               Untextured blocks, 32-byte quads
//            21               Untextured blocks, 20-byte quads
//
//
//  #define STBVOX_CONFIG_PRECISION_Z  <integer>   // OPTIONAL
//     Defines the number of bits of fractional position for Z.
//     Only 0 or 1 are valid. 1 is the default. If 0, then a
//     single mesh has twice the legal Z range; e.g. in
//     modes 0,1,20,21, Z in the mesh can extend to 511 instead
//     of 255. However, half-height blocks cannot be used.
//
// All of the following are just #ifdef tested so need no values, and are optional.
//
//    STBVOX_CONFIG_BLOCKTYPE_SHORT
//        use unsigned 16-bit values for 'blocktype' in the input instead of 8-bit values
//
//    STBVOX_CONFIG_OPENGL_MODELVIEW
//        use the gl_ModelView matrix rather than the explicit uniform
//
//    STBVOX_CONFIG_HLSL
//        NOT IMPLEMENTED! Define HLSL shaders instead of GLSL shaders
//
//    STBVOX_CONFIG_PREFER_TEXBUFFER
//        Stores many of the uniform arrays in texture buffers instead,
//        so they can be larger and may be more efficient on some hardware.
//
//    STBVOX_CONFIG_LIGHTING_SIMPLE
//        Creates a simple lighting engine with a single point light source
//        in addition to the default half-lambert ambient light.
//
//    STBVOX_CONFIG_LIGHTING
//        Declares a lighting function hook; you must append a lighting function
//        to the shader before compiling it:
//            vec3 compute_lighting(vec3 pos, vec3 norm, vec3 albedo, vec3 ambient);
//        'ambient' is the half-lambert ambient light with vertex ambient-occlusion applied
//
//    STBVOX_CONFIG_FOG_SMOOTHSTEP
//        Defines a simple unrealistic fog system designed to maximize
//        unobscured view distance while not looking too weird when things
//        emerge from the fog. Configured using an extra array element
//        in the STBVOX_UNIFORM_ambient uniform.
//
//    STBVOX_CONFIG_FOG
//        Defines a fog function hook; you must append a fog function to
//        the shader before compiling it:
//            vec3 compute_fog(vec3 color, vec3 relative_pos, float fragment_alpha);
//        "color" is the incoming pre-fogged color, fragment_alpha is the alpha value,
//        and relative_pos is the vector from the point to the camera in worldspace
//
//    STBVOX_CONFIG_DISABLE_TEX2
//        This disables all processing of texture 2 in the shader in case
//        you don't use it. Eventually this could be replaced with a mode
//        that omits the unused data entirely.
//
//    STBVOX_CONFIG_TEX1_EDGE_CLAMP
//    STBVOX_CONFIG_TEX2_EDGE_CLAMP
//        If you want to edge clamp the textures, instead of letting them wrap,
//        set this flag. By default stb_voxel_render relies on texture wrapping
//        to simplify texture coordinate generation. This flag forces it to do
//        it correctly, although there can still be minor artifacts.
//
//    STBVOX_CONFIG_ROTATION_IN_LIGHTING
//        Changes the meaning of the 'lighting' mesher input variable to also
//        store the rotation; see later discussion.
//
//    STBVOX_CONFIG_VHEIGHT_IN_LIGHTING
//        Changes the meaning of the 'lighting' mesher input variable to also
//        store the vheight; see later discussion. Cannot use both this and
//        the previous variable.
//
//    STBVOX_CONFIG_PREMULTIPLIED_ALPHA
//        Adjusts the shader calculations on the assumption that tex1.rgba,
//        tex2.rgba, and color.rgba all use premultiplied values, and that
//        the output of the fragment shader should be premultiplied.
//
//    STBVOX_CONFIG_UNPREMULTIPLY
//        Only meaningful if STBVOX_CONFIG_PREMULTIPLIED_ALPHA is defined.
//        Changes the behavior described above so that the inputs are
//        still premultiplied alpha, but the output of the fragment
//        shader is not premultiplied alpha. This is needed when allowing
//        non-unit alpha values but not doing alpha-blending (for example
//        when alpha testing).
//

//////////////////////////////////////////////////////////////////////////////
//
// MESHING
//
// A mesh represents a (typically) small chunk of a larger world.
// Meshes encode coordinates using small integers, so those
// coordinates must be relative to some base location.
// All of the coordinates in the functions below use
// these relative coordinates unless explicitly stated
// otherwise.
//
// Input to the meshing step is documented further down

STBVXDEC void stbvox_init_mesh_maker(stbvox_mesh_maker *mm);
// Call this function to initialize a mesh-maker context structure
// used to build meshes. You should have one context per thread
// that's building meshes.

STBVXDEC void stbvox_set_buffer(stbvox_mesh_maker *mm, int mesh, int slot, void *buffer, size_t len);
// Call this to set the buffer into which stbvox will write the mesh
// it creates. It can build more than one mesh in parallel (distinguished
// by the 'mesh' parameter), and each mesh can be made up of more than
// one buffer (distinguished by the 'slot' parameter).
//
// Multiple meshes are under your control; use the 'selector' input
// variable to choose which mesh each voxel's vertices are written to.
// For example, you can use this to generate separate meshes for opaque
// and transparent data.
//
// You can query the number of slots by calling stbvox_get_buffer_count
// described below. The meaning of the buffer for each slot depends
// on STBVOX_CONFIG_MODE.
//
//   In mode 0 & mode 20, there is only one slot. The mesh data for that
//   slot is two interleaved vertex attributes: attr_vertex, a single
//   32-bit uint, and attr_face, a single 32-bit uint.
//
//   In mode 1 & mode 21, there are two slots. The first buffer should
//   be four times as large as the second buffer. The first buffer
//   contains a single vertex attribute: 'attr_vertex', a single 32-bit uint.
//   The second buffer contains texture buffer data (an array of 32-bit uints)
//   that will be accessed through the sampler identified by STBVOX_UNIFORM_face_data.

STBVXDEC int stbvox_get_buffer_count(stbvox_mesh_maker *mm);
// Returns the number of buffers needed per mesh as described above.

STBVXDEC int stbvox_get_buffer_size_per_quad(stbvox_mesh_maker *mm, int slot);
// Returns how much of a given buffer will get used per quad. This
// allows you to choose correct relative sizes for each buffer, although
// the values are fixed based on the configuration you've selected at
// compile time, and the details are described in stbvox_set_buffer.

STBVXDEC void stbvox_set_default_mesh(stbvox_mesh_maker *mm, int mesh);
// Selects which mesh the mesher will output to (see previous function)
// if the input doesn't specify a per-voxel selector. (I doubt this is
// useful, but it's here just in case.)

STBVXDEC stbvox_input_description *stbvox_get_input_description(stbvox_mesh_maker *mm);
// This function call returns a pointer to the stbvox_input_description part
// of stbvox_mesh_maker (which you should otherwise treat as opaque). You
// zero this structure, then fill out the relevant pointers to the data
// describing your voxel object/world.
//
// See further documentation at the description of stbvox_input_description below.

STBVXDEC void stbvox_set_input_stride(stbvox_mesh_maker *mm, int x_stride_in_elements, int y_stride_in_elements);
// This sets the stride between successive elements of the 3D arrays
// in the stbvox_input_description. Z values are always stored consecutively.
// (The preferred coordinate system for stbvox is X right, Y forwards, Z up.)

STBVXDEC void stbvox_set_input_range(stbvox_mesh_maker *mm, int x0, int y0, int z0, int x1, int y1, int z1);
// This sets the range of values in the 3D array for the voxels that
// the mesh generator will convert. The lower values are inclusive,
// the higher values are exclusive, so (0,0,0) to (16,16,16) generates
// mesh data associated with voxels up to (15,15,15) but no higher.
//
// The mesh generate generates faces at the boundary between open space
// and solid space but associates them with the solid space, so if (15,0,0)
// is open and (16,0,0) is solid, then the mesh will contain the boundary
// between them if x0 <= 16 and x1 > 16.
//
// Note that the mesh generator will access array elements 1 beyond the
// limits set in these parameters. For example, if you set the limits
// to be (0,0,0) and (16,16,16), then the generator will access all of
// the voxels between (-1,-1,-1) and (16,16,16), including (16,16,16).
// You may have to do pointer arithmetic to make it work.
//
// For example, caveview processes mesh chunks that are 32x32x16, but it
// does this using input buffers that are 34x34x18.
//
// The lower limits are x0 >= 0, y0 >= 0, and z0 >= 0.
//
// The upper limits are mode dependent, but all the current methods are
// limited to x1 < 127, y1 < 127, z1 < 255. Note that these are not
// powers of two; if you want to use power-of-two chunks (to make
// it efficient to decide which chunk a coordinate falls in), you're
// limited to at most x1=64, y1=64, z1=128. For classic Minecraft-style
// worlds with limited vertical extent, I recommend using a single
// chunk for the entire height, which limits the height to 255 blocks
// (one less than Minecraft), and only chunk the map in X & Y.

STBVXDEC int stbvox_make_mesh(stbvox_mesh_maker *mm);
// Call this function to create mesh data for the currently configured
// set of input data. This appends to the currently configured mesh output
// buffer. Returns 1 on success. If there is not enough room in the buffer,
// it outputs as much as it can, and returns 0; you need to switch output
// buffers (either by calling stbvox_set_buffer to set new buffers, or
// by copying the data out and calling stbvox_reset_buffers), and then
// call this function again without changing any of the input parameters.
//
// Note that this function appends; you can call it multiple times to
// build a single mesh. For example, caveview uses chunks that are
// 32x32x255, but builds the mesh for it by processing 32x32x16 at atime
// (this is faster as it is reuses the same 34x34x18 input buffers rather
// than needing 34x34x257 input buffers).

// Once you're done creating a mesh into a given buffer,
// consider the following functions:

STBVXDEC int stbvox_get_quad_count(stbvox_mesh_maker *mm, int mesh);
// Returns the number of quads in the mesh currently generated by mm.
// This is the sum of all consecutive stbvox_make_mesh runs appending
// to the same buffer. 'mesh' distinguishes between the multiple user
// meshes available via 'selector' or stbvox_set_default_mesh.
//
// Typically you use this function when you're done building the mesh
// and want to record how to draw it.
//
// Note that there are no index buffers; the data stored in the buffers
// should be drawn as quads (e.g. with GL_QUAD); if your API does not
// support quads, you can create a single index buffer large enough to
// draw your largest vertex buffer, and reuse it for every rendering.
// (Note that if you use 32-bit indices, you'll use 24 bytes of bandwidth
// per quad, more than the 20 bytes for the vertex/face mesh data.)

STBVXDEC void stbvox_set_mesh_coordinates(stbvox_mesh_maker *mm, int x, int y, int z);
// Sets the global coordinates for this chunk, such that (0,0,0) relative
// coordinates will be at (x,y,z) in global coordinates.

STBVXDEC void stbvox_get_bounds(stbvox_mesh_maker *mm, float bounds[2][3]);
// Returns the bounds for the mesh in global coordinates. Use this
// for e.g. frustum culling the mesh. @BUG: this just uses the
// values from stbvox_set_input_range(), so if you build by
// appending multiple values, this will be wrong, and you need to
// set stbvox_set_input_range() to the full size. Someday this
// will switch to tracking the actual bounds of the *mesh*, though.

STBVXDEC void stbvox_get_transform(stbvox_mesh_maker *mm, float transform[3][3]);
// Returns the 'transform' data for the shader uniforms. It is your
// job to set this to the shader before drawing the mesh. It is the
// only uniform that needs to change per-mesh. Note that it is not
// a 3x3 matrix, but rather a scale to decode fixed point numbers as
// floats, a translate from relative to global space, and a special
// translation for texture coordinate generation that avoids
// floating-point precision issues. @TODO: currently we add the
// global translation to the vertex, than multiply by modelview,
// but this means if camera location and vertex are far from the
// origin, we lose precision. Need to make a special modelview with
// the translation (or some of it) factored out to avoid this.

STBVXDEC void stbvox_reset_buffers(stbvox_mesh_maker *mm);
// Call this function if you're done with the current output buffer
// but want to reuse it (e.g. you're done appending with
// stbvox_make_mesh and you've copied the data out to your graphics API
// so can reuse the buffer).

//////////////////////////////////////////////////////////////////////////////
//
// RENDERING
//

STBVXDEC char *stbvox_get_vertex_shader(void);
// Returns the (currently GLSL-only) vertex shader.

STBVXDEC char *stbvox_get_fragment_shader(void);
// Returns the (currently GLSL-only) fragment shader.
// You can override the lighting and fogging calculations
// by appending data to the end of these; see the #define
// documentation for more information.

STBVXDEC char *stbvox_get_fragment_shader_alpha_only(void);
// Returns a slightly cheaper fragment shader that computes
// alpha but not color. This is useful for e.g. a depth-only
// pass when using alpha test.

typedef struct stbvox_uniform_info stbvox_uniform_info;

STBVXDEC int stbvox_get_uniform_info(stbvox_uniform_info *info, int uniform);
// Gets the information about a uniform necessary for you to
// set up each uniform with a minimal amount of explicit code.
// See the sample code after the structure definition for stbvox_uniform_info,
// further down in this header section.
//
// "uniform" is from the list immediately following. For many
// of these, default values are provided which you can set.
// Most values are shared for most draw calls; e.g. for stateful
// APIs you can set most of the state only once. Only
// STBVOX_UNIFORM_transform needs to change per draw call.
//
// STBVOX_UNIFORM_texscale
//    64- or 128-long vec4 array. (128 only if STBVOX_CONFIG_PREFER_TEXBUFFER)
//    x: scale factor to apply to texture #1. must be a power of two. 1.0 means 'face-sized'
//    y: scale factor to apply to texture #2. must be a power of two. 1.0 means 'face-sized'
//    z: blend mode indexed by texture #2. 0.0 is alpha compositing; 1.0 is multiplication.
//    w: unused currently. @TODO use to support texture animation?
//
//    Texscale is indexed by the bottom 6 or 7 bits of the texture id; thus for
//    example the texture at index 0 in the array and the texture in index 128 of
//    the array must be scaled the same. This means that if you only have 64 or 128
//    unique textures, they all get distinct values anyway; otherwise you have
//    to group them in pairs or sets of four.
//
// STBVOX_UNIFORM_ambient
//    4-long vec4 array:
//      ambient[0].xyz   - negative of direction of a directional light for half-lambert
//      ambient[1].rgb   - color of light scaled by NdotL (can be negative)
//      ambient[2].rgb   - constant light added to above calculation;
//                         effectively light ranges from ambient[2]-ambient[1] to ambient[2]+ambient[1]
//      ambient[3].rgb   - fog color for STBVOX_CONFIG_FOG_SMOOTHSTEP
//      ambient[3].a     - reciprocal of squared distance of farthest fog point (viewing distance)


                               //  +----- has a default value
                               //  |  +-- you should always use the default value
enum                           //  V  V
{                              //  ------------------------------------------------
   STBVOX_UNIFORM_face_data,   //  n      the sampler with the face texture buffer
   STBVOX_UNIFORM_transform,   //  n      the transform data from stbvox_get_transform
   STBVOX_UNIFORM_tex_array,   //  n      an array of two texture samplers containing the two texture arrays
   STBVOX_UNIFORM_texscale,    //  Y      a table of texture properties, see above
   STBVOX_UNIFORM_color_table, //  Y      64 vec4 RGBA values; a default palette is provided; if A > 1.0, fullbright
   STBVOX_UNIFORM_normals,     //  Y  Y   table of normals, internal-only
   STBVOX_UNIFORM_texgen,      //  Y  Y   table of texgen vectors, internal-only
   STBVOX_UNIFORM_ambient,     //  n      lighting & fog info, see above
   STBVOX_UNIFORM_camera_pos,  //  Y      camera position in global voxel space (for lighting & fog)

   STBVOX_UNIFORM_count,
};

enum
{
   STBVOX_UNIFORM_TYPE_none,
   STBVOX_UNIFORM_TYPE_sampler,
   STBVOX_UNIFORM_TYPE_vec2,
   STBVOX_UNIFORM_TYPE_vec3,
   STBVOX_UNIFORM_TYPE_vec4,
};

struct stbvox_uniform_info
{
   int type;                    // which type of uniform
   int bytes_per_element;       // the size of each uniform array element (e.g. vec3 = 12 bytes)
   int array_length;            // length of the uniform array
   char *name;                  // name in the shader @TODO use numeric binding
   float *default_value;        // if not NULL, you can use this as the uniform pointer
   int use_tex_buffer;          // if true, then the uniform is a sampler but the data can come from default_value
};

//////////////////////////////////////////////////////////////////////////////
//
// Uniform sample code
//

#if 0
// Run this once per frame before drawing all the meshes.
// You still need to separately set the 'transform' uniform for every mesh.
void setup_uniforms(GLuint shader, float camera_pos[4], GLuint tex1, GLuint tex2)
{
   int i;
   glUseProgram(shader); // so uniform binding works
   for (i=0; i < STBVOX_UNIFORM_count; ++i) {
      stbvox_uniform_info sui;
      if (stbvox_get_uniform_info(&sui, i)) {
         GLint loc = glGetUniformLocation(shader, sui.name);
         if (loc != 0) {
            switch (i) {
               case STBVOX_UNIFORM_camera_pos: // only needed for fog
                  glUniform4fv(loc, sui.array_length, camera_pos);
                  break;

               case STBVOX_UNIFORM_tex_array: {
                  GLuint tex_unit[2] = { 0, 1 }; // your choice of samplers
                  glUniform1iv(loc, 2, tex_unit);

                  glActiveTexture(GL_TEXTURE0 + tex_unit[0]); glBindTexture(GL_TEXTURE_2D_ARRAY, tex1);
                  glActiveTexture(GL_TEXTURE0 + tex_unit[1]); glBindTexture(GL_TEXTURE_2D_ARRAY, tex2);
                  glActiveTexture(GL_TEXTURE0); // reset to default
                  break;
               }

               case STBVOX_UNIFORM_face_data:
                  glUniform1i(loc, SAMPLER_YOU_WILL_BIND_PER_MESH_FACE_DATA_TO);
                  break;

               case STBVOX_UNIFORM_ambient:     // you definitely want to override this
               case STBVOX_UNIFORM_color_table: // you might want to override this
               case STBVOX_UNIFORM_texscale:    // you may want to override this
                  glUniform4fv(loc, sui.array_length, sui.default_value);
                  break;

               case STBVOX_UNIFORM_normals:     // you never want to override this
               case STBVOX_UNIFORM_texgen:      // you never want to override this
                  glUniform3fv(loc, sui.array_length, sui.default_value);
                  break;
            }
         }
      }
   }
}
#endif

#ifdef __cplusplus
}
#endif

//////////////////////////////////////////////////////////////////////////////
//
// INPUT TO MESHING
//

// Shapes of blocks that aren't always cubes
enum
{
   STBVOX_GEOM_empty,
   STBVOX_GEOM_knockout,  // creates a hole in the mesh
   STBVOX_GEOM_solid,
   STBVOX_GEOM_transp,    // solid geometry, but transparent contents so neighbors generate normally, unless same blocktype

   // following 4 can be represented by vheight as well
   STBVOX_GEOM_slab_upper,
   STBVOX_GEOM_slab_lower,
   STBVOX_GEOM_floor_slope_north_is_top,
   STBVOX_GEOM_ceil_slope_north_is_bottom,

   STBVOX_GEOM_floor_slope_north_is_top_as_wall_UNIMPLEMENTED,   // same as floor_slope above, but uses wall's texture & texture projection
   STBVOX_GEOM_ceil_slope_north_is_bottom_as_wall_UNIMPLEMENTED,
   STBVOX_GEOM_crossed_pair,    // corner-to-corner pairs, with normal vector bumped upwards
   STBVOX_GEOM_force,           // like GEOM_transp, but faces visible even if neighbor is same type, e.g. minecraft fancy leaves

   // these access vheight input
   STBVOX_GEOM_floor_vheight_03 = 12,  // diagonal is SW-NE
   STBVOX_GEOM_floor_vheight_12,       // diagonal is SE-NW
   STBVOX_GEOM_ceil_vheight_03,
   STBVOX_GEOM_ceil_vheight_12,

   STBVOX_GEOM_count, // number of geom cases
};

enum
{
   STBVOX_FACE_east,
   STBVOX_FACE_north,
   STBVOX_FACE_west,
   STBVOX_FACE_south,
   STBVOX_FACE_up,
   STBVOX_FACE_down,

   STBVOX_FACE_count,
};

#ifdef STBVOX_CONFIG_BLOCKTYPE_SHORT
typedef unsigned short stbvox_block_type;
#else
typedef unsigned char stbvox_block_type;
#endif

// 24-bit color
typedef struct
{
   unsigned char r,g,b;
} stbvox_rgb;

#define STBVOX_COLOR_TEX1_ENABLE   64
#define STBVOX_COLOR_TEX2_ENABLE  128

// This is the data structure you fill out. Most of the arrays can be
// NULL, except when one is required to get the value to index another.
//
// The compass system used in the following descriptions is:
//     east means increasing x
//     north means increasing y
//     up means increasing z
struct stbvox_input_description
{
   unsigned char lighting_at_vertices;
   // The default is lighting values (i.e. ambient occlusion) are at block
   // center, and the vertex light is gathered from those adjacent block
   // centers that the vertex is facing. This makes smooth lighting
   // consistent across adjacent faces with the same orientation.
   //
   // Setting this flag to non-zero gives you explicit control
   // of light at each vertex, but now the lighting/ao will be
   // shared by all vertices at the same point, even if they
   // have different normals.

