Just found this on IGN:

Open the console window by pressing ~ (or the key above Tab), then enter con_restricted 0 and hit Enter. Now you can enter the following codes for the desired effect:

Codes to change graphics and game settings:

sys_spec_gameeffects = 3 []
sys_spec_objectdetail = 3 []
sys_spec_particles = 3 []
sys_spec_physics = 3 []
sys_spec_postprocessing = 3 []
sys_spec_shading = 3 []
sys_spec_shadows = 3 []
sys_spec_sound = 3 []
sys_spec_texture = 3 []
sys_spec_water = 3 []

Source: IGN

I guess you can change those numbers from 1 to 3?

I hope with further updates this options became part of a submenu instead of manually writing them on the console.

Actually that is what the Advanced Graphics Editor that wasdie wrote does.

His post is http://www.gamesas.com/forums/viewtopic.php?f=40&t=12953&hilit=advanced+graphics

It gives you a graphical interface to make the changes with.

Cool, I missed that, but it should be ingame anyway