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/** @file Implementation of the post processing step to join identical vertices
 * for all imported meshes
 */

#include "AssimpPCH.h"
#ifndef ASSIMP_BUILD_NO_JOINVERTICES_PROCESS

#include "JoinVerticesProcess.h"
#include "ProcessHelper.h"
#include "Vertex.h"
#include "TinyFormatter.h"

using namespace Assimp;
// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
JoinVerticesProcess::JoinVerticesProcess()
{
	// nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
JoinVerticesProcess::~JoinVerticesProcess()
{
	// nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool JoinVerticesProcess::IsActive( unsigned int pFlags) const
{
	return (pFlags & aiProcess_JoinIdenticalVertices) != 0;
}
// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void JoinVerticesProcess::Execute( aiScene* pScene)
{
	DefaultLogger::get()->debug("JoinVerticesProcess begin");

	// get the total number of vertices BEFORE the step is executed
	int iNumOldVertices = 0;
	if (!DefaultLogger::isNullLogger()) {
		for( unsigned int a = 0; a < pScene->mNumMeshes; a++)	{
			iNumOldVertices +=	pScene->mMeshes[a]->mNumVertices;
		}
	}

	// execute the step
	int iNumVertices = 0;
	for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
		iNumVertices +=	ProcessMesh( pScene->mMeshes[a],a);

	// if logging is active, print detailed statistics
	if (!DefaultLogger::isNullLogger())
	{
		if (iNumOldVertices == iNumVertices)
		{
			DefaultLogger::get()->debug("JoinVerticesProcess finished ");
		} else
		{
			char szBuff[128]; // should be sufficiently large in every case
			sprintf(szBuff,"JoinVerticesProcess finished | Verts in: %i out: %i | ~%.1f%%",
				iNumOldVertices,
				iNumVertices,
				((iNumOldVertices - iNumVertices) / (float)iNumOldVertices) * 100.f);
			DefaultLogger::get()->info(szBuff);
		}
	}

	pScene->mFlags |= AI_SCENE_FLAGS_NON_VERBOSE_FORMAT;
}

// ------------------------------------------------------------------------------------------------
// Unites identical vertices in the given mesh
int JoinVerticesProcess::ProcessMesh( aiMesh* pMesh, unsigned int meshIndex)
{
	BOOST_STATIC_ASSERT( AI_MAX_NUMBER_OF_COLOR_SETS    == 8);
	BOOST_STATIC_ASSERT( AI_MAX_NUMBER_OF_TEXTURECOORDS == 8);

	// Return early if we don't have any positions
	if (!pMesh->HasPositions() || !pMesh->HasFaces()) {
		return 0;
	}

	// We'll never have more vertices afterwards.
	std::vector<Vertex> uniqueVertices;
	uniqueVertices.reserve( pMesh->mNumVertices);

	// For each vertex the index of the vertex it was replaced by.
	// Since the maximal number of vertices is 2^31-1, the most significand bit can be used to mark
	//	whether a new vertex was created for the index (true) or if it was replaced by an existing
	//	unique vertex (false). This saves an additional std::vector<bool> and greatly enhances
	//	branching performance.
	BOOST_STATIC_ASSERT(AI_MAX_VERTICES == 0x7fffffff);
	std::vector<unsigned int> replaceIndex( pMesh->mNumVertices, 0xffffffff);

	// A little helper to find locally close vertices faster.
	// Try to reuse the lookup table from the last step.
	const static float epsilon = 1e-5f;
	// float posEpsilonSqr;
	SpatialSort* vertexFinder = NULL;
	SpatialSort _vertexFinder;

	typedef std::pair<SpatialSort,float> SpatPair;
	if (shared)	{
		std::vector<SpatPair >* avf;
		shared->GetProperty(AI_SPP_SPATIAL_SORT,avf);
		if (avf)	{
			SpatPair& blubb = (*avf)[meshIndex];
			vertexFinder  = &blubb.first;
			// posEpsilonSqr = blubb.second;
		}
	}
	if (!vertexFinder)	{
		// bad, need to compute it.
		_vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof( aiVector3D));
		vertexFinder = &_vertexFinder; 
		// posEpsilonSqr = ComputePositionEpsilon(pMesh);
	}

	// Squared because we check against squared length of the vector difference
	static const float squareEpsilon = epsilon * epsilon;

	// Again, better waste some bytes than a realloc ...
	std::vector<unsigned int> verticesFound;
	verticesFound.reserve(10);

	// Run an optimized code path if we don't have multiple UVs or vertex colors.
	// This should yield false in more than 99% of all imports ...
	const bool complex = ( pMesh->GetNumColorChannels() > 0 || pMesh->GetNumUVChannels() > 1);

