operaguy: Thank you for the comments about the diamond prop I made. I don't know about its 'perfect 57 facet brilliant cut' though! I made the model in Cinema4D using a plugin - my proper work with it was seperating all the faces and making a texture map.

I agree Posers' render engine (and materials) are often underated. The refraction looks great on your render.

Can't make my mind up about the reflection though - should the reflection when looking at the grazing angles be greater than when viewing a surface full on? That said if Poser doesn't support fresnel then that's probably the best it's going to get. Can the strength of reflection for individual faces be controled with a texture map (this would rule out animations though).

Most people percieve a diamond to be perfectly transparent so I think your render is spot on with that.

I look forward to seeing the animation.