   // these are mostly 3D maps you use to define your voxel world, using x_stride and y_stride
   // note that for cache efficiency, you want to use the block_foo palettes as much as possible instead

   stbvox_rgb *rgb;
   // Indexed by 3D coordinate.
   // 24-bit voxel color for STBVOX_CONFIG_MODE = 20 or 21 only

   unsigned char *lighting;
   // Indexed by 3D coordinate. The lighting value / ambient occlusion
   // value that is used to define the vertex lighting values.
   // The raw lighting values are defined at the center of blocks
   // (or at vertex if 'lighting_at_vertices' is true).
   //
   // If the macro STBVOX_CONFIG_ROTATION_IN_LIGHTING is defined,
   // then an additional 2-bit block rotation value is stored
   // in this field as well.
   //
   // Encode with STBVOX_MAKE_LIGHTING_EXT(lighting,rot)--here
   // 'lighting' should still be 8 bits, as the macro will
   // discard the bottom bits automatically. Similarly, if
   // using STBVOX_CONFIG_VHEIGHT_IN_LIGHTING, encode with
   // STBVOX_MAKE_LIGHTING_EXT(lighting,vheight).
   //
   // (Rationale: rotation needs to be independent of blocktype,
   // but is only 2 bits so doesn't want to be its own array.
   // Lighting is the one thing that was likely to already be
   // in use and that I could easily steal 2 bits from.)

   stbvox_block_type *blocktype;
   // Indexed by 3D coordinate. This is a core "block type" value, which is used
   // to index into other arrays; essentially a "palette". This is much more
   // memory-efficient and performance-friendly than storing the values explicitly,
   // but only makes sense if the values are always synchronized.
   //
   // If a voxel's blocktype is 0, it is assumed to be empty (STBVOX_GEOM_empty),
   // and no other blocktypes should be STBVOX_GEOM_empty. (Only if you do not
   // have blocktypes should STBVOX_GEOM_empty ever used.)
   //
   // Normally it is an unsigned byte, but you can override it to be
   // a short if you have too many blocktypes.

   unsigned char *geometry;
   // Indexed by 3D coordinate. Contains the geometry type for the block.
   // Also contains a 2-bit rotation for how the whole block is rotated.
   // Also includes a 2-bit vheight value when using shared vheight values.
   // See the separate vheight documentation.
   // Encode with STBVOX_MAKE_GEOMETRY(geom, rot, vheight)

   unsigned char *block_geometry;
   // Array indexed by blocktype containing the geometry for this block, plus
   // a 2-bit "simple rotation". Note rotation has limited use since it's not
   // independent of blocktype.
   //
   // Encode with STBVOX_MAKE_GEOMETRY(geom,simple_rot,0)

   unsigned char *block_tex1;
   // Array indexed by blocktype containing the texture id for texture #1.

   unsigned char (*block_tex1_face)[6];
   // Array indexed by blocktype and face containing the texture id for texture #1.
   // The N/E/S/W face choices can be rotated by one of the rotation selectors;
   // The top & bottom face textures will rotate to match.
   // Note that it only makes sense to use one of block_tex1 or block_tex1_face;
   // this pattern repeats throughout and this notice is not repeated.

   unsigned char *tex2;
   // Indexed by 3D coordinate. Contains the texture id for texture #2
   // to use on all faces of the block.

   unsigned char *block_tex2;
   // Array indexed by blocktype containing the texture id for texture #2.

   unsigned char (*block_tex2_face)[6];
   // Array indexed by blocktype and face containing the texture id for texture #2.
   // The N/E/S/W face choices can be rotated by one of the rotation selectors;
   // The top & bottom face textures will rotate to match.

   unsigned char *color;
   // Indexed by 3D coordinate. Contains the color for all faces of the block.
   // The core color value is 0..63.
   // Encode with STBVOX_MAKE_COLOR(color_number, tex1_enable, tex2_enable)
   
   unsigned char *block_color;
   // Array indexed by blocktype containing the color value to apply to the faces.
   // The core color value is 0..63.
   // Encode with STBVOX_MAKE_COLOR(color_number, tex1_enable, tex2_enable)

   unsigned char (*block_color_face)[6];
   // Array indexed by blocktype and face containing the color value to apply to that face.
   // The core color value is 0..63.
   // Encode with STBVOX_MAKE_COLOR(color_number, tex1_enable, tex2_enable)

   unsigned char *block_texlerp;
   // Array indexed by blocktype containing 3-bit scalar for texture #2 alpha
   // (known throughout as 'texlerp'). This is constant over every face even
   // though the property is potentially per-vertex.

   unsigned char (*block_texlerp_face)[6];
   // Array indexed by blocktype and face containing 3-bit scalar for texture #2 alpha.
   // This is constant over the face even though the property is potentially per-vertex.

   unsigned char *block_vheight;
   // Array indexed by blocktype containing the vheight values for the
   // top or bottom face of this block. These will rotate properly if the
   // block is rotated. See discussion of vheight.
   // Encode with STBVOX_MAKE_VHEIGHT(sw_height, se_height, nw_height, ne_height)

   unsigned char *selector;
   // Array indexed by 3D coordinates indicating which output mesh to select.

   unsigned char *block_selector;
   // Array indexed by blocktype indicating which output mesh to select.

   unsigned char *side_texrot;
   // Array indexed by 3D coordinates encoding 2-bit texture rotations for the
   // faces on the E/N/W/S sides of the block.
   // Encode with STBVOX_MAKE_SIDE_TEXROT(rot_e, rot_n, rot_w, rot_s)

   unsigned char *block_side_texrot;
   // Array indexed by blocktype encoding 2-bit texture rotations for the faces
   // on the E/N/W/S sides of the block.
   // Encode with STBVOX_MAKE_SIDE_TEXROT(rot_e, rot_n, rot_w, rot_s)

   unsigned char *overlay;                 // index into palettes listed below
   // Indexed by 3D coordinate. If 0, there is no overlay. If non-zero,
   // it indexes into to the below arrays and overrides the values
   // defined by the blocktype.

   unsigned char (*overlay_tex1)[6];
   // Array indexed by overlay value and face, containing an override value
   // for the texture id for texture #1. If 0, the value defined by blocktype
   // is used.

   unsigned char (*overlay_tex2)[6];
   // Array indexed by overlay value and face, containing an override value
   // for the texture id for texture #2. If 0, the value defined by blocktype
   // is used.

   unsigned char (*overlay_color)[6];
   // Array indexed by overlay value and face, containing an override value
   // for the face color. If 0, the value defined by blocktype is used.

   unsigned char *overlay_side_texrot;
   // Array indexed by overlay value, encoding 2-bit texture rotations for the faces
   // on the E/N/W/S sides of the block.
   // Encode with STBVOX_MAKE_SIDE_TEXROT(rot_e, rot_n, rot_w, rot_s)

   unsigned char *rotate;
   // Indexed by 3D coordinate. Allows independent rotation of several
   // parts of the voxel, where by rotation I mean swapping textures
   // and colors between E/N/S/W faces.
   //    Block: rotates anything indexed by blocktype
   //    Overlay: rotates anything indexed by overlay
   //    EColor: rotates faces defined in ecolor_facemask
   // Encode with STBVOX_MAKE_MATROT(block,overlay,ecolor)

   unsigned char *tex2_for_tex1;
   // Array indexed by tex1 containing the texture id for texture #2.
   // You can use this if the two are always/almost-always strictly
   // correlated (e.g. if tex2 is a detail texture for tex1), as it
   // will be more efficient (touching fewer cache lines) than using
   // e.g. block_tex2_face.

   unsigned char *tex2_replace;
   // Indexed by 3D coordinate. Specifies the texture id for texture #2
   // to use on a single face of the voxel, which must be E/N/W/S (not U/D).
   // The texture id is limited to 6 bits unless tex2_facemask is also
   // defined (see below).
   // Encode with STBVOX_MAKE_TEX2_REPLACE(tex2, face)

   unsigned char *tex2_facemask;
   // Indexed by 3D coordinate. Specifies which of the six faces should
   // have their tex2 replaced by the value of tex2_replace. In this
   // case, all 8 bits of tex2_replace are used as the texture id.
   // Encode with STBVOX_MAKE_FACE_MASK(east,north,west,south,up,down)

   unsigned char *extended_color;
   // Indexed by 3D coordinate. Specifies a value that indexes into
   // the ecolor arrays below (both of which must be defined).

   unsigned char *ecolor_color;
   // Indexed by extended_color value, specifies an optional override
   // for the color value on some faces.
   // Encode with STBVOX_MAKE_COLOR(color_number, tex1_enable, tex2_enable)

   unsigned char *ecolor_facemask;
   // Indexed by extended_color value, this specifies which faces the
   // color in ecolor_color should be applied to. The faces can be
   // independently rotated by the ecolor value of 'rotate', if it exists.
   // Encode with STBVOX_MAKE_FACE_MASK(e,n,w,s,u,d)

   unsigned char *color2;
   // Indexed by 3D coordinates, specifies an alternative color to apply
   // to some of the faces of the block.
   // Encode with STBVOX_MAKE_COLOR(color_number, tex1_enable, tex2_enable)

   unsigned char *color2_facemask;
   // Indexed by 3D coordinates, specifies which faces should use the
   // color defined in color2. No rotation value is applied.
   // Encode with STBVOX_MAKE_FACE_MASK(e,n,w,s,u,d)
   
   unsigned char *color3;
   // Indexed by 3D coordinates, specifies an alternative color to apply
   // to some of the faces of the block.
   // Encode with STBVOX_MAKE_COLOR(color_number, tex1_enable, tex2_enable)

   unsigned char *color3_facemask;
   // Indexed by 3D coordinates, specifies which faces should use the
   // color defined in color3. No rotation value is applied. 
   // Encode with STBVOX_MAKE_FACE_MASK(e,n,w,s,u,d)
   
   unsigned char *texlerp_simple;
   // Indexed by 3D coordinates, this is the smallest texlerp encoding
   // that can do useful work. It consits of three values: baselerp,
   // vertlerp, and face_vertlerp. Baselerp defines the value
   // to use on all of the faces but one, from the STBVOX_TEXLERP_BASE
   // values. face_vertlerp is one of the 6 face values (or STBVOX_FACE_NONE)
   // which specifies the face should use the vertlerp values.
   // Vertlerp defines a lerp value at every vertex of the mesh.
   // Thus, one face can have per-vertex texlerp values, and those
   // values are encoded in the space so that they will be shared
   // by adjacent faces that also use vertlerp, allowing continuity
   // (this is used for the "texture crossfade" bit of the release video).
   // Encode with STBVOX_MAKE_TEXLERP_SIMPLE(baselerp, vertlerp, face_vertlerp)

   // The following texlerp encodings are experimental and maybe not
   // that useful. 

   unsigned char *texlerp;
   // Indexed by 3D coordinates, this defines four values:
   //   vertlerp is a lerp value at every vertex of the mesh (using STBVOX_TEXLERP_BASE values).
   //   ud is the value to use on up and down faces, from STBVOX_TEXLERP_FACE values
   //   ew is the value to use on east and west faces, from STBVOX_TEXLERP_FACE values
   //   ns is the value to use on north and south faces, from STBVOX_TEXLERP_FACE values
   // If any of ud, ew, or ns is STBVOX_TEXLERP_FACE_use_vert, then the
   // vertlerp values for the vertices are gathered and used for those faces.
   // Encode with STBVOX_MAKE_TEXLERP(vertlerp,ud,ew,sw)

   unsigned short *texlerp_vert3;
   // Indexed by 3D coordinates, this works with texlerp and
   // provides a unique texlerp value for every direction at
   // every vertex. The same rules of whether faces share values
   // applies. The STBVOX_TEXLERP_FACE vertlerp value defined in
   // texlerp is only used for the down direction. The values at
   // each vertex in other directions are defined in this array,
   // and each uses the STBVOX_TEXLERP3 values (i.e. full precision
   // 3-bit texlerp values).
   // Encode with STBVOX_MAKE_VERT3(vertlerp_e,vertlerp_n,vertlerp_w,vertlerp_s,vertlerp_u)

   unsigned short *texlerp_face3;          // e:3,n:3,w:3,s:3,u:2,d:2
   // Indexed by 3D coordinates, this provides a compact way to
   // fully specify the texlerp value indepenendly for every face,
   // but doesn't allow per-vertex variation. E/N/W/S values are
   // encoded using STBVOX_TEXLERP3 values, whereas up and down
   // use STBVOX_TEXLERP_SIMPLE values.
   // Encode with STBVOX_MAKE_FACE3(face_e,face_n,face_w,face_s,face_u,face_d)

   unsigned char *vheight;                 // STBVOX_MAKE_VHEIGHT   -- sw:2, se:2, nw:2, ne:2, doesn't rotate
   // Indexed by 3D coordinates, this defines the four
   // vheight values to use if the geometry is STBVOX_GEOM_vheight*.
   // See the vheight discussion.

   unsigned char *packed_compact;
   // Stores block rotation, vheight, and texlerp values:
   //    block rotation: 2 bits
   //    vertex vheight: 2 bits
   //    use_texlerp   : 1 bit
   //    vertex texlerp: 3 bits
   // If STBVOX_CONFIG_UP_TEXLERP_PACKED is defined, then 'vertex texlerp' is
   // used for up faces if use_texlerp is 1. If STBVOX_CONFIG_DOWN_TEXLERP_PACKED
   // is defined, then 'vertex texlerp' is used for down faces if use_texlerp is 1.
   // Note if those symbols are defined but packed_compact is NULL, the normal
   // texlerp default will be used.
   // Encode with STBVOX_MAKE_PACKED_COMPACT(rot, vheight, texlerp, use_texlerp)
};
// @OPTIMIZE allow specializing; build a single struct with all of the
// 3D-indexed arrays combined so it's AoS instead of SoA for better
// cache efficiency


//////////////////////////////////////////////////////////////////////////////
//
//  VHEIGHT DOCUMENTATION
//
//  "vheight" is the internal name for the special block types
//  with sloped tops or bottoms. "vheight" stands for "vertex height".
//
//  Note that these blocks are very flexible (there are 256 of them,
//  although at least 17 of them should never be used), but they
//  also have a disadvantage that they generate extra invisible
//  faces; the generator does not currently detect whether adjacent
//  vheight blocks hide each others sides, so those side faces are
//  always generated. For a continuous ground terrain, this means
//  that you may generate 5x as many quads as needed. See notes
//  on "improvements for shipping products" in the introduction.

enum
{
   STBVOX_VERTEX_HEIGHT_0,
   STBVOX_VERTEX_HEIGHT_half,
   STBVOX_VERTEX_HEIGHT_1,
   STBVOX_VERTEX_HEIGHT_one_and_a_half,
};
// These are the "vheight" values. Vheight stands for "vertex height".
// The idea is that for a "floor vheight" block, you take a cube and
// reposition the top-most vertices at various heights as specified by
// the vheight values. Similarly, a "ceiling vheight" block takes a
// cube and repositions the bottom-most vertices.
//
// A floor block only adjusts the top four vertices; the bottom four vertices
// remain at the bottom of the block. The height values are 2 bits,
// measured in halves of a block; so you can specify heights of 0/2,
// 1/2, 2/2, or 3/2. 0 is the bottom of the block, 1 is halfway
// up the block, 2 is the top of the block, and 3 is halfway up the
// next block (and actually outside of the block). The value 3 is
// actually legal for floor vheight (but not ceiling), and allows you to:
//
//     (A) have smoother terrain by having slopes that cross blocks,
//         e.g. (1,1,3,3) is a regular-seeming slope halfway between blocks
//     (B) make slopes steeper than 45-degrees, e.g. (0,0,3,3)
//
// (Because only z coordinates have half-block precision, and x&y are
// limited to block corner precision, it's not possible to make these
// things "properly" out of blocks, e.g. a half-slope block on its side
// or a sloped block halfway between blocks that's made out of two blocks.)
//
// If you define STBVOX_CONFIG_OPTIMIZED_VHEIGHT, then the top face
// (or bottom face for a ceiling vheight block) will be drawn as a
// single quad even if the four vertex heights aren't planar, and a
// single normal will be used over the entire quad. If you
// don't define it, then if the top face is non-planar, it will be
// split into two triangles, each with their own normal/lighting.
// (Note that since all output from stb_voxel_render is quad meshes,
// triangles are actually rendered as degenerate quads.) In this case,
// the distinction between STBVOX_GEOM_floor_vheight_03 and
// STBVOX_GEOM_floor_vheight_12 comes into play; the former introduces
// an edge from the SW to NE corner (i.e. from <0,0,?> to <1,1,?>),
// while the latter introduces an edge from the NW to SE corner
// (i.e. from <0,1,?> to <1,0,?>.) For a "lazy mesh" look, use
// exclusively _03 or _12. For a "classic mesh" look, alternate
// _03 and _12 in a checkerboard pattern. For a "smoothest surface"
// look, choose the edge based on actual vertex heights.
//
// The four vertex heights can come from several places. The simplest
// encoding is to just use the 'vheight' parameter which stores four
// explicit vertex heights for every block. This allows total independence,
// but at the cost of the largest memory usage, 1 byte per 3D block.
// Encode this with STBVOX_MAKE_VHEIGHT(vh_sw, vh_se, vh_nw, vh_ne).
// These coordinates are absolute, not affected by block rotations.
//
// An alternative if you just want to encode some very specific block
// types, not all the possibilities--say you just want half-height slopes,
// so you want (0,0,1,1) and (1,1,2,2)--then you can use block_vheight
// to specify them. The geometry rotation will cause block_vheight values
// to be rotated (because it's as if you're just defining a type of
// block). This value is also encoded with STBVOX_MAKE_VHEIGHT.
//
// If you want to save memory and you're creating a "continuous ground"
// sort of effect, you can make each vertex of the lattice share the
// vheight value; that is, two adjacent blocks that share a vertex will
// always get the same vheight value for that vertex. Then you need to
// store two bits of vheight for every block, which you do by storing it
// as part another data structure. Store the south-west vertex's vheight
// with the block. You can either use the "geometry" mesh variable (it's
// a parameter to STBVOX_MAKE_GEOMETRY) or you can store it in the
// "lighting" mesh variable if you defined STBVOX_CONFIG_VHEIGHT_IN_LIGHTING,
// using STBVOX_MAKE_LIGHTING_EXT(lighting,vheight).
//
// Note that if you start with a 2D height map and generate vheight data from
// it, you don't necessarily store only one value per (x,y) coordinate,
// as the same value may need to be set up at multiple z heights. For
// example, if height(8,8) = 13.5, then you want the block at (8,8,13)
// to store STBVOX_VERTEX_HEIGHT_half, and this will be used by blocks
// at (7,7,13), (8,7,13), (7,8,13), and (8,8,13). However, if you're
// allowing steep slopes, it might be the case that you have a block
// at (7,7,12) which is supposed to stick up to 13.5; that means
// you also need to store STBVOX_VERTEX_HEIGHT_one_and_a_half at (8,8,12).

enum
{
   STBVOX_TEXLERP_FACE_0,
   STBVOX_TEXLERP_FACE_half,
   STBVOX_TEXLERP_FACE_1,
   STBVOX_TEXLERP_FACE_use_vert,
};

enum
{
   STBVOX_TEXLERP_BASE_0,    // 0.0
   STBVOX_TEXLERP_BASE_2_7,  // 2/7
   STBVOX_TEXLERP_BASE_5_7,  // 4/7
   STBVOX_TEXLERP_BASE_1     // 1.0
};

enum
{
   STBVOX_TEXLERP3_0_8,
   STBVOX_TEXLERP3_1_8,
   STBVOX_TEXLERP3_2_8,
   STBVOX_TEXLERP3_3_8,
   STBVOX_TEXLERP3_4_8,
   STBVOX_TEXLERP3_5_8,
   STBVOX_TEXLERP3_6_8,
   STBVOX_TEXLERP3_7_8,
};

#define STBVOX_FACE_NONE  7

#define STBVOX_BLOCKTYPE_EMPTY    0

#ifdef STBVOX_BLOCKTYPE_SHORT
#define STBVOX_BLOCKTYPE_HOLE  65535
#else
#define STBVOX_BLOCKTYPE_HOLE    255
#endif

