I modeled a character with three layer S.S.S and it renders fine until I place the character in front of a mirror in the scene. The color in the reflection is distorted. It seems as if the three layer S.S.S. is not rendering in the mirror properly. Any suggestions?
Unfortunately, the initial release logs for the SSS shading mention that the SSS may be incorrect when rendered in mirrors if the reflected object is not directly visible in the scene.
One of the biggest drawbacks in the Internal Renderer that isn’t present when using external engines through a script is that many advanced features have limitations of how they can be used together (frosted glass above a shiny floor can’t be done for example), in some cases you can go for quite a few years without such a limit being removed.
However, in this case, I do wonder though if you can use the nodes that use face normal/vector data to do a (hackish), corrective shading method to minimize the effect, I haven’t tried it, so I don’t know.
It´s a known issue, ace dragon is right, it´s a shading trick not a raytraced solution (so it´s fast, as it was intended), also, frosted, textured, or whatever kind of glass-or material for that matter- can be made using Nodes(via material, texture or plain compositing) to overcome the internal render´s limitations, but require a little more work.