SSS is a very nice shader which works really great with a good lighting setup, but sometimes is so expensive shader when you´re using Mental Ray.
Find below a couple of tecniques to deal better with SSS. Just keep in mind that those tricks could improve your render times a bit, but never will reach the same quality than using SSS for itself.
- I’m using this simple scene, with one key light (left), one fill light (right) and one rim light.
- A SSS compound is connected to the material surface input, and the SSS_lightmap (you can find that node in the render tree -> user tools) connected to the lightmap input of the SimpleSSS. And then, the Simple SSS lightimap connected to the material lightmap input.
- Write the output and resolution of your lightmap.
- Hit a render and check the render time.
- Disconnect the lightmap.
- Render again and check the render times as well. We have imprpved the times.
- If you need to really fake the SSS and render so fast, you can bake the SSS to texture using RenderMap, but keep in mind that the result will be much worst than using SSS. Anyways you can do that for background asset or similar.
- Now you can use another cheaper shader like blinn, phong or even constant with your baked SSS.
- As you can see the render is now so fast.