Interestingly, I realised that the sphere using MeshFaceMaterial in canvas_materials.html has been broken for aaaages.

Projector: Implemented side: THREE.FrontSide, THREE.BackSide, THREE.DoubleSide as per discussion in #2285.

Document Material, and remove doubleSided and flipSided properties from Object3D docs, to reflect changes in commit  b838b38f

Cloth.js will need some cleaning but I guess it's better to let @zz85 finish it first (if more work is planned on it).

Added support for picking up <double_sided> flags inside <effect>/<extra>, applying it to the Material. This is half of Issue #2280.