There are really two effects you are trying to achieve:

1. scattered light transmission (like red hand over a flashlight - the light passes through the volume and is scattered, attenuated by depth and coloured by the material
2. backscatter (like the glow you see looking at something front lit) where light penetrates a volume and is scattered back along the light path or at an angle to it.

In reality they are the same phenomenom the difference being the angle between the scattered light and the light source (in 1, the angle is > 90 degrees and in 2 it is < 90 degrees).

both attributes are needed to fake translucent materials like skin. The curve filter with iridescence technique can be used to control the intensity of glow or transparency of a surface at changing angles to a light and so it can fake some of both effects as any organic object tends to become thinner (smaller crossectional area) towards an edge. Fake or real fresnel can help make the effect more realisticby attenuating effects away from edges. That being said, it is all still based on the angle of a surface to a light and not actually based on determining a volume and so it breaks down in places. You could try using a UV-mapped texture map to define what parts of a model are "thin" or not instead of frake fresnel to attenuate the light effect (the map is black aside from fingers, ears, nostrils etc).

I think it is going to require a new renderer or at least a new lighting model to get a good SSS effect.

Message edited on: 06/16/2005 03:36