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bfr_tutorial_3_2.cpp
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bfr_tutorial_3_2.cpp
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//
// Copyright 2021 Pixar
//
// Licensed under the Apache License, Version 2.0 (the "Apache License")
// with the following modification; you may not use this file except in
// compliance with the Apache License and the following modification to it:
// Section 6. Trademarks. is deleted and replaced with:
//
// 6. Trademarks. This License does not grant permission to use the trade
// names, trademarks, service marks, or product names of the Licensor
// and its affiliates, except as required to comply with Section 4(c) of
// the License and to reproduce the content of the NOTICE file.
//
// You may obtain a copy of the Apache License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the Apache License with the above modification is
// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the Apache License for the specific
// language governing permissions and limitations under the Apache License.
//
//------------------------------------------------------------------------------
// Tutorial description:
//
// This tutorial is a variation of tutorials showing simple uniform
// tessellation. Rather than constructing and evaluating a Surface at
// a time, this tutorial shows how Surfaces can be created and saved
// for repeated use.
//
// A simple SurfaceCache class is created that creates and stores the
// Surface for each face, along with the patch points associated with
// it. The main tessellation function remains essentially the same,
// but here it access the Surfaces from the SurfaceCache rather than
// computing them locally.
//
// Note that while this example illustrated the retention of all
// Surfaces for a mesh, this behavior is not recommended. It does not
// scale well for large meshes and undermines the memory savings that
// transient use of Surfaces is designed to achieve. Rather than
// storing Surfaces for all faces, maintaining a priority queue for a
// fixed number may be a reasonable compromise.
//
#include <opensubdiv/far/topologyRefiner.h>
#include <opensubdiv/bfr/refinerSurfaceFactory.h>
#include <opensubdiv/bfr/surface.h>
#include <opensubdiv/bfr/tessellation.h>
#include <vector>
#include <memory>
#include <string>
#include <cstring>
#include <cstdio>
// Local headers with support for this tutorial in "namespace tutorial"
#include "./meshLoader.h"
#include "./objWriter.h"
using namespace OpenSubdiv;
//
// Simple command line arguments to provide input and run-time options:
//
class Args {
public:
std::string inputObjFile;
std::string outputObjFile;
Sdc::SchemeType schemeType;
int tessUniformRate;
bool tessQuadsFlag;
public:
Args(int argc, char * argv[]) :
inputObjFile(),
outputObjFile(),
schemeType(Sdc::SCHEME_CATMARK),
tessUniformRate(5),
tessQuadsFlag(false) {
for (int i = 1; i < argc; ++i) {
if (strstr(argv[i], ".obj")) {
if (inputObjFile.empty()) {
inputObjFile = std::string(argv[i]);
} else {
fprintf(stderr,
"Warning: Extra Obj file '%s' ignored\n", argv[i]);
}
} else if (!strcmp(argv[i], "-o")) {
if (++i < argc) outputObjFile = std::string(argv[i]);
} else if (!strcmp(argv[i], "-bilinear")) {
schemeType = Sdc::SCHEME_BILINEAR;
} else if (!strcmp(argv[i], "-catmark")) {
schemeType = Sdc::SCHEME_CATMARK;
} else if (!strcmp(argv[i], "-loop")) {
schemeType = Sdc::SCHEME_LOOP;
} else if (!strcmp(argv[i], "-res")) {
if (++i < argc) tessUniformRate = atoi(argv[i]);
} else if (!strcmp(argv[i], "-quads")) {
tessQuadsFlag = true;
} else {
fprintf(stderr,
"Warning: Unrecognized argument '%s' ignored\n", argv[i]);
}
}
}
private:
Args() { }
};
//
// This simple class creates and dispenses Surfaces for all faces of
// a mesh. It consists primarily of an array of simple structs (entries)
// for each face and a single array of patch points for all Surfaces
// created.
//
// There are many ways to create such a cache depending on requirements.
// This is a simple example, but the interface presents some options that
// are worth considering. A SurfaceCache is constructed here given the
// following:
//
// - a reference to the SurfaceFactory:
// - the cache could just as easily take a reference to the mesh
// and construct the SurfaceFactory internally
//
// - the position data for the mesh:
// - this is needed to compute patch points for the Surfaces
// - if caching UVs or any other primvar, other data needs to be
// provided -- along with the interpolation type for that data
// (vertex, face-varying, etc.)
