USDScene : Load bounds from UsdGeomModelAPI extents hints

Changes

@@ -1,7 +1,10 @@
 10.5.x.x (relative to 10.5.8.0)
 ========
 
+Improvements
+------------
 
+- USDScene : `hasBound()` and `readBound()` now use `UsdGeomModelAPI` extents hints if they are available. This behaviour can be disabled by setting the `IECOREUSD_USE_MODELAPI_BOUNDS` environment variable to a value of `0`.
 
 10.5.8.0 (relative to 10.5.7.1)
 ========

contrib/IECoreUSD/src/IECoreUSD/USDScene.cpp

@@ -58,6 +58,7 @@ IECORE_PUSH_DEFAULT_VISIBILITY
 #include "pxr/usd/usdGeom/camera.h"
 #include "pxr/usd/usdGeom/gprim.h"
 #include "pxr/usd/usdGeom/metrics.h"
+#include "pxr/usd/usdGeom/modelAPI.h"
 #include "pxr/usd/usdGeom/pointInstancer.h"
 #include "pxr/usd/usdGeom/primvar.h"
 #include "pxr/usd/usdGeom/primvarsAPI.h"
@@ -528,6 +529,33 @@ Imath::M44d localTransform( const pxr::UsdPrim &prim, pxr::UsdTimeCode time )
 	return result;
 }
 
+static const bool g_useModelAPIBounds = []() -> bool {
+	const char *c = getenv( "IECOREUSD_USE_MODELAPI_BOUNDS" );
+	if( !c )
+	{
+		return true;
+	}
+	return strcmp( c, "0" );
+}();
+
+pxr::UsdAttribute boundAttribute( const pxr::UsdPrim &prim )
+{
+	if( auto boundable = pxr::UsdGeomBoundable( prim ) )
+	{
+		return boundable.GetExtentAttr();
+	}
+
+	if( g_useModelAPIBounds )
+	{
+		if( auto modelAPI = pxr::UsdGeomModelAPI( prim ) )
+		{
+			return modelAPI.GetExtentsHintAttr();
+		}
+	}
+
+	return pxr::UsdAttribute();
+}
+
 // Used to assign a unique hash to each USD file. Using a global counter rather than the file name
 // means that we treat the same file as separate if it is closed and reopened. This means it's not
 // a problem if USD changes things when a file is reopened. USD appears to not in general guarantee
@@ -820,30 +848,32 @@ std::string USDScene::fileName() const
 
 Imath::Box3d USDScene::readBound( double time ) const
 {
-	pxr::UsdGeomBoundable boundable = pxr::UsdGeomBoundable( m_location->prim );
-	if( !boundable )
-	{
-		return Imath::Box3d();
-	}
-
-	pxr::UsdAttribute attr = boundable.GetExtentAttr();
+	pxr::UsdAttribute attr = boundAttribute( m_location->prim );
 	if( !attr.IsValid() )
 	{
 		return Imath::Box3d();
 	}
 
 	pxr::VtArray<pxr::GfVec3f> extents;
-	attr.Get<pxr::VtArray<pxr::GfVec3f> >( &extents, m_root->getTime( time ) );
+	attr.Get( &extents, m_root->getTime( time ) );
 
-	if( extents.size() == 2 )
+	// When coming from UsdGeomModelAPI, `extents` may contain several bounds,
+	// on a per-purpose basis. Take the union, since the SceneInterface API only
+	// has a single bound per location.
+	Imath::Box3d result;
+	for( size_t i = 0; i + 1 < extents.size(); i += 2 )
 	{
-		return Imath::Box3d(
-			DataAlgo::fromUSD( extents[0] ),
-			DataAlgo::fromUSD( extents[1] )
+		const Imath::Box3d b(
+			DataAlgo::fromUSD( extents[i] ),
+			DataAlgo::fromUSD( extents[i+1] )
 		);
+		if( !b.isEmpty() )
+		{
+			result.extendBy( b );
+		}
 	}
 
