For one frame or an animation? Using the Premium Render feature in Bryce5 and the Depth of Field and Soft Shadows effects, some extra light sources, reflections, transparencies, etc.... On my G4 450 with 896MB RAM I've had massive renders like this go for 12 hours or more, but I usually make them several thousand pixels wide if I'm going to all that trouble, which also adds to the time. Some take so long I stop them in the middle and do a save. Depending on the size and complexity a full broadcast size animation (720x486) around 10 seconds can take anywhere from a few minutes to several days depending upon any of the factors mentioned above.