#define STBVOX_MAKE_GEOMETRY(geom, rotate, vheight) ((geom) + (rotate)*16 + (vheight)*64)
#define STBVOX_MAKE_VHEIGHT(v_sw, v_se, v_nw, v_ne) ((v_sw) + (v_se)*4 + (v_nw)*16 + (v_ne)*64)
#define STBVOX_MAKE_MATROT(block, overlay, color)  ((block) + (overlay)*4 + (color)*64)
#define STBVOX_MAKE_TEX2_REPLACE(tex2, tex2_replace_face) ((tex2) + ((tex2_replace_face) & 3)*64)
#define STBVOX_MAKE_TEXLERP(ns2, ew2, ud2, vert)  ((ew2) + (ns2)*4 + (ud2)*16 + (vert)*64)
#define STBVOX_MAKE_TEXLERP_SIMPLE(baselerp,vert,face)   ((vert)*32 + (face)*4 + (baselerp))
#define STBVOX_MAKE_TEXLERP1(vert,e2,n2,w2,s2,u4,d2) STBVOX_MAKE_TEXLERP(s2, w2, d2, vert)
#define STBVOX_MAKE_TEXLERP2(vert,e2,n2,w2,s2,u4,d2) ((u2)*16 + (n2)*4 + (s2))
#define STBVOX_MAKE_FACE_MASK(e,n,w,s,u,d)  ((e)+(n)*2+(w)*4+(s)*8+(u)*16+(d)*32)
#define STBVOX_MAKE_SIDE_TEXROT(e,n,w,s) ((e)+(n)*4+(w)*16+(s)*64)
#define STBVOX_MAKE_COLOR(color,t1,t2) ((color)+(t1)*64+(t2)*128)
#define STBVOX_MAKE_TEXLERP_VERT3(e,n,w,s,u)   ((e)+(n)*8+(w)*64+(s)*512+(u)*4096)
#define STBVOX_MAKE_TEXLERP_FACE3(e,n,w,s,u,d) ((e)+(n)*8+(w)*64+(s)*512+(u)*4096+(d)*16384)
#define STBVOX_MAKE_PACKED_COMPACT(rot, vheight, texlerp, def) ((rot)+4*(vheight)+16*(use)+32*(texlerp))

#define STBVOX_MAKE_LIGHTING_EXT(lighting, rot)  (((lighting)&~3)+(rot))
#define STBVOX_MAKE_LIGHTING(lighting)       (lighting)

#ifndef STBVOX_MAX_MESHES
#define STBVOX_MAX_MESHES      2           // opaque & transparent
#endif

#define STBVOX_MAX_MESH_SLOTS  3           // one vertex & two faces, or two vertex and one face


// don't mess with this directly, it's just here so you can
// declare stbvox_mesh_maker on the stack or as a global
struct stbvox_mesh_maker
{
   stbvox_input_description input;
   int cur_x, cur_y, cur_z;       // last unprocessed voxel if it splits into multiple buffers
   int x0,y0,z0,x1,y1,z1;
   int x_stride_in_bytes;
   int y_stride_in_bytes;
   int config_dirty;
   int default_mesh;
   unsigned int tags;

   int cube_vertex_offset[6][4]; // this allows access per-vertex data stored block-centered (like texlerp, ambient)
   int vertex_gather_offset[6][4];

   int pos_x,pos_y,pos_z;
   int full;

   // computed from user input
   char *output_cur   [STBVOX_MAX_MESHES][STBVOX_MAX_MESH_SLOTS];
   char *output_end   [STBVOX_MAX_MESHES][STBVOX_MAX_MESH_SLOTS];
   char *output_buffer[STBVOX_MAX_MESHES][STBVOX_MAX_MESH_SLOTS];
   int   output_len   [STBVOX_MAX_MESHES][STBVOX_MAX_MESH_SLOTS];

   // computed from config
   int   output_size  [STBVOX_MAX_MESHES][STBVOX_MAX_MESH_SLOTS]; // per quad
   int   output_step  [STBVOX_MAX_MESHES][STBVOX_MAX_MESH_SLOTS]; // per vertex or per face, depending
   int   num_mesh_slots;

   float default_tex_scale[128][2];
};

#endif //  INCLUDE_STB_VOXEL_RENDER_H


#ifdef STB_VOXEL_RENDER_IMPLEMENTATION

#include <stdlib.h>
#include <assert.h>
#include <string.h> // memset

// have to use our own names to avoid the _MSC_VER path having conflicting type names
#ifndef _MSC_VER
   #include <stdint.h>
   typedef uint16_t stbvox_uint16;
   typedef uint32_t stbvox_uint32;
#else
   typedef unsigned short stbvox_uint16;
   typedef unsigned int   stbvox_uint32;
#endif

#ifdef _MSC_VER
   #define STBVOX_NOTUSED(v)  (void)(v)
#else
   #define STBVOX_NOTUSED(v)  (void)sizeof(v)
#endif



#ifndef STBVOX_CONFIG_MODE
#error "Must defined STBVOX_CONFIG_MODE to select the mode"
#endif

#if defined(STBVOX_CONFIG_ROTATION_IN_LIGHTING) && defined(STBVOX_CONFIG_VHEIGHT_IN_LIGHTING)
#error "Can't store both rotation and vheight in lighting"
#endif


// The following are candidate voxel modes. Only modes 0, 1, and 20, and 21 are
// currently implemented. Reducing the storage-per-quad further
// shouldn't improve performance, although obviously it allow you
// to create larger worlds without streaming.
//
//        
//                      -----------  Two textures -----------       -- One texture --     ---- Color only ----
//            Mode:     0     1     2     3     4     5     6        10    11    12      20    21    22    23    24
// ============================================================================================================
//  uses Tex Buffer     n     Y     Y     Y     Y     Y     Y         Y     Y     Y       n     Y     Y     Y     Y
//   bytes per quad    32    20    14    12    10     6     6         8     8     4      32    20    10     6     4
//       non-blocks   all   all   some  some  some slabs stairs     some  some  none    all   all  slabs slabs  none
//             tex1   256   256   256   256   256   256   256       256   256   256       n     n     n     n     n
//             tex2   256   256   256   256   256   256   128         n     n     n       n     n     n     n     n
//           colors    64    64    64    64    64    64    64         8     n     n     2^24  2^24  2^24  2^24  256
//        vertex ao     Y     Y     Y     Y     Y     n     n         Y     Y     n       Y     Y     Y     n     n
//   vertex texlerp     Y     Y     Y     n     n     n     n         -     -     -       -     -     -     -     -
//      x&y extents   127   127   128    64    64   128    64        64   128   128     127   127   128   128   128
//        z extents   255   255   128    64?   64?   64    64        32    64   128     255   255   128    64   128

// not sure why I only wrote down the above "result data" and didn't preserve
// the vertex formats, but here I've tried to reconstruct the designs...
//     mode # 3 is wrong, one byte too large, but they may have been an error originally

//            Mode:     0     1     2     3     4     5     6        10    11    12      20    21    22    23    24
// =============================================================================================================
//   bytes per quad    32    20    14    12    10     6     6         8     8     4            20    10     6     4
//                                                                 
//    vertex x bits     7     7     0     6     0     0     0         0     0     0             7     0     0     0
//    vertex y bits     7     7     0     0     0     0     0         0     0     0             7     0     0     0
//    vertex z bits     9     9     7     4     2     0     0         2     2     0             9     2     0     0
//   vertex ao bits     6     6     6     6     6     0     0         6     6     0             6     6     0     0
//  vertex txl bits     3     3     3     0     0     0     0         0     0     0            (3)    0     0     0
//
//   face tex1 bits    (8)    8     8     8     8     8     8         8     8     8                    
//   face tex2 bits    (8)    8     8     8     8     8     7         -     -     -         
//  face color bits    (8)    8     8     8     8     8     8         3     0     0            24    24    24     8
// face normal bits    (8)    8     8     8     6     4     7         4     4     3             8     3     4     3
//      face x bits                 7     0     6     7     6         6     7     7             0     7     7     7
//      face y bits                 7     6     6     7     6         6     7     7             0     7     7     7
//      face z bits                 2     2     6     6     6         5     6     7             0     7     6     7


#if STBVOX_CONFIG_MODE==0 || STBVOX_CONFIG_MODE==1

   #define STBVOX_ICONFIG_VERTEX_32
   #define STBVOX_ICONFIG_FACE1_1

#elif STBVOX_CONFIG_MODE==20 || STBVOX_CONFIG_MODE==21

   #define STBVOX_ICONFIG_VERTEX_32
   #define STBVOX_ICONFIG_FACE1_1
   #define STBVOX_ICONFIG_UNTEXTURED

#else
#error "Selected value of STBVOX_CONFIG_MODE is not supported"
#endif

#if STBVOX_CONFIG_MODE==0 || STBVOX_CONFIG_MODE==20
#define STBVOX_ICONFIG_FACE_ATTRIBUTE
#endif

#ifndef STBVOX_CONFIG_HLSL
// the fallback if all others are exhausted is GLSL
#define STBVOX_ICONFIG_GLSL
#endif

#ifdef STBVOX_CONFIG_OPENGL_MODELVIEW
#define STBVOX_ICONFIG_OPENGL_3_1_COMPATIBILITY
#endif

#if defined(STBVOX_ICONFIG_VERTEX_32)
   typedef stbvox_uint32 stbvox_mesh_vertex;
   #define stbvox_vertex_encode(x,y,z,ao,texlerp) \
      ((stbvox_uint32) ((x)+((y)<<7)+((z)<<14)+((ao)<<23)+((texlerp)<<29)))
#elif defined(STBVOX_ICONFIG_VERTEX_16_1)  // mode=2
   typedef stbvox_uint16 stbvox_mesh_vertex;
   #define stbvox_vertex_encode(x,y,z,ao,texlerp) \
      ((stbvox_uint16) ((z)+((ao)<<7)+((texlerp)<<13)
#elif defined(STBVOX_ICONFIG_VERTEX_16_2)  // mode=3
   typedef stbvox_uint16 stbvox_mesh_vertex;
   #define stbvox_vertex_encode(x,y,z,ao,texlerp) \
      ((stbvox_uint16) ((x)+((z)<<6))+((ao)<<10))
#elif defined(STBVOX_ICONFIG_VERTEX_8)
   typedef stbvox_uint8 stbvox_mesh_vertex;
   #define stbvox_vertex_encode(x,y,z,ao,texlerp) \
      ((stbvox_uint8) ((z)+((ao)<<6))
#else
   #error "internal error, no vertex type"
#endif

#ifdef STBVOX_ICONFIG_FACE1_1
   typedef struct
   {
      unsigned char tex1,tex2,color,face_info;
   } stbvox_mesh_face;
#else
   #error "internal error, no face type"
#endif


// 20-byte quad format:
//
// per vertex:
//
//     x:7
//     y:7
//     z:9
//     ao:6
//     tex_lerp:3
//
// per face:
//
//     tex1:8
//     tex2:8
//     face:8
//     color:8


// Faces:
//
// Faces use the bottom 3 bits to choose the texgen
// mode, and all the bits to choose the normal.
// Thus the bottom 3 bits have to be:
//      e, n, w, s, u, d, u, d
//
// These use compact names so tables are readable

enum
{
   STBVF_e,
   STBVF_n,
   STBVF_w,
   STBVF_s,
   STBVF_u,
   STBVF_d,
   STBVF_eu,
   STBVF_ed,

   STBVF_eu_wall,
   STBVF_nu_wall,
   STBVF_wu_wall,
   STBVF_su_wall,
   STBVF_ne_u,
   STBVF_ne_d,
   STBVF_nu,
   STBVF_nd,

   STBVF_ed_wall,
   STBVF_nd_wall,
   STBVF_wd_wall,
   STBVF_sd_wall,
   STBVF_nw_u,
   STBVF_nw_d,
   STBVF_wu,
   STBVF_wd,

   STBVF_ne_u_cross,
   STBVF_nw_u_cross,
   STBVF_sw_u_cross,
   STBVF_se_u_cross,
   STBVF_sw_u,
   STBVF_sw_d,
   STBVF_su,
   STBVF_sd,

   // @TODO we need more than 5 bits to encode the normal to fit the following
   // so for now we use the right projection but the wrong normal
   STBVF_se_u = STBVF_su,
   STBVF_se_d = STBVF_sd,

   STBVF_count,
};

/////////////////////////////////////////////////////////////////////////////
//
//    tables -- i'd prefer if these were at the end of the file, but: C++
//

static float stbvox_default_texgen[2][32][3] =
{
   { {  0, 1,0 }, { 0, 0, 1 }, {  0,-1,0 }, { 0, 0,-1 },
     { -1, 0,0 }, { 0, 0, 1 }, {  1, 0,0 }, { 0, 0,-1 },
     {  0,-1,0 }, { 0, 0, 1 }, {  0, 1,0 }, { 0, 0,-1 },
     {  1, 0,0 }, { 0, 0, 1 }, { -1, 0,0 }, { 0, 0,-1 },

     {  1, 0,0 }, { 0, 1, 0 }, { -1, 0,0 }, { 0,-1, 0 },
     { -1, 0,0 }, { 0,-1, 0 }, {  1, 0,0 }, { 0, 1, 0 },
     {  1, 0,0 }, { 0, 1, 0 }, { -1, 0,0 }, { 0,-1, 0 },
     { -1, 0,0 }, { 0,-1, 0 }, {  1, 0,0 }, { 0, 1, 0 },
   },
   { { 0, 0,-1 }, {  0, 1,0 }, { 0, 0, 1 }, {  0,-1,0 },
     { 0, 0,-1 }, { -1, 0,0 }, { 0, 0, 1 }, {  1, 0,0 },
     { 0, 0,-1 }, {  0,-1,0 }, { 0, 0, 1 }, {  0, 1,0 },
     { 0, 0,-1 }, {  1, 0,0 }, { 0, 0, 1 }, { -1, 0,0 },

     { 0,-1, 0 }, {  1, 0,0 }, { 0, 1, 0 }, { -1, 0,0 },
     { 0, 1, 0 }, { -1, 0,0 }, { 0,-1, 0 }, {  1, 0,0 },
     { 0,-1, 0 }, {  1, 0,0 }, { 0, 1, 0 }, { -1, 0,0 },
     { 0, 1, 0 }, { -1, 0,0 }, { 0,-1, 0 }, {  1, 0,0 },
   },
};

#define STBVOX_RSQRT2   0.7071067811865f
#define STBVOX_RSQRT3   0.5773502691896f

static float stbvox_default_normals[32][3] =
{
   { 1,0,0 },  // east
   { 0,1,0 },  // north
   { -1,0,0 }, // west
   { 0,-1,0 }, // south
   { 0,0,1 },  // up
   { 0,0,-1 }, // down
   {  STBVOX_RSQRT2,0, STBVOX_RSQRT2 }, // east & up
   {  STBVOX_RSQRT2,0, -STBVOX_RSQRT2 }, // east & down

   {  STBVOX_RSQRT2,0, STBVOX_RSQRT2 }, // east & up
   { 0, STBVOX_RSQRT2, STBVOX_RSQRT2 }, // north & up
   { -STBVOX_RSQRT2,0, STBVOX_RSQRT2 }, // west & up
   { 0,-STBVOX_RSQRT2, STBVOX_RSQRT2 }, // south & up
   {  STBVOX_RSQRT3, STBVOX_RSQRT3, STBVOX_RSQRT3 }, // ne & up
   {  STBVOX_RSQRT3, STBVOX_RSQRT3,-STBVOX_RSQRT3 }, // ne & down
   { 0, STBVOX_RSQRT2, STBVOX_RSQRT2 }, // north & up
   { 0, STBVOX_RSQRT2, -STBVOX_RSQRT2 }, // north & down

   {  STBVOX_RSQRT2,0, -STBVOX_RSQRT2 }, // east & down
   { 0, STBVOX_RSQRT2, -STBVOX_RSQRT2 }, // north & down
   { -STBVOX_RSQRT2,0, -STBVOX_RSQRT2 }, // west & down
   { 0,-STBVOX_RSQRT2, -STBVOX_RSQRT2 }, // south & down
   { -STBVOX_RSQRT3, STBVOX_RSQRT3, STBVOX_RSQRT3 }, // NW & up
   { -STBVOX_RSQRT3, STBVOX_RSQRT3,-STBVOX_RSQRT3 }, // NW & down
   { -STBVOX_RSQRT2,0, STBVOX_RSQRT2 }, // west & up
   { -STBVOX_RSQRT2,0, -STBVOX_RSQRT2 }, // west & down

   {  STBVOX_RSQRT3, STBVOX_RSQRT3,STBVOX_RSQRT3 }, // NE & up crossed
   { -STBVOX_RSQRT3, STBVOX_RSQRT3,STBVOX_RSQRT3 }, // NW & up crossed
   { -STBVOX_RSQRT3,-STBVOX_RSQRT3,STBVOX_RSQRT3 }, // SW & up crossed
   {  STBVOX_RSQRT3,-STBVOX_RSQRT3,STBVOX_RSQRT3 }, // SE & up crossed
   { -STBVOX_RSQRT3,-STBVOX_RSQRT3, STBVOX_RSQRT3 }, // SW & up
   { -STBVOX_RSQRT3,-STBVOX_RSQRT3,-STBVOX_RSQRT3 }, // SW & up
   { 0,-STBVOX_RSQRT2, STBVOX_RSQRT2 }, // south & up
   { 0,-STBVOX_RSQRT2, -STBVOX_RSQRT2 }, // south & down
};

static float stbvox_default_texscale[128][4] =
{
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
   {1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},{1,1,0,0},
};

static unsigned char stbvox_default_palette_compact[64][3] =
{
   { 255,255,255 }, { 238,238,238 }, { 221,221,221 }, { 204,204,204 },
   { 187,187,187 }, { 170,170,170 }, { 153,153,153 }, { 136,136,136 },
   { 119,119,119 }, { 102,102,102 }, {  85, 85, 85 }, {  68, 68, 68 },
   {  51, 51, 51 }, {  34, 34, 34 }, {  17, 17, 17 }, {   0,  0,  0 },
   { 255,240,240 }, { 255,220,220 }, { 255,160,160 }, { 255, 32, 32 },
   { 200,120,160 }, { 200, 60,150 }, { 220,100,130 }, { 255,  0,128 },
   { 240,240,255 }, { 220,220,255 }, { 160,160,255 }, {  32, 32,255 },
   { 120,160,200 }, {  60,150,200 }, { 100,130,220 }, {   0,128,255 },
   { 240,255,240 }, { 220,255,220 }, { 160,255,160 }, {  32,255, 32 },
   { 160,200,120 }, { 150,200, 60 }, { 130,220,100 }, { 128,255,  0 },
   { 255,255,240 }, { 255,255,220 }, { 220,220,180 }, { 255,255, 32 },
   { 200,160,120 }, { 200,150, 60 }, { 220,130,100 }, { 255,128,  0 },
   { 255,240,255 }, { 255,220,255 }, { 220,180,220 }, { 255, 32,255 },
   { 160,120,200 }, { 150, 60,200 }, { 130,100,220 }, { 128,  0,255 },
   { 240,255,255 }, { 220,255,255 }, { 180,220,220 }, {  32,255,255 },
   { 120,200,160 }, {  60,200,150 }, { 100,220,130 }, {   0,255,128 },
};

static float stbvox_default_ambient[4][4] =
{
   { 0,0,1      ,0 }, // reversed lighting direction
   { 0.5,0.5,0.5,0 }, // directional color
   { 0.5,0.5,0.5,0 }, // constant color
   { 0.5,0.5,0.5,1.0f/1000.0f/1000.0f }, // fog data for simple_fog
};

static float stbvox_default_palette[64][4];

static void stbvox_build_default_palette(void)
{
   int i;
   for (i=0; i < 64; ++i) {
      stbvox_default_palette[i][0] = stbvox_default_palette_compact[i][0] / 255.0f;
      stbvox_default_palette[i][1] = stbvox_default_palette_compact[i][1] / 255.0f;
      stbvox_default_palette[i][2] = stbvox_default_palette_compact[i][2] / 255.0f;
      stbvox_default_palette[i][3] = 1.0f;
   }
}

//////////////////////////////////////////////////////////////////////////////
//
// Shaders
//

#if defined(STBVOX_ICONFIG_OPENGL_3_1_COMPATIBILITY)
   #define STBVOX_SHADER_VERSION "#version 150 compatibility\n"
#elif defined(STBVOX_ICONFIG_OPENGL_3_0)
   #define STBVOX_SHADER_VERSION "#version 130\n"
#elif defined(STBVOX_ICONFIG_GLSL)
   #define STBVOX_SHADER_VERSION "#version 150\n"
#else
   #define STBVOX_SHADER_VERSION ""
#endif

static const char *stbvox_vertex_program =
{
      STBVOX_SHADER_VERSION

   #ifdef STBVOX_ICONFIG_FACE_ATTRIBUTE  // NOT TAG_face_sampled
      "in uvec4 attr_face;\n"
   #else
      "uniform usamplerBuffer facearray;\n"
   #endif

   #ifdef STBVOX_ICONFIG_FACE_ARRAY_2
      "uniform usamplerBuffer facearray2;\n"
   #endif

      // vertex input data
      "in uint attr_vertex;\n"

      // per-buffer data
      "uniform vec3 transform[3];\n"

      // per-frame data
      "uniform vec4 camera_pos;\n"  // 4th value is used for arbitrary hacking

      // to simplify things, we avoid using more than 256 uniform vectors
      // in fragment shader to avoid possible 1024 component limit, so
      // we access this table in the fragment shader.
      "uniform vec3 normal_table[32];\n"

      #ifndef STBVOX_CONFIG_OPENGL_MODELVIEW
         "uniform mat4x4 model_view;\n"
      #endif

      // fragment output data
      "flat out uvec4  facedata;\n"
      "     out  vec3  voxelspace_pos;\n"
      "     out  vec3  vnormal;\n"
      "     out float  texlerp;\n"
      "     out float  amb_occ;\n"

