mat_dxlevel
mat_dxlevel is a console variable available in all 
Source games except 
Left 4 Dead engine branch (or some third-party branches) and above.
Note:This command is not available in any game made using Left 4 Dead engine branch and later branches, or in some third-party branches.Furthermore, since around Source 2007 up to Source 2013, only DirectX 8.0 and 8.1 levels are supported, DX7 and earlier was dropped (except in Portal with RTX).
mat_dxlevel changes the DirectX (feature level) mode used within a Source game. The player is only able to use modes that their hardware supports. The format is
mat_dxlevel [DirectX version] mat_dxlevel 60 - Source 2004-2006 only mat_dxlevel 70 - Source 2006/RTX Remix only mat_dxlevel 80 mat_dxlevel 81 - Softer shadow ...
For DirectX 9 the value depends on the hardware's capability:
mat_dxlevel 90 - DX9 with Shader Model 2 mat_dxlevel 92 - Mac/Linux only, same as dxlevel 95 mat_dxlevel 95 - DX9 with Shader Model 3 mat_dxlevel 98 - Xbox 360 only, always enabled mat_dxlevel 100 - Source Filmmaker and Dota 2 (pre-Reborn), always enabled, game will still runs on D3D9, however.
This can also be specified with Launch Options, use +mat_dxlevel [DirectX version] on the launch options of any Source game to do so. Alternatively, you can use -dxlevel [DirectX version], however this specifies a number of extra presets, including but not limited to:
- Resolution
- Windowed/Fullscreen status
- MSAA sample count (
mat_antialias) - Motion blur (mat_motion_blur_*)
- Shadow depth textures
- Gamma (mat_monitorgamma)
Note:This command does not change the Direct3D renderer to run on other versions. All Source games will always run on Direct3D 9 (or 11/12 in some third-party games), regardless which mat_dxlevel is specified.
Warning:Using -dxlevel launch parameter makes alt tabbing in and out of the game really slow, this will also resets all video configs. It's better to use +mat_dxlevel launch parameter instead, or to place mat_dxlevel command inside a config file.Futhermore,
-dxlevel should be only used a workaround to fix the issue that the game (especially all Source 2013 games except Team Fortress 2) defaults on DX8 mode which may happen on some modern hardware.