ToMayaMeshConverter : No longer set normals

Currently, when converting from a Cortex object to a Maya Mesh,
we set the normals anytime the normals are stored in the scc.
Setting the normals explicitly implies these are static values
and so Maya locks them rather than computing them on the fly.

Locked normales are undesirable in many parts of the Pipeline,
especially for deforming geometry as not recomputing them leads
to unexpected results, e.g. wrong tangents or incorrect shader
computations.

This change removes the normal transfer from the scc to the
Maya geometry and instead we rely on Maya to compute them.

Author: chrisc-lee

src/IECoreMaya/ToMayaMeshConverter.cpp

@@ -183,6 +183,10 @@ void ToMayaMeshConverter::addUVSet( MFnMesh &fnMesh, const MIntArray &polygonCou
 
 bool ToMayaMeshConverter::doConversion( IECore::ConstObjectPtr from, MObject &to, IECore::ConstCompoundObjectPtr operands ) const
 {
+	// Note: Normals are not set on the Mesh from the scc as by setting them 
+	// explicitly we are implying they should be locked which is not 
+	// supported, instead we rely on Maya computing the normals everytime
+	
 	MStatus s;
 
 	IECoreScene::ConstMeshPrimitivePtr mesh = IECore::runTimeCast<const IECoreScene::MeshPrimitive>( from );
@@ -263,79 +267,6 @@ bool ToMayaMeshConverter::doConversion( IECore::ConstObjectPtr from, MObject &to
 		return false;
 	}
 
-	it = mesh->variables.find("N");
-	if ( it != mesh->variables.end() )
-	{
-		if (it->second.interpolation == IECoreScene::PrimitiveVariable::FaceVarying )
-		{
-			/// \todo Employ some M*Array converters to simplify this
-			MVectorArray vertexNormalsArray;
-			IECore::ConstV3fVectorDataPtr n = IECore::runTimeCast<const IECore::V3fVectorData>(it->second.data);
-			if (n)
-			{
-				IECoreScene::PrimitiveVariable::IndexedView<Imath::V3f> normalView = IECoreScene::PrimitiveVariable::IndexedView<Imath::V3f>( it->second );
-				vertexNormalsArray.setLength( normalView.size() );
-
-				size_t i = 0;
-				for(const auto& normal : normalView)
-				{
-					vertexNormalsArray[i++] = IECore::convert<MVector, Imath::V3f>( normal );
-				}
-			}
-			else
-			{
-				IECore::ConstV3dVectorDataPtr n = IECore::runTimeCast<const IECore::V3dVectorData>(it->second.data);
-				if (n)
-				{
-					IECoreScene::PrimitiveVariable::IndexedView<Imath::V3d> normalView = IECoreScene::PrimitiveVariable::IndexedView<Imath::V3d>( it->second );
-					vertexNormalsArray.setLength( normalView.size() );
-
-					size_t i = 0;
-					for(const auto& normal : normalView)
-					{
-						vertexNormalsArray[i++] = IECore::convert<MVector, Imath::V3d>( normal );
-					}
-				}
-				else
-				{
-					IECore::msg( IECore::Msg::Warning, "ToMayaMeshConverter::doConversion", boost::format( "PrimitiveVariable \"N\" has unsupported type \"%s\"." ) % it->second.data->typeName() );
-				}
-			}
-
-			if ( vertexNormalsArray.length() )
-			{
-				MStatus status;
-				MItMeshPolygon itPolygon( mObj, &status );
-				if( status != MS::kSuccess )
-				{
-					IECore::msg( IECore::Msg::Warning, "ToMayaMeshConverter::doConversion", "Failed to create mesh iterator" );
-				}
-
-				unsigned v = 0;
-				MIntArray vertexIds;
-				MIntArray faceIds;
-
-				for ( ; !itPolygon.isDone(); itPolygon.next() )
-				{
-					for ( v=0; v < itPolygon.polygonVertexCount(); ++v )
-					{
-						faceIds.append( itPolygon.index() );
-						vertexIds.append( itPolygon.vertexIndex( v ) );
-					}
-				}
-
-				if( !fnMesh.setFaceVertexNormals( vertexNormalsArray, faceIds, vertexIds ) )
-				{
-					IECore::msg( IECore::Msg::Warning, "ToMayaMeshConverter::doConversion", "Setting normals failed" );
-				}
-			}
-		}
-		else
-		{
-			IECore::msg( IECore::Msg::Warning, "ToMayaMeshConverter::doConversion", "PrimitiveVariable \"N\" has unsupported interpolation (expected FaceVarying)." );
-		}
-	}
-
 	/// Add UV sets
 	for ( it = mesh->variables.begin(); it != mesh->variables.end(); ++it )
 	{