randym77: Other problems covered by this solution in addition to refraction and reflection artifacts are several related to ray-traced shadows, shadows cast by trans-mapped and unmapped semi-transparent objects, proximity errors and shading of micro-polygon displacements. These are a few off the top of my head, but since I don't know all there is to know about Firefly and haven't even tried to test every function, it is fairly safe to say that there might be others involving computations of small numbers. For example procedural shaders which produce unexpected results on small patterns; artifacts appearing in the detail of bump-mapped surfaces; irregularities in the shape and shading of highlights such as those produced by glossy and anisotropic nodes. And who knows... this MIGHT be the cause of all those shading issues we see when two surfaces are very close together, and we have to use displacement to fix them. It might end up as a long list, but I leave the discovery of the rest to someone else. I'm tired of all this hard work and I want to go PLAY ;-)