Mental ray is the render engine for the project.
In order to create an occlusion pass:
1. create a new render layer with the desire objects in it. Right click on the layer and select Overrides>Create Material Override.
2. Choose mib_amb_occlusion in the Incandescene channel. Make sure the material you are using is white.
3. Render. Composite it on top of the original render in photoshop. (Mutliply)
The following render settings are used: ( in render globals )
Under Quality Tab:
- Sampling Mode: Fixed Sampling 2
- Raytracing: Reflections/Refractions 10
Max Trace Depth 20
Reflection/Refraction Blur Limit 1
Under Features Tab:
- Secondary Effects: Raytracing