Sree3D is the realtime preview, correct. The P4 renderer is Larry's work, from what I can see a "standard" scanline Phong renderer. No radiosity, no ray-tracing. The Poser 5 renderer is a node-based REYES-renderer that can use ray tracing for certain features like reflections. Where Phong renderer are interpolating polygons normals when shading a pixel, REYES renderers divide polygons in micropolygons that are smaller than a pixel.