Creating custom occlusion maps

The skin shader for this model includes Sub Surface Scattering (SSS). This effect is mostly noticeable at the edges of the model as well as the ears. The AO Shader does a great job of accentuating details, but in this instance the Occlusion in the ears hides most of the SSS effect.

What we will do is create a map for the AO shader that will control the strength of the effect, making it weaker at the ears so we keep more of our hard earned SSS.

		Above: an example of the Ambient Occlusion/Displacement with and without the 'weight' map. I didn't want the Occlusion to obscure the detailing of the horn nub displacement as well as the ears. Left: The resulting composite render. The Sub Surface Scattering is still very visible on the left ear. Below: The weight map for the Occlusion. (Wireframe included for your reference)

The application of this technique is quite simple. Using the existing mapping coordinates we paint a simple grayscale image indicating where we want less of the Ambient Occlusion effect. The darker the area, the less Occlusion will be rendered. Absolute black results in no Occlusion rendered on those polygons.

Once we have our map painted, we apply it to our custom Occlusion Material. Click On the Surface Slot in which we have our Ambient Occlusion Base Material. Next click the map box next to the Dark Parameter. Select Bitmap.

Next scroll down to the Output options on our Weight map. Click Invert. This will invert our image. We could have drawn the map initially this way, white on black, but I find it easier to paint black on white over the wireframe and simply invert it in max as opposed to painting it White on Black.

Apply our material to the object in question. Press render. Shake it like a polaroid picture.

Next Page: Alternative applications for the shader