The vertex data for glTF morph targets are deltas rather than final values, so we were passing incorrect data into the SurfaceOrientation helper. This has been a long-standing bug that affected models with morphing, including Buster Drone. However in practice we have observed visual issues only with AnimatedMorphCube. Tested against AnimatedMorphCube, Buster Drone, Cesium Man, Fox, and Littlest Tokyo. Fixes #1609