PDA

View Full Version : What exactly does Scattering Cutoff do in the Skin node?



jrandom
04-15-2013, 12:09 AM
The v10 manual says:


Evaluation of the ray will not occur if the absorption value for the ray length is below the cutoff value.

Trouble is, I can't find any definition for what the "absorption value" is.

MannaTheBerserk
04-15-2013, 11:10 AM
The v10 manual says:



Trouble is, I can't find any definition for what the "absorption value" is.


The word "Cutoff" makes me think of something I use in Mental Ray for Maya shader misss_fast_skin, apart from the fact that the name is "Cutout".

If it is the same thing than it could probably be an object transparency channel which allows b/w textures to actually mask parts of your geometry.

The absorption could have something to do with the depth one ray could reach, given the thickness of your object and the world measurement unit that the software is calculating the thickness by.


Of course I am thinking by comparing something I already know for sure ( miss shader and Mental Ray, which is an hybrid ray-tracer ) with something I don't ( Lightwave way of tracing and its shading network behavior ).

Something to think about though.

Matt
04-17-2013, 09:05 PM
I believe it will work like all the other cutoff parameters in LW, if the rays contribute less than the threshold to the shading, they are marked for random deletion and subsequent further evaluation, speeding up render times.

jrandom
04-17-2013, 10:58 PM
So, say, if a ray is a part of a long chain of bundles of rays, since that one ray doesn't contribute much to the final calculation it may be randomly not evaluated?