Merge pull request #1354 from johnhaddon/usdResetXFormStackFix

USDScene : Handle USDGeomXformable's `ResetXformStack`

Author: johnhaddon

contrib/IECoreUSD/src/IECoreUSD/USDScene.cpp

@@ -438,6 +438,47 @@ class ShaderNetworkCache : public LRUCache<pxr::SdfPath, IECoreScene::ConstShade
 
 };
 
+Imath::M44d localTransform( const pxr::UsdPrim &prim, pxr::UsdTimeCode time )
+{
+	pxr::UsdGeomXformable transformable( prim );
+	if( !transformable )
+	{
+		return Imath::M44d();
+	}
+
+	pxr::GfMatrix4d transform;
+	bool reset = false;
+	transformable.GetLocalTransformation( &transform, &reset, time );
+	Imath::M44d result = DataAlgo::fromUSD( transform );
+
+	if( reset )
+	{
+		// Apply inverse of parent's world transform.
+		Imath::M44d parentWorldTransform;
+		pxr::UsdPrim parentPrim = prim.GetParent();
+		while( parentPrim )
+		{
+			parentWorldTransform = parentWorldTransform * localTransform( parentPrim, time );
+			parentPrim = parentPrim.GetParent();
+		}
+		result = result * parentWorldTransform.inverse();
+	}
+
+	if( ( prim.GetParent().IsPseudoRoot() || reset ) && pxr::UsdGeomGetStageUpAxis( prim.GetStage() ) == pxr::UsdGeomTokens->z )
+	{
+		// Apply Z-up to Y-up correction
+		static Imath::M44d b(
+			0, 0, 1, 0,
+			1, 0, 0, 0,
+			0, 1, 0, 0,
+			0, 0, 0, 1
+		);
+		result = result * b;
+	}
+
+	return result;
+}
+
 } // namespace
 
 class USDScene::Location : public RefCounted
@@ -720,33 +761,7 @@ ConstDataPtr USDScene::readTransform( double time ) const
 
 Imath::M44d USDScene::readTransformAsMatrix( double time ) const
 {
-	pxr::UsdGeomXformable transformable( m_location->prim );
-	if( !transformable )
-	{
-		return Imath::M44d();
-	}
-
-	bool zUp = m_location->prim.GetParent().IsPseudoRoot() && pxr::UsdGeomGetStageUpAxis( m_root->getStage() ) == pxr::UsdGeomTokens->z;
-
-	pxr::GfMatrix4d transform;
-	bool reset = false;
-
-	transformable.GetLocalTransformation( &transform, &reset, m_root->getTime( time ) );
-	Imath::M44d returnValue = DataAlgo::fromUSD( transform );
-
-	if ( zUp )
-	{
-		static Imath::M44d b
-			(
-				0, 0, 1, 0,
-				1, 0, 0, 0,
-				0, 1, 0, 0,
-				0, 0, 0, 1
-			);
-
-		returnValue = returnValue * b;
-	}
-	return returnValue;
+	return localTransform( m_location->prim, m_root->getTime( time ) );
 }
 
 ConstObjectPtr USDScene::readObject( double time, const Canceller *canceller ) const
@@ -1396,7 +1411,26 @@ void USDScene::transformHash( double time, IECore::MurmurHash &h ) const
 	{
 		h.append( m_root->fileName() );
 		appendPrimOrMasterPath( m_location->prim, h );
-		if( xformable.TransformMightBeTimeVarying() )
+
+		bool mightBeTimeVarying = xformable.TransformMightBeTimeVarying();
+		if( !mightBeTimeVarying && xformable.GetResetXformStack() )
+		{
+			// Because we have to apply the inverse of our parent's transform, if
+			// that is time varying then so are we.
+			pxr::UsdPrim parentPrim = m_location->prim.GetParent();
+			while( parentPrim )
+			{
+				pxr::UsdGeomXformable parentXFormable( parentPrim );
+				if( parentXFormable && parentXFormable.TransformMightBeTimeVarying() )
+				{
+					mightBeTimeVarying = true;
+					break;
+				}
+				parentPrim = parentPrim.GetParent();
+			}
+		}
+
+		if( mightBeTimeVarying )
 		{
 			h.append( time );
 		}

contrib/IECoreUSD/test/IECoreUSD/USDSceneTest.py

@@ -3406,5 +3406,77 @@ def testRoundTripIndexedNormals( self ) :
 		root = IECoreScene.SceneInterface.create( fileName, IECore.IndexedIO.OpenMode.Read )
 		self.assertEqual( root.child( "mesh").readObject( 0.0 ), mesh )
 
