Merge pull request ImageEngine#1260 from johnhaddon/usdDoubleSided

USDScene : Support `doubleSided` attribute

contrib/IECoreUSD/src/IECoreUSD/USDScene.cpp

@@ -56,6 +56,7 @@ IECORE_PUSH_DEFAULT_VISIBILITY
 #include "pxr/usd/usd/stage.h"
 #include "pxr/usd/usdGeom/bboxCache.h"
 #include "pxr/usd/usdGeom/camera.h"
+#include "pxr/usd/usdGeom/gprim.h"
 #include "pxr/usd/usdGeom/metrics.h"
 #include "pxr/usd/usdGeom/pointInstancer.h"
 #include "pxr/usd/usdGeom/primvar.h"
@@ -803,6 +804,7 @@ namespace
 
 const IECore::InternedString g_purposeAttributeName( "usd:purpose" );
 const IECore::InternedString g_kindAttributeName( "usd:kind" );
+const IECore::InternedString g_doubleSidedAttributeName( "doubleSided" );
 
 } // namespace
 
@@ -828,6 +830,10 @@ bool USDScene::hasAttribute( const SceneInterface::Name &name ) const
 		pxr::TfToken kind;
 		return model.GetKind( &kind );
 	}
+	else if( name == g_doubleSidedAttributeName )
+	{
+		return pxr::UsdGeomGprim( m_location->prim ).GetDoubleSidedAttr().HasAuthoredValue();
+	}
 	else if( auto attribute = AttributeAlgo::findUSDAttribute( m_location->prim, name.string() ) )
 	{
 		return attribute.HasAuthoredValue();
@@ -876,6 +882,11 @@ void USDScene::attributeNames( SceneInterface::NameList &attrs ) const
 		attrs.push_back( g_kindAttributeName );
 	}
 
+	if( pxr::UsdGeomGprim( m_location->prim ).GetDoubleSidedAttr().HasAuthoredValue() )
+	{
+		attrs.push_back( g_doubleSidedAttributeName );
+	}
+
 	std::vector<pxr::UsdAttribute> attributes = m_location->prim.GetAuthoredAttributes();
 	for( const auto &attribute : attributes )
 	{
@@ -961,6 +972,16 @@ ConstObjectPtr USDScene::readAttribute( const SceneInterface::Name &name, double
 		}
 		return new StringData( kind.GetString() );
 	}
+	else if( name == g_doubleSidedAttributeName )
+	{
+		pxr::UsdAttribute attr = pxr::UsdGeomGprim( m_location->prim ).GetDoubleSidedAttr();
+		bool doubleSided;
+		if( attr.HasAuthoredValue() && attr.Get( &doubleSided, m_root->getTime( time ) ) )
+		{
+			return new BoolData( doubleSided );
+		}
+		return nullptr;
+	}
 	else if( pxr::UsdAttribute attribute = AttributeAlgo::findUSDAttribute( m_location->prim, name.string() ) )
 	{
 		return DataAlgo::fromUSD( attribute, m_root->getTime( time ) );
@@ -1022,6 +1043,28 @@ void USDScene::writeAttribute( const SceneInterface::Name &name, const Object *a
 			}
 		}
 	}
+	else if( name == g_doubleSidedAttributeName )
+	{
+		if( auto *data = reportedCast<const BoolData>( attribute, "USDScene::writeAttribute", name.c_str() ) )
+		{
+			pxr::UsdGeomGprim gprim( m_location->prim );
+			if( gprim )
+			{
+				gprim.GetDoubleSidedAttr().Set( data->readable(), m_root->getTime( time ) );
+			}
+			else
+			{
+				// We're hamstrung by the fact that USD considers `doubleSided` to be a property
+				// of a Gprim and not an inheritable attribute as it was in RenderMan and is in Cortex.
+				// We can't author a Gprim here, because it isn't a concrete type, so we must rely on
+				// `writeObject()` having been called first to get a suitable concrete type in place.
+				IECore::msg(
+					IECore::Msg::Warning, "USDScene::writeAttribute",
+					boost::format( "Unable to write attribute \"%1%\" to \"%2%\", because it is not a Gprim" ) % name % m_location->prim.GetPath()
+				);
+			}
+		}
+	}
 	else if( const IECoreScene::ShaderNetwork *shaderNetwork = runTimeCast<const ShaderNetwork>( attribute ) )
 	{
 		m_shaders[name] = shaderNetwork;
@@ -1356,6 +1399,13 @@ void USDScene::attributesHash( double time, IECore::MurmurHash &h ) const
 		// Kind can not be animated so no need to update `mightBeTimeVarying`.
 	}
 
