IIRC, the manual describes the file structure (pretty-much 1 piece of information per pixel rendered in each file).
What to use it for?
Mostly, you might write a 'shader' for Cinema 4D. Use the script running facility of Render4D to post-process a frame and add your own hair, grass, procedural textures, whatever, before it gets passed to storage or integration.
Another idea, maybe you'd like to render lots of scenes for a point-and-click adventure. You could (possibly) use the depth map for working out collision detection and the object map for ensuring all important objects are visible to the player.
If you're interested in writing shaders, however, you might like to take a look at nVidia's Cg (C for Graphics). It looks interesting indeed.
benJamin