      // @TODO handle the HLSL way to do this
      "void main()\n"
      "{\n"
      #ifdef STBVOX_ICONFIG_FACE_ATTRIBUTE
         "   facedata = attr_face;\n"
      #else
         "   int faceID = gl_VertexID >> 2;\n"
         "   facedata   = texelFetch(facearray, faceID);\n"
      #endif

      // extract data for vertex
      "   vec3 offset;\n"
      "   offset.x = float( (attr_vertex       ) & 127u );\n"             // a[0..6]
      "   offset.y = float( (attr_vertex >>  7u) & 127u );\n"             // a[7..13]
      "   offset.z = float( (attr_vertex >> 14u) & 511u );\n"             // a[14..22]
      "   amb_occ  = float( (attr_vertex >> 23u) &  63u ) / 63.0;\n"      // a[23..28]
      "   texlerp  = float( (attr_vertex >> 29u)        ) /  7.0;\n"      // a[29..31]

      "   vnormal = normal_table[(facedata.w>>2u) & 31u];\n"
      "   voxelspace_pos = offset * transform[0];\n"  // mesh-to-object scale
      "   vec3 position  = voxelspace_pos + transform[1];\n"  // mesh-to-object translate

      #ifdef STBVOX_DEBUG_TEST_NORMALS
         "   if ((facedata.w & 28u) == 16u || (facedata.w & 28u) == 24u)\n"
         "      position += vnormal.xyz * camera_pos.w;\n"
      #endif

      #ifndef STBVOX_CONFIG_OPENGL_MODELVIEW
         "   gl_Position = model_view * vec4(position,1.0);\n"
      #else
         "   gl_Position = gl_ModelViewProjectionMatrix * vec4(position,1.0);\n"
      #endif

      "}\n"
};


static const char *stbvox_fragment_program =
{
      STBVOX_SHADER_VERSION

      // rlerp is lerp but with t on the left, like god intended
      #if defined(STBVOX_ICONFIG_GLSL)
         "#define rlerp(t,x,y) mix(x,y,t)\n"
      #elif defined(STBVOX_CONFIG_HLSL)
         "#define rlerp(t,x,y) lerp(x,y,t)\n"
      #else
         #error "need definition of rlerp()"
      #endif


      // vertex-shader output data
      "flat in uvec4  facedata;\n"
      "     in  vec3  voxelspace_pos;\n"
      "     in  vec3  vnormal;\n"
      "     in float  texlerp;\n"
      "     in float  amb_occ;\n"

      // per-buffer data
      "uniform vec3 transform[3];\n"

      // per-frame data
      "uniform vec4 camera_pos;\n"  // 4th value is used for arbitrary hacking

      // probably constant data
      "uniform vec4 ambient[4];\n"

      #ifndef STBVOX_ICONFIG_UNTEXTURED
         // generally constant data
         "uniform sampler2DArray tex_array[2];\n"

         #ifdef STBVOX_CONFIG_PREFER_TEXBUFFER
            "uniform samplerBuffer color_table;\n"
            "uniform samplerBuffer texscale;\n"
            "uniform samplerBuffer texgen;\n"
         #else
            "uniform vec4 color_table[64];\n"
            "uniform vec4 texscale[64];\n" // instead of 128, to avoid running out of uniforms
            "uniform vec3 texgen[64];\n"
         #endif
      #endif

      "out vec4  outcolor;\n"

      #if defined(STBVOX_CONFIG_LIGHTING) || defined(STBVOX_CONFIG_LIGHTING_SIMPLE)
      "vec3 compute_lighting(vec3 pos, vec3 norm, vec3 albedo, vec3 ambient);\n"
      #endif
      #if defined(STBVOX_CONFIG_FOG) || defined(STBVOX_CONFIG_FOG_SMOOTHSTEP)
      "vec3 compute_fog(vec3 color, vec3 relative_pos, float fragment_alpha);\n"
      #endif

      "void main()\n"
      "{\n"
      "   vec3 albedo;\n"
      "   float fragment_alpha;\n"

      #ifndef STBVOX_ICONFIG_UNTEXTURED
         // unpack the values
         "   uint tex1_id = facedata.x;\n"
         "   uint tex2_id = facedata.y;\n"
         "   uint texprojid = facedata.w & 31u;\n"
         "   uint color_id  = facedata.z;\n"

         #ifndef STBVOX_CONFIG_PREFER_TEXBUFFER
            // load from uniforms / texture buffers 
            "   vec3 texgen_s = texgen[texprojid];\n"
            "   vec3 texgen_t = texgen[texprojid+32u];\n"
            "   float tex1_scale = texscale[tex1_id & 63u].x;\n"
            "   vec4 color = color_table[color_id & 63u];\n"
            #ifndef STBVOX_CONFIG_DISABLE_TEX2
            "   vec4 tex2_props = texscale[tex2_id & 63u];\n"
            #endif
         #else
            "   vec3 texgen_s = texelFetch(texgen, int(texprojid)).xyz;\n"
            "   vec3 texgen_t = texelFetch(texgen, int(texprojid+32u)).xyz;\n"
            "   float tex1_scale = texelFetch(texscale, int(tex1_id & 127u)).x;\n"
            "   vec4 color = texelFetch(color_table, int(color_id & 63u));\n"
            #ifndef STBVOX_CONFIG_DISABLE_TEX2
            "   vec4 tex2_props = texelFetch(texscale, int(tex1_id & 127u));\n"
            #endif
         #endif

         #ifndef STBVOX_CONFIG_DISABLE_TEX2
         "   float tex2_scale = tex2_props.y;\n"
         "   bool texblend_mode = tex2_props.z != 0.0;\n"
         #endif
         "   vec2 texcoord;\n"
         "   vec3 texturespace_pos = voxelspace_pos + transform[2].xyz;\n"
         "   texcoord.s = dot(texturespace_pos, texgen_s);\n"
         "   texcoord.t = dot(texturespace_pos, texgen_t);\n"

         "   vec2  texcoord_1 = tex1_scale * texcoord;\n"
         #ifndef STBVOX_CONFIG_DISABLE_TEX2
         "   vec2  texcoord_2 = tex2_scale * texcoord;\n"
         #endif

         #ifdef STBVOX_CONFIG_TEX1_EDGE_CLAMP
         "   texcoord_1 = texcoord_1 - floor(texcoord_1);\n"
         "   vec4 tex1 = textureGrad(tex_array[0], vec3(texcoord_1, float(tex1_id)), dFdx(tex1_scale*texcoord), dFdy(tex1_scale*texcoord));\n"
         #else
         "   vec4 tex1 = texture(tex_array[0], vec3(texcoord_1, float(tex1_id)));\n"
         #endif

         #ifndef STBVOX_CONFIG_DISABLE_TEX2
         #ifdef STBVOX_CONFIG_TEX2_EDGE_CLAMP
         "   texcoord_2 = texcoord_2 - floor(texcoord_2);\n"
         "   vec4 tex2 = textureGrad(tex_array[0], vec3(texcoord_2, float(tex2_id)), dFdx(tex2_scale*texcoord), dFdy(tex2_scale*texcoord));\n"
         #else
         "   vec4 tex2 = texture(tex_array[1], vec3(texcoord_2, float(tex2_id)));\n"
         #endif
         #endif

         "   bool emissive = (color.a > 1.0);\n"
         "   color.a = min(color.a, 1.0);\n"

         // recolor textures
         "   if ((color_id &  64u) != 0u) tex1.rgba *= color.rgba;\n"
         "   fragment_alpha = tex1.a;\n"
         #ifndef STBVOX_CONFIG_DISABLE_TEX2
            "   if ((color_id & 128u) != 0u) tex2.rgba *= color.rgba;\n"

            #ifdef STBVOX_CONFIG_PREMULTIPLIED_ALPHA
            "   tex2.rgba *= texlerp;\n"
            #else
            "   tex2.a *= texlerp;\n"
            #endif

            "   if (texblend_mode)\n"
            "      albedo = tex1.xyz * rlerp(tex2.a, vec3(1.0,1.0,1.0), 2.0*tex2.xyz);\n"
            "   else {\n"
            #ifdef STBVOX_CONFIG_PREMULTIPLIED_ALPHA
            "      albedo = (1.0-tex2.a)*tex1.xyz + tex2.xyz;\n"
            #else
            "      albedo = rlerp(tex2.a, tex1.xyz, tex2.xyz);\n"
            #endif
            "      fragment_alpha = tex1.a*(1-tex2.a)+tex2.a;\n"
            "   }\n"
         #else
            "      albedo = tex1.xyz;\n"
         #endif

      #else // UNTEXTURED
         "   vec4 color;"
         "   color.xyz = vec3(facedata.xyz) / 255.0;\n"
         "   bool emissive = false;\n"
         "   albedo = color.xyz;\n"
         "   fragment_alpha = 1.0;\n"
      #endif

      #ifdef STBVOX_ICONFIG_VARYING_VERTEX_NORMALS
         // currently, there are no modes that trigger this path; idea is that there
         // could be a couple of bits per vertex to perturb the normal to e.g. get curved look
         "   vec3 normal = normalize(vnormal);\n"
      #else
         "   vec3 normal = vnormal;\n"
      #endif

      "   vec3 ambient_color = dot(normal, ambient[0].xyz) * ambient[1].xyz + ambient[2].xyz;\n"

      "   ambient_color = clamp(ambient_color, 0.0, 1.0);"
      "   ambient_color *= amb_occ;\n"

      "   vec3 lit_color;\n"
      "   if (!emissive)\n"
      #if defined(STBVOX_ICONFIG_LIGHTING) || defined(STBVOX_CONFIG_LIGHTING_SIMPLE)
         "      lit_color = compute_lighting(voxelspace_pos + transform[1], normal, albedo, ambient_color);\n"
      #else
         "      lit_color = albedo * ambient_color ;\n"
      #endif
      "   else\n"
      "      lit_color = albedo;\n"

      #if defined(STBVOX_ICONFIG_FOG) || defined(STBVOX_CONFIG_FOG_SMOOTHSTEP)
         "   vec3 dist = voxelspace_pos + (transform[1] - camera_pos.xyz);\n"
         "   lit_color = compute_fog(lit_color, dist, fragment_alpha);\n"
      #endif
      
      #ifdef STBVOX_CONFIG_UNPREMULTIPLY
      "   vec4 final_color = vec4(lit_color/fragment_alpha, fragment_alpha);\n"
      #else
      "   vec4 final_color = vec4(lit_color, fragment_alpha);\n"
      #endif
      "   outcolor = final_color;\n"
      "}\n"

   #ifdef STBVOX_CONFIG_LIGHTING_SIMPLE
      "\n"
      "uniform vec3 light_source[2];\n"
      "vec3 compute_lighting(vec3 pos, vec3 norm, vec3 albedo, vec3 ambient)\n"
      "{\n"
      "   vec3 light_dir = light_source[0] - pos;\n"
      "   float lambert = dot(light_dir, norm) / dot(light_dir, light_dir);\n"
      "   vec3 diffuse = clamp(light_source[1] * clamp(lambert, 0.0, 1.0), 0.0, 1.0);\n"
      "   return (diffuse + ambient) * albedo;\n"
      "}\n"
   #endif

   #ifdef STBVOX_CONFIG_FOG_SMOOTHSTEP
      "\n"
      "vec3 compute_fog(vec3 color, vec3 relative_pos, float fragment_alpha)\n"
      "{\n"
      "   float f = dot(relative_pos,relative_pos)*ambient[3].w;\n"
      //"   f = rlerp(f, -2,1);\n"
      "   f = clamp(f, 0.0, 1.0);\n" 
      "   f = 3.0*f*f - 2.0*f*f*f;\n" // smoothstep
      //"   f = f*f;\n"  // fade in more smoothly
      #ifdef STBVOX_CONFIG_PREMULTIPLIED_ALPHA
      "   return rlerp(f, color.xyz, ambient[3].xyz*fragment_alpha);\n"
      #else
      "   return rlerp(f, color.xyz, ambient[3].xyz);\n"
      #endif
      "}\n"
   #endif
};


// still requires full alpha lookups, including tex2 if texblend is enabled
static const char *stbvox_fragment_program_alpha_only =
{
   STBVOX_SHADER_VERSION

   // vertex-shader output data
   "flat in uvec4  facedata;\n"
   "     in  vec3  voxelspace_pos;\n"
   "     in float  texlerp;\n"

   // per-buffer data
   "uniform vec3 transform[3];\n"

   #ifndef STBVOX_ICONFIG_UNTEXTURED
      // generally constant data
      "uniform sampler2DArray tex_array[2];\n"

      #ifdef STBVOX_CONFIG_PREFER_TEXBUFFER
         "uniform samplerBuffer texscale;\n"
         "uniform samplerBuffer texgen;\n"
      #else
         "uniform vec4 texscale[64];\n" // instead of 128, to avoid running out of uniforms
         "uniform vec3 texgen[64];\n"
      #endif
   #endif

   "out vec4  outcolor;\n"

   "void main()\n"
   "{\n"
   "   vec3 albedo;\n"
   "   float fragment_alpha;\n"

   #ifndef STBVOX_ICONFIG_UNTEXTURED
      // unpack the values
      "   uint tex1_id = facedata.x;\n"
      "   uint tex2_id = facedata.y;\n"
      "   uint texprojid = facedata.w & 31u;\n"
      "   uint color_id  = facedata.z;\n"

      #ifndef STBVOX_CONFIG_PREFER_TEXBUFFER
         // load from uniforms / texture buffers 
         "   vec3 texgen_s = texgen[texprojid];\n"
         "   vec3 texgen_t = texgen[texprojid+32u];\n"
         "   float tex1_scale = texscale[tex1_id & 63u].x;\n"
         "   vec4 color = color_table[color_id & 63u];\n"
         "   vec4 tex2_props = texscale[tex2_id & 63u];\n"
      #else
         "   vec3 texgen_s = texelFetch(texgen, int(texprojid)).xyz;\n"
         "   vec3 texgen_t = texelFetch(texgen, int(texprojid+32u)).xyz;\n"
         "   float tex1_scale = texelFetch(texscale, int(tex1_id & 127u)).x;\n"
         "   vec4 color = texelFetch(color_table, int(color_id & 63u));\n"
         "   vec4 tex2_props = texelFetch(texscale, int(tex2_id & 127u));\n"
      #endif

      #ifndef STBVOX_CONFIG_DISABLE_TEX2
      "   float tex2_scale = tex2_props.y;\n"
      "   bool texblend_mode = tex2_props.z &((facedata.w & 128u) != 0u);\n"
      #endif

      "   color.a = min(color.a, 1.0);\n"

      "   vec2 texcoord;\n"
      "   vec3 texturespace_pos = voxelspace_pos + transform[2].xyz;\n"
      "   texcoord.s = dot(texturespace_pos, texgen_s);\n"
      "   texcoord.t = dot(texturespace_pos, texgen_t);\n"

      "   vec2  texcoord_1 = tex1_scale * texcoord;\n"
      "   vec2  texcoord_2 = tex2_scale * texcoord;\n"

      #ifdef STBVOX_CONFIG_TEX1_EDGE_CLAMP
      "   texcoord_1 = texcoord_1 - floor(texcoord_1);\n"
      "   vec4 tex1 = textureGrad(tex_array[0], vec3(texcoord_1, float(tex1_id)), dFdx(tex1_scale*texcoord), dFdy(tex1_scale*texcoord));\n"
      #else
      "   vec4 tex1 = texture(tex_array[0], vec3(texcoord_1, float(tex1_id)));\n"
      #endif

      "   if ((color_id &  64u) != 0u) tex1.a *= color.a;\n"
      "   fragment_alpha = tex1.a;\n"

      #ifndef STBVOX_CONFIG_DISABLE_TEX2
      "   if (!texblend_mode) {\n"
         #ifdef STBVOX_CONFIG_TEX2_EDGE_CLAMP
         "      texcoord_2 = texcoord_2 - floor(texcoord_2);\n"
         "      vec4 tex2 = textureGrad(tex_array[0], vec3(texcoord_2, float(tex2_id)), dFdx(tex2_scale*texcoord), dFdy(tex2_scale*texcoord));\n"
         #else
         "      vec4 tex2 = texture(tex_array[1], vec3(texcoord_2, float(tex2_id)));\n"
         #endif

         "      tex2.a *= texlerp;\n"
         "      if ((color_id & 128u) != 0u) tex2.rgba *= color.a;\n"
         "      fragment_alpha = tex1.a*(1-tex2.a)+tex2.a;\n"
         "}\n"
      "\n"
      #endif

   #else // UNTEXTURED
      "   fragment_alpha = 1.0;\n"
   #endif

   "   outcolor = vec4(0.0, 0.0, 0.0, fragment_alpha);\n"
   "}\n"
};


STBVXDEC char *stbvox_get_vertex_shader(void)
{
   return (char *) stbvox_vertex_program;
}

STBVXDEC char *stbvox_get_fragment_shader(void)
{
   return (char *) stbvox_fragment_program;
}

STBVXDEC char *stbvox_get_fragment_shader_alpha_only(void)
{
   return (char *) stbvox_fragment_program_alpha_only;
}

static float stbvox_dummy_transform[3][3];

#ifdef STBVOX_CONFIG_PREFER_TEXBUFFER
#define STBVOX_TEXBUF 1
#else
#define STBVOX_TEXBUF 0
#endif

static stbvox_uniform_info stbvox_uniforms[] =
{
   { STBVOX_UNIFORM_TYPE_sampler  ,  4,   1, (char*) "facearray"    , 0                           },
   { STBVOX_UNIFORM_TYPE_vec3     , 12,   3, (char*) "transform"    , stbvox_dummy_transform[0]   },
   { STBVOX_UNIFORM_TYPE_sampler  ,  4,   2, (char*) "tex_array"    , 0                           },
   { STBVOX_UNIFORM_TYPE_vec4     , 16, 128, (char*) "texscale"     , stbvox_default_texscale[0] , STBVOX_TEXBUF },
   { STBVOX_UNIFORM_TYPE_vec4     , 16,  64, (char*) "color_table"  , stbvox_default_palette[0]  , STBVOX_TEXBUF },
   { STBVOX_UNIFORM_TYPE_vec3     , 12,  32, (char*) "normal_table" , stbvox_default_normals[0]   },
   { STBVOX_UNIFORM_TYPE_vec3     , 12,  64, (char*) "texgen"       , stbvox_default_texgen[0][0], STBVOX_TEXBUF },
   { STBVOX_UNIFORM_TYPE_vec4     , 16,   4, (char*) "ambient"      , stbvox_default_ambient[0]   },
   { STBVOX_UNIFORM_TYPE_vec4     , 16,   1, (char*) "camera_pos"   , stbvox_dummy_transform[0]   },
};

STBVXDEC int stbvox_get_uniform_info(stbvox_uniform_info *info, int uniform)
{
   if (uniform < 0 || uniform >= STBVOX_UNIFORM_count)
      return 0;

   *info = stbvox_uniforms[uniform];
   return 1;
}

#define STBVOX_GET_GEO(geom_data)  ((geom_data) & 15)

typedef struct
{
   unsigned char block:2;
   unsigned char overlay:2;
   unsigned char facerot:2;
   unsigned char ecolor:2;
} stbvox_rotate;

typedef struct
{
   unsigned char x,y,z;
} stbvox_pos;

static unsigned char stbvox_rotate_face[6][4] =
{
   { 0,1,2,3 },
   { 1,2,3,0 },
   { 2,3,0,1 },
   { 3,0,1,2 },
   { 4,4,4,4 },
   { 5,5,5,5 },   
};

#define STBVOX_ROTATE(x,r)   stbvox_rotate_face[x][r] // (((x)+(r))&3)

stbvox_mesh_face stbvox_compute_mesh_face_value(stbvox_mesh_maker *mm, stbvox_rotate rot, int face, int v_off, int normal)
{
   stbvox_mesh_face face_data = { 0 };
   stbvox_block_type bt = mm->input.blocktype[v_off];
   unsigned char bt_face = STBVOX_ROTATE(face, rot.block);
   int facerot = rot.facerot;

