Thanks for the info, RageCGI. I'll play around with those settings. I recall Alex Alvarez using an expression though... Hmm... Anyway, I'm playing around with instanced rain drops because I'm thinking of working on a scene where a volume spotlight sweeps an area at night in the rain. I can get highlights from the drops when the spotlight shines on them with this method, then you don't see the rest of the rain drops outside of the spotlight's beam. I know I could composite HW into the rendered scene and mask out the drops I don't want, but I wanted to explore this avenue too. If you have any ideas, please let me know. I was also thinking of rendering a spotlight beam on its own just to use it as an alpha element in Combustion. Thanks again!