It has long been accepted that the Bryce ray trace render engine does not have caustic reflections. You can see a reflection in (on) the surface of a mirror, but light will not 'bounce' off of the mirror surface and land on another surface (indeed, light won't bounce off of any surface). Bryce5 introduced a new render feature called "True Ambience". It has been met largely with disdain from users. It isn't particularly realistic (so far) and use of it can result in punishing render times. Not long after Bryce5 came out I started fiddling with True Ambience. I was intrigued with the notion of surfaces giving off light (as opposed to points, as with regular Bryce lights), and I started looking for alternative techniques to multi light arrays to provide soft lighting. Although I was able to come up with a workable soft light system, it wouldn't work with imported meshes (the polygons would not smooth) and the render times became as bad as with light arrays. It was interesting, but not much use. More recently I noticed something in a True Ambience soft light render I was doing that surprised me and intrigued me even more. I found that mirrored surfaces appeared to bounce the light (from a light emitting surface) onto other surfaces. This isn't supposed to happen - these are caustic reflections and Bryce does not have those. This means that true ambient light isn't just "a glow that is applied to other ambient surfaces based on the shape of the emitting object and the squared fall off of brightness with distance". The light coming from surfaces in True Ambience is actual virtual rays/photons that have optical properties. These properties are limited, but in some ways they are more realistic than the properties of Bryce's normal raytracing lights. There will follow (lousy internet connection permitting) a series of pictures illustrating these properties. This isn't the 'useful and practical' application of True Ambience I mentioned in another thread yesterday, it's just more bizarre fiddling at the edge of one of Bryce's frontiers that is mildly interesting. It is to me, anyway. ;-)