assimp.assimp/code/TriangulateProcess.cpp

/*
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Open Asset Import Library (ASSIMP)
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*/

/** @file Implementation of the post processing step to split up
 * all faces with more than three indices into triangles.
 */

#include "AssimpPCH.h"
#include "TriangulateProcess.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
TriangulateProcess::TriangulateProcess()
{
	// nothing to do here
}

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

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

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

	bool bHas = false;
	for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
	{
		if(	TriangulateMesh( pScene->mMeshes[a]))
			bHas = true;
	}
	if (bHas)DefaultLogger::get()->info ("TriangulateProcess finished. All polygons have been triangulated");
	else     DefaultLogger::get()->debug("TriangulateProcess finished. There was nothing to do.");
}

// ------------------------------------------------------------------------------------------------
// Triangulates the given mesh.
bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
{
	// check whether we will need to do something ...
	// FIX: now we have aiMesh::mPrimitiveTypes, so this is only here for test cases
	if (!pMesh->mPrimitiveTypes)
	{
		bool bNeed = false;
		for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
		{
			const aiFace& face = pMesh->mFaces[a];
			if( face.mNumIndices != 3)
			{
				bNeed = true;
			}
		}
		if (!bNeed)return false;
	}
	else if (!(pMesh->mPrimitiveTypes & aiPrimitiveType_POLYGON))
		return false;

	// the output mesh will contain triangles, but no polys anymore
	pMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
	pMesh->mPrimitiveTypes &= ~aiPrimitiveType_POLYGON;

	// Find out how many output faces we'll have
	unsigned int numOut = 0;
	for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
	{
		aiFace& face = pMesh->mFaces[a];
		if( face.mNumIndices <= 3)
			numOut++;

		else numOut += face.mNumIndices-2;
	}

	// Just another check whether aiMesh::mPrimitiveTypes is correct
	assert(numOut != pMesh->mNumFaces);
	
	aiFace* out = new aiFace[numOut], *curOut = out;
	for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
	{
		aiFace& face = pMesh->mFaces[a];

		// if it's a simple primitive, just copy it
		if( face.mNumIndices <= 3)
		{
			aiFace& nface = *curOut++;
			nface.mNumIndices = face.mNumIndices;
			nface.mIndices    = face.mIndices;
		} 
		else
		{
			for( unsigned int b = 0, end = face.mNumIndices - 2; b < end; b++)
			{
				aiFace& nface = *curOut++;
				nface.mNumIndices = 3;
				
				// Reuse the buffer for the very last element to save another allocation
				if (b == end-1)
					nface.mIndices = face.mIndices;
				else
				{
					nface.mIndices = new unsigned int[3];
					nface.mIndices[0] = face.mIndices[0];
				}

				nface.mIndices[1] = face.mIndices[b+1];
				nface.mIndices[2] = face.mIndices[b+2];
			}
		}
		face.mIndices = NULL;
	}

	// kill the old faces
	delete [] pMesh->mFaces;

	// ... and store the new ones
	pMesh->mFaces    = out;
	pMesh->mNumFaces = numOut;
	return true;
}