   #ifdef STBVOX_ICONFIG_UNTEXTURED
   if (mm->input.rgb) {
      face_data.tex1  = mm->input.rgb[v_off].r;
      face_data.tex2  = mm->input.rgb[v_off].g;
      face_data.color = mm->input.rgb[v_off].b;
      face_data.face_info = (normal<<2);
      return face_data;
   }
   #else
   unsigned char color_face;

   if (mm->input.color)
      face_data.color = mm->input.color[v_off];

   if (mm->input.block_tex1)
      face_data.tex1 = mm->input.block_tex1[bt];
   else if (mm->input.block_tex1_face)
      face_data.tex1 = mm->input.block_tex1_face[bt][bt_face];
   else
      face_data.tex1 = bt;

   if (mm->input.block_tex2)
      face_data.tex2 = mm->input.block_tex2[bt];
   else if (mm->input.block_tex2_face)
      face_data.tex2 = mm->input.block_tex2_face[bt][bt_face];

   if (mm->input.block_color) {
      unsigned char mcol = mm->input.block_color[bt];
      if (mcol)
         face_data.color = mcol;
   } else if (mm->input.block_color_face) {
      unsigned char mcol = mm->input.block_color_face[bt][bt_face];
      if (mcol)
         face_data.color = mcol;
   }

   if (face <= STBVOX_FACE_south) {
      if (mm->input.side_texrot)
         facerot = mm->input.side_texrot[v_off] >> (2 * face);
      else if (mm->input.block_side_texrot)
         facerot = mm->input.block_side_texrot[v_off] >> (2 * bt_face);
   }

   if (mm->input.overlay) {
      int over_face = STBVOX_ROTATE(face, rot.overlay);
      unsigned char over = mm->input.overlay[v_off];
      if (over) {
         if (mm->input.overlay_tex1) {
            unsigned char rep1 = mm->input.overlay_tex1[over][over_face];
            if (rep1)
               face_data.tex1 = rep1;
         }
         if (mm->input.overlay_tex2) {
            unsigned char rep2 = mm->input.overlay_tex2[over][over_face];
            if (rep2)
               face_data.tex2 = rep2;
         }
         if (mm->input.overlay_color) {
            unsigned char rep3 = mm->input.overlay_color[over][over_face];
            if (rep3)
               face_data.color = rep3;
         }

         if (mm->input.overlay_side_texrot && face <= STBVOX_FACE_south)
            facerot = mm->input.overlay_side_texrot[over] >> (2*over_face);
      }
   }

   if (mm->input.tex2_for_tex1)
      face_data.tex2 = mm->input.tex2_for_tex1[face_data.tex1];
   if (mm->input.tex2)
      face_data.tex2 = mm->input.tex2[v_off];
   if (mm->input.tex2_replace) {
      if (mm->input.tex2_facemask[v_off] & (1 << face))
         face_data.tex2 = mm->input.tex2_replace[v_off];
   }

   color_face = STBVOX_ROTATE(face, rot.ecolor);
   if (mm->input.extended_color) {
      unsigned char ec = mm->input.extended_color[v_off];
      if (mm->input.ecolor_facemask[ec] & (1 << color_face))
         face_data.color = mm->input.ecolor_color[ec];
   }

   if (mm->input.color2) {
      if (mm->input.color2_facemask[v_off] & (1 << color_face))
         face_data.color = mm->input.color2[v_off];
      if (mm->input.color3 && (mm->input.color3_facemask[v_off] & (1 << color_face)))
         face_data.color = mm->input.color3[v_off];
   }
   #endif

   face_data.face_info = (normal<<2) + facerot;
   return face_data;
}

// these are the types of faces each block can have
enum
{
   STBVOX_FT_none    ,
   STBVOX_FT_upper   ,
   STBVOX_FT_lower   ,
   STBVOX_FT_solid   ,
   STBVOX_FT_diag_012,
   STBVOX_FT_diag_023,
   STBVOX_FT_diag_013,
   STBVOX_FT_diag_123,
   STBVOX_FT_force   , // can't be covered up, used for internal faces, also hides nothing
   STBVOX_FT_partial , // only covered by solid, never covers anything else

   STBVOX_FT_count
};

static unsigned char stbvox_face_lerp[6] = { 0,2,0,2,4,4 };
static unsigned char stbvox_vert3_lerp[5] = { 0,3,6,9,12 };
static unsigned char stbvox_vert_lerp_for_face_lerp[4] = { 0, 4, 7, 7 };
static unsigned char stbvox_face3_lerp[6] = { 0,3,6,9,12,14 };
static unsigned char stbvox_vert_lerp_for_simple[4] = { 0,2,5,7 };
static unsigned char stbvox_face3_updown[8] = { 0,2,5,7,0,2,5,7 }; // ignore top bit

// vertex offsets for face vertices
static unsigned char stbvox_vertex_vector[6][4][3] =
{
   { { 1,0,1 }, { 1,1,1 }, { 1,1,0 }, { 1,0,0 } }, // east
   { { 1,1,1 }, { 0,1,1 }, { 0,1,0 }, { 1,1,0 } }, // north
   { { 0,1,1 }, { 0,0,1 }, { 0,0,0 }, { 0,1,0 } }, // west
   { { 0,0,1 }, { 1,0,1 }, { 1,0,0 }, { 0,0,0 } }, // south
   { { 0,1,1 }, { 1,1,1 }, { 1,0,1 }, { 0,0,1 } }, // up
   { { 0,0,0 }, { 1,0,0 }, { 1,1,0 }, { 0,1,0 } }, // down
};

// stbvox_vertex_vector, but read coordinates as binary numbers, zyx
static unsigned char stbvox_vertex_selector[6][4] =
{
   { 5,7,3,1 },
   { 7,6,2,3 },
   { 6,4,0,2 },
   { 4,5,1,0 },
   { 6,7,5,4 },
   { 0,1,3,2 },
};

static stbvox_mesh_vertex stbvox_vmesh_delta_normal[6][4] =
{
   {  stbvox_vertex_encode(1,0,1,0,0) , 
      stbvox_vertex_encode(1,1,1,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0)  },
   {  stbvox_vertex_encode(1,1,1,0,0) ,
      stbvox_vertex_encode(0,1,1,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0)  },
   {  stbvox_vertex_encode(0,1,1,0,0) ,
      stbvox_vertex_encode(0,0,1,0,0) ,
      stbvox_vertex_encode(0,0,0,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0)  },
   {  stbvox_vertex_encode(0,0,1,0,0) ,
      stbvox_vertex_encode(1,0,1,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0) ,
      stbvox_vertex_encode(0,0,0,0,0)  },
   {  stbvox_vertex_encode(0,1,1,0,0) ,
      stbvox_vertex_encode(1,1,1,0,0) ,
      stbvox_vertex_encode(1,0,1,0,0) ,
      stbvox_vertex_encode(0,0,1,0,0)  },
   {  stbvox_vertex_encode(0,0,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0)  }
};

static stbvox_mesh_vertex stbvox_vmesh_pre_vheight[6][4] =
{
   {  stbvox_vertex_encode(1,0,0,0,0) , 
      stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0)  },
   {  stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0)  },
   {  stbvox_vertex_encode(0,1,0,0,0) ,
      stbvox_vertex_encode(0,0,0,0,0) ,
      stbvox_vertex_encode(0,0,0,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0)  },
   {  stbvox_vertex_encode(0,0,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0) ,
      stbvox_vertex_encode(0,0,0,0,0)  },
   {  stbvox_vertex_encode(0,1,0,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0) ,
      stbvox_vertex_encode(0,0,0,0,0)  },
   {  stbvox_vertex_encode(0,0,0,0,0) ,
      stbvox_vertex_encode(1,0,0,0,0) ,
      stbvox_vertex_encode(1,1,0,0,0) ,
      stbvox_vertex_encode(0,1,0,0,0)  }
};

static stbvox_mesh_vertex stbvox_vmesh_delta_half_z[6][4] =
{
   { stbvox_vertex_encode(1,0,2,0,0) , 
     stbvox_vertex_encode(1,1,2,0,0) ,
     stbvox_vertex_encode(1,1,0,0,0) ,
     stbvox_vertex_encode(1,0,0,0,0)  },
   { stbvox_vertex_encode(1,1,2,0,0) ,
     stbvox_vertex_encode(0,1,2,0,0) ,
     stbvox_vertex_encode(0,1,0,0,0) ,
     stbvox_vertex_encode(1,1,0,0,0)  },
   { stbvox_vertex_encode(0,1,2,0,0) ,
     stbvox_vertex_encode(0,0,2,0,0) ,
     stbvox_vertex_encode(0,0,0,0,0) ,
     stbvox_vertex_encode(0,1,0,0,0)  },
   { stbvox_vertex_encode(0,0,2,0,0) ,
     stbvox_vertex_encode(1,0,2,0,0) ,
     stbvox_vertex_encode(1,0,0,0,0) ,
     stbvox_vertex_encode(0,0,0,0,0)  },
   { stbvox_vertex_encode(0,1,2,0,0) ,
     stbvox_vertex_encode(1,1,2,0,0) ,
     stbvox_vertex_encode(1,0,2,0,0) ,
     stbvox_vertex_encode(0,0,2,0,0)  },
   { stbvox_vertex_encode(0,0,0,0,0) ,
     stbvox_vertex_encode(1,0,0,0,0) ,
     stbvox_vertex_encode(1,1,0,0,0) ,
     stbvox_vertex_encode(0,1,0,0,0)  }
};

static stbvox_mesh_vertex stbvox_vmesh_crossed_pair[6][4] =
{
   { stbvox_vertex_encode(1,0,2,0,0) , 
     stbvox_vertex_encode(0,1,2,0,0) ,
     stbvox_vertex_encode(0,1,0,0,0) ,
     stbvox_vertex_encode(1,0,0,0,0)  },
   { stbvox_vertex_encode(1,1,2,0,0) ,
     stbvox_vertex_encode(0,0,2,0,0) ,
     stbvox_vertex_encode(0,0,0,0,0) ,
     stbvox_vertex_encode(1,1,0,0,0)  },
   { stbvox_vertex_encode(0,1,2,0,0) ,
     stbvox_vertex_encode(1,0,2,0,0) ,
     stbvox_vertex_encode(1,0,0,0,0) ,
     stbvox_vertex_encode(0,1,0,0,0)  },
   { stbvox_vertex_encode(0,0,2,0,0) ,
     stbvox_vertex_encode(1,1,2,0,0) ,
     stbvox_vertex_encode(1,1,0,0,0) ,
     stbvox_vertex_encode(0,0,0,0,0)  },
   // not used, so we leave it non-degenerate to make sure it doesn't get gen'd accidentally
   { stbvox_vertex_encode(0,1,2,0,0) ,
     stbvox_vertex_encode(1,1,2,0,0) ,
     stbvox_vertex_encode(1,0,2,0,0) ,
     stbvox_vertex_encode(0,0,2,0,0)  },
   { stbvox_vertex_encode(0,0,0,0,0) ,
     stbvox_vertex_encode(1,0,0,0,0) ,
     stbvox_vertex_encode(1,1,0,0,0) ,
     stbvox_vertex_encode(0,1,0,0,0)  }
};

#define STBVOX_MAX_GEOM     16
#define STBVOX_NUM_ROTATION  4

// this is used to determine if a face is ever generated at all
static unsigned char stbvox_hasface[STBVOX_MAX_GEOM][STBVOX_NUM_ROTATION] =
{
   { 0,0,0,0 }, // empty
   { 0,0,0,0 }, // knockout
   { 63,63,63,63 }, // solid
   { 63,63,63,63 }, // transp
   { 63,63,63,63 }, // slab
   { 63,63,63,63 }, // slab
   { 1|2|4|48, 8|1|2|48, 4|8|1|48, 2|4|8|48, }, // floor slopes
   { 1|2|4|48, 8|1|2|48, 4|8|1|48, 2|4|8|48, }, // ceil slopes
   { 47,47,47,47 }, // wall-projected diagonal with down face
   { 31,31,31,31 }, // wall-projected diagonal with up face
   { 63,63,63,63 }, // crossed-pair has special handling, but avoid early-out
   { 63,63,63,63 }, // force
   { 63,63,63,63 }, // vheight
   { 63,63,63,63 }, // vheight
   { 63,63,63,63 }, // vheight
   { 63,63,63,63 }, // vheight
};

// this determines which face type above is visible on each side of the geometry
static unsigned char stbvox_facetype[STBVOX_GEOM_count][6] =
{
   { 0, },  // STBVOX_GEOM_empty
   { STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid }, // knockout
   { STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid, STBVOX_FT_solid }, // solid
   { STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force }, // transp

   { STBVOX_FT_upper, STBVOX_FT_upper, STBVOX_FT_upper, STBVOX_FT_upper, STBVOX_FT_solid, STBVOX_FT_force },
   { STBVOX_FT_lower, STBVOX_FT_lower, STBVOX_FT_lower, STBVOX_FT_lower, STBVOX_FT_force, STBVOX_FT_solid },
   { STBVOX_FT_diag_123, STBVOX_FT_solid, STBVOX_FT_diag_023, STBVOX_FT_none, STBVOX_FT_force, STBVOX_FT_solid },
   { STBVOX_FT_diag_012, STBVOX_FT_solid, STBVOX_FT_diag_013, STBVOX_FT_none, STBVOX_FT_solid, STBVOX_FT_force },

   { STBVOX_FT_diag_123, STBVOX_FT_solid, STBVOX_FT_diag_023, STBVOX_FT_force, STBVOX_FT_none, STBVOX_FT_solid },
   { STBVOX_FT_diag_012, STBVOX_FT_solid, STBVOX_FT_diag_013, STBVOX_FT_force, STBVOX_FT_solid, STBVOX_FT_none },
   { STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, 0,0 }, // crossed pair
   { STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force, STBVOX_FT_force }, // GEOM_force

   { STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial, STBVOX_FT_force, STBVOX_FT_solid }, // floor vheight, all neighbors forced
   { STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial, STBVOX_FT_force, STBVOX_FT_solid }, // floor vheight, all neighbors forced
   { STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial, STBVOX_FT_solid, STBVOX_FT_force }, // ceil vheight, all neighbors forced
   { STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial,STBVOX_FT_partial, STBVOX_FT_solid, STBVOX_FT_force }, // ceil vheight, all neighbors forced
};

// This table indicates what normal to use for the "up" face of a sloped geom
// @TODO this could be done with math given the current arrangement of the enum, but let's not require it
static unsigned char stbvox_floor_slope_for_rot[4] =
{
   STBVF_su,
   STBVF_wu, // @TODO: why is this reversed from what it should be? this is a north-is-up face, so slope should be south&up
   STBVF_nu,
   STBVF_eu,
};

static unsigned char stbvox_ceil_slope_for_rot[4] =
{
   STBVF_sd,
   STBVF_ed,
   STBVF_nd,
   STBVF_wd,
};

// this table indicates whether, for each pair of types above, a face is visible.
// each value indicates whether a given type is visible for all neighbor types
static unsigned short stbvox_face_visible[STBVOX_FT_count] =
{
   // we encode the table by listing which cases cause *obscuration*, and bitwise inverting that
   // table is pre-shifted by 5 to save a shift when it's accessed
   (unsigned short) ((~0x07ffu                                          )<<5),  // none is completely obscured by everything
   (unsigned short) ((~((1u<<STBVOX_FT_solid) | (1<<STBVOX_FT_upper)   ))<<5),  // upper
   (unsigned short) ((~((1u<<STBVOX_FT_solid) | (1<<STBVOX_FT_lower)   ))<<5),  // lower
   (unsigned short) ((~((1u<<STBVOX_FT_solid)                          ))<<5),  // solid is only completely obscured only by solid
   (unsigned short) ((~((1u<<STBVOX_FT_solid) | (1<<STBVOX_FT_diag_013)))<<5),  // diag012 matches diag013
   (unsigned short) ((~((1u<<STBVOX_FT_solid) | (1<<STBVOX_FT_diag_123)))<<5),  // diag023 matches diag123
   (unsigned short) ((~((1u<<STBVOX_FT_solid) | (1<<STBVOX_FT_diag_012)))<<5),  // diag013 matches diag012
   (unsigned short) ((~((1u<<STBVOX_FT_solid) | (1<<STBVOX_FT_diag_023)))<<5),  // diag123 matches diag023
   (unsigned short) ((~0u                                               )<<5),  // force is always rendered regardless, always forces neighbor
   (unsigned short) ((~((1u<<STBVOX_FT_solid)                          ))<<5),  // partial is only completely obscured only by solid
};

// the vertex heights of the block types, in binary vertex order (zyx):
// lower: SW, SE, NW, NE; upper: SW, SE, NW, NE
static stbvox_mesh_vertex stbvox_geometry_vheight[8][8] =
{
   #define STBVOX_HEIGHTS(a,b,c,d,e,f,g,h) \
     { stbvox_vertex_encode(0,0,a,0,0),  \
       stbvox_vertex_encode(0,0,b,0,0),  \
       stbvox_vertex_encode(0,0,c,0,0),  \
       stbvox_vertex_encode(0,0,d,0,0),  \
       stbvox_vertex_encode(0,0,e,0,0),  \
       stbvox_vertex_encode(0,0,f,0,0),  \
       stbvox_vertex_encode(0,0,g,0,0),  \
       stbvox_vertex_encode(0,0,h,0,0) }

   STBVOX_HEIGHTS(0,0,0,0, 2,2,2,2),
   STBVOX_HEIGHTS(0,0,0,0, 2,2,2,2),
   STBVOX_HEIGHTS(0,0,0,0, 2,2,2,2),
   STBVOX_HEIGHTS(0,0,0,0, 2,2,2,2),
   STBVOX_HEIGHTS(1,1,1,1, 2,2,2,2),
   STBVOX_HEIGHTS(0,0,0,0, 1,1,1,1),
   STBVOX_HEIGHTS(0,0,0,0, 0,0,2,2),
   STBVOX_HEIGHTS(2,2,0,0, 2,2,2,2),
};

// rotate vertices defined as [z][y][x] coords
static unsigned char stbvox_rotate_vertex[8][4] =
{
   { 0,1,3,2 }, // zyx=000
   { 1,3,2,0 }, // zyx=001
   { 2,0,1,3 }, // zyx=010
   { 3,2,0,1 }, // zyx=011
   { 4,5,7,6 }, // zyx=100
   { 5,7,6,4 }, // zyx=101
   { 6,4,5,7 }, // zyx=110
   { 7,6,4,5 }, // zyx=111
};

#ifdef STBVOX_CONFIG_OPTIMIZED_VHEIGHT
// optimized vheight generates a single normal over the entire face, even if it's not planar
static unsigned char stbvox_optimized_face_up_normal[4][4][4][4] =
{
   {
      {
         { STBVF_u   , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
         { STBVF_nw_u, STBVF_nu  , STBVF_nu  , STBVF_ne_u, },
         { STBVF_nw_u, STBVF_nu  , STBVF_nu  , STBVF_nu  , },
         { STBVF_nw_u, STBVF_nw_u, STBVF_nu  , STBVF_nu  , },
      },{
         { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
         { STBVF_u   , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
         { STBVF_nw_u, STBVF_nu  , STBVF_nu  , STBVF_ne_u, },
         { STBVF_nw_u, STBVF_nu  , STBVF_nu  , STBVF_nu  , },
      },{
         { STBVF_eu  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
         { STBVF_u   , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
         { STBVF_nw_u, STBVF_nu  , STBVF_nu  , STBVF_ne_u, },
      },{
         { STBVF_eu  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
         { STBVF_eu  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
         { STBVF_u   , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
      },
   },{
      {
         { STBVF_sw_u, STBVF_u   , STBVF_ne_u, STBVF_ne_u, },
         { STBVF_wu  , STBVF_nw_u, STBVF_nu  , STBVF_nu  , },
         { STBVF_wu  , STBVF_nw_u, STBVF_nu  , STBVF_nu  , },
         { STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, STBVF_nu  , },
      },{
         { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_u   , STBVF_ne_u, STBVF_ne_u, },
         { STBVF_wu  , STBVF_nw_u, STBVF_nu  , STBVF_nu  , },
         { STBVF_wu  , STBVF_nw_u, STBVF_nu  , STBVF_nu  , },
      },{
         { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_u   , STBVF_ne_u, STBVF_ne_u, },
         { STBVF_wu  , STBVF_nw_u, STBVF_nu  , STBVF_nu  , },
      },{
         { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_u   , STBVF_ne_u, STBVF_ne_u, },
      },
   },{
      {
         { STBVF_sw_u, STBVF_sw_u, STBVF_u   , STBVF_ne_u, },
         { STBVF_wu  , STBVF_wu  , STBVF_nw_u, STBVF_nu  , },
         { STBVF_wu  , STBVF_wu  , STBVF_nw_u, STBVF_nu  , },
         { STBVF_wu  , STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, },
      },{
         { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_sw_u, STBVF_u   , STBVF_ne_u, },
         { STBVF_wu  , STBVF_wu  , STBVF_nw_u, STBVF_nu  , },
         { STBVF_wu  , STBVF_wu  , STBVF_nw_u, STBVF_nu  , },
      },{
         { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_sw_u, STBVF_u   , STBVF_ne_u, },
         { STBVF_wu  , STBVF_wu  , STBVF_nw_u, STBVF_nu  , },
      },{
         { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
         { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_sw_u, STBVF_u   , STBVF_ne_u, },
      },
   },{
      {
         { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_u   , },
         { STBVF_sw_u, STBVF_wu  , STBVF_wu  , STBVF_nw_u, },
         { STBVF_wu  , STBVF_wu  , STBVF_wu  , STBVF_nw_u, },
         { STBVF_wu  , STBVF_wu  , STBVF_nw_u, STBVF_nw_u, },
      },{
         { STBVF_sw_u, STBVF_su  , STBVF_su  , STBVF_su  , },
         { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_u   , },
         { STBVF_sw_u, STBVF_wu  , STBVF_wu  , STBVF_nw_u, },
         { STBVF_wu  , STBVF_wu  , STBVF_wu  , STBVF_nw_u, },
      },{
         { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_su  , STBVF_su  , STBVF_su  , },
         { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_u   , },
         { STBVF_sw_u, STBVF_wu  , STBVF_wu  , STBVF_nw_u, },
      },{
         { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
         { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
         { STBVF_sw_u, STBVF_su  , STBVF_su  , STBVF_su  , },
         { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_u   , },
      },
   },
};
#else
// which normal to use for a given vheight that's planar
// @TODO: this table was constructed by hand and may have bugs
//                                 nw se sw
static unsigned char stbvox_planar_face_up_normal[4][4][4] =
{   
   {                                                      // sw,se,nw,ne;  ne = se+nw-sw
      { STBVF_u   , 0         , 0         , 0          }, //  0,0,0,0; 1,0,0,-1; 2,0,0,-2; 3,0,0,-3;
      { STBVF_u   , STBVF_u   , 0         , 0          }, //  0,1,0,1; 1,1,0, 0; 2,1,0,-1; 3,1,0,-2;
      { STBVF_wu  , STBVF_nw_u, STBVF_nu  , 0          }, //  0,2,0,2; 1,2,0, 1; 2,2,0, 0; 3,2,0,-1;
      { STBVF_wu  , STBVF_nw_u, STBVF_nw_u, STBVF_nu   }, //  0,3,0,3; 1,3,0, 2; 2,3,0, 1; 3,3,0, 0;
   },{
      { STBVF_u   , STBVF_u   , 0         , 0          }, //  0,0,1,1; 1,0,1, 0; 2,0,1,-1; 3,0,1,-2;
      { STBVF_sw_u, STBVF_u   , STBVF_ne_u, 0          }, //  0,1,1,2; 1,1,1, 1; 2,1,1, 0; 3,1,1,-1;
      { STBVF_sw_u, STBVF_u   , STBVF_u   , STBVF_ne_u }, //  0,2,1,3; 1,2,1, 2; 2,2,1, 1; 3,2,1, 0;
      { 0         , STBVF_wu  , STBVF_nw_u, STBVF_nu   }, //  0,3,1,4; 1,3,1, 3; 2,3,1, 2; 3,3,1, 1;
   },{
      { STBVF_su  , STBVF_se_u, STBVF_eu  , 0          }, //  0,0,2,2; 1,0,2, 1; 2,0,2, 0; 3,0,2,-1;
      { STBVF_sw_u, STBVF_u   , STBVF_u   , STBVF_ne_u }, //  0,1,2,3; 1,1,2, 2; 2,1,2, 1; 3,1,2, 0;
      { 0         , STBVF_sw_u, STBVF_u   , STBVF_ne_u }, //  0,2,2,4; 1,2,2, 3; 2,2,2, 2; 3,2,2, 1;
      { 0         , 0         , STBVF_u   , STBVF_u    }, //  0,3,2,5; 1,3,2, 4; 2,3,2, 3; 3,3,2, 2;
   },{
      { STBVF_su  , STBVF_se_u, STBVF_se_u, STBVF_eu   }, //  0,0,3,3; 1,0,3, 2; 2,0,3, 1; 3,0,3, 0;
      { 0         , STBVF_su  , STBVF_se_u, STBVF_eu   }, //  0,1,3,4; 1,1,3, 3; 2,1,3, 2; 3,1,3, 1;
      { 0         , 0         , STBVF_u   , STBVF_u    }, //  0,2,3,5; 1,2,3, 4; 2,2,3, 3; 3,2,3, 2;
      { 0         , 0         , 0         , STBVF_u    }, //  0,3,3,6; 1,3,3, 5; 2,3,3, 4; 3,3,3, 3;
   }
};