	// Now check each vertex if it brings something new to the table
	for( unsigned int a = 0; a < pMesh->mNumVertices; a++)	{
		// collect the vertex data
		Vertex v(pMesh,a);

		// collect all vertices that are close enough to the given position
		vertexFinder->FindIdenticalPositions( v.position, verticesFound);
		unsigned int matchIndex = 0xffffffff;

		// check all unique vertices close to the position if this vertex is already present among them
		for( unsigned int b = 0; b < verticesFound.size(); b++)	{

			const unsigned int vidx = verticesFound[b];
			const unsigned int uidx = replaceIndex[ vidx];
			if( uidx & 0x80000000)
				continue;

			const Vertex& uv = uniqueVertices[ uidx];
			// Position mismatch is impossible - the vertex finder already discarded all non-matching positions

			// We just test the other attributes even if they're not present in the mesh.
			// In this case they're initialized to 0 so the comparision succeeds. 
			// By this method the non-present attributes are effectively ignored in the comparision.
			if( (uv.normal - v.normal).SquareLength() > squareEpsilon)
				continue;
			if( (uv.texcoords[0] - v.texcoords[0]).SquareLength() > squareEpsilon)
				continue;
			if( (uv.tangent - v.tangent).SquareLength() > squareEpsilon)
				continue;
			if( (uv.bitangent - v.bitangent).SquareLength() > squareEpsilon)
				continue;

			// Usually we won't have vertex colors or multiple UVs, so we can skip from here
			// Actually this increases runtime performance slightly, at least if branch
			// prediction is on our side.
			if (complex){
				// manually unrolled because continue wouldn't work as desired in an inner loop, 
				// also because some compilers seem to fail the task. Colors and UV coords
				// are interleaved since the higher entries are most likely to be
				// zero and thus useless. By interleaving the arrays, vertices are,
				// on average, rejected earlier.

				if( (uv.texcoords[1] - v.texcoords[1]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[0], v.colors[0]) > squareEpsilon)
					continue;

				if( (uv.texcoords[2] - v.texcoords[2]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[1], v.colors[1]) > squareEpsilon)
					continue;

				if( (uv.texcoords[3] - v.texcoords[3]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[2], v.colors[2]) > squareEpsilon)
					continue;

				if( (uv.texcoords[4] - v.texcoords[4]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[3], v.colors[3]) > squareEpsilon)
					continue;

				if( (uv.texcoords[5] - v.texcoords[5]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[4], v.colors[4]) > squareEpsilon)
					continue;

				if( (uv.texcoords[6] - v.texcoords[6]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[5], v.colors[5]) > squareEpsilon)
					continue;

				if( (uv.texcoords[7] - v.texcoords[7]).SquareLength() > squareEpsilon)
					continue;
				if( GetColorDifference( uv.colors[6], v.colors[6]) > squareEpsilon)
					continue;
				
				if( GetColorDifference( uv.colors[7], v.colors[7]) > squareEpsilon)
					continue;
			}

			// we're still here -> this vertex perfectly matches our given vertex
			matchIndex = uidx;
			break;
		}

		// found a replacement vertex among the uniques?
		if( matchIndex != 0xffffffff)
		{
			// store where to found the matching unique vertex
			replaceIndex[a] = matchIndex | 0x80000000;
		}
		else
		{
			// no unique vertex matches it upto now -> so add it
			replaceIndex[a] = (unsigned int)uniqueVertices.size();
			uniqueVertices.push_back( v);
		}
	}

	if (!DefaultLogger::isNullLogger() && DefaultLogger::get()->getLogSeverity() == Logger::VERBOSE)	{
		DefaultLogger::get()->debug((Formatter::format(),
			"Mesh ",meshIndex,
			" (",
			(pMesh->mName.length ? pMesh->mName.data : "unnamed"),
			") | Verts in: ",pMesh->mNumVertices,
			" out: ",
			uniqueVertices.size(),
			" | ~",
			((pMesh->mNumVertices - uniqueVertices.size()) / (float)pMesh->mNumVertices) * 100.f,
			"%"
		));
	}

	// replace vertex data with the unique data sets
	pMesh->mNumVertices = (unsigned int)uniqueVertices.size();

	// ----------------------------------------------------------------------------
	// NOTE - we're *not* calling Vertex::SortBack() because it would check for 
	// presence of every single vertex component once PER VERTEX. And our CPU 
	// dislikes branches, even if they're easily predictable.
	// ----------------------------------------------------------------------------

