Very impressive. I've been working on a 3D-ish rain module myself for a while (sprite based particle system), but haven't so far found a viable way to draw transparent rain in front of characters and objects without slowing the system down massively (and without giving up on lighting and tint effects as you would do if also RawDrawing the characters). I'd be interested in how you'll manage this - for non-transparent rain Overlays would perhaps be the best solution.