First off, I'm thrilled that everyone is finally realizing the magnificance of those realistic shadows that a feature like HDRI brings.  I've been testing out the Bryce 6 HDRI and it looks very good, however, let me lay out my thoughts as I see it: this HDRI option is simply too slow for hi-resolution work or animations, and it does not seem to work very well for indoor scenes(unless there is some trick to it).  This brings me to something called Ambient Occlusion. Anyone heard of it?  Ambient Occlusion is an options found in some of the other 3D programs and it creates a realistic shadow pass on all the objects of your choosing, giving you a most fabulous, stunning soft shadowy effect, similar to HDRI, only it's about 20 to 50 times faster than HDRI. So I'm wondering, could we ever get Ambient Occlusion in Bryce, or is that too hard to do.

"An Example is worth Ten Thousand Words"