+	def testResetXFormStack( self ) :
+
+		fileName = os.path.join( self.temporaryDirectory(), "resetXFormStack.usda" )
+		stage = pxr.Usd.Stage.CreateNew( fileName )
+
+		g1 = pxr.UsdGeom.Xform.Define( stage, "/g1" )
+		g1.AddScaleOp().Set( pxr.Gf.Vec3f( 1, 2, 3 ) )
+
+		g2 = pxr.UsdGeom.Xform.Define( stage, "/g1/g2" )
+		g2.AddTranslateOp().Set( pxr.Gf.Vec3f( 4, 5, 6 ) )
+
+		g3 = pxr.UsdGeom.Xform.Define( stage, "/g1/g2/g3" )
+		g3.AddTranslateOp().Set( pxr.Gf.Vec3f( 1, 0, 1 ) )
+		g3.SetResetXformStack( True )
+
+		pxr.UsdGeom.Sphere.Define( stage, "/g1/g2/g3/s" )
+
+		stage.GetRootLayer().Save()
+		del stage
+
+		worldTransform = imath.M44d()
+		location = IECoreScene.SceneInterface.create( fileName, IECore.IndexedIO.OpenMode.Read )
+		for name in [ "g1", "g2", "g3", "s" ] :
+			location = location.child( name )
+			worldTransform = location.readTransformAsMatrix( 0 ) * worldTransform
+			self.assertEqual(
+				location.hash( location.HashType.TransformHash, 1 ), # There is no animation,
+				location.hash( location.HashType.TransformHash, 2 ), # so hashes should be identical
+			)
+
+		self.assertEqual( worldTransform, imath.M44d().translate( imath.V3f( 1, 0, 1 ) ) )
+
+	def testResetXFormStackHash( self ) :
+
+		fileName = os.path.join( self.temporaryDirectory(), "resetXFormStackHash.usda" )
+		stage = pxr.Usd.Stage.CreateNew( fileName )
+
+		# /g1 (animated transform)
+		#  /g2a (reset transform stack)
+		#  /g2b
+
+		g1 = pxr.UsdGeom.Xform.Define( stage, "/g1" )
+		scaleOp = g1.AddScaleOp()
+		scaleOp.Set( pxr.Gf.Vec3f( 2 ), 1 )
+		scaleOp.Set( pxr.Gf.Vec3f( 4 ), 2 )
+
+		g2a = pxr.UsdGeom.Xform.Define( stage, "/g1/g2a" )
+		g2a.SetResetXformStack( True )
+		pxr.UsdGeom.Xform.Define( stage, "/g1/g2b" )
+
+		stage.GetRootLayer().Save()
+		del stage
+
+		root = IECoreScene.SceneInterface.create( fileName, IECore.IndexedIO.OpenMode.Read )
+		g2a = root.scene( [ "g1", "g2a" ] )
+		g2b = root.scene( [ "g1", "g2b" ] )
+
+		# Hash should be animated because the reset needs to account
+		# for animation on parent.
+
+		self.assertNotEqual(
+			g2a.hash( g2a.HashType.TransformHash, 1 ),
+			g2a.hash( g2a.HashType.TransformHash, 2 ),
+		)
+
+		# Hash should be static, because there is no reset.
+
+		self.assertEqual(
+			g2b.hash( g2a.HashType.TransformHash, 1 ),
+			g2b.hash( g2a.HashType.TransformHash, 2 ),
+		)
+
 if __name__ == "__main__":
 	unittest.main()