// these tables were constructed automatically using a variant of the code
// below; however, they seem wrong, so who knows
static unsigned char stbvox_face_up_normal_012[4][4][4] =
{
   {
      { STBVF_u   , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
      { STBVF_wu  , STBVF_nu  , STBVF_ne_u, STBVF_ne_u, },
      { STBVF_wu  , STBVF_nw_u, STBVF_nu  , STBVF_ne_u, },
      { STBVF_wu  , STBVF_nw_u, STBVF_nw_u, STBVF_nu  , },
   },{
      { STBVF_su  , STBVF_eu  , STBVF_ne_u, STBVF_ne_u, },
      { STBVF_sw_u, STBVF_u   , STBVF_ne_u, STBVF_ne_u, },
      { STBVF_sw_u, STBVF_wu  , STBVF_nu  , STBVF_ne_u, },
      { STBVF_sw_u, STBVF_wu  , STBVF_nw_u, STBVF_nu  , },
   },{
      { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
      { STBVF_sw_u, STBVF_su  , STBVF_eu  , STBVF_ne_u, },
      { STBVF_sw_u, STBVF_sw_u, STBVF_u   , STBVF_ne_u, },
      { STBVF_sw_u, STBVF_sw_u, STBVF_wu  , STBVF_nu  , },
   },{
      { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
      { STBVF_sw_u, STBVF_su  , STBVF_eu  , STBVF_eu  , },
      { STBVF_sw_u, STBVF_sw_u, STBVF_su  , STBVF_eu  , },
      { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_u   , },
   }
};

static unsigned char stbvox_face_up_normal_013[4][4][4] =
{
   {
      { STBVF_u   , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
      { STBVF_nw_u, STBVF_nu  , STBVF_ne_u, STBVF_ne_u, },
      { STBVF_nw_u, STBVF_nw_u, STBVF_nu  , STBVF_ne_u, },
      { STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, STBVF_nu  , },
   },{
      { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
      { STBVF_wu  , STBVF_u   , STBVF_eu  , STBVF_eu  , },
      { STBVF_nw_u, STBVF_nw_u, STBVF_nu  , STBVF_ne_u, },
      { STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, STBVF_nu  , },
   },{
      { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
      { STBVF_sw_u, STBVF_su  , STBVF_eu  , STBVF_eu  , },
      { STBVF_wu  , STBVF_wu  , STBVF_u   , STBVF_eu  , },
      { STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, STBVF_nu  , },
   },{
      { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_eu  , },
      { STBVF_sw_u, STBVF_su  , STBVF_su  , STBVF_su  , },
      { STBVF_sw_u, STBVF_sw_u, STBVF_su  , STBVF_eu  , },
      { STBVF_wu  , STBVF_wu  , STBVF_wu  , STBVF_u   , },
   }
};

static unsigned char stbvox_face_up_normal_023[4][4][4] =
{
   {
      { STBVF_u   , STBVF_nu  , STBVF_nu  , STBVF_nu  , },
      { STBVF_eu  , STBVF_eu  , STBVF_ne_u, STBVF_ne_u, },
      { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
      { STBVF_eu  , STBVF_eu  , STBVF_eu  , STBVF_eu  , },
   },{
      { STBVF_wu  , STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, },
      { STBVF_su  , STBVF_u   , STBVF_nu  , STBVF_nu  , },
      { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
      { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
   },{
      { STBVF_wu  , STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, },
      { STBVF_sw_u, STBVF_wu  , STBVF_nw_u, STBVF_nw_u, },
      { STBVF_su  , STBVF_su  , STBVF_u   , STBVF_nu  , },
      { STBVF_su  , STBVF_su  , STBVF_eu  , STBVF_eu  , },
   },{
      { STBVF_wu  , STBVF_nw_u, STBVF_nw_u, STBVF_nw_u, },
      { STBVF_sw_u, STBVF_wu  , STBVF_nw_u, STBVF_nw_u, },
      { STBVF_sw_u, STBVF_sw_u, STBVF_wu  , STBVF_nw_u, },
      { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_u   , },
   }
};

static unsigned char stbvox_face_up_normal_123[4][4][4] =
{
   {
      { STBVF_u   , STBVF_nu  , STBVF_nu  , STBVF_nu  , },
      { STBVF_eu  , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
      { STBVF_eu  , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
      { STBVF_eu  , STBVF_ne_u, STBVF_ne_u, STBVF_ne_u, },
   },{
      { STBVF_sw_u, STBVF_wu  , STBVF_nw_u, STBVF_nw_u, },
      { STBVF_su  , STBVF_u   , STBVF_nu  , STBVF_nu  , },
      { STBVF_eu  , STBVF_eu  , STBVF_ne_u, STBVF_ne_u, },
      { STBVF_eu  , STBVF_eu  , STBVF_ne_u, STBVF_ne_u, },
   },{
      { STBVF_sw_u, STBVF_sw_u, STBVF_wu  , STBVF_nw_u, },
      { STBVF_sw_u, STBVF_sw_u, STBVF_wu  , STBVF_nw_u, },
      { STBVF_su  , STBVF_su  , STBVF_u   , STBVF_nu  , },
      { STBVF_su  , STBVF_eu  , STBVF_eu  , STBVF_ne_u, },
   },{
      { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_wu  , },
      { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_wu  , },
      { STBVF_sw_u, STBVF_sw_u, STBVF_sw_u, STBVF_wu  , },
      { STBVF_su  , STBVF_su  , STBVF_su  , STBVF_u   , },
   }
};
#endif

void stbvox_get_quad_vertex_pointer(stbvox_mesh_maker *mm, int mesh, stbvox_mesh_vertex **vertices, stbvox_mesh_face face)
{
   char *p = mm->output_cur[mesh][0];
   int step = mm->output_step[mesh][0];

   // allocate a new quad from the mesh
   vertices[0] = (stbvox_mesh_vertex *) p; p += step;
   vertices[1] = (stbvox_mesh_vertex *) p; p += step;
   vertices[2] = (stbvox_mesh_vertex *) p; p += step;
   vertices[3] = (stbvox_mesh_vertex *) p; p += step;
   mm->output_cur[mesh][0] = p;

   // output the face
   #ifdef STBVOX_ICONFIG_FACE_ATTRIBUTE
      // write face as interleaved vertex data
      *(stbvox_mesh_face *) (vertices[0]+1) = face;
      *(stbvox_mesh_face *) (vertices[1]+1) = face;
      *(stbvox_mesh_face *) (vertices[2]+1) = face;
      *(stbvox_mesh_face *) (vertices[3]+1) = face;
   #else
      *(stbvox_mesh_face *) mm->output_cur[mesh][1] = face;
      mm->output_cur[mesh][1] += 4;
   #endif
}

void stbvox_make_mesh_for_face(stbvox_mesh_maker *mm, stbvox_rotate rot, int face, int v_off, stbvox_pos pos, stbvox_mesh_vertex vertbase, stbvox_mesh_vertex *face_coord, unsigned char mesh, int normal)
{
   stbvox_mesh_face face_data = stbvox_compute_mesh_face_value(mm,rot,face,v_off, normal);

   // still need to compute ao & texlerp for each vertex

   // first compute texlerp into p1
   stbvox_mesh_vertex p1[4] = { 0 };

   #if defined(STBVOX_CONFIG_DOWN_TEXLERP_PACKED) && defined(STBVOX_CONFIG_UP_TEXLERP_PACKED)
      #define STBVOX_USE_PACKED(f) ((f) == STBVOX_FACE_up || (f) == STBVOX_FACE_down)
   #elif defined(STBVOX_CONFIG_UP_TEXLERP_PACKED)
      #define STBVOX_USE_PACKED(f) ((f) == STBVOX_FACE_up                           )
   #elif defined(STBVOX_CONFIG_DOWN_TEXLERP_PACKED)
      #define STBVOX_USE_PACKED(f) (                         (f) == STBVOX_FACE_down)
   #endif

   #if defined(STBVOX_CONFIG_DOWN_TEXLERP_PACKED) || defined(STBVOX_CONFIG_UP_TEXLERP_PACKED)
   if (STBVOX_USE_PACKED(face)) {
      if (!mm->input.packed_compact || 0==(mm->input.packed_compact[v_off]&16))
         goto set_default;
      p1[0] = (mm->input.packed_compact[v_off + mm->cube_vertex_offset[face][0]] >> 5);
      p1[1] = (mm->input.packed_compact[v_off + mm->cube_vertex_offset[face][1]] >> 5);
      p1[2] = (mm->input.packed_compact[v_off + mm->cube_vertex_offset[face][2]] >> 5);
      p1[3] = (mm->input.packed_compact[v_off + mm->cube_vertex_offset[face][3]] >> 5);
      p1[0] = stbvox_vertex_encode(0,0,0,0,p1[0]);
      p1[1] = stbvox_vertex_encode(0,0,0,0,p1[1]);
      p1[2] = stbvox_vertex_encode(0,0,0,0,p1[2]);
      p1[3] = stbvox_vertex_encode(0,0,0,0,p1[3]);
      goto skip;
   }
   #endif

   if (mm->input.block_texlerp) {
      stbvox_block_type bt = mm->input.blocktype[v_off];
      unsigned char val = mm->input.block_texlerp[bt];
      p1[0] = p1[1] = p1[2] = p1[3] = stbvox_vertex_encode(0,0,0,0,val);
   } else if (mm->input.block_texlerp_face) {
      stbvox_block_type bt = mm->input.blocktype[v_off];
      unsigned char bt_face = STBVOX_ROTATE(face, rot.block);
      unsigned char val = mm->input.block_texlerp_face[bt][bt_face];
      p1[0] = p1[1] = p1[2] = p1[3] = stbvox_vertex_encode(0,0,0,0,val);
   } else if (mm->input.texlerp_face3) {
      unsigned char val = (mm->input.texlerp_face3[v_off] >> stbvox_face3_lerp[face]) & 7;
      if (face >= STBVOX_FACE_up)
         val = stbvox_face3_updown[val];
      p1[0] = p1[1] = p1[2] = p1[3] = stbvox_vertex_encode(0,0,0,0,val);
   } else if (mm->input.texlerp_simple) {
      unsigned char val = mm->input.texlerp_simple[v_off];
      unsigned char lerp_face = (val >> 2) & 7;
      if (lerp_face == face) {
         p1[0] = (mm->input.texlerp_simple[v_off + mm->cube_vertex_offset[face][0]] >> 5) & 7;
         p1[1] = (mm->input.texlerp_simple[v_off + mm->cube_vertex_offset[face][1]] >> 5) & 7;
         p1[2] = (mm->input.texlerp_simple[v_off + mm->cube_vertex_offset[face][2]] >> 5) & 7;
         p1[3] = (mm->input.texlerp_simple[v_off + mm->cube_vertex_offset[face][3]] >> 5) & 7;
         p1[0] = stbvox_vertex_encode(0,0,0,0,p1[0]);
         p1[1] = stbvox_vertex_encode(0,0,0,0,p1[1]);
         p1[2] = stbvox_vertex_encode(0,0,0,0,p1[2]);
         p1[3] = stbvox_vertex_encode(0,0,0,0,p1[3]);
      } else {
         unsigned char base = stbvox_vert_lerp_for_simple[val&3];
         p1[0] = p1[1] = p1[2] = p1[3] = stbvox_vertex_encode(0,0,0,0,base);
      }
   } else if (mm->input.texlerp) {
      unsigned char facelerp = (mm->input.texlerp[v_off] >> stbvox_face_lerp[face]) & 3;
      if (facelerp == STBVOX_TEXLERP_FACE_use_vert) {
         if (mm->input.texlerp_vert3 && face != STBVOX_FACE_down) {
            unsigned char shift = stbvox_vert3_lerp[face];
            p1[0] = (mm->input.texlerp_vert3[mm->cube_vertex_offset[face][0]] >> shift) & 7;
            p1[1] = (mm->input.texlerp_vert3[mm->cube_vertex_offset[face][1]] >> shift) & 7;
            p1[2] = (mm->input.texlerp_vert3[mm->cube_vertex_offset[face][2]] >> shift) & 7;
            p1[3] = (mm->input.texlerp_vert3[mm->cube_vertex_offset[face][3]] >> shift) & 7;
         } else {
            p1[0] = stbvox_vert_lerp_for_simple[mm->input.texlerp[mm->cube_vertex_offset[face][0]]>>6];
            p1[1] = stbvox_vert_lerp_for_simple[mm->input.texlerp[mm->cube_vertex_offset[face][1]]>>6];
            p1[2] = stbvox_vert_lerp_for_simple[mm->input.texlerp[mm->cube_vertex_offset[face][2]]>>6];
            p1[3] = stbvox_vert_lerp_for_simple[mm->input.texlerp[mm->cube_vertex_offset[face][3]]>>6];
         }
         p1[0] = stbvox_vertex_encode(0,0,0,0,p1[0]);
         p1[1] = stbvox_vertex_encode(0,0,0,0,p1[1]);
         p1[2] = stbvox_vertex_encode(0,0,0,0,p1[2]);
         p1[3] = stbvox_vertex_encode(0,0,0,0,p1[3]);
      } else {
         p1[0] = p1[1] = p1[2] = p1[3] = stbvox_vertex_encode(0,0,0,0,stbvox_vert_lerp_for_face_lerp[facelerp]);
      }
   } else {
      #if defined(STBVOX_CONFIG_UP_TEXLERP_PACKED) || defined(STBVOX_CONFIG_DOWN_TEXLERP_PACKED)
      set_default:
      #endif
      p1[0] = p1[1] = p1[2] = p1[3] = stbvox_vertex_encode(0,0,0,0,7); // @TODO make this configurable
   }

   #if defined(STBVOX_CONFIG_UP_TEXLERP_PACKED) || defined(STBVOX_CONFIG_DOWN_TEXLERP_PACKED)
   skip:
   #endif

   // now compute lighting and store to vertices
   {
      stbvox_mesh_vertex *mv[4];
      stbvox_get_quad_vertex_pointer(mm, mesh, mv, face_data);

      if (mm->input.lighting) {
         // @TODO: lighting at block centers, but not gathered, instead constant-per-face
         if (mm->input.lighting_at_vertices) {
            int i;
            for (i=0; i < 4; ++i) {
               *mv[i] = vertbase + face_coord[i]
                          + stbvox_vertex_encode(0,0,0,mm->input.lighting[v_off + mm->cube_vertex_offset[face][i]] & 63,0)
                          + p1[i];
            }
         } else {
            unsigned char *amb = &mm->input.lighting[v_off];
            int i,j;
            #if defined(STBVOX_CONFIG_ROTATION_IN_LIGHTING) || defined(STBVOX_CONFIG_VHEIGHT_IN_LIGHTING)
            #define STBVOX_GET_LIGHTING(light) ((light) & ~3)
            #define STBVOX_LIGHTING_ROUNDOFF   8
            #else
            #define STBVOX_GET_LIGHTING(light) (light)
            #define STBVOX_LIGHTING_ROUNDOFF   2
            #endif

            for (i=0; i < 4; ++i) {
               // for each vertex, gather from the four neighbor blocks it's facing
               unsigned char *vamb = &amb[mm->cube_vertex_offset[face][i]];
               int total=0;
               for (j=0; j < 4; ++j)
                  total += STBVOX_GET_LIGHTING(vamb[mm->vertex_gather_offset[face][j]]);
               *mv[i] = vertbase + face_coord[i]
                          + stbvox_vertex_encode(0,0,0,(total+STBVOX_LIGHTING_ROUNDOFF)>>4,0)
                          + p1[i];
                          // >> 4 is because:
                          //   >> 2 to divide by 4 to get average over 4 samples
                          //   >> 2 because input is 8 bits, output is 6 bits
            }

            // @TODO: note that gathering baked *lighting*
            // is different from gathering baked ao; baked ao can count
            // solid blocks as 0 ao, but baked lighting wants average
            // of non-blocked--not take average & treat blocked as 0. And
            // we can't bake the right value into the solid blocks
            // because they can have different lighting values on
            // different sides. So we need to actually gather and
            // then divide by 0..4 (which we can do with a table-driven
            // multiply, or have an 'if' for the 3 case)

         }
      } else {
         vertbase += stbvox_vertex_encode(0,0,0,63,0);
         *mv[0] = vertbase + face_coord[0] + p1[0];
         *mv[1] = vertbase + face_coord[1] + p1[1];
         *mv[2] = vertbase + face_coord[2] + p1[2];
         *mv[3] = vertbase + face_coord[3] + p1[3];
      }
   }
}

// get opposite-facing normal & texgen for opposite face, used to map up-facing vheight data to down-facing data
static unsigned char stbvox_reverse_face[STBVF_count] =
{
   STBVF_w, STBVF_s, STBVF_e, STBVF_n, STBVF_d   , STBVF_u   , STBVF_wd, STBVF_wu,
         0,       0,       0,       0, STBVF_sw_d, STBVF_sw_u, STBVF_sd, STBVF_su,
         0,       0,       0,       0, STBVF_se_d, STBVF_se_u, STBVF_ed, STBVF_eu,
         0,       0,       0,       0, STBVF_ne_d, STBVF_ne_d, STBVF_nd, STBVF_nu
};

#ifndef STBVOX_CONFIG_OPTIMIZED_VHEIGHT
// render non-planar quads by splitting into two triangles, rendering each as a degenerate quad
static void stbvox_make_12_split_mesh_for_face(stbvox_mesh_maker *mm, stbvox_rotate rot, int face, int v_off, stbvox_pos pos, stbvox_mesh_vertex vertbase, stbvox_mesh_vertex *face_coord, unsigned char mesh, unsigned char *ht)
{
   stbvox_mesh_vertex v[4];

   unsigned char normal1 = stbvox_face_up_normal_012[ht[2]][ht[1]][ht[0]];
   unsigned char normal2 = stbvox_face_up_normal_123[ht[3]][ht[2]][ht[1]];

   if (face == STBVOX_FACE_down) {
      normal1 = stbvox_reverse_face[normal1];
      normal2 = stbvox_reverse_face[normal2];
   }

