Good catch, JDWohlever. This is fascinating. Ambient materials under the 'true ambience' setting are illuminated by anything light in colour it would seem; be it another ambient material or a diffuse material with a lot of light on it. In the image above, the left hand white square is made of four cubes with a 100 percent ambient white setting. The white square on the right is made as JDWohlever describes above (white diffuse with one max power parallel light pointing at it). They render exactly the same in appearance but the right hand side of the image (bounced light) renders in a quarter of the time! This is great, it speeds up true ambient work a lot. The squashed cube in the middle has mirrored sides. As you can see, this 'ambient illumination' is reflected in both cases. Mirrors work properly still - very useful. BTW, there is no blurry reflection used here. This is just a true ambient light casting test. One thing this technique isn't, of course, is a 'pure, true radiosity' solution. It's a damn fine step towards a realistic looking simulation.