+	auto doubleSidedAttr = pxr::UsdGeomGprim( m_location->prim ).GetDoubleSidedAttr();
+	if( doubleSidedAttr && doubleSidedAttr.HasAuthoredValue() )
+	{
+		haveAttributes = true;
+		mightBeTimeVarying |= doubleSidedAttr.ValueMightBeTimeVarying();
+	}
+
 	std::vector<pxr::UsdAttribute> attributes = m_location->prim.GetAuthoredAttributes();
 	for( const auto &attribute : attributes )
 	{

contrib/IECoreUSD/test/IECoreUSD/USDSceneTest.py

@@ -2967,5 +2967,85 @@ def testExposedShaderInput( self ) :
 		self.assertEqual( network.getOutput(), "surface" )
 		self.assertEqual( network.getShader( "surface" ).parameters["diffuse_roughness"].value, 0.75 )
 
+	def testReadDoubleSidedAttribute( self ) :
+
+		root = IECoreScene.SceneInterface.create(
+			os.path.join( os.path.dirname( __file__ ), "data", "doubleSidedAttribute.usda" ),
+			IECore.IndexedIO.OpenMode.Read
+		)
+
+		for name, doubleSided in {
+			"sphere" : None,
+			"singleSidedSphere" : False,
+			"doubleSidedSphere" : True
+		}.items() :
+			object = root.child( name )
+			if doubleSided is None :
+				self.assertFalse( object.hasAttribute( "doubleSided" ) )
+				self.assertNotIn( "doubleSided", object.attributeNames() )
+			else :
+				self.assertTrue( object.hasAttribute( "doubleSided" ) )
+				self.assertIn( "doubleSided", object.attributeNames() )
+				self.assertEqual( object.readAttribute( "doubleSided", 1 ), IECore.BoolData( doubleSided ) )
+
+	def testWriteDoubleSidedAttribute( self ) :
+
+		# Write via SceneInterface
+
+		fileName = os.path.join( self.temporaryDirectory(), "doubleSidedAttribute.usda" )
+		root = IECoreScene.SceneInterface.create( fileName, IECore.IndexedIO.OpenMode.Write )
+
+		toWrite = (
+			( "singleSidedSphere", "before", False ),
+			( "doubleSidedSphere", "before", True ),
+			( "doubleSidedSphereWrittenAfter", "after", True ),
+			( "doubleSidedNoObject", "never", True ),
+			( "sphere", "before", None ),
+		)
+
+		for name, writeObject, doubleSided in toWrite :
+
+			child = root.createChild( name )
+			if writeObject == "before" :
+				child.writeObject( IECoreScene.SpherePrimitive(), 1 )
+
+			if doubleSided is not None :
+
+				with IECore.CapturingMessageHandler() as mh :
+					child.writeAttribute( "doubleSided", IECore.BoolData( doubleSided ), 1 )
+
+				if writeObject != "before" :
+					self.assertEqual( len( mh.messages ), 1 )
+					self.assertEqual(
+						mh.messages[0].message,
+						'Unable to write attribute "doubleSided" to "/{}", because it is not a Gprim'.format(
+							name
+						)
+					)
+
+			if writeObject == "after" :
+				child.writeObject( IECoreScene.SpherePrimitive(), 1 )
+
+		del root, child
+
+		# Verify via USD API
+
+		stage = pxr.Usd.Stage.Open( fileName )
+
+		for name, writeObject, doubleSided in toWrite :
+
+			if writeObject != "before" :
+				doubleSided = None
+
+			if doubleSided is None :
+				self.assertFalse(
+					pxr.UsdGeom.Gprim( stage.GetPrimAtPath( "/" + name ) ).GetDoubleSidedAttr().HasAuthoredValue(),
+				)
+			else :
+				self.assertEqual(
+					pxr.UsdGeom.Gprim( stage.GetPrimAtPath( "/" + name ) ).GetDoubleSidedAttr().Get( 1 ),
+					doubleSided
+				)
+
 if __name__ == "__main__":
 	unittest.main()

contrib/IECoreUSD/test/IECoreUSD/data/doubleSidedAttribute.usda

@@ -0,0 +1,16 @@
+#usda 1.0
+
+def Sphere "doubleSidedSphere"
+{
+    uniform bool doubleSided = 1
+}
+
+def Sphere "singleSidedSphere"
+{
+    uniform bool doubleSided = 0
+}
+
+def Sphere "sphere"
+{
+}
+