   // the floor side face_coord is stored in order NW,NE,SE,SW, but ht[] is stored SW,SE,NW,NE
   v[0] = face_coord[2];
   v[1] = face_coord[3];
   v[2] = face_coord[0];
   v[3] = face_coord[2];
   stbvox_make_mesh_for_face(mm, rot, face, v_off, pos, vertbase, v, mesh, normal1);
   v[1] = face_coord[0];
   v[2] = face_coord[1];
   stbvox_make_mesh_for_face(mm, rot, face, v_off, pos, vertbase, v, mesh, normal2);
}

static void stbvox_make_03_split_mesh_for_face(stbvox_mesh_maker *mm, stbvox_rotate rot, int face, int v_off, stbvox_pos pos, stbvox_mesh_vertex vertbase, stbvox_mesh_vertex *face_coord, unsigned char mesh, unsigned char *ht)
{
   stbvox_mesh_vertex v[4];

   unsigned char normal1 = stbvox_face_up_normal_013[ht[3]][ht[1]][ht[0]];
   unsigned char normal2 = stbvox_face_up_normal_023[ht[3]][ht[2]][ht[0]];

   if (face == STBVOX_FACE_down) {
      normal1 = stbvox_reverse_face[normal1];
      normal2 = stbvox_reverse_face[normal2];
   }

   v[0] = face_coord[1];
   v[1] = face_coord[2];
   v[2] = face_coord[3];
   v[3] = face_coord[1];
   stbvox_make_mesh_for_face(mm, rot, face, v_off, pos, vertbase, v, mesh, normal1);
   v[1] = face_coord[3];
   v[2] = face_coord[0];
   stbvox_make_mesh_for_face(mm, rot, face, v_off, pos, vertbase, v, mesh, normal2);  // this one is correct!
}
#endif

#ifndef STBVOX_CONFIG_PRECISION_Z
#define STBVOX_CONFIG_PRECISION_Z 1
#endif

// simple case for mesh generation: we have only solid and empty blocks
static void stbvox_make_mesh_for_block(stbvox_mesh_maker *mm, stbvox_pos pos, int v_off, stbvox_mesh_vertex *vmesh)
{
   int ns_off = mm->y_stride_in_bytes;
   int ew_off = mm->x_stride_in_bytes;

   unsigned char *blockptr = &mm->input.blocktype[v_off];
   stbvox_mesh_vertex basevert = stbvox_vertex_encode(pos.x, pos.y, pos.z << STBVOX_CONFIG_PRECISION_Z , 0,0);

   stbvox_rotate rot = { 0,0,0,0 };
   unsigned char simple_rot = 0;

   unsigned char mesh = mm->default_mesh;

   if (mm->input.selector)
      mesh = mm->input.selector[v_off];
   else if (mm->input.block_selector)
      mesh = mm->input.block_selector[mm->input.blocktype[v_off]];
  
   // check if we're going off the end
   if (mm->output_cur[mesh][0] + mm->output_size[mesh][0]*6 > mm->output_end[mesh][0]) {
      mm->full = 1;
      return;
   }

   #ifdef STBVOX_CONFIG_ROTATION_IN_LIGHTING
   simple_rot = mm->input.lighting[v_off] & 3;
   #endif

   if (mm->input.packed_compact)
      simple_rot = mm->input.packed_compact[v_off] & 3;

   if (blockptr[ 1]==0) {
      rot.facerot = simple_rot;
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_up  , v_off, pos, basevert, vmesh+4*STBVOX_FACE_up, mesh, STBVOX_FACE_up);
   }
   if (blockptr[-1]==0) {
      rot.facerot = (-simple_rot) & 3;
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_down, v_off, pos, basevert, vmesh+4*STBVOX_FACE_down, mesh, STBVOX_FACE_down);
   }

   if (mm->input.rotate) {
      unsigned char val = mm->input.rotate[v_off];
      rot.block   = (val >> 0) & 3;
      rot.overlay = (val >> 2) & 3;
      //rot.tex2    = (val >> 4) & 3;
      rot.ecolor  = (val >> 6) & 3;
   } else {
      rot.block = rot.overlay = rot.ecolor = simple_rot;
   }
   rot.facerot = 0;

   if (blockptr[ ns_off]==0)
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_north, v_off, pos, basevert, vmesh+4*STBVOX_FACE_north, mesh, STBVOX_FACE_north);
   if (blockptr[-ns_off]==0)
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_south, v_off, pos, basevert, vmesh+4*STBVOX_FACE_south, mesh, STBVOX_FACE_south);
   if (blockptr[ ew_off]==0)
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_east , v_off, pos, basevert, vmesh+4*STBVOX_FACE_east, mesh, STBVOX_FACE_east);
   if (blockptr[-ew_off]==0)
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_west , v_off, pos, basevert, vmesh+4*STBVOX_FACE_west, mesh, STBVOX_FACE_west);
}

// complex case for mesh generation: we have lots of different
// block types, and we don't want to generate faces of blocks
// if they're hidden by neighbors.
//
// we use lots of tables to determine this: we have a table
// which tells us what face type is generated for each type of
// geometry, and then a table that tells us whether that type
// is hidden by a neighbor.
static void stbvox_make_mesh_for_block_with_geo(stbvox_mesh_maker *mm, stbvox_pos pos, int v_off)
{
   int ns_off = mm->y_stride_in_bytes;
   int ew_off = mm->x_stride_in_bytes;
   int visible_faces, visible_base;
   unsigned char mesh;

   // first gather the geometry info for this block and all neighbors

   unsigned char bt, nbt[6];
   unsigned char geo, ngeo[6];
   unsigned char rot, nrot[6];

   bt = mm->input.blocktype[v_off];
   nbt[0] = mm->input.blocktype[v_off + ew_off];
   nbt[1] = mm->input.blocktype[v_off + ns_off];
   nbt[2] = mm->input.blocktype[v_off - ew_off];
   nbt[3] = mm->input.blocktype[v_off - ns_off];
   nbt[4] = mm->input.blocktype[v_off +      1];
   nbt[5] = mm->input.blocktype[v_off -      1];
   if (mm->input.geometry) {
      int i;
      geo = mm->input.geometry[v_off];
      ngeo[0] = mm->input.geometry[v_off + ew_off];
      ngeo[1] = mm->input.geometry[v_off + ns_off];
      ngeo[2] = mm->input.geometry[v_off - ew_off];
      ngeo[3] = mm->input.geometry[v_off - ns_off];
      ngeo[4] = mm->input.geometry[v_off +      1];
      ngeo[5] = mm->input.geometry[v_off -      1];

      rot = (geo >> 4) & 3;
      geo &= 15;
      for (i=0; i < 6; ++i) {
         nrot[i] = (ngeo[i] >> 4) & 3;
         ngeo[i] &= 15;
      }
   } else {
      int i;
      assert(mm->input.block_geometry);
      geo = mm->input.block_geometry[bt];
      for (i=0; i < 6; ++i)
         ngeo[i] = mm->input.block_geometry[nbt[i]];
      if (mm->input.selector) {
         #ifndef STBVOX_CONFIG_ROTATION_IN_LIGHTING
         if (mm->input.packed_compact == NULL) {
            rot     = (mm->input.selector[v_off         ] >> 4) & 3;
            nrot[0] = (mm->input.selector[v_off + ew_off] >> 4) & 3;
            nrot[1] = (mm->input.selector[v_off + ns_off] >> 4) & 3;
            nrot[2] = (mm->input.selector[v_off - ew_off] >> 4) & 3;
            nrot[3] = (mm->input.selector[v_off - ns_off] >> 4) & 3;
            nrot[4] = (mm->input.selector[v_off +      1] >> 4) & 3;
            nrot[5] = (mm->input.selector[v_off -      1] >> 4) & 3;
         }
         #endif
      } else {
         #ifndef STBVOX_CONFIG_ROTATION_IN_LIGHTING
         if (mm->input.packed_compact == NULL) {
            rot = (geo>>4)&3;
            geo &= 15;
            for (i=0; i < 6; ++i) {
               nrot[i] = (ngeo[i]>>4)&3;
               ngeo[i] &= 15;
            }
         }
         #endif
      }
   }

   #ifndef STBVOX_CONFIG_ROTATION_IN_LIGHTING
   if (mm->input.packed_compact) {
      rot = mm->input.packed_compact[rot] & 3;
      nrot[0] = mm->input.packed_compact[v_off + ew_off] & 3;
      nrot[1] = mm->input.packed_compact[v_off + ns_off] & 3;
      nrot[2] = mm->input.packed_compact[v_off - ew_off] & 3;
      nrot[3] = mm->input.packed_compact[v_off - ns_off] & 3;
      nrot[4] = mm->input.packed_compact[v_off +      1] & 3;
      nrot[5] = mm->input.packed_compact[v_off -      1] & 3;
   }
   #else
   rot = mm->input.lighting[v_off] & 3;
   nrot[0] = (mm->input.lighting[v_off + ew_off]) & 3;
   nrot[1] = (mm->input.lighting[v_off + ns_off]) & 3;
   nrot[2] = (mm->input.lighting[v_off - ew_off]) & 3;
   nrot[3] = (mm->input.lighting[v_off - ns_off]) & 3;
   nrot[4] = (mm->input.lighting[v_off +      1]) & 3;
   nrot[5] = (mm->input.lighting[v_off -      1]) & 3;
   #endif

   if (geo == STBVOX_GEOM_transp) {
      // transparency has a special rule: if the blocktype is the same,
      // and the faces are compatible, then can hide them; otherwise,
      // force them on
      // Note that this means we don't support any transparentshapes other
      // than solid blocks, since detecting them is too complicated. If
      // you wanted to do something like minecraft water, you probably
      // should just do that with a separate renderer anyway. (We don't
      // support transparency sorting so you need to use alpha test
      // anyway)
      int i;
      for (i=0; i < 6; ++i)
         if (nbt[i] != bt) {
            nbt[i] = 0;
            ngeo[i] = STBVOX_GEOM_empty;
         } else
            ngeo[i] = STBVOX_GEOM_solid;
      geo = STBVOX_GEOM_solid;
   }

   // now compute the face visibility
   visible_base = stbvox_hasface[geo][rot];
   // @TODO: assert(visible_base != 0); // we should have early-outted earlier in this case
   visible_faces = 0;

   // now, for every face that might be visible, check if neighbor hides it
   if (visible_base & (1 << STBVOX_FACE_east)) {
      int  type = stbvox_facetype[ geo   ][(STBVOX_FACE_east+ rot   )&3];
      int ntype = stbvox_facetype[ngeo[0]][(STBVOX_FACE_west+nrot[0])&3];
      visible_faces |= ((stbvox_face_visible[type]) >> (ntype + 5 - STBVOX_FACE_east)) & (1 << STBVOX_FACE_east);
   }
   if (visible_base & (1 << STBVOX_FACE_north)) {
      int  type = stbvox_facetype[ geo   ][(STBVOX_FACE_north+ rot   )&3];
      int ntype = stbvox_facetype[ngeo[1]][(STBVOX_FACE_south+nrot[1])&3];
      visible_faces |= ((stbvox_face_visible[type]) >> (ntype + 5 - STBVOX_FACE_north)) & (1 << STBVOX_FACE_north);
   }
   if (visible_base & (1 << STBVOX_FACE_west)) {
      int  type = stbvox_facetype[ geo   ][(STBVOX_FACE_west+ rot   )&3];
      int ntype = stbvox_facetype[ngeo[2]][(STBVOX_FACE_east+nrot[2])&3];
      visible_faces |= ((stbvox_face_visible[type]) >> (ntype + 5 - STBVOX_FACE_west)) & (1 << STBVOX_FACE_west);
   }
   if (visible_base & (1 << STBVOX_FACE_south)) {
      int  type = stbvox_facetype[ geo   ][(STBVOX_FACE_south+ rot   )&3];
      int ntype = stbvox_facetype[ngeo[3]][(STBVOX_FACE_north+nrot[3])&3];
      visible_faces |= ((stbvox_face_visible[type]) >> (ntype + 5 - STBVOX_FACE_south)) & (1 << STBVOX_FACE_south);
   }
   if (visible_base & (1 << STBVOX_FACE_up)) {
      int  type = stbvox_facetype[ geo   ][STBVOX_FACE_up];
      int ntype = stbvox_facetype[ngeo[4]][STBVOX_FACE_down];
      visible_faces |= ((stbvox_face_visible[type]) >> (ntype + 5 - STBVOX_FACE_up)) & (1 << STBVOX_FACE_up);
   }
   if (visible_base & (1 << STBVOX_FACE_down)) {
      int  type = stbvox_facetype[ geo   ][STBVOX_FACE_down];
      int ntype = stbvox_facetype[ngeo[5]][STBVOX_FACE_up];
      visible_faces |= ((stbvox_face_visible[type]) >> (ntype + 5 - STBVOX_FACE_down)) & (1 << STBVOX_FACE_down);
   }

   if (geo == STBVOX_GEOM_force)
      geo = STBVOX_GEOM_solid;

   assert((geo == STBVOX_GEOM_crossed_pair) ? (visible_faces == 15) : 1);

   // now we finally know for sure which faces are getting generated
   if (visible_faces == 0)
      return;

   mesh = mm->default_mesh;
   if (mm->input.selector)
      mesh = mm->input.selector[v_off];
   else if (mm->input.block_selector)
      mesh = mm->input.block_selector[bt];
  
   if (geo <= STBVOX_GEOM_ceil_slope_north_is_bottom) {
      // this is the simple case, we can just use regular block gen with special vmesh calculated with vheight
      stbvox_mesh_vertex basevert;
      stbvox_mesh_vertex vmesh[6][4];
      stbvox_rotate rotate = { 0,0,0,0 };
      unsigned char simple_rot = rot;
      int i;
      // we only need to do this for the displayed faces, but it's easier
      // to just do it up front; @OPTIMIZE check if it's faster to do it
      // for visible faces only
      for (i=0; i < 6*4; ++i) {
         int vert = stbvox_vertex_selector[0][i];
         vert = stbvox_rotate_vertex[vert][rot];
         vmesh[0][i] = stbvox_vmesh_pre_vheight[0][i]
                     + stbvox_geometry_vheight[geo][vert];
      }

      basevert = stbvox_vertex_encode(pos.x, pos.y, pos.z << STBVOX_CONFIG_PRECISION_Z, 0,0);
      if (mm->input.selector) {
         mesh = mm->input.selector[v_off];
      } else if (mm->input.block_selector)
         mesh = mm->input.block_selector[bt];


      // check if we're going off the end
      if (mm->output_cur[mesh][0] + mm->output_size[mesh][0]*6 > mm->output_end[mesh][0]) {
         mm->full = 1;
         return;
      }

      if (geo >= STBVOX_GEOM_floor_slope_north_is_top) {
         if (visible_faces & (1 << STBVOX_FACE_up)) {
            int normal = geo == STBVOX_GEOM_floor_slope_north_is_top ? stbvox_floor_slope_for_rot[simple_rot] : STBVOX_FACE_up;
            rotate.facerot = simple_rot;
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_up  , v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, normal);
         }
         if (visible_faces & (1 << STBVOX_FACE_down)) {
            int normal = geo == STBVOX_GEOM_ceil_slope_north_is_bottom ? stbvox_ceil_slope_for_rot[simple_rot] : STBVOX_FACE_down;
            rotate.facerot = (-rotate.facerot) & 3;
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, normal);
         }
      } else {
         if (visible_faces & (1 << STBVOX_FACE_up)) {
            rotate.facerot = simple_rot;
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_up  , v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, STBVOX_FACE_up);
         }
         if (visible_faces & (1 << STBVOX_FACE_down)) {
            rotate.facerot = (-rotate.facerot) & 3;
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, STBVOX_FACE_down);
         }
      }

      if (mm->input.rotate) {
         unsigned char val = mm->input.rotate[v_off];
         rotate.block   = (val >> 0) & 3;
         rotate.overlay = (val >> 2) & 3;
         //rotate.tex2    = (val >> 4) & 3;
         rotate.ecolor  = (val >> 6) & 3;
      } else {
         rotate.block = rotate.overlay = rotate.ecolor = simple_rot;
      }

      rotate.facerot = 0;

      if (visible_faces & (1 << STBVOX_FACE_north))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_north, v_off, pos, basevert, vmesh[STBVOX_FACE_north], mesh, STBVOX_FACE_north);
      if (visible_faces & (1 << STBVOX_FACE_south))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_south, v_off, pos, basevert, vmesh[STBVOX_FACE_south], mesh, STBVOX_FACE_south);
      if (visible_faces & (1 << STBVOX_FACE_east))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_east , v_off, pos, basevert, vmesh[STBVOX_FACE_east ], mesh, STBVOX_FACE_east);
      if (visible_faces & (1 << STBVOX_FACE_west))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_west , v_off, pos, basevert, vmesh[STBVOX_FACE_west ], mesh, STBVOX_FACE_west);
   }
   if (geo >= STBVOX_GEOM_floor_vheight_03) {
      // this case can also be generated with regular block gen with special vmesh,
      // except:
      //     if we want to generate middle diagonal for 'weird' blocks
      //     it's more complicated to detect neighbor matchups
      stbvox_mesh_vertex vmesh[6][4];
      stbvox_mesh_vertex cube[8];
      stbvox_mesh_vertex basevert;
      stbvox_rotate rotate = { 0,0,0,0 };
      unsigned char simple_rot = rot;
      unsigned char ht[4];
      int extreme;

      // extract the heights
      #ifdef STBVOX_CONFIG_VHEIGHT_IN_LIGHTING
      ht[0] = mm->input.lighting[v_off              ] & 3;
      ht[1] = mm->input.lighting[v_off+ew_off       ] & 3;
      ht[2] = mm->input.lighting[v_off       +ns_off] & 3;
      ht[3] = mm->input.lighting[v_off+ew_off+ns_off] & 3;
      #else
      if (mm->input.vheight) {
         unsigned char v =  mm->input.vheight[v_off];
         ht[0] = (v >> 0) & 3;
         ht[1] = (v >> 2) & 3;
         ht[2] = (v >> 4) & 3;
         ht[3] = (v >> 6) & 3;
      } else if (mm->input.block_vheight) {
         unsigned char v = mm->input.block_vheight[bt];
         unsigned char raw[4];
         int i;

         raw[0] = (v >> 0) & 3;
         raw[1] = (v >> 2) & 3;
         raw[2] = (v >> 4) & 3;
         raw[3] = (v >> 6) & 3;

         for (i=0; i < 4; ++i)
            ht[i] = raw[stbvox_rotate_vertex[i][rot]];
      } else if (mm->input.packed_compact) {
         ht[0] = (mm->input.packed_compact[v_off              ] >> 2) & 3;
         ht[1] = (mm->input.packed_compact[v_off+ew_off       ] >> 2) & 3;
         ht[2] = (mm->input.packed_compact[v_off       +ns_off] >> 2) & 3;
         ht[3] = (mm->input.packed_compact[v_off+ew_off+ns_off] >> 2) & 3;
      } else if (mm->input.geometry) {
         ht[0] = mm->input.geometry[v_off              ] >> 6;
         ht[1] = mm->input.geometry[v_off+ew_off       ] >> 6;
         ht[2] = mm->input.geometry[v_off       +ns_off] >> 6;
         ht[3] = mm->input.geometry[v_off+ew_off+ns_off] >> 6;
      } else {
         assert(0);
      }
      #endif

      // flag whether any sides go off the top of the block, which means
      // our visible_faces test was wrong
      extreme = (ht[0] == 3 || ht[1] == 3 || ht[2] == 3 || ht[3] == 3);

      if (geo >= STBVOX_GEOM_ceil_vheight_03) {
         cube[0] = stbvox_vertex_encode(0,0,ht[0],0,0);
         cube[1] = stbvox_vertex_encode(0,0,ht[1],0,0);
         cube[2] = stbvox_vertex_encode(0,0,ht[2],0,0);
         cube[3] = stbvox_vertex_encode(0,0,ht[3],0,0);
         cube[4] = stbvox_vertex_encode(0,0,2,0,0);
         cube[5] = stbvox_vertex_encode(0,0,2,0,0);
         cube[6] = stbvox_vertex_encode(0,0,2,0,0);
         cube[7] = stbvox_vertex_encode(0,0,2,0,0);
      } else {
         cube[0] = stbvox_vertex_encode(0,0,0,0,0);
         cube[1] = stbvox_vertex_encode(0,0,0,0,0);
         cube[2] = stbvox_vertex_encode(0,0,0,0,0);
         cube[3] = stbvox_vertex_encode(0,0,0,0,0);
         cube[4] = stbvox_vertex_encode(0,0,ht[0],0,0);
         cube[5] = stbvox_vertex_encode(0,0,ht[1],0,0);
         cube[6] = stbvox_vertex_encode(0,0,ht[2],0,0);
         cube[7] = stbvox_vertex_encode(0,0,ht[3],0,0);
      }
      if (!mm->input.vheight && mm->input.block_vheight) {
         // @TODO: support block vheight here, I've forgotten what needs to be done specially
      }

