I've been tackling this issue with my map for a couple months now. Whenever I try to build cubemaps, I must be doing something wrong, because I continue to get errors. I use these commands from the wiki: mat_specular 0 buildcubemaps mat_specular 1 disconnect sv_cheats 1 mat_reloadallmaterials sv_cheats 0 I've compiled in HDR, and built cubemaps in both HDR and not-HDR, but I still get the same purple/black checkerboard patterns when I test it on a server. Any help would be greatly appreciated. Here's some screens.