assimp.assimp/code/FindInstancesProcess.cpp

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/** @file  FindInstancesProcess.cpp
 *  @brief Implementation of the aiProcess_FindInstances postprocessing step
*/

#include "AssimpPCH.h"
#include "FindInstancesProcess.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
FindInstancesProcess::FindInstancesProcess()
{}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
FindInstancesProcess::~FindInstancesProcess()
{}

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool FindInstancesProcess::IsActive( unsigned int pFlags) const
{
	return 0 != (pFlags & aiProcess_FindInstances);
}

// ------------------------------------------------------------------------------------------------
// Compare the bones of two meshes
bool CompareBones(const aiMesh* orig, const aiMesh* inst)
{
	for (unsigned int i = 0; i < orig->mNumBones;++i) {
		aiBone* aha = orig->mBones[i];
		aiBone* oha = inst->mBones[i];

		if (aha->mNumWeights   != oha->mNumWeights   ||
			aha->mOffsetMatrix != oha->mOffsetMatrix ||
			aha->mNumWeights   != oha->mNumWeights) {
			return false;
		}

		// compare weight per weight ---
		for (unsigned int n = 0; n < aha->mNumWeights;++n) {
			if  (aha->mWeights[n].mVertexId != oha->mWeights[n].mVertexId ||
				(aha->mWeights[n].mWeight - oha->mWeights[n].mWeight) < 10e-3f) {
				return false;
			}
		}
	}
	return true;
}

// ------------------------------------------------------------------------------------------------
// Update mesh indices in the node graph
void UpdateMeshIndices(aiNode* node, unsigned int* lookup)
{
	for (unsigned int n = 0; n < node->mNumMeshes;++n)
		node->mMeshes[n] = lookup[node->mMeshes[n]];

	for (unsigned int n = 0; n < node->mNumChildren;++n)
		UpdateMeshIndices(node->mChildren[n],lookup);
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void FindInstancesProcess::Execute( aiScene* pScene)
{
	DefaultLogger::get()->debug("FindInstancesProcess begin");
	if (pScene->mNumMeshes) {

		// use a pseudo hash for all meshes in the scene to quickly find 
		// the ones which are possibly equal. This step is executed early 
		// in the pipeline, so we could, depending on the file format,
		// have several thousand small meshes. That's too much for a brute
		// everyone-against-everyone check involving up to 25 comparisons
		// each.
		boost::scoped_array<uint64_t> hashes (new uint64_t[pScene->mNumMeshes]);
		boost::scoped_array<unsigned int> remapping (new unsigned int[pScene->mNumMeshes]);

		unsigned int numMeshesOut = 0;
		for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {

			aiMesh* inst = pScene->mMeshes[i];
			hashes[i] = GetMeshHash(inst);

			for (int a = i-1; a > 0; --a) {
				if (hashes[i] == hashes[a])
				{
					aiMesh* orig = pScene->mMeshes[a];
					if (!orig)
						continue;
					
					// check for hash collision .. we needn't check
					// the vertex format, it *must* match due to the
					// (brilliant) construction of the hash
					if (orig->mNumBones       != inst->mNumBones      ||
						orig->mNumFaces       != inst->mNumFaces      ||
						orig->mNumVertices    != inst->mNumVertices   ||
						orig->mMaterialIndex  != inst->mMaterialIndex ||
						orig->mPrimitiveTypes != inst->mPrimitiveTypes)
						continue;

					// up to now the meshes are equal. find an appropriate
					// epsilon to compare position differences against
					float epsilon = ComputePositionEpsilon(inst);
					epsilon *= epsilon;

					// now compare vertex positions, normals,
					// tangents and bitangents using this epsilon.
					if (orig->HasPositions()) {
						if(!CompareArrays(orig->mVertices,inst->mVertices,orig->mNumVertices,epsilon))
							continue;
					}
					if (orig->HasNormals()) {
						if(!CompareArrays(orig->mNormals,inst->mNormals,orig->mNumVertices,epsilon))
							continue;
					}
					if (orig->HasTangentsAndBitangents()) {
						if (!CompareArrays(orig->mTangents,inst->mTangents,orig->mNumVertices,epsilon) ||
							!CompareArrays(orig->mBitangents,inst->mBitangents,orig->mNumVertices,epsilon))
							continue;
					}

