about "Occlusion Interval Maps "

[goodback]

When I read "Chapter 13. Generating Soft Shadows Using Occlusion Interval Maps " in GPU gems. I want to generate "Occlusion Interval Maps "
but there are just talk about" We computed all data for our scene using a custom shader in the mental ray software package"
what kind custom shader where I can found it? there are some tutorial about it ?

please help me