Introduction...

Welcome to the mental ray fast subsurface scattering skin shader Information.
Before we begin, we should talk a little about what subsurface scattering ("sss" for short)
actually is, and what it looks like, and how it enhances the apparent smoothness of a surface.

Almost everyone knows about the most "obvious" e effect of subsurface scattering - when light
passes through a thin translucent object. This e ect is easy to point out and easy to see.
But for skin this e effect is secondary and of marginal importance since it only shows up in thin
areas such as ears. What is of greater importance is the di usion of light within the shallow
top layer of the skin.
While the human optical subsystem is specially tuned to view other humans, the very
important e effects of subsurface scattering are, paradoxically, very diffcult to actually see.
Generally, these e effects - unless you know what to look for - are of the variety that you do
not "see" until they are absent, when it becomes obvious that something is missing". For
this reason it is also very easy to overdo the e effect, and to put too strong sss e effects in one's
renderings.
Two things to look for are the apparent "softening" of bumps and small structures, and a
slight "bleed" of light into shadow areas, di using the otherwise sharp shadow edges.
Notice how the bumps on the left object are very harsh, and how the shadow edge is completely
sharp, whereas, on the right, the bumps feel softer and there is a slight color bleed into the
shadow area.

Thursday, November 6, 2008


This tutorial will be about putting a realistic skin on our friend Globulous.
A le, globulous-before, is available on demand1 which you can render. It is fully textured
but uses a simple base phong material without using any subsurface scattering.
If you render you will see something like this, which looks more like plastic than human skin.
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