Wrapper : Put IECoreUSD plugin in PXR_PLUGINPATH_NAME

This will be necessary to pick up the custom metadata registered by ImageEngine/cortex#1188. And that in turn is needed to allow constant primitive variables to round-trip properly in future.

bin/gaffer

@@ -122,6 +122,8 @@ prependToPath "$GAFFER_ROOT/glsl" IECOREGL_SHADER_INCLUDE_PATHS
 prependToPath "$GAFFER_ROOT/fonts" IECORE_FONT_PATHS
 prependToPath "$HOME/gaffer/ops:$GAFFER_ROOT/ops" IECORE_OP_PATHS
 
+prependToPath "$GAFFER_ROOT/resources/IECoreUSD" PXR_PLUGINPATH_NAME
+
 prependToPath "$HOME/gaffer/opPresets:$GAFFER_ROOT/opPresets" IECORE_OP_PRESET_PATHS
 prependToPath "$HOME/gaffer/procedurals:$GAFFER_ROOT/procedurals" IECORE_PROCEDURAL_PATHS
 prependToPath "$HOME/gaffer/proceduralPresets:$GAFFER_ROOT/proceduralPresets" IECORE_PROCEDURAL_PRESET_PATHS

python/GafferSceneTest/SceneWriterTest.py

@@ -347,5 +347,31 @@ def testFileNameWithFrameDependency( self ) :
  self.assertEqual( plane.numObjectSamples(), 1 )
  self.assertEqual( plane.objectSampleTime( 0 ), context.getTime() )
 
+ def testUSDConstantPrimitiveVariables( self ) :
+
+ plane = GafferScene.Plane()
+
+ planeFilter = GafferScene.PathFilter()
+ planeFilter["paths"].setValue( IECore.StringVectorData( [ "/plane" ] ) )
+
+ primitiveVariables = GafferScene.PrimitiveVariables()
+ primitiveVariables["in"].setInput( plane["out"] )
+ primitiveVariables["filter"].setInput( planeFilter["out"] )
+ primitiveVariables["primitiveVariables"].addChild( Gaffer.NameValuePlug( "test", 10 ) )
+
+ self.assertEqual( primitiveVariables["out"].object( "/plane" )["test"].data.value, 10 )
+ self.assertEqual( primitiveVariables["out"].attributes( "/plane" ), IECore.CompoundObject() )
+
+ sceneWriter = GafferScene.SceneWriter()
+ sceneWriter["in"].setInput( primitiveVariables["out"] )
+ sceneWriter["fileName"].setValue( os.path.join( self.temporaryDirectory(), "test.usda" ) )
+ sceneWriter["task"].execute()
+
+ sceneReader = GafferScene.SceneReader()
+ sceneReader["fileName"].setInput( sceneWriter["fileName"] )
+
+ self.assertEqual( sceneReader["out"].object( "/plane" )["test"].data.value, 10 )
+ self.assertEqual( sceneReader["out"].attributes( "/plane" ), IECore.CompoundObject() )
+
 if __name__ == "__main__":
  unittest.main()