IECoreUSD : Option for relative prototype paths inside a PointInstancer

If you set the env var IECOREUSD_POINTINSTANCER_RELATIVEPROTOTYPES=1, if an instancer named "/inst" contains an internal prototype path like "/inst/Prototypes/proto", that prototype path will now be loaded as "./Prototypes/proto". This is compatible with how point instancers will now be handled in Gaffer, allowing them to be relocated within the scene hierarchy.

Author: danieldresser-ie

Changes

@@ -1,6 +1,11 @@
 10.5.x.x (relative to 10.5.12.0)
 ========
 
+Features
+--------
+
+- PointInstancerAlgo : Added support for the env var IECOREUSD_POINTINSTANCER_RELATIVEPROTOTYPES. If this is set to "1", then when USD PointInstancers are loaded as point clouds, if they contain prototype paths beneath themselves in the hierarchy, those prototype paths will be loaded as relative paths, starting with "./". This aligns with how Gaffer will now handle prototype paths, and allows point instancers to be relocated in the hierarchy.
+
 Fixes
 -----
 

contrib/IECoreUSD/src/IECoreUSD/PointInstancerAlgo.cpp

@@ -53,6 +53,19 @@ 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 +121,38 @@ IECore::ObjectPtr readPointInstancer( pxr::UsdGeomPointInstancer &pointInstancer
 
 	// Prototype paths
 
+	const static bool gafferUSDPointInstancersRelativeProtoypes = checkEnvFlag( "IECOREUSD_POINTINSTANCER_RELATIVEPROTOTYPES", 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 ) )
+			{
+				// The ./ prefix shouldn't be necessary - we want to just use the abscence of a leading
+				// slash to indicate relative paths. We can remove the prefix here once we deprecate the
+				// env var GAFFERSCENE_INSTANCER_EXPLICITABSOLUTEPATHS and have Gaffer always require a leading
+				// slash for absolute paths
+				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

@@ -42,6 +42,8 @@
 import shutil
 import tempfile
 import imath
+import subprocess
+import sys
 import threading
 import time
 
@@ -4486,6 +4488,39 @@ 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("IECOREUSD_POINTINSTANCER_RELATIVEPROTOTYPES", "0") == "0", "Set IECOREUSD_POINTINSTANCER_RELATIVEPROTOTYPES to run relative version of this 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' ] ) )
+
+	def testPointInstancerRelativeRunner( self ) :
+		env = os.environ.copy()
+		env["IECOREUSD_POINTINSTANCER_RELATIVEPROTOTYPES"] = "1"
+
+		try :
+			subprocess.check_output(
+				[ sys.executable, __file__, "USDSceneTest.testPointInstancerRelative" ],
+				env = env, stderr = subprocess.STDOUT
+			)
+		except subprocess.CalledProcessError as e :
+			self.fail( e.output )
+
+	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 ) :
 

contrib/IECoreUSD/test/IECoreUSD/data/pointInstancerWeirdPrototypes.usda

@@ -0,0 +1,26 @@
+#usda 1.0
+(
+)
+
+def PointInstancer "inst" (
+	kind = "group"
+)
+{
+	point3f[] positions = [(0, 0, -20), (0, 0, -16), (0, 0, -12), (0, 0, -8), (0, 0, -4), (0, 0, 0), (0, 0, 4), (0, 0, 8), (0, 0, 12), (0, 0, 16)]
+	int[] protoIndices = [0, 1, 0, 1, 0, 1, 0, 1, 0, 1]
+	rel prototypes = [ </inst/Prototypes/sphere>, </cube> ]
+
+	def Scope "Prototypes" (
+		kind = "group"
+	)
+	{
+		def Sphere "sphere"
+		{
+			double radius = 1
+		}
+	}
+}
+
+def Cube "cube"
+{
+}