-	return Imath::Box3d();
+	return result;
 }
 
 ConstDataPtr USDScene::readTransform( double time ) const
@@ -873,14 +903,7 @@ void USDScene::path( SceneInterface::Path &p ) const
 
 bool USDScene::hasBound() const
 {
-	pxr::UsdGeomBoundable boundable = pxr::UsdGeomBoundable( m_location->prim );
-	pxr::UsdAttribute attr;
-
-	if( boundable )
-	{
-		attr = boundable.GetExtentAttr();
-	}
-
+	pxr::UsdAttribute attr = boundAttribute( m_location->prim );
 	return attr.IsValid();
 }
 

contrib/IECoreUSD/test/IECoreUSD/USDSceneTest.py

@@ -4211,5 +4211,51 @@ def testTreatLightAsPointOrLine( self ) :
 		self.assertEqual( root.child( "sphereLight" ).readAttribute( "light", 0 ), sphereLightShader )
 		self.assertEqual( root.child( "cylinderLight" ).readAttribute( "light", 0 ), cylinderLightShader )
 
+	def testModelBound( self ) :
+
+		fileName = os.path.join( self.temporaryDirectory(), "modelBound.usda" )
+
+		stage = pxr.Usd.Stage.CreateNew( fileName )
+		pxr.UsdGeom.Xform.Define( stage, "/withoutModelAPI" )
+		pxr.UsdGeom.Xform.Define( stage, "/withModelAPI" )
+		pxr.UsdGeom.Xform.Define( stage, "/withModelAPIAndExtent" )
+
+		pxr.UsdGeom.ModelAPI.Apply( stage.GetPrimAtPath( "/withModelAPI" ) )
+		modelAPI = pxr.UsdGeom.ModelAPI.Apply( stage.GetPrimAtPath( "/withModelAPIAndExtent" ) )
+		modelAPI.SetExtentsHint( [ ( 1, 2, 3 ), ( 4, 5, 6 ) ] )
+
+		stage.GetRootLayer().Save()
+		del stage
+
+		root = IECoreScene.SceneInterface.create( fileName, IECore.IndexedIO.OpenMode.Read )
+		self.assertFalse( root.hasBound() )
+
+		self.assertFalse( root.child( "withoutModelAPI" ).hasBound() )
+		self.assertFalse( root.child( "withModelAPI" ).hasBound() )
+		self.assertTrue( root.child( "withModelAPIAndExtent" ).hasBound() )
+		self.assertEqual( root.child( "withModelAPIAndExtent" ).readBound( 0 ), imath.Box3d( imath.V3d( 1, 2, 3 ), imath.V3d( 4, 5, 6 ) ) )
+
+	def testPerPurposeModelBound( self ) :
+
+		fileName = os.path.join( self.temporaryDirectory(), "testPerPurposeModelBound.usda" )
+
+		stage = pxr.Usd.Stage.CreateNew( fileName )
+		pxr.UsdGeom.Xform.Define( stage, "/group" )
+		cube = pxr.UsdGeom.Cube.Define( stage, "/group/proxy" )
+		cube.CreatePurposeAttr().Set( "proxy" )
+
+		bboxCache = pxr.UsdGeom.BBoxCache( pxr.Usd.TimeCode( 0 ), [ "default", "render", "proxy", "guide" ] )
+		modelAPI = pxr.UsdGeom.ModelAPI.Apply( stage.GetPrimAtPath( "/group" ) )
+		modelAPI.SetExtentsHint( modelAPI.ComputeExtentsHint( bboxCache ) )
+
+		stage.GetRootLayer().Save()
+		del stage
+
+		root = IECoreScene.SceneInterface.create( fileName, IECore.IndexedIO.OpenMode.Read )
+		self.assertFalse( root.hasBound() )
+
+		self.assertTrue( root.child( "group" ).hasBound() )
+		self.assertEqual( root.child( "group" ).readBound( 0 ), imath.Box3d( imath.V3d( -1 ), imath.V3d( 1 ) ) )
+
 if __name__ == "__main__":
 	unittest.main()