					// use a constant epsilon for colors and UV coordinates
					static const float uvEpsilon = 10e-4f;

					BOOST_STATIC_ASSERT(4 == AI_MAX_NUMBER_OF_COLOR_SETS);

					// as in JIV: manually unrolled as continue wouldn't work as desired in inner loops
					if (orig->mTextureCoords[0]) {
						if(!CompareArrays(orig->mTextureCoords[0],inst->mTextureCoords[0],orig->mNumVertices,uvEpsilon))
							continue;
						if (orig->mTextureCoords[1]) {
							if(!CompareArrays(orig->mTextureCoords[1],inst->mTextureCoords[1],orig->mNumVertices,uvEpsilon))
								continue;
							if (orig->mTextureCoords[2]) {
								if(!CompareArrays(orig->mTextureCoords[2],inst->mTextureCoords[2],orig->mNumVertices,uvEpsilon))
									continue;
								if (orig->mTextureCoords[3]) {
									if(!CompareArrays(orig->mTextureCoords[3],inst->mTextureCoords[3],orig->mNumVertices,uvEpsilon))
										continue;
								}
							}
						}
					}

					BOOST_STATIC_ASSERT(4 == AI_MAX_NUMBER_OF_COLOR_SETS);

					// and the same nasty stuff for vertex colors ...
					if (orig->mColors[0]) {
						if(!CompareArrays(orig->mColors[0],inst->mColors[0],orig->mNumVertices,uvEpsilon))
							continue;
						if (orig->mTextureCoords[1]) {
							if(!CompareArrays(orig->mColors[1],inst->mColors[1],orig->mNumVertices,uvEpsilon))
								continue;
							if (orig->mTextureCoords[2]) {
								if(!CompareArrays(orig->mColors[2],inst->mColors[2],orig->mNumVertices,uvEpsilon))
									continue;
								if (orig->mTextureCoords[3]) {
									if(!CompareArrays(orig->mColors[3],inst->mColors[3],orig->mNumVertices,uvEpsilon))
										continue;
								}
							}
						}
					}

					// It seems to be strange, but we really need to check whether the
					// bones are identical too. Although it's extremely unprobable
					// that they're not if control reaches here, but we need to deal
					// with unprobable cases, too.
					if (!CompareBones(orig,inst))
						continue;

					// FIXME: Ignore the faces for the moment ... ok!?
				
					// We're still here. Or in other words: 'inst' is an instance of 'orig'.
					// Place a marker in our list that we can easily update mesh indices.
					remapping[i] = a;

					// Delete the instanced mesh, we don't need it anymore
					delete inst;
					pScene->mMeshes[i] = NULL;
				}
			}

			// If we didn't find a match for the current mesh: keep it
			if (pScene->mMeshes[i]) {
				remapping[i] = numMeshesOut++;
			}
		}
		ai_assert(0 != numMeshesOut);
		if (numMeshesOut != pScene->mNumMeshes) {

			// Collapse the meshes array by removing all NULL entries
			for (unsigned int real = 0, i = 0; real < numMeshesOut; ++i) {
				if (pScene->mMeshes[i])
					pScene->mMeshes[real++] = pScene->mMeshes[i];
			}

			// And update the nodegraph with our nice lookup table
			UpdateMeshIndices(pScene->mRootNode,remapping.get());

			// write to log
			if (!DefaultLogger::isNullLogger()) {
			
				char buffer[512];
				::sprintf(buffer,"FindInstancesProcess finished. Found %i instances",pScene->mNumMeshes-numMeshesOut);
				DefaultLogger::get()->info(buffer); 
			}
			pScene->mNumMeshes = numMeshesOut;
		}
		else DefaultLogger::get()->debug("FindInstancesProcess finished. No instanced meshes found"); 
	}
}