USD ShaderAlgo : Resolve NodeGraph interface connections correctly

Changes

@@ -1,7 +1,10 @@
 10.6.x.x (relative to 10.6.3.0)
 ========
 
+Fixes
+-----
 
+- USDScene : Fixed handling of connections involving UsdShadeNodeGraph interface parameters.
 
 10.6.3.0 (relative to 10.6.2.2)
 ========

contrib/IECoreUSD/src/IECoreUSD/ShaderAlgo.cpp

@@ -50,6 +50,7 @@
 #endif
 
 #include "pxr/usd/usdGeom/primvarsAPI.h"
+#include "pxr/usd/usdShade/utils.h"
 
 #include "boost/algorithm/string/predicate.hpp"
 #include "boost/algorithm/string/replace.hpp"
@@ -255,34 +256,40 @@ IECore::InternedString readShaderNetworkWalk( const pxr::SdfPath &anchorPath, co
 	std::vector<IECoreScene::ShaderNetwork::Connection> connections;
 	for( pxr::UsdShadeInput &i : usdShader.GetInputs() )
 	{
-		pxr::UsdShadeConnectableAPI usdSource;
-		pxr::TfToken usdSourceName;
-		pxr::UsdShadeAttributeType usdSourceType;
+		auto sourceAttributes = i.GetValueProducingAttributes();
+		if( sourceAttributes.size() == 0 )
+		{
+			continue;
+		}
+		else if( sourceAttributes.size() > 1 )
+		{
+			IECore::msg(
+				IECore::Msg::Warning, "ShaderAlgo",
+				boost::format( "Input `%1%` has multiple inputs" )
+					% i.GetAttr().GetPath()
+			);
+		}
 
-		pxr::UsdAttribute valueAttribute = i;
-		if( i.GetConnectedSource( &usdSource, &usdSourceName, &usdSourceType ) )
+		const pxr::UsdShadeAttributeType type = pxr::UsdShadeUtils::GetType( sourceAttributes[0].GetName() );
+		if( type == pxr::UsdShadeAttributeType::Output )
 		{
-			if( usdSourceType == pxr::UsdShadeAttributeType::Output )
+			const IECoreScene::ShaderNetwork::Parameter sourceHandle = readShaderNetworkWalk(
+					anchorPath, pxr::UsdShadeOutput( sourceAttributes[0] ), timeCode, shaderNetwork
+			);
+			connections.push_back( {
+				sourceHandle, { handle, fromUSDParameterName( i.GetBaseName() ) }
+			} );
+			if( IECore::DataPtr d = IECoreUSD::DataAlgo::fromUSD( pxr::UsdAttribute( i ), timeCode ) )
 			{
-				const IECoreScene::ShaderNetwork::Parameter sourceHandle = readShaderNetworkWalk(
-					anchorPath, usdSource.GetOutput( usdSourceName ), timeCode, shaderNetwork
-				);
-				connections.push_back( {
-					sourceHandle, { handle, fromUSDParameterName( i.GetBaseName() ) }
-				} );
-			}
-			else
-			{
-				// Connected to an exposed input on the material container. We don't
-				// have an equivalent in IECoreScene::ShaderNetwork yet, so just take
-				// the parameter value from the exposed input.
-				valueAttribute = usdSource.GetInput( usdSourceName );
+				parameters[fromUSDParameterName( i.GetBaseName() )] = d;
 			}
 		}
-
-		if( IECore::DataPtr d = IECoreUSD::DataAlgo::fromUSD( pxr::UsdAttribute( valueAttribute ), timeCode ) )
+		else if( type == pxr::UsdShadeAttributeType::Input )
 		{
-			parameters[fromUSDParameterName( i.GetBaseName() )] = d;
+			if( IECore::DataPtr d = IECoreUSD::DataAlgo::fromUSD( sourceAttributes[0], timeCode ) )
+			{
+				parameters[fromUSDParameterName( i.GetBaseName() )] = d;
+			}
 		}
 	}
 

contrib/IECoreUSD/test/IECoreUSD/USDSceneTest.py

@@ -4733,5 +4733,39 @@ def testAnimatedLight( self ) :
 			self.assertNotEqual( shaderNetworks[frame], shaderNetworks[0] )
 			self.assertEqual( shaderNetworks[frame].outputShader().parameters["exposure"].value, frame / 2.0 )
 
