Starting BSP Overdraw Optimizations (Patreon)

BSP models & maps overdraw is the biggest source of slowdowns in Retroquad's renderer, making a number of compatible custom maps unplayable. Large amounts of surfaces with semitransparencies, colormasking, soft depth and other effects can bring Retroquad to a crawl.

Now I'm starting to do a big amount of changes in the code to implement a new system for BSP overdraw. Quake 2 already has an alternate system for semitransparent surfaces, but I'm devising my approach from scratch.