Am 02.06.2014 um 19:07 schrieb s.day:
> Hi,
> 
> Thought I was getting used to using SSLT but I think I have something wrong
> somewhere as my poor ant looks like he is about to spontaneously combust..
> 
> I am probably doing something stupid so feel free to point it out, I have had a
> few attempts at adjusting the SSLT settings but I seem to go from not much
> effect to burning him, any ideas/tips would be really appreciated (the most
> appreciated thing would be faster SSLT though ;-)


Hi Sean,

sorry I never got around to analyzing this earlier.

I /think/ I have an idea what may be going on here.

The key to it all is probably that you have interpolation between two
textures involved, with significantly different pigment and subsurface
translucency settings.

Now in subsurface scattering textures the pigment does not do exactly
the same as in classic textures: It does /not/ directly govern the
surface's colour. Instead, from the pigment and the translucency POV-Ray
computes another set of parameters, called the scattering and absorption
coefficients. These govern how much light entering the object is subject
to being scattered and to being entirely absorbed, respectively.

The translation from pigment and translucency to these internal
parameters is chosen in such a way that for a sufficiently large slab
the resulting surface colour effectively /does/ match the pigment
colour. However, as the object gets smaller -- or as you increase the
translucency setting -- the effect of both scattering and absorption
become less and less pronounced. In the end, the object effectively gets
transparent.

Now one more thing to note here is that if the subsurface scattering
parameters are chosen in such a way that absorption is much stronger
than scattering, small objects will appear transparent but tinted.

Now your image has two different textures involved: One of them has
comparatively low transparency; this is the texture that governs the
overall look of the material, which gives it a quite credible opaque
look in general.

The other texture, however, has settings that result in low scattering
but high absorption. This means two things: First, the low scattering
would give the object a glass-like appearance. Second, the high
absorption means that it would be a very dark glass, through which we
can see only exceptionally bright stuff. Which in turn means that this
texture does not have any effect on the overall appearance of the object
(except that interpolating it in means to dim the overall brightness) --
/except/ where the very bright sky probe is visible, which due to the
high refractive index and the convex shape is at the bottom of the object.

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