Method mesh

src/IECoreScene/MeshAlgoSplit.cpp:816–967

MeshPrimitivePtr IECoreScene::MeshAlgo::MeshSplitter::mesh( int segmentId, const IECore::Canceller *canceller ) const
{
	if( segmentId < 0 || segmentId > (int)m_meshIndices.size() )
	{
		throw IECore::Exception( "Invalid segment id " + std::to_string( segmentId ) );
	}

	// Based on our index, and the index of the next mesh in m_meshIndices, we know how many faces to output
	const int startIndex = m_meshIndices[ segmentId ];
	const int endIndex = ( segmentId + 1 < (int)m_meshIndices.size() ) ? m_meshIndices[ segmentId + 1 ] : m_faceRemap.size();
	const int numFaces = endIndex - startIndex;

	IntVectorDataPtr verticesPerFaceData = new IntVectorData();
	std::vector<int> &verticesPerFace = verticesPerFaceData->writable();
	verticesPerFace.reserve( numFaces );
	int totalFaceVerts = 0;
	const std::vector<int> &sourceVertexIds = m_mesh->vertexIds()->readable();
	const std::vector<int> &sourceVerticesPerFace = m_mesh->verticesPerFace()->readable();

	Canceller::check( canceller );
	// Outputting the verticesPerFace is straightforward - just read the source mesh's verticesPerFace
	// through m_faceRemap
	for( int i = startIndex; i < endIndex; i++ )
	{
		int originalFaceIndex = m_faceRemap[i];
		int faceVerts = sourceVerticesPerFace[ originalFaceIndex ];
		verticesPerFace.push_back( faceVerts );
		totalFaceVerts += faceVerts;
	}

	// For the vertexIds, we need to iterate through all the original faces that are referenced in m_faceRemap,
	// and we need to use them to build a Reindexer that only references the vertices we are actually using
	Canceller::check( canceller );
	Reindexer vertReindexer( m_mesh->variableSize( PrimitiveVariable::Interpolation::Vertex ), totalFaceVerts );
	for( int i = startIndex; i < endIndex; i++ )
	{
		if( i % 1000 == 0 )
		{
			Canceller::check( canceller );
		}

		int originalFaceIndex = m_faceRemap[i];
		int faceVerts = sourceVerticesPerFace[ originalFaceIndex ];
		int faceStart = m_faceIndices[ originalFaceIndex ];
		for( int j = 0; j < faceVerts; j++ )
		{
			vertReindexer.addIndex( sourceVertexIds[ faceStart + j ] );
		}
	}

	// We need to track which original vertex our vertices came from so we can pull primvar data from them.
	Canceller::check( canceller );
	std::vector<int> vertRemapBackwards;
	vertReindexer.getDataRemapping( vertRemapBackwards );

	MeshPrimitivePtr ret = new MeshPrimitive( verticesPerFaceData, vertReindexer.getNewIndices(), m_mesh->interpolation() );

	// In order to remap the corners, we test every vertex in the original corner list, and see if it is