CoordinateSystem: Backwards compatibility

CoordinateSystem used to have a transform property which has been
removed in favour of accessing transforms independently of objects.

We provide a way to retrieve this information from SceneInterfaces
written prior to removal, as blind data.

Author: yannci

src/IECoreScene/CoordinateSystem.cpp

@@ -34,8 +34,12 @@
 
 #include "IECoreScene/CoordinateSystem.h"
 
+#include "IECore/SimpleTypedData.h"
 #include "IECore/MurmurHash.h"
 
+#include "Imath/ImathMatrix.h"
+#include "Imath/ImathMatrixAlgo.h"
+
 using namespace IECore;
 using namespace IECoreScene;
 using namespace boost;
@@ -104,6 +108,30 @@ void CoordinateSystem::load( LoadContextPtr context )
 	unsigned int v = m_ioVersion;
 	ConstIndexedIOPtr container = context->container( staticTypeName(), v );
 	container->read( g_nameEntry, m_name );
+
+	// CoordinateSystem used to have a transform property, but that has
+	// been removed in favour of transforms being accessed independently
+	// of objects in SceneInterface (and Gaffer). If a legacy transform
+	// exists, load it and stash it as blind data for use by legacy tools.
+
+	ConstIndexedIOPtr matrixTransformContainer = container;
+	for( auto name : { "transform", "data", "MatrixTransform", "data" } )
+	{
+		matrixTransformContainer = matrixTransformContainer->subdirectory( name, IndexedIO::MissingBehaviour::NullIfMissing );
+		if( !matrixTransformContainer )
+		{
+			break;
+		}
+	}
+
+	const IndexedIO::EntryID matrixEntry( "matrix" );
+	if( matrixTransformContainer && matrixTransformContainer->hasEntry( matrixEntry ) )
+	{
+		M44fDataPtr matrix = new M44fData;
+		float *f = matrix->writable().getValue();
+		matrixTransformContainer->read( matrixEntry, f, 16 );
+		blindData()->writable()["LegacyTransform"] = matrix;
+	}
 }
 
 void CoordinateSystem::hash( MurmurHash &h ) const

test/IECoreScene/CoordinateSystemTest.py

@@ -87,6 +87,14 @@ def testEquality( self ) :
 		self.assertNotEqual( c2, c1 )
 		c1.setName( "test" )
 
+	def testLegacyTransform( self ) :
+
+		c = IECore.ObjectReader( os.path.join( "test", "IECoreScene", "data", "coordinateSystemLegacyTransform.cob" ) ).read()
+		self.assertTrue( c.blindData().has_key( "LegacyTransform" ) )
+
+		expected = imath.M44f().translate( imath.V3f( 0, 2, 0 ) )
+		self.assertEqual( c.blindData()["LegacyTransform"].value, expected )
+
 	def tearDown( self ) :
 
 		if os.path.exists( os.path.join( "test", "IECore", "data", "coordSys.cob" ) ) :