I've found that part of the process is getting the right gemstone cut, and importing it into carrara using the correct settings. carrara is surprisingly sensitive to small variations in the cut of the stone. I started with a new poser diamond file that was just posted here, and it gave a pool of caustics under the gem, but no brilliance nor fire. the latter (splitting white light into a spectrum) is likely beyond carrara's capabilities. however, using a brilliant-cut poser model from the lapidary site gave reasonable results for reflected caustics, but not for refracted caustics that are displayed in the above image. hence, I daresay, unless antoine pops into this forum on occasion, I'll hafta ask him directly. did he remain with the firm after daz bought eovia?