MeshAlgo::deleteFaces : Fix crease handling

Author: danieldresser-ie

src/IECoreScene/MeshAlgoDeleteFaces.cpp

@@ -111,25 +111,35 @@ void deleteCreases( MeshPrimitive *out, const MeshPrimitive *in, const std::vect
 			Canceller::check( canceller );
 		}
 
-		int outLength = 0;
-		for( int j = 0; j < lengths[i]; ++j )
+		int j = 0;
+		while( j < lengths[i] )
 		{
-			int id = remapping[ ids[creaseIdOffset + j] ];
-			if( id != -1 )
+			// Skip non included verts
+			while( j < lengths[i] && remapping[ ids[ creaseIdOffset + j ] ] == -1 )
 			{
-				// \todo: This is not strictly correct. We might be adding creases
-				// for edges that no longer exist (ie when a particular creased face
-				// was deleted, but all of its original vertices remain).
-				outIds.push_back( id );
-				++outLength;
+				j++;
 			}
+			int startCrease = j;
 
-		}
+			// Scan until we reach the end, or a vert that isn't included.
+			// If there in a non-included vert in the middle of a crease of length 5 or more,
+			// we may need to output more than one crease per input crease.
+			while( j < lengths[i] && remapping[ ids[ creaseIdOffset + j ] ] != -1 )
+			{
+				j++;
+			}
 
-		if( outLength > 0 )
-		{
-			outLengths.push_back( outLength );
-			outSharpnesses.push_back( sharpnesses[i] );
+			// We've either reached the end, or a non-included vert - output a crease
+			if( j - startCrease >= 2 )
+			{
+				for( int k = startCrease; k < j; k++ )
+				{
+					// \todo - a little wasteful here, should be caching these lookups in the remapping map
+					outIds.push_back( remapping[ ids[ creaseIdOffset + k ] ] );
+				}
+				outLengths.push_back( j - startCrease );
+				outSharpnesses.push_back( sharpnesses[i] );
+			}
 		}
 
 		creaseIdOffset += lengths[i];

test/IECoreScene/MeshAlgoDeleteFacesTest.py

@@ -328,6 +328,10 @@ def testCornersAndCreases( self ) :
 		cornerIds = [ 1, 2 ]
 		cornerSharpnesses = [ 1.0, 2.0 ]
 		mesh.setCorners( IECore.IntVectorData( cornerIds ), IECore.FloatVectorData( cornerSharpnesses ) )
+
+		# First test - the first 3 vertex crease include two edges through vertex 1, which is not
+		# used in the second triangle, and is getting deleted.  This whole crease will be deleted, since
+		# neither edge is in the final mesh
 		creaseLengths = [ 3, 2 ]
 		creaseIds = [ 0, 1, 2, 2, 3 ]  # note that these are vertex ids
 		creaseSharpnesses = [ 1.0, 2.0 ]
@@ -345,10 +349,35 @@ def testCornersAndCreases( self ) :
 
 		self.assertEqual( facesDeletedMesh.cornerIds(), IECore.IntVectorData( [ 1 ] ) )
 		self.assertEqual( facesDeletedMesh.cornerSharpnesses(), IECore.FloatVectorData( [ 2.0 ] ) )
+		self.assertEqual( facesDeletedMesh.creaseLengths(), IECore.IntVectorData( [ 2 ] ) )
+		self.assertEqual( facesDeletedMesh.creaseIds(), IECore.IntVectorData( [ 1, 2 ] ) )
+		self.assertEqual( facesDeletedMesh.creaseSharpnesses(), IECore.FloatVectorData( [ 2.0 ] ) )
+
+		# Second test - the first crease includes two edges, one is deleted, the other is left
+		creaseLengths = [ 3, 2 ]
+		creaseIds = [ 0, 2, 1, 2, 3 ]  # note that these are vertex ids
+		creaseSharpnesses = [ 1.0, 2.0 ]
+		mesh.setCreases( IECore.IntVectorData( creaseLengths ), IECore.IntVectorData( creaseIds ), IECore.FloatVectorData( creaseSharpnesses ) )
+
+		facesDeletedMesh = IECoreScene.MeshAlgo.deleteFaces( mesh, mesh["delete"] )
+
 		self.assertEqual( facesDeletedMesh.creaseLengths(), IECore.IntVectorData( [ 2, 2 ] ) )
 		self.assertEqual( facesDeletedMesh.creaseIds(), IECore.IntVectorData( [ 0, 1, 1, 2 ] ) )
 		self.assertEqual( facesDeletedMesh.creaseSharpnesses(), IECore.FloatVectorData( [ 1.0, 2.0 ] ) )
 
+		#Third test - one long crease of 4 edges, where the middle vertex is removed, resulting in two 1
+		# edge creases
+		creaseLengths = [ 5 ]
+		creaseIds = [ 3, 0, 1, 2, 3 ]  # note that these are vertex ids
+		creaseSharpnesses = [ 3.0 ]
+		mesh.setCreases( IECore.IntVectorData( creaseLengths ), IECore.IntVectorData( creaseIds ), IECore.FloatVectorData( creaseSharpnesses ) )
+
+		facesDeletedMesh = IECoreScene.MeshAlgo.deleteFaces( mesh, mesh["delete"] )
+
+		self.assertEqual( facesDeletedMesh.creaseLengths(), IECore.IntVectorData( [ 2, 2 ] ) )
+		self.assertEqual( facesDeletedMesh.creaseIds(), IECore.IntVectorData( [ 2, 0, 1, 2 ] ) )
+		self.assertEqual( facesDeletedMesh.creaseSharpnesses(), IECore.FloatVectorData( [ 3.0, 3.0 ] ) )
+
 	def testBadPrimitiveVariables( self ):
 
 		planeMesh = IECoreScene.MeshPrimitive.createPlane( imath.Box2f( imath.V2f( 0 ), imath.V2f( 2 ) ), imath.V2i( 1, 1 ) )