A few things: * Always set the background color of the reflection and refraction nodes to the background color of your scene, or if you're using an background image/movie, use that one in conjunction with a sphere-map node. * When using refraction, set the transparency of the Poser Surface to 0 (as described in the manual and the room help - the manual is better than its reputation). Yes, that may sound odd at first, but that's the way it is in all things RenderMan. * As soon as you did that, you can reduce the reflaction_value and reflection_value to values < 1.0. No real material is 100% reflective or refractive, and this will cause problems with multiple bounces. * Multiple bounces - that's one problem you will have as soon as your glasses are thicker than one polygon. A refraction ray will bounce back and forth in the glass, until it hits the max number of ray trace bounces and is being rendered black. The higher your reflection_value is, the more this black pixel will be visible in your final render. Try to have low reflection_values, or make it single-sided (you can fake reflections with an environment map, which is more predictable and renders much faster). hope this helps.