//
// - option to "cache patch points":
// - the cache could store the Surfaces only or also include
// their patch points
// - storing patch points takes more memory but will eliminate
// any preparation time for evaluation of the Surface
//
// - option to "cache all surfaces":
// - the benefits to caching simple linear or regular surfaces
// are minimal -- and may even be detrimental
// - so only caching non-linear irregular surfaces is an option
// worth considering
//
// The SurfaceCache implementation here provides the options noted above.
// But for simplicity, the actual usage of the SurfaceCache does not deal
// with the permutations of additional work that is necessary when the
// Surfaces or their patch points are not cached.
//
class SurfaceCache {
public:
typedef Bfr::Surface<float> Surface;
typedef Bfr::RefinerSurfaceFactory<> SurfaceFactory;
public:
SurfaceCache(SurfaceFactory const & surfaceFactory,
std::vector<float> const & meshPoints,
bool cachePatchPoints = true,
bool cacheAllSurfaces = true);
SurfaceCache() = delete;
~SurfaceCache() = default;
//
// Public methods to retrieved cached Surfaces and their pre-computed
// patch points:
//
bool FaceHasLimitSurface(int face) { return _entries[face].hasLimit; }
Surface const * GetSurface(int face) { return _entries[face].surface.get();}
float const * GetPatchPoints(int face) { return getPatchPoints(face); }
private:
// Simple struct to keep track of Surface and more for each face:
struct FaceEntry {
FaceEntry() : surface(), hasLimit(false), pointOffset(-1) { }
std::unique_ptr<Surface const> surface;
bool hasLimit;
int pointOffset;
};
// Non-const version to be used internally to aide assignment:
float * getPatchPoints(int face) {
return (_entries[face].surface && !_points.empty()) ?
(_points.data() + _entries[face].pointOffset * 3) : 0;
}
private:
std::vector<FaceEntry> _entries;
std::vector<float> _points;
};
SurfaceCache::SurfaceCache(SurfaceFactory const & surfaceFactory,
std::vector<float> const & meshPoints,
bool cachePatchPoints,
bool cacheAllSurfaces) {
int numFaces = surfaceFactory.GetNumFaces();
_entries.resize(numFaces);
int numPointsInCache = 0;
for (int face = 0; face < numFaces; ++face) {
Surface * s = surfaceFactory.CreateVertexSurface<float>(face);
if (s) {
FaceEntry & entry = _entries[face];
entry.hasLimit = true;
if (cacheAllSurfaces || (!s->IsRegular() && !s->IsLinear())) {
entry.surface.reset(s);
entry.pointOffset = numPointsInCache;
numPointsInCache += s->GetNumPatchPoints();
} else {
delete s;
}
}
}
if (cachePatchPoints) {
_points.resize(numPointsInCache * 3);
for (int face = 0; face < numFaces; ++face) {
float * patchPoints = getPatchPoints(face);
if (patchPoints) {
GetSurface(face)->PreparePatchPoints(meshPoints.data(), 3,
patchPoints, 3);
}
}
}
}
//
// The main tessellation function: given a mesh and vertex positions,
// tessellate each face -- writing results in Obj format.
//
void
tessellateToObj(Far::TopologyRefiner const & meshTopology,
std::vector<float> const & meshVertexPositions,
Args const & options) {
//
// Use simpler local type names for the Surface and its factory:
//
typedef Bfr::RefinerSurfaceFactory<> SurfaceFactory;
typedef Bfr::Surface<float> Surface;
//
// Initialize the SurfaceFactory for the given base mesh (very low
// cost in terms of both time and space) and tessellate each face
// independently (i.e. no shared vertices):
//
// Note that the SurfaceFactory is not thread-safe by default due to
// use of an internal cache. Creating a separate instance of the
// SurfaceFactory for each thread is one way to safely parallelize
// this loop. Another (preferred) is to assign a thread-safe cache
// to the single instance.
//
// First declare any evaluation options when initializing (though
// none are used in this simple case):
//
SurfaceFactory::Options surfaceOptions;
SurfaceFactory meshSurfaceFactory(meshTopology, surfaceOptions);
//
// Initialize a SurfaceCache to construct Surfaces for all faces.
