I've been playing around with writing custom glsl shaders for the viewport and i am wondering if there is any documentation available that details the properties and methods available to us. I have found the following pages very helpful:

http://www.sidefx.com/docs/houdini/shade/glsl.html [www.sidefx.com]
http://www.sidefx.com/docs/houdini/shade/opengl.html [www.sidefx.com]

However these pages barely scratch the surface of what is going on. For instance I have dug around a bit in the glsl folder that Houdini uses internally and there are plenty of methods being used there that are not mentioned on the above pages. I'm not talking about built in glsl methods, i'm talking about methods written by the Houdini team.

Where can I fine additional documentation on Houdini's implementation of glsl for the viewport?

Thank you

There's no formal documentation for all of them, but the function definitions can be found in HFS/houdini/glsl/houlib/GL32.