Fast SSS shader - veins when backlit?

[X14Halo]

I have something like a bat wing (with thickness) with a SSS shader on it. I got it to feel like skin, and it has a nice translucent/glowy feel when backlit. However, whenever I try to make red veins show up only when it is backlit, they always seem to show up on the front lit side too, which I don't want. I tried painting in veins on the subsurface and scatter color maps and it does not get the result I like. Anybody have any ideas how to get veins to show up only when it is backlit, and to be able to control the color of them? These are basically the settings I am using: http://adamvfx.com/vrayskinstudy/settings/SSS2.jpg

[tashko.zashev]

Hi,

Is it possible to send us the scene file (or a part of it) to: vray@chaosgroup.com so we will try to help you with this issue.

[griml0ck]

This is the maya forum but the sss shader is the same between maya and max I think. You could try painting a map in for the scatter radius/scatter color. If you paint for the subsurface color/diffuse it will show up in the front scattering as well as you have seen. This effect is easier to make with mentalrays sss shader as you can have 4 layers instead of two which vray has. Another solution would be to model the veins either in zbrush or mudbox and use displacement, haven't tested this but the shader might give you a more accurate look if you have more thickness were the veins are. A 3rd option would be to make a separate sss shader for the veins were you have a map for the scatter radius/color so they only show up when backlit. And blend that shader with your other shader. Will probably make for very slow rendering but might give you the result you want. Good luck!