Custom export python script for blender and custom import javascript for threejs to enable morphing of vertex normal in morph targets. It might seems a bit technical, but without this, the object loaded in threejs doesn’t react to light correctly: without this export, if faces change direction after deformation, the lack of normal morphing implies that the illumination of faces is not correct. Try without, it will be clear 🙂

Test it here:

Or check this video:

Anyway, the script is here: faces, with some javascript in comment to load it.