To open rendering options, LMB the mesh when you're not in painting mode. Open DynaMask on your folder or layer, then open the Material IDs rollout. Click the Links button. CTRL+LMB each masked area you'd like to add to your current mask. That should do it. :)
1. At some point last night I found out how to switch rendering modes to actually see the opacity map I've added to my mesh. For whatever reason I can't seem to find where on earth that option is and all the topics mentioning it either skip past it or solve it without documenting. Where are the rendering modes for 3DO?…