Micropolygons work beautifully for local only shading, but that is a very limited model and a thing of the past. The milage that you can get out of this model t

Micropolygons work beautifully for local only shading, but that is a very limited model and a thing of the past. The milage that you can get out of this model that was designed for severely memory constrained systems (high resolution cinematic animations on computers with 4MB if RAM) is enormous. But once you bounce rays randomly through a geometrically complex scene, you either re-tesselate all possibly intersected geometry dynamically again and again with a comsiderable runtime overhead or you pre-tessellate the entire scene based on camera position and film resolution. The later approach is the basis for VFX at the moment, but some renderers like Renderman still can do dynamic on demand tessellation where required AFAIK.