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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On Fri, 05 Apr 2002 10:22:16 +0200, Thomas Willhalm <wil### [at] fmiuni-konstanzde>
wrote:
> 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.
> 

Yeah that may work.. Not sure if it is actually what the developers of the method did.
I think they
upon consideration that they simply simluted the light passing through an outer
surface, reflecting
off something on the inside, then exiting at some unexpected point as a result of
bending, etc. that
occures between the real and faked surfaces.

So your interpretation is a bit more like what I thought than perhaps the original
since you can
declare a surface, scattering and subsurface layers, while the original may assume
that no such
second layer exists. It would still be better than what is now possible, but realism
would be
improved on say human models by adding a second layer capable of showing details like
veins,
etc. I don't believe I saw any indication that this was allowed. But I don't really
have a real clear
understanding of the math involded so didn't pay that close attention to how/if it
could be used in
such a way.

As to if it is faster... Only trying it would tell. However, it has to be at least a
little easier to understand
for those of us who look at media and go, 'Huh!?!'. lol And if it was also faster then
it would make life
a lot easier for everyone where it is applicable.

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