Kai schrieb:

> I've tried the suggested subsurface scattering.
> The glow effect, the disappearing object and the
> shadow edges are ok. I used black pigment, as
> the surface seems to be dominated by the subsurface's color.

Yes, the subsurface scattering algorithm employed does indeed account 
for diffuse illumination, and so should best be used with "diffuse 0" 
or, as you did, a black pigment (at least as it is currently implemented).

> Overall a not to bad result, but for me it's still hard
> to get a feeling for the params. Hue and lightness of
> the surface are not easy to control.

While the current syntax is ideal for specifying materials with known 
physical parameters, and also particularly well-suited for the 
underlying algorithm, it is also known to be hard to control.

I recommend not spending too much time trying to master the parameters, 
as the syntax will be subject to change; while it is not trivial to 
"reverse engineer" the physical parameters of a material from its 
apparent color under uniform lighting conditions (what would normally be 
described in POV-Ray by the combination of pigment and diffuse value) as 
well as the "mean free path" of light traveling through the material (an 
RGB parameter that is said to be comparatively intuitive, governing how 
"translucent" the material will appear), there are algorithms to find 
matching parameters, so there's hope that the final SDL syntax for 
subsurface scattering will hide the physical coefficients from the user, 
and instead use the classic pigment/diffuse parameters plus an 
additional "translucency" RGB parameter.

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