      // build vertex mesh
      {
         int i;
         for (i=0; i < 6*4; ++i) {
            int vert = stbvox_vertex_selector[0][i];
            vmesh[0][i] = stbvox_vmesh_pre_vheight[0][i]
                        + cube[vert];
         }
      }

      basevert = stbvox_vertex_encode(pos.x, pos.y, pos.z << STBVOX_CONFIG_PRECISION_Z, 0,0);
      // check if we're going off the end
      if (mm->output_cur[mesh][0] + mm->output_size[mesh][0]*6 > mm->output_end[mesh][0]) {
         mm->full = 1;
         return;
      }

      // @TODO generate split faces
      if (visible_faces & (1 << STBVOX_FACE_up)) {
         if (geo >= STBVOX_GEOM_ceil_vheight_03)
            // flat
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_up  , v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, STBVOX_FACE_up);
         else {
         #ifndef STBVOX_CONFIG_OPTIMIZED_VHEIGHT
            // check if it's non-planar
            if (cube[5] + cube[6] != cube[4] + cube[7]) {
               // not planar, split along diagonal and make degenerate quads
               if (geo == STBVOX_GEOM_floor_vheight_03)
                  stbvox_make_03_split_mesh_for_face(mm, rotate, STBVOX_FACE_up, v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, ht);
               else
                  stbvox_make_12_split_mesh_for_face(mm, rotate, STBVOX_FACE_up, v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, ht);
            } else
               stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_up  , v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, stbvox_planar_face_up_normal[ht[2]][ht[1]][ht[0]]);
         #else
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_up  , v_off, pos, basevert, vmesh[STBVOX_FACE_up], mesh, stbvox_optimized_face_up_normal[ht[3]][ht[2]][ht[1]][ht[0]]);
         #endif
         }
      }
      if (visible_faces & (1 << STBVOX_FACE_down)) {
         if (geo < STBVOX_GEOM_ceil_vheight_03)
            // flat
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, STBVOX_FACE_down);
         else {
         #ifndef STBVOX_CONFIG_OPTIMIZED_VHEIGHT
            // check if it's non-planar
            if (cube[1] + cube[2] != cube[0] + cube[3]) {
               // not planar, split along diagonal and make degenerate quads
               if (geo == STBVOX_GEOM_ceil_vheight_03)
                  stbvox_make_03_split_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, ht);
               else
                  stbvox_make_12_split_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, ht);
            } else
               stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, stbvox_reverse_face[stbvox_planar_face_up_normal[ht[2]][ht[1]][ht[0]]]);
         #else
            stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_down, v_off, pos, basevert, vmesh[STBVOX_FACE_down], mesh, stbvox_reverse_face[stbvox_optimized_face_up_normal[ht[3]][ht[2]][ht[1]][ht[0]]]);
         #endif
         }
      }

      if (mm->input.rotate) {
         unsigned char val = mm->input.rotate[v_off];
         rotate.block   = (val >> 0) & 3;
         rotate.overlay = (val >> 2) & 3;
         //rotate.tex2    = (val >> 4) & 3;
         rotate.ecolor  = (val >> 6) & 3;
      } else if (mm->input.selector) {
         rotate.block = rotate.overlay = rotate.ecolor = simple_rot;
      }

      if ((visible_faces & (1 << STBVOX_FACE_north)) || (extreme && (ht[2] == 3 || ht[3] == 3)))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_north, v_off, pos, basevert, vmesh[STBVOX_FACE_north], mesh, STBVOX_FACE_north);
      if ((visible_faces & (1 << STBVOX_FACE_south)) || (extreme && (ht[0] == 3 || ht[1] == 3))) 
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_south, v_off, pos, basevert, vmesh[STBVOX_FACE_south], mesh, STBVOX_FACE_south);
      if ((visible_faces & (1 << STBVOX_FACE_east)) || (extreme && (ht[1] == 3 || ht[3] == 3)))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_east , v_off, pos, basevert, vmesh[STBVOX_FACE_east ], mesh, STBVOX_FACE_east);
      if ((visible_faces & (1 << STBVOX_FACE_west)) || (extreme && (ht[0] == 3 || ht[2] == 3)))
         stbvox_make_mesh_for_face(mm, rotate, STBVOX_FACE_west , v_off, pos, basevert, vmesh[STBVOX_FACE_west ], mesh, STBVOX_FACE_west);
   }

   if (geo == STBVOX_GEOM_crossed_pair) {
      // this can be generated with a special vmesh
      stbvox_mesh_vertex basevert = stbvox_vertex_encode(pos.x, pos.y, pos.z << STBVOX_CONFIG_PRECISION_Z , 0,0);
      unsigned char simple_rot=0;
      stbvox_rotate rot = { 0,0,0,0 };
      unsigned char mesh = mm->default_mesh;
      if (mm->input.selector) {
         mesh = mm->input.selector[v_off];
         simple_rot = mesh >> 4;
         mesh &= 15;
      } 
      if (mm->input.block_selector) {
         mesh = mm->input.block_selector[bt];
      }

      // check if we're going off the end
      if (mm->output_cur[mesh][0] + mm->output_size[mesh][0]*4 > mm->output_end[mesh][0]) {
         mm->full = 1;
         return;
      }

      if (mm->input.rotate) {
         unsigned char val = mm->input.rotate[v_off];
         rot.block   = (val >> 0) & 3;
         rot.overlay = (val >> 2) & 3;
         //rot.tex2    = (val >> 4) & 3;
         rot.ecolor  = (val >> 6) & 3;
      } else if (mm->input.selector) {
         rot.block = rot.overlay = rot.ecolor = simple_rot;
      }
      rot.facerot = 0;

      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_north, v_off, pos, basevert, stbvox_vmesh_crossed_pair[STBVOX_FACE_north], mesh, STBVF_ne_u_cross);
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_south, v_off, pos, basevert, stbvox_vmesh_crossed_pair[STBVOX_FACE_south], mesh, STBVF_sw_u_cross);
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_east , v_off, pos, basevert, stbvox_vmesh_crossed_pair[STBVOX_FACE_east ], mesh, STBVF_se_u_cross);
      stbvox_make_mesh_for_face(mm, rot, STBVOX_FACE_west , v_off, pos, basevert, stbvox_vmesh_crossed_pair[STBVOX_FACE_west ], mesh, STBVF_nw_u_cross);
   }


   // @TODO
   // STBVOX_GEOM_floor_slope_north_is_top_as_wall,
   // STBVOX_GEOM_ceil_slope_north_is_bottom_as_wall,
}

static void stbvox_make_mesh_for_column(stbvox_mesh_maker *mm, int x, int y, int z0)
{
   stbvox_pos pos;
   int v_off = x * mm->x_stride_in_bytes + y * mm->y_stride_in_bytes;
   int ns_off = mm->y_stride_in_bytes;
   int ew_off = mm->x_stride_in_bytes;
   pos.x = x;
   pos.y = y;
   pos.z = 0;
   if (mm->input.geometry) {
      unsigned char *bt  = mm->input.blocktype + v_off;
      unsigned char *geo = mm->input.geometry + v_off;
      int z;
      for (z=z0; z < mm->z1; ++z) {
         if (bt[z] && ( !bt[z+ns_off] || !STBVOX_GET_GEO(geo[z+ns_off]) || !bt[z-ns_off] || !STBVOX_GET_GEO(geo[z-ns_off])
                      || !bt[z+ew_off] || !STBVOX_GET_GEO(geo[z+ew_off]) || !bt[z-ew_off] || !STBVOX_GET_GEO(geo[z-ew_off])
                      || !bt[z-1] || !STBVOX_GET_GEO(geo[z-1]) || !bt[z+1] || !STBVOX_GET_GEO(geo[z+1])))
         {  // TODO check up and down
            pos.z = z;
            stbvox_make_mesh_for_block_with_geo(mm, pos, v_off+z);
            if (mm->full) {
               mm->cur_z = z;
               return;
            }
         }
      }
   } else if (mm->input.block_geometry) {
      int z;
      unsigned char *bt  = mm->input.blocktype + v_off;
      unsigned char *geo = mm->input.block_geometry;
      for (z=z0; z < mm->z1; ++z) {
         if (bt[z] && (    geo[bt[z+ns_off]] != STBVOX_GEOM_solid
                        || geo[bt[z-ns_off]] != STBVOX_GEOM_solid
                        || geo[bt[z+ew_off]] != STBVOX_GEOM_solid
                        || geo[bt[z-ew_off]] != STBVOX_GEOM_solid
                        || geo[bt[z-1]] != STBVOX_GEOM_solid
                        || geo[bt[z+1]] != STBVOX_GEOM_solid))
         {
            pos.z = z;
            stbvox_make_mesh_for_block_with_geo(mm, pos, v_off+z);
            if (mm->full) {
               mm->cur_z = z;
               return;
            }
         }
      }
   } else {
      unsigned char *bt = mm->input.blocktype + v_off;
      int z;
      #if STBVOX_CONFIG_PRECISION_Z == 1
      stbvox_mesh_vertex *vmesh = stbvox_vmesh_delta_half_z[0];
      #else
      stbvox_mesh_vertex *vmesh = stbvox_vmesh_delta_normal[0];
      #endif
      for (z=z0; z < mm->z1; ++z) {
         // if it's solid and at least one neighbor isn't solid
         if (bt[z] && (!bt[z+ns_off] || !bt[z-ns_off] || !bt[z+ew_off] || !bt[z-ew_off] || !bt[z-1] || !bt[z+1])) {
            pos.z = z;
            stbvox_make_mesh_for_block(mm, pos, v_off+z, vmesh);
            if (mm->full) {
               mm->cur_z = z;
               return;
            }
         }
      }
   }
}

static void stbvox_bring_up_to_date(stbvox_mesh_maker *mm)
{
   if (mm->config_dirty) {
      int i;
      #ifdef STBVOX_ICONFIG_FACE_ATTRIBUTE
         mm->num_mesh_slots = 1;
         for (i=0; i < STBVOX_MAX_MESHES; ++i) {
            mm->output_size[i][0] = 32;
            mm->output_step[i][0] = 8;
         }
      #else
         mm->num_mesh_slots = 2;
         for (i=0; i < STBVOX_MAX_MESHES; ++i) {
            mm->output_size[i][0] = 16;
            mm->output_step[i][0] = 4;
            mm->output_size[i][1] = 4;
            mm->output_step[i][1] = 4;
         }
      #endif

      mm->config_dirty = 0;
   }
}

int stbvox_make_mesh(stbvox_mesh_maker *mm)
{
   int x,y;
   stbvox_bring_up_to_date(mm);
   mm->full = 0;
   if (mm->cur_x > mm->x0 || mm->cur_y > mm->y0 || mm->cur_z > mm->z0) {
      stbvox_make_mesh_for_column(mm, mm->cur_x, mm->cur_y, mm->cur_z);
      if (mm->full)
         return 0;
      ++mm->cur_y;
      while (mm->cur_y < mm->y1 && !mm->full) {
         stbvox_make_mesh_for_column(mm, mm->cur_x, mm->cur_y, mm->z0);
         if (mm->full)
            return 0;
         ++mm->cur_y;
      }
      ++mm->cur_x;
   }
   for (x=mm->cur_x; x < mm->x1; ++x) {
      for (y=mm->y0; y < mm->y1; ++y) {
         stbvox_make_mesh_for_column(mm, x, y, mm->z0);
         if (mm->full) {
            mm->cur_x = x;
            mm->cur_y = y;
            return 0;
         }
      }
   }
   return 1;
}

void stbvox_init_mesh_maker(stbvox_mesh_maker *mm)
{
   memset(mm, 0, sizeof(*mm));
   stbvox_build_default_palette();

   mm->config_dirty = 1;
   mm->default_mesh = 0;
}

int stbvox_get_buffer_count(stbvox_mesh_maker *mm)
{
   stbvox_bring_up_to_date(mm);
   return mm->num_mesh_slots;
}

int stbvox_get_buffer_size_per_quad(stbvox_mesh_maker *mm, int n)
{
   return mm->output_size[0][n];
}

void stbvox_reset_buffers(stbvox_mesh_maker *mm)
{
   int i;
   for (i=0; i < STBVOX_MAX_MESHES*STBVOX_MAX_MESH_SLOTS; ++i) {
      mm->output_cur[0][i] = 0;
      mm->output_buffer[0][i] = 0;
   }
}

void stbvox_set_buffer(stbvox_mesh_maker *mm, int mesh, int slot, void *buffer, size_t len)
{
   int i;
   stbvox_bring_up_to_date(mm);
   mm->output_buffer[mesh][slot] = (char *) buffer;
   mm->output_cur   [mesh][slot] = (char *) buffer;
   mm->output_len   [mesh][slot] = (int) len;
   mm->output_end   [mesh][slot] = (char *) buffer + len;
   for (i=0; i < STBVOX_MAX_MESH_SLOTS; ++i) {
      if (mm->output_buffer[mesh][i]) {
         assert(mm->output_len[mesh][i] / mm->output_size[mesh][i] == mm->output_len[mesh][slot] / mm->output_size[mesh][slot]);
      }
   }
}

void stbvox_set_default_mesh(stbvox_mesh_maker *mm, int mesh)
{
   mm->default_mesh = mesh;
}

int stbvox_get_quad_count(stbvox_mesh_maker *mm, int mesh)
{
   return (int) ((mm->output_cur[mesh][0] - mm->output_buffer[mesh][0]) / mm->output_size[mesh][0]);
}

stbvox_input_description *stbvox_get_input_description(stbvox_mesh_maker *mm)
{
   return &mm->input;
}

void stbvox_set_input_range(stbvox_mesh_maker *mm, int x0, int y0, int z0, int x1, int y1, int z1)
{
   mm->x0 = x0;
   mm->y0 = y0;
   mm->z0 = z0;

   mm->x1 = x1;
   mm->y1 = y1;
   mm->z1 = z1;

   mm->cur_x = x0;
   mm->cur_y = y0;
   mm->cur_z = z0;

   // @TODO validate that this range is representable in this mode
}

void stbvox_get_transform(stbvox_mesh_maker *mm, float transform[3][3])
{
   // scale
   transform[0][0] = 1.0;
   transform[0][1] = 1.0;
   #if STBVOX_CONFIG_PRECISION_Z==1
   transform[0][2] = 0.5f;
   #else
   transform[0][2] = 1.0f;
   #endif
   // translation
   transform[1][0] = (float) (mm->pos_x);
   transform[1][1] = (float) (mm->pos_y);
   transform[1][2] = (float) (mm->pos_z);
   // texture coordinate projection translation
   transform[2][0] = (float) (mm->pos_x & 255); // @TODO depends on max texture scale
   transform[2][1] = (float) (mm->pos_y & 255);
   transform[2][2] = (float) (mm->pos_z & 255);
}

void stbvox_get_bounds(stbvox_mesh_maker *mm, float bounds[2][3])
{
   bounds[0][0] = (float) (mm->pos_x + mm->x0);
   bounds[0][1] = (float) (mm->pos_y + mm->y0);
   bounds[0][2] = (float) (mm->pos_z + mm->z0);
   bounds[1][0] = (float) (mm->pos_x + mm->x1);
   bounds[1][1] = (float) (mm->pos_y + mm->y1);
   bounds[1][2] = (float) (mm->pos_z + mm->z1);
}

void stbvox_set_mesh_coordinates(stbvox_mesh_maker *mm, int x, int y, int z)
{
   mm->pos_x = x;
   mm->pos_y = y;
   mm->pos_z = z;
}

void stbvox_set_input_stride(stbvox_mesh_maker *mm, int x_stride_in_bytes, int y_stride_in_bytes)
{
   int f,v;
   mm->x_stride_in_bytes = x_stride_in_bytes;
   mm->y_stride_in_bytes = y_stride_in_bytes;
   for (f=0; f < 6; ++f) {
      for (v=0; v < 4; ++v) {
         mm->cube_vertex_offset[f][v]   =   stbvox_vertex_vector[f][v][0]    * mm->x_stride_in_bytes
                                         +  stbvox_vertex_vector[f][v][1]    * mm->y_stride_in_bytes
                                         +  stbvox_vertex_vector[f][v][2]                           ;
         mm->vertex_gather_offset[f][v] =  (stbvox_vertex_vector[f][v][0]-1) * mm->x_stride_in_bytes
                                         + (stbvox_vertex_vector[f][v][1]-1) * mm->y_stride_in_bytes
                                         + (stbvox_vertex_vector[f][v][2]-1)                        ; 
      }
   }
}

/////////////////////////////////////////////////////////////////////////////
//
//    offline computation of tables
//

#if 0
// compute optimized vheight table
static char *normal_names[32] =
{
   0,0,0,0,"u   ",0, "eu  ",0,
   0,0,0,0,"ne_u",0, "nu  ",0,
   0,0,0,0,"nw_u",0, "wu  ",0,
   0,0,0,0,"sw_u",0, "su  ",0,
};

static char *find_best_normal(float x, float y, float z)
{
   int best_slot = 4;
   float best_dot = 0;
   int i;
   for (i=0; i < 32; ++i) {
      if (normal_names[i]) {
         float dot = x * stbvox_default_normals[i][0] + y * stbvox_default_normals[i][1] + z * stbvox_default_normals[i][2];
         if (dot > best_dot) {
            best_dot = dot;
            best_slot = i;
         }
      }
   }
   return normal_names[best_slot];
}

int main(int argc, char **argv)
{
   int sw,se,nw,ne;
   for (ne=0; ne < 4; ++ne) {
      for (nw=0; nw < 4; ++nw) {
         for (se=0; se < 4; ++se) {
            printf("        { ");
            for (sw=0; sw < 4; ++sw) {
               float x = (float) (nw + sw - ne - se);
               float y = (float) (sw + se - nw - ne);
               float z = 2;
               printf("STBVF_%s, ", find_best_normal(x,y,z));
            }
            printf("},\n");
         }
      }
   }
   return 0;
}
#endif

// @TODO
//
//   - test API for texture rotation on side faces
//   - API for texture rotation on top & bottom
//   - better culling of vheight faces with vheight neighbors
//   - better culling of non-vheight faces with vheight neighbors
//   - gather vertex lighting from slopes correctly
//   - better support texture edge_clamp: currently if you fall
//     exactly on 1.0 you get wrapped incorrectly; this is rare, but
//     can avoid: compute texcoords in vertex shader, offset towards
//     center before modding, need 2 bits per vertex to know offset direction)
//   - other mesh modes (10,6,4-byte quads)
//
//
// With TexBuffer for the fixed vertex data, we can actually do
// minecrafty non-blocks like stairs -- we still probably only
// want 256 or so, so we can't do the equivalent of all the vheight
// combos, but that's ok. The 256 includes baked rotations, but only
// some of them need it, and lots of block types share some faces.
//
// mode 5 (6 bytes):   mode 6 (6 bytes)
//   x:7                x:6
//   y:7                y:6
//   z:6                z:6
//   tex1:8             tex1:8
//   tex2:8             tex2:7
//   color:8            color:8
//   face:4             face:7
//
//
//  side faces (all x4)        top&bottom faces (2x)    internal faces (1x)
//     1  regular                1 regular
//     2  slabs                                             2
//     8  stairs                 4 stairs                  16
//     4  diag side                                         8
//     4  upper diag side                                   8
//     4  lower diag side                                   8
//                                                          4 crossed pairs
//
//    23*4                   +   5*4                    +  46
//  == 92 + 20 + 46 = 158
//
//   Must drop 30 of them to fit in 7 bits:
//       ceiling half diagonals: 16+8 = 24
//   Need to get rid of 6 more.
//       ceiling diagonals: 8+4 = 12
//   This brings it to 122, so can add a crossed-pair variant.
//       (diagonal and non-diagonal, or randomly offset)
//   Or carpet, which would be 5 more.
//
//
// Mode 4 (10 bytes):
//  v:  z:2,light:6
//  f:  x:6,y:6,z:7, t1:8,t2:8,c:8,f:5
//
// Mode ? (10 bytes)
//  v:  xyz:5 (27 values), light:3
//  f:  x:7,y:7,z:6, t1:8,t2:8,c:8,f:4
// (v:  x:2,y:2,z:2,light:2)

#endif // STB_VOXEL_RENDER_IMPLEMENTATION

/*
------------------------------------------------------------------------------
This software is available under 2 licenses -- choose whichever you prefer.
------------------------------------------------------------------------------
ALTERNATIVE A - MIT License
Copyright (c) 2017 Sean Barrett
Permission is hereby granted, free of charge, to any person obtaining a copy of 
this software and associated documentation files (the "Software"), to deal in 
the Software without restriction, including without limitation the rights to 
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies 
of the Software, and to permit persons to whom the Software is furnished to do 
so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all 
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.
------------------------------------------------------------------------------
ALTERNATIVE B - Public Domain (www.unlicense.org)
This is free and unencumbered software released into the public domain.
Anyone is free to copy, modify, publish, use, compile, sell, or distribute this 
software, either in source code form or as a compiled binary, for any purpose, 
commercial or non-commercial, and by any means.
In jurisdictions that recognize copyright laws, the author or authors of this 
software dedicate any and all copyright interest in the software to the public 
domain. We make this dedication for the benefit of the public at large and to 
the detriment of our heirs and successors. We intend this dedication to be an 
overt act of relinquishment in perpetuity of all present and future rights to 
this software under copyright law.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
------------------------------------------------------------------------------
*/