tl:dr Antialiasing is controlled by mat_antialias and mat_aaquality.
Q: Why mat_antialias is set to 0 by default?
A:
pazerBecause the values of these cvars are loaded as part of the material system config that is stored in the registry. They arent loaded and stored like normal cvars.
source
Q:
stephwhats the harm in setting it to 0 anyway?
A:
pazermat_antialias 0
mat_forceaniso 0
Don't set these to 0. The minimum value of these cvars is 1, and setting them to 0 will just cause a material system reload = breaking mumble overlay/increasing game startup time. Think about it: mat_antialias controls the number of samples taken per pixel on your screen. If you took 0 samples per pixel, your screen would be entirely black :P
Reading directly from the game's code, the same hardcoded minimum exists for mat_forceaniso:
pConfig->m_nForceAnisotropicLevel = max( mat_forceaniso.GetInt(), 1 );
source
Antialiasing off
mat_aaquality 0
mat_antialias 1
MSAA x2
mat_aaquality 0
mat_antialias 2
CSAA x8
mat_aaquality 2
mat_antialias 4