+	def testMaterialSubgraph( self ) :
+
+		scene = IECoreScene.SceneInterface.create( os.path.dirname( __file__ ) + "/data/materialSubgraph.usda", IECore.IndexedIO.OpenMode.Read )
+		sphere = scene.child( "sphere" )
+		shaderNetwork = sphere.readAttribute( "ri:surface", 0.0 )
+
+		# We don't currently have the concept of a subgraph in a ShaderNetwork,
+		# so we only load the leaf nodes, and we "flatten" the connections and
+		# values.
+
+		self.assertEqual( set( shaderNetwork.shaders().keys() ), { "lamaSurface", "pxrVary", "nodeGraph/lamaAdd", "nodeGraph/lamaDiffuse1", "nodeGraph/lamaDiffuse2" } )
+
+		self.assertEqual( shaderNetwork.getOutput(), ( "lamaSurface", "bxdf_out" ) )
+		self.assertEqual( shaderNetwork.shaders()["lamaSurface"].parameters, IECore.CompoundData() )
+		self.assertEqual( shaderNetwork.input( ( "lamaSurface", "materialFront" ) ), ( "nodeGraph/lamaAdd", "bxdf_out" ) )
+
+		self.assertEqual( shaderNetwork.shaders()["nodeGraph/lamaAdd"].parameters, IECore.CompoundData() )
+		self.assertEqual( shaderNetwork.input( ( "nodeGraph/lamaAdd", "material1" ) ), ( "nodeGraph/lamaDiffuse1", "bxdf_out" ) )
+		self.assertEqual( shaderNetwork.input( ( "nodeGraph/lamaAdd", "material2" ) ), ( "nodeGraph/lamaDiffuse2", "bxdf_out" ) )
+
+		self.assertEqual( shaderNetwork.shaders()["nodeGraph/lamaDiffuse1"].parameters, IECore.CompoundData( { "diffuseColor" : imath.Color3f( 2 ) } ) )
+		self.assertEqual( shaderNetwork.inputConnections( "nodeGraph/lamaDiffuse1" ), [] )
+
+		self.assertEqual( shaderNetwork.shaders()["nodeGraph/lamaDiffuse2"].parameters, IECore.CompoundData() )
+		self.assertEqual( shaderNetwork.input( ( "nodeGraph/lamaDiffuse2", "diffuseColor" ) ), ( "pxrVary", "resultRGB" ) )
+
+	def testMaterialTerminalFromSubgraph( self ) :
+
+		scene = IECoreScene.SceneInterface.create( os.path.dirname( __file__ ) + "/data/materialSubgraph.usda", IECore.IndexedIO.OpenMode.Read )
+		sphere = scene.child( "sphere" )
+		shaderNetwork = sphere.readAttribute( "ri:surface", 0.0 )
+
+		self.assertEqual( shaderNetwork.outputShader().name, "LamaSurface" )
+
 if __name__ == "__main__":
 	unittest.main()

contrib/IECoreUSD/test/IECoreUSD/data/materialSubgraph.usda

@@ -0,0 +1,59 @@
+#usda 1.0
+
+def Sphere "sphere" (
+	prepend apiSchemas = ["MaterialBindingAPI"]
+)
+{
+	rel material:binding = </material>
+}
+
+def Material "material"
+{
+	token outputs:ri:surface.connect = </material/lamaSurface.outputs:bxdf_out>
+
+	def Shader "lamaSurface"
+	{
+		uniform token info:id = "LamaSurface"
+		token inputs:materialFront.connect = </material/nodeGraph.outputs:bxdf_out>
+		token outputs:bxdf_out
+	}
+
+	def NodeGraph "nodeGraph"
+	{
+		color3f inputs:diffuseColorA = ( 2, 2, 2 )
+
+		color3f inputs:diffuseColorB = (1, 1, 1)
+		color3f inputs:diffuseColorB.connect = </material/pxrVary.outputs:resultRGB>
+
+		token outputs:bxdf_out.connect = </material/nodeGraph/lamaAdd.outputs:bxdf_out>
+
+		def Shader "lamaAdd"
+		{
+			uniform token info:id = "LamaAdd"
+			token inputs:material1.connect = </material/nodeGraph/lamaDiffuse1.outputs:bxdf_out>
+			token inputs:material2.connect = </material/nodeGraph/lamaDiffuse2.outputs:bxdf_out>
+			token outputs:bxdf_out
+		}
+
+		def Shader "lamaDiffuse1"
+		{
+			uniform token info:id = "LamaDiffuse"
+			color3f inputs:diffuseColor.connect = </material/nodeGraph.inputs:diffuseColorA>
+			token outputs:bxdf_out
+		}
+
+		def Shader "lamaDiffuse2"
+		{
+			uniform token info:id = "LamaDiffuse"
+			color3f inputs:diffuseColor.connect = </material/nodeGraph.inputs:diffuseColorB>
+			token outputs:bxdf_out
+		}
+
+	}
+
+	def Shader "pxrVary"
+	{
+		uniform token info:id = "PxrVary"
+		color3f outputs:resultRGB
+	}
+}

contrib/IECoreUSD/test/IECoreUSD/data/materialTerminalFromSubgraph.usda

@@ -0,0 +1,26 @@
+#usda 1.0
+
+def Sphere "sphere" (
+	prepend apiSchemas = ["MaterialBindingAPI"]
+)
+{
+	rel material:binding = </material>
+}
+
+def Material "material"
+{
+	token outputs:ri:surface.connect = </material/nodeGraph.outputs:bxdf_out>
+
+	def NodeGraph "nodeGraph"
+	{
+
+		token outputs:bxdf_out.connect = </material/nodeGraph/lamaSurface.outputs:bxdf_out>
+
+		def Shader "lamaSurface"
+		{
+			uniform token info:id = "LamaSurface"
+			token outputs:bxdf_out
+		}
+
+	}
+}