clipka <ano### [at] anonymousorg> wrote:

> The original Jensen et al. paper has actual values for some materials -
> see Figure 5 (b) on page 5:
>
> http://graphics.stanford.edu/papers/bssrdf/bssrdf.pdf
>
> The sigma[a] coefficients basically specify how much absorption a light
> ray of a given wavelength suffers, per mm travelled in the medium (hence
> the 1/mm dimension; that's "odometer" distance btw, not simply |A-B|);
> the sigma-prime[s] coefficients specify how many scattering events a
> light ray of a given wavelength suffers on average (again per mm
> travelled in the medium), multiplied by a correctional factor to account
> for non-isotropic scattering.

Great resource, at least that gives me some reference values expressed the same
way as the expected input... right? what does the odometer measure change...?
(from the point of view of a user referring to the said paper?)

> These coefficients are admittedly hard to use and non-intuitive, as it
> is difficult to predict the resulting apparent material colour, so I
> expect future versions to add another layer to automatically compute
> fitting coefficients, based on a user-specified apparent material colour
> and some other RGB parameter to control the "waxiness" of the material
> (probably the "mean free path", which should be intuitive enough for
> this purpose).

Why not take it as an opportunity of giving Blender and Povray a common
approach? (it could happen working from both sides since Blender is being
rewritten)? It might help later... I'm not  a coder though and will use
whatever coders implement, or at least try to :)


A little off topic, if you want I can post in a new thread?
I'm experiencing quite heavy render times with SSTL
(still have to check this but it seemed strangely faster with fast radiosity
than without)

Anyway I suppose I need to balance with alternatives for other, but secondary
SSSish materials in my scene... so I'm wondering how does the fastSSS macro by
Samuel Benge compare to SSTL regarding realistic (human) look and rendering
times? or even maybe to directly using scattering media? I'm not at all
questionning the usefullness of SSTL. In fact it seemed the easiest to use from
Pov skin techniques I tried so far) I would also like to avoid wasting too much
time on any obsolete solution before searching for something faster to compute
(Sorry that sounds so demanding!)

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