// From this point forward the SurfaceFactory is no longer used to
// access Surfaces. Note also that usage below is specific to the
// options used to initialize the SurfaceCache:
//
bool cachePatchPoints = true;
bool cacheAllSurfaces = true;
SurfaceCache surfaceCache(meshSurfaceFactory, meshVertexPositions,
cachePatchPoints, cacheAllSurfaces);
//
// As with previous tutorials, output data associated with the face
// can be declared in the scope local to each face. But since dynamic
// memory is involved with these variables, it is preferred to declare
// them outside that loop to preserve and reuse that dynamic memory.
//
std::vector<float> outCoords;
std::vector<float> outPos, outDu, outDv;
std::vector<int> outFacets;
//
// Assign Tessellation Options applied for all faces. Tessellations
// allow the creating of either 3- or 4-sided faces -- both of which
// are supported here via a command line option:
//
int const tessFacetSize = 3 + options.tessQuadsFlag;
Bfr::Tessellation::Options tessOptions;
tessOptions.SetFacetSize(tessFacetSize);
tessOptions.PreserveQuads(options.tessQuadsFlag);
//
// Process each face, writing the output of each in Obj format:
//
tutorial::ObjWriter objWriter(options.outputObjFile);
int numFaces = meshSurfaceFactory.GetNumFaces();
for (int faceIndex = 0; faceIndex < numFaces; ++faceIndex) {
//
// Retrieve the Surface for this face when present:
//
if (!surfaceCache.FaceHasLimitSurface(faceIndex)) continue;
Surface const & faceSurface = * surfaceCache.GetSurface(faceIndex);
//
// Declare a simple uniform Tessellation for the Parameterization
// of this face and identify coordinates of the points to evaluate:
//
Bfr::Tessellation tessPattern(faceSurface.GetParameterization(),
options.tessUniformRate, tessOptions);
int numOutCoords = tessPattern.GetNumCoords();
outCoords.resize(numOutCoords * 2);
tessPattern.GetCoords(outCoords.data());
//
// Retrieve the patch points for the Surface, then use them to
// evaluate output points for all identified coordinates:
//
float const * facePatchPoints = surfaceCache.GetPatchPoints(faceIndex);
int pointSize = 3;
outPos.resize(numOutCoords * pointSize);
outDu.resize(numOutCoords * pointSize);
outDv.resize(numOutCoords * pointSize);
for (int i = 0, j = 0; i < numOutCoords; ++i, j += pointSize) {
faceSurface.Evaluate(&outCoords[i*2],
facePatchPoints, pointSize,
&outPos[j], &outDu[j], &outDv[j]);
}
//
// Identify the faces of the Tessellation:
//
// Note the need to offset vertex indices for the output faces --
// using the number of vertices generated prior to this face. One
// of several Tessellation methods to transform the facet indices
// simply translates all indices by the desired offset.
//
int objVertexIndexOffset = objWriter.GetNumVertices();
int numFacets = tessPattern.GetNumFacets();
outFacets.resize(numFacets * tessFacetSize);
tessPattern.GetFacets(outFacets.data());
tessPattern.TransformFacetCoordIndices(outFacets.data(),
objVertexIndexOffset);
//
// Write the evaluated points and faces connecting them as Obj:
//
objWriter.WriteGroupName("baseFace_", faceIndex);
objWriter.WriteVertexPositions(outPos);
objWriter.WriteVertexNormals(outDu, outDv);
objWriter.WriteFaces(outFacets, tessFacetSize, true, false);
}
}
//
// Load command line arguments, specified or default geometry and process:
//
int
main(int argc, char * argv[]) {
Args args(argc, argv);
Far::TopologyRefiner * meshTopology = 0;
std::vector<float> meshVtxPositions;
std::vector<float> meshFVarUVs;
meshTopology = tutorial::createTopologyRefiner(
args.inputObjFile, args.schemeType, meshVtxPositions, meshFVarUVs);
if (meshTopology == 0) {
return EXIT_FAILURE;
}
tessellateToObj(*meshTopology, meshVtxPositions, args);
delete meshTopology;
return EXIT_SUCCESS;
}
//------------------------------------------------------------------------------