Ben from RobotDuck has posted an explanation of how he achieved "high dynamic range" (HDR) rendering in Shockwave3D. You can see the effect in action here, but basically, it's a means of mimicing the eye's response to light by adjusting the exposure levels of the geometry depending on how long the camera has been in a dark or light area.
For instance, on a bright, sunny day, if you look into a shadowy building from the outside, it will look very dark because your eyes are adjusted to the light outside. But from the inside looking out, it will look brighter, because your eyes are adjusted to the darkness, but the outside will look very light.
The effect is achieved by multiplying and adding dynamically-generated light maps to produce an exposure effect. A good read.