View Full Version : MR : Maya Brdf Scatter Shader

03-29-2005, 07:59 PM
Brdf Scatter shader is based on the research paper "A Practical Model for Subsurface Light Transport" by Henrik Wann Jensen. The shader implements a BRDF approximation of a bssrdf as described in the research paper. It can handle materials that look more like wax, jade, and porcelain type objects. With the right settings it can also look like other materials but won't look as good like a full BSSRDF. Use's no form of raytracing so the shader is as fast as a normal lambert depending on the shading network.

Brdf Scatter Shader (http://www.digiteck3d.com/pages/sections/tools/brdfScatter/brdfScatterShader.zip)
Os: NT/2000/XP
Maya Version: 4.0 / 4.5 / 5.0 / 6.0
:Mental Ray Version included:



Dr. Ira Kane
03-29-2005, 09:23 PM
thanks for the contribution.

03-30-2005, 12:46 AM
Hmm, I don't really see any SSS going on here. Maybe you miscalculated some of the math =)

03-30-2005, 01:40 AM
Hmm, I don't really see any SSS going on here. Maybe you miscalculated some of the math =)

ditto.. i was staring really hard to try and notice the SSS... seem to be missing something.

03-30-2005, 02:01 AM
Nice work on getting this shader implemented in MentalRay. I look forward to using it.

Bill, Azshall: This shader does look to be performing the correct math for the BRDF model. If you would have read the paper, you would know that the BRDF model does not include the calculations for light transport below the surface as the BSSRDF does. BRDF just assumes that light entering the material leaves at the same point...thus no SSS effect.:deal:

03-30-2005, 04:59 AM
You have a link to the paper Powell, maybe that will help to keep my foot from my mouth. Thanks =)

03-30-2005, 06:25 AM
Big thanks for this fast shader. Can you include the 3 sample scenes you showed? I have troubles getting the same results with he MR version of your shader. I'm not an experienced Maya user so it's definitely my ignorance.
It would be nice if you could include the Maya shader (.mll plugin) for version v.6.5.
Thank you.

03-30-2005, 07:35 AM
thx for your contribution

03-30-2005, 08:06 AM
Heres a link to the paper:

A Practical Model for Subsurface Light Transport (http://graphics.stanford.edu/papers/bssrdf/)

03-30-2005, 04:14 PM
hey Powell thanks for clarifing that up for me. I guess in those pics it would be hard to see or compare any SSS effect so I've made an image to compare it to a normal lamber with one directional light. So the difference in material can be seen. hey mouser100 I've attached the test scene of the pic i just attched with the teapot so you can have an example. As to the maya6.5 plugin I really don't know when i can update for maya6.5 since I don't have access to the 6.5 dev kit.

Also a note on the MR port of this shader compared to the maya version is that in the maya version it takes light intensity into account. So in the maya version you can get that nice light behind the object effect. But due to my limited knowledge of MR or just a Flaw of MR, I'am not sure how to access the light intensity "without shadows" in MR like you can in maya's API. So if there are any MR shader writers out that could help with any info i would appreciate it greatly :D

03-31-2005, 12:28 AM
visually remindes me of lightwrapping.

03-31-2005, 12:49 AM
Thanks for the link Powell. I recall going over that paper several years ago when I was first getting into mental ray and most of it was over my limited head heh.

Thanks for the clarification, and thanks for the contribution Miguel, happy coding.

03-31-2005, 07:26 PM
no Pro BillSpradlin :thumbsup:

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