MLS or normal+colour smooth

High frequency noise is removed, but colour-based smoothing over larger areas is disabled since it also flattens the surface. MLS and APSS use normals (and sphere fitting) to reduce the flattening effect, can we do similar. Also, the colour similarity smoothing needs to depend on whether it is in the middle of a large colourless area or next to the edge of said area or in a small colourless area.