Fullbright vs luma textures

Quick example of how these are used.

Fullbrights are based on the pixels in the material, from the .bsp Luma textures are external.

gl_lumatextures	gl_fb_bmodels	fullbright pixels	luma texture
0	0	ignored	ignored
1	0	ignored	mixed with material, pre-lightmap
0	1	applied after lightmap	ignored
1	1	ignored	added, post-lightmap

See qqshka's change here for bmodels (maps/ammo etc) and his later change here for the normal alias models, pointing out "actually its fullbright not luma"