Digital Dawn Toolkit
There's a new version (4.3) of the Digital Dawn Graphics Toolkit available, a library of almost 100 documented C++ classes for building real-time 3D applications. Here's the buzz from the DDG site:
The reason the this toolkit came into being was because I was tired of reimplementing all sorts of infrastructure each time I wanted to try out some graphics algorithm. By placing this generic functionality in a library and adding to it over time I have been able to develop a flexible architecture allowing me to rapidly design and implement new graphics concepts.
The reason I made this work public is to help other graphics developers to quickly try their own implementation or to serve as examples. "