glshim

This is a shim providing OpenGL 1.x functionality to OpenGL ES accelerated cards.

Most function of OpenGL up to 1.5 are supported, with some notable exceptions:

• Reading of Depth or Stencil buffer will not work
• GL_FEEDBACK mode is not implemented
• OcclusionQuery is not implemented

Some know limitations:

• GL_SELECT as some limitation in its implementation (for exemple, current Depth buffer or binded texture are not taken into account)
• NPOT texture are supported, but not with GL_REPEAT / GL_MIRRORED, only GL_CLAMP will work properly
• Framebuffer use FRAMEBUFFER_OES extension (that must be present in the GLES 1.1 stack)
• Multiple Color attachment on Framebuffer are not supported
• Probably many other things

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Compiling

for Pandora

cmake . -DPANDORA=1; make GL

or for the Raspberry Pi

cmake . -DBCMHOST=1; make GL

or for the ODroid

cmake . -DODROID=1; make GL

or for Android

An Android.mk is provided that should compile with an NDK

or use ccmake Alternatively, you can use the curses-bases ccmake to select wich platform to use interactively.

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GLU

Standard GLU do works without any issues.

But you can also find a GLES optimized version og GLU there https://github.com/lunixbochs/glues

git clone git@github.com:lunixbochs/glues.git; git checkout glu; cmake .; make

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Installation

Put lib/libGL.so.1 in your LD_LIBRARY_PATH.

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Usage

There are many environnement variable to control glshim behavour. All are numeric, except LIBGL_VERSION that take a string.

LIBGL_FB

Controls the Framebuffer output

• 0 : Default, using standard x11 rendering
• 1 : Use Framebuffer output (x11 bypassed, only fullscreen)
• 2 : Use Framebuffer, but also an intermediary FBO

LIBGL_XREFRESH

Debug helper in specific cases

• 0 : Default, nothing special
• 1 : xrefresh will be called on cleanup

LIBGL_STACKTRACE

Automatic Backtrace log

• 0 : Default, nothing special
• 1 : stacktrace will be printed on crash

LIBGL_VSYNC

VSync control

• 0 : Default, nothing special
• 1 : vsync enabled

LIBGL_RECYCLEFBO

Recycling FBO special case (don't delete a created FBO, but recycle it if needed)

• 0 : Default, nothing special
• 1 : Recycling of FBO enabled

LIBGL_MIPMAP

Handling of Manual and Automatic MIPMAP

• 0 : Default, nothing special
• 1 : AutoMipMap forced
• 2 : guess AutoMipMap (based on manual mipmaping on textures)
• 3 : ignore MipMap (mipmap creation / use entirely disabled)
• 4 : ignore AutoMipMap on non-squared textures

LIBGL_TEXCOPY

Make a local copy of every texture for easy glGetTexImage2D

• 0 : Default, nothing special
• 1 : Texture copy enabled

LIBGL_SHRINK

Texture shrinking control

• 0 : Default, nothing special
• 1 : everything / 2 (using original algorithm for size reduction, all other shink mode use a refined algorithm)
• 2 : only textures wich one size > 512 are / 2
• 3 : only textures wich one size > 256 are / 2
• 4 : only textures wich one size > 256 are / 2, and the one > 1024 are / 4
• 5 : only textures wich one size > 256 are resized to 256 (if possible, because only /2 and /4 exists), but empty texture are not shrinked
• 6 : only textures wich one size > 128 are / 2, thoses >= 512 are resized to 256 (if possible, because only /2 and /4 exists), but empty texture are not shrinked
• 7 : only textures wich one size > 512 are / 2, but empty texture are not shrinked
• 8 : advertise a max texture size of 8192, but every texture wich one size > 2048 are shrinked to 2048
• 9 : advertise a max texture size of 8192, but every texture wich one size > 4096 are / 4 and the one > 512 are / 2, but empty texture are not shrinked
• 10: advertise a max texture size of 8192, but every texture wich one size > 2048 are / 4 and the one > 512 are / 2, but empty texture are not shrinked

LIBGL_TEXDUMP

Texture dump

• 0 : Default, nothing special
• 1 : Texture dump enabled

LIBGL_ALPHAHACK

Experimental: enable Alpha test only when using texture that contains an alpha channel

• 0 : Default, nothing special
• 1 : Alpha Hack enabled

LIBGL_STREAM

PANDORA only: enable Texture Streaming (works only on RGB textures)

• 0 : Default, nothing special
• 1 : Enabled on empty RGB textures
• 2 : Enabled on all RGB textures

LIBGL_COPY

Control the glCopyTex(Sub)Image2D hack (they are buggy on pandora and don't work most of the time)

• 0 : Don't use native glCopyTex(Sub)Image2D, but a workaround function using FBO
• 1 : No glCopyTexImage2D / glCopyTexSubImage2D hack, use native ones

LIBGL_NOLUMALPHA

Control the availability of the LUMUNANCE_ALPHA format (can be buggy on Pandora model CC)

• 0 : Default,GL_LUMINANCE_ALPHA is available and used if needed
• 1 : GL_LUMINANCE_ALPHA hardware support disabled (a GL_RGBA texture will be used instead)

LIBGL_BLENDHACK

Experimental: Change Blend GL_SRC_ALPHA, GL_ONE to GL_ONE, GL_ONE

• 0 : Default, nothing special
• 1 : Change Blend GL_SRC_ALPHA, GL_ONE to GL_ONE, GL_ONE (can be usefull for Xash3D engine)

LIBGL_BLENDCOLOR

Hack: Export a (faked) glBlendColor

• 0 : Default, don't expose gBlendColor
• 1 : Exposed the function (if no hadware support, faked function willbe used)

LIBGL_VERSION

Hack: Control the glGetString version. Overide version string (should be in the form of "1.x")

LIBGL_BATCH

Experimental: Batch mode (fuse of contigous Display list, to limit Draw calls)

• 0 : Default, only Draw list created during a glList are fused (i.e. contigous glBegin / glEnd inside a List)
• 1 : Force a maximum of call to be batched (like if all was inside a big glList)
• 2 : Disable Batch mode completly, no fuse of draw list

LIBGL_NOERROR

Hack: glGetError() always return GL_NOERROR

• 0 : Default, glGetError behave as it should
• 1 : glGetError never fail.

LIBGL_GAMMA

Pandora Hack: Set a Gamma value (in decimal formal, 1.0 means no gamma boost)

• X.Y : Use X.Y as gamma when creating context (typical value can be 1.6 or 2.0)