If you are already an experienced shader writer, Mental Mill doesn’t have much to offer, auto-generated code won’t appeal. But for TDs who haven’t the experience or time needed to get a shader going, it’s a huge boon. It’s also a way to get a feel for shader code, letting you experiment and see how the code changes as a concept is changed.
Here’s the mental mill blog, with some info for softimage users.
What’s important for everyone to know about Mental Mill is that the same “tree” can be used to generate code for multiple rendering types – with a few caveats, you can create a shader for Mental Ray, a matching realtime shader, and a renderman compliant shader all in one go (ummm, Arnold? Oh well). For softimage users, this can give you custom solutions you can see in both the viewport and at render time. Here’s a video which covers creation of a realtime shader, for instance…
http://www.youtube.com/watch?v=E3biGBm2mkM&feature=youtubegdataplayer