IECoreUSD : Load prototype paths inside a PointInstancer as relative

By default, if an instancer named "/inst" contains an internal prototype path like "/inst/Prototypes/proto", that prototype path will now be loaded as "./Prototypes/proto".
You can set the env var GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES=0 to get the old behaviour, where prototype paths were always absolute.
Or can set the env var GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS=1 to get the newest behaviour, where prototype paths are assumed to be relative unless they start with a slash, so the prototype path would be loaded as "Prototypes/proto".

Author: danieldresser-ie

contrib/IECoreUSD/src/IECoreUSD/PointInstancerAlgo.cpp

@@ -53,6 +53,20 @@ using namespace IECoreUSD;
 namespace
 {
 
+bool checkEnvFlag( const char *envVar, bool def )
+{
+	const char *value = getenv( envVar );
+	if( value )
+	{
+		return std::string( value ) != "0";
+	}
+	else
+	{
+		return def;
+	}
+
+}
+
 IECore::ObjectPtr readPointInstancer( pxr::UsdGeomPointInstancer &pointInstancer, pxr::UsdTimeCode time, const Canceller *canceller )
 {
 	pxr::VtVec3fArray pointsData;
@@ -108,16 +122,42 @@ IECore::ObjectPtr readPointInstancer( pxr::UsdGeomPointInstancer &pointInstancer
 
 	// Prototype paths
 
+	const static bool gafferUSDPointInstancersRelativeProtoypes = checkEnvFlag( "GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES", true );
+	const static bool gafferSceneInstancerExplicitAbsolutePaths = checkEnvFlag( "GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS", false );
+
 	pxr::SdfPathVector targets;
 	Canceller::check( canceller );
 	pointInstancer.GetPrototypesRel().GetForwardedTargets( &targets );
 
+	const pxr::SdfPath &primPath = pointInstancer.GetPath();
+
 	IECore::StringVectorDataPtr prototypeRootsData = new IECore::StringVectorData();
 	auto &prototypeRoots = prototypeRootsData->writable();
 	prototypeRoots.reserve( targets.size() );
 	for( const auto &t : targets )
 	{
-		prototypeRoots.push_back( t.GetString() );
+		if( !gafferUSDPointInstancersRelativeProtoypes )
+		{
+			prototypeRoots.push_back( t.GetString() );
+		}
+		else
+		{
+			if( t.HasPrefix( primPath ) )
+			{
+				if( gafferSceneInstancerExplicitAbsolutePaths )
+				{
+					prototypeRoots.push_back( t.MakeRelativePath( primPath ).GetString() );
+				}
+				else
+				{
+					prototypeRoots.push_back( "./" + t.MakeRelativePath( primPath ).GetString() );
+				}
+			}
+			else
+			{
+				prototypeRoots.push_back( t.GetString() );
+			}
+		}
 	}
 
 	newPoints->variables["prototypeRoots"] = IECoreScene::PrimitiveVariable( IECoreScene::PrimitiveVariable::Constant, prototypeRootsData );

contrib/IECoreUSD/test/IECoreUSD/USDSceneTest.py

@@ -4451,6 +4451,37 @@ def testAssetPathSlashes ( self ) :
 		self.assertNotIn( "\\", xform.readAttribute( "render:testAsset", 0 ).value )
 		self.assertTrue( pathlib.Path( xform.readAttribute( "render:testAsset", 0 ).value ).is_file() )
 
+
+	@unittest.skipIf( os.environ.get("GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS") == "1" or os.environ.get("GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES") == "0", "GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS or GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES is set, running alternate test" )
+	def testPointInstancerRelative( self ) :
+		root = IECoreScene.SceneInterface.create(
+			os.path.join( os.path.dirname( __file__ ), "data", "pointInstancerWeirdPrototypes.usda" ),
+			IECore.IndexedIO.OpenMode.Read
+		)
+		pointInstancer = root.child( "inst" )
+		obj = pointInstancer.readObject(0.0)
+		self.assertEqual( obj["prototypeRoots"].data, IECore.StringVectorData( [ './Prototypes/sphere', '/cube' ] ) )
+
+	@unittest.skipIf( not os.environ.get("GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS") == "1" or os.environ.get("GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES") == "0", "Set GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS and don't disable GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES to test this" )
+	def testPointInstancerRelativeNewStyle( self ) :
+		root = IECoreScene.SceneInterface.create(
+			os.path.join( os.path.dirname( __file__ ), "data", "pointInstancerWeirdPrototypes.usda" ),
+			IECore.IndexedIO.OpenMode.Read
+		)
+		pointInstancer = root.child( "inst" )
+		obj = pointInstancer.readObject(0.0)
+		self.assertEqual( obj["prototypeRoots"].data, IECore.StringVectorData( [ 'Prototypes/sphere', '/cube' ] ) )
+
+	@unittest.skipIf( not os.environ.get("GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES") == "0", "Set GAFFERUSD_POINTINSTANCER_RELATIVEPROTOTYPES=0 to test" )
+	def testPointInstancerAbsolute( self ) :
+		root = IECoreScene.SceneInterface.create(
+			os.path.join( os.path.dirname( __file__ ), "data", "pointInstancerWeirdPrototypes.usda" ),
+			IECore.IndexedIO.OpenMode.Read
+		)
+		pointInstancer = root.child( "inst" )
+		obj = pointInstancer.readObject(0.0)
+		self.assertEqual( obj["prototypeRoots"].data, IECore.StringVectorData( [ '/inst/Prototypes/sphere', '/cube' ] ) )
+
 	@unittest.skipIf( not haveVDB, "No IECoreVDB" )
 	def testUsdVolVolumeSlashes( self ) :