Patrick Elliott wrote:

> On Wed, 03 Apr 2002 16:45:02 +0200, Thomas Willhalm
> <wil### [at] fmiuni-konstanzde> wrote:
>> Patrick Elliott wrote:
>> > 
>> > Yeah to subsurface scattering! You can use media, but if you
>> > specifically want to use a thin, single layer mesh that has no
>> > 'interior', media won't work.
>> 
>> Where should your subsurface scattering stop if you have only a single
>> layer? The clou with subsurface scattering is that there happens
>> something to your light _below_the_surface_, right? So there has to be a
>> notion of "inside" and "outside". That's why you need an object with well
>> defined inside and outside to get this thing working. The "inside"
>> modifies the light. That's what "media" does. So, using "media" for
>> subsurface scattering is natural. (However, "media" should be extended to
>> support other scattering functions.)
> 
> Yes well... On the scale of a large object the thickness of the actual
> portion of the surface that is A) visible and B) contributes to the
> scattering is very small, it makes no practical sense under such
> circumstances to fill the entire object with media. This is especially
> true if you wanted to use a solid texture 'under' the surface. If the
> thickness of the scattering layer is 1/1000th of the objects total width
> it is not practical to make it into a solid mesh with a clear interior. 

So, what you really want is a "thick" triangle. By this I mean a triangle
that creates a second layer on the fly possibly without needing additional
memory. Special variants could be created where the main triangle has the
solid texture and the other sides of your prism are clear. Such a thick
triangle would do what you want.

I'm not sure whether this would really be much faster and produce satisfying
results. But you're right that it's achievable.

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