Modulok - Subsurface Scattering | Mental Ray for Maya

ALL INFORMATION PRESENTED IS WHAT THE AUTHOR ASSUMES TO BE TECHNICALLY ACCURATE, HOWEVER ALL CONTENT IS SUBJECT TO CHANGE WITHOUT NOTICE. IF A TECHNICAL INACCURACY IS FOUND, CONTACT THE AUTHOR SO THE CONTENT MAY BE CORRECTED.

What is sub-surface scattering?

It is the indirect transmission of light as it passes through a turbid medium. Things like wax, plant leaves, certain types of plastic, skin, to an extent one could think of sub surface scattering occurring in all living creatures to some degree, as well as a few man made materials. When you stop to really look around it is present all around us in the real world, even if to a subtle degree. If you've ever taken a flashlight and shined it through the thin skin between your fingers, or through your cheeks, the red glow you see is the result of light from the flashlight, indirectly (scattering) through your flesh (the turbid medium).

In Mental Ray version 3.3 we can achieve this effect in a physically correct, as well as non-physically correct manner through the use of a few mental ray shaders. Mental ray for maya version 3.4 and later include the shaders, therefore they need not be acquired through a 3rd party. For those of you who are using Maya version 6.0 with mental ray version 3.3, you may have to scour Autodesk's website for them. Failing that, if you're really deserving, email me and inquire about acquiring it.

After downloading the file (it should be called something like "gmk_maya6_sss_mi_plugin.zip" ) install the shader, following the included installation documentation. Below is an appended version of the instructions included in the readMe.txt file.

To install the subsurface scattering shaders for Maya 6.0 :

paste subsurface.mi in mental ray for Maya shader declaration path (/mentalray/include)
paste subsurface.{DSO} in mental ray for Maya shader path (/mentalray/lib) (The file you choose will depend on your operating system)
put link and include statement in /mentalray/maya.rayrc An example of maya.rayrc is provided at tutorials/maya.rayrc (basically you've got to edit your rayrc file with a text editor such as notepat to include links to the files you just dropped into your mental ray directory. This is so that when the shaders are called, mental ray knows where to look for them. Look at the example rayrc file, it's pretty simplistic, but if you have trouble ask on the forum and I'll help ya out.)
copy mel scripts to /scripts/AETemplates (This is so when you open the attribute editor up for these shaders, there is something to display)
copy icons to /icons

Sub-surface scattering is relatively new in the hands of the general CG community (at least it was when this tutorial was written), as such there isn't much documentation on the matter. As a result I can only present what I have discovered through use of these phenomena, and cannot assure complete technical accuracy, but will do my best to present only information I have been led to believe is accurate, theoretical, or otherwise. If you find the material presented within to be technically innacurate (and I'm not talking about spheling mistakes) please contact me so that I may update this tutorial.

All included video clips use the tech smith screen capture codec for the smallest in size and highest in quality for web distribution. For those on windows systems you may download the codec here. Run the installer and windows media player should be able to play all included clips.

Q: Will you make videos/text in [insert some random file format that only you like]?

A: Probably not. I make .AVI using the Tech Smith Screen Capture codec for the highest quality to size ratio for web distribution. If you're on a Mac using OS/X.x and cannot view the video files, you're going to have to get used to disappointment.

Mac whiners may check this thread for information on how to convert the videos to a format that will play on Mac.

Thread

If using windows media player, be sure playback size is set to 100% for the best visual clarity.

Just thought I'd state this up front...my mic sucks ass. So in several of the video lectures the sound isn't exactly dolby digital quality. The volume is somewhat spirattic...ya know...just FYI.