	// Position
	delete [] pMesh->mVertices;
	pMesh->mVertices = new aiVector3D[pMesh->mNumVertices];
	for( unsigned int a = 0; a < pMesh->mNumVertices; a++)
		pMesh->mVertices[a] = uniqueVertices[a].position;

	// Normals, if present
	if( pMesh->mNormals)
	{
		delete [] pMesh->mNormals;
		pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
		for( unsigned int a = 0; a < pMesh->mNumVertices; a++) {
			pMesh->mNormals[a] = uniqueVertices[a].normal;
		}
	}
	// Tangents, if present
	if( pMesh->mTangents)
	{
		delete [] pMesh->mTangents;
		pMesh->mTangents = new aiVector3D[pMesh->mNumVertices];
		for( unsigned int a = 0; a < pMesh->mNumVertices; a++) {
			pMesh->mTangents[a] = uniqueVertices[a].tangent;
		}
	}
	// Bitangents as well
	if( pMesh->mBitangents)
	{
		delete [] pMesh->mBitangents;
		pMesh->mBitangents = new aiVector3D[pMesh->mNumVertices];
		for( unsigned int a = 0; a < pMesh->mNumVertices; a++) {
			pMesh->mBitangents[a] = uniqueVertices[a].bitangent;
		}
	}
	// Vertex colors
	for( unsigned int a = 0; pMesh->HasVertexColors(a); a++)
	{
		delete [] pMesh->mColors[a];
		pMesh->mColors[a] = new aiColor4D[pMesh->mNumVertices];
		for( unsigned int b = 0; b < pMesh->mNumVertices; b++) {
			pMesh->mColors[a][b] = uniqueVertices[b].colors[a];
		}
	}
	// Texture coords
	for( unsigned int a = 0; pMesh->HasTextureCoords(a); a++)
	{
		delete [] pMesh->mTextureCoords[a];
		pMesh->mTextureCoords[a] = new aiVector3D[pMesh->mNumVertices];
		for( unsigned int b = 0; b < pMesh->mNumVertices; b++) {
			pMesh->mTextureCoords[a][b] = uniqueVertices[b].texcoords[a];
		}
	}

	// adjust the indices in all faces
	for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
	{
		aiFace& face = pMesh->mFaces[a];
		for( unsigned int b = 0; b < face.mNumIndices; b++)	{
			face.mIndices[b] = replaceIndex[face.mIndices[b]] & ~0x80000000;
		}
	}

	// adjust bone vertex weights.
	for( int a = 0; a < (int)pMesh->mNumBones; a++)
	{
		aiBone* bone = pMesh->mBones[a];
		std::vector<aiVertexWeight> newWeights;
		newWeights.reserve( bone->mNumWeights);

		for( unsigned int b = 0; b < bone->mNumWeights; b++)
		{
			const aiVertexWeight& ow = bone->mWeights[b];
			// if the vertex is a unique one, translate it
			if( !(replaceIndex[ow.mVertexId] & 0x80000000))
			{
				aiVertexWeight nw;
				nw.mVertexId = replaceIndex[ow.mVertexId];
				nw.mWeight = ow.mWeight;
				newWeights.push_back( nw);
			}
		}

		if (newWeights.size() > 0) {
			// kill the old and replace them with the translated weights
			delete [] bone->mWeights;
			bone->mNumWeights = (unsigned int)newWeights.size();

			bone->mWeights = new aiVertexWeight[bone->mNumWeights];
			memcpy( bone->mWeights, &newWeights[0], bone->mNumWeights * sizeof( aiVertexWeight));
		}
		else {
		
			/*  NOTE:
			 *
			 *  In the algorithm above we're assuming that there are no vertices
			 *  with a different bone weight setup at the same position. That wouldn't
			 *  make sense, but it is not absolutely impossible. SkeletonMeshBuilder
			 *  for example generates such input data if two skeleton points
			 *  share the same position. Again this doesn't make sense but is
			 *  reality for some model formats (MD5 for example uses these special
			 *  nodes as attachment tags for its weapons). 
			 *
			 *  Then it is possible that a bone has no weights anymore .... as a quick
			 *  workaround, we're just removing these bones. If they're animated,
			 *  model geometry might be modified but at least there's no risk of a crash.
			 */
			delete bone;
			--pMesh->mNumBones;
			for (unsigned int n = a; n < pMesh->mNumBones; ++n)  {
				pMesh->mBones[n] = pMesh->mBones[n+1];
			}

			--a; 
			DefaultLogger::get()->warn("Removing bone -> no weights remaining");
		}
	}
	return pMesh->mNumVertices;
}

#endif // !! ASSIMP_BUILD_NO_JOINVERTICES_PROCESS
