Direct3D
Direct3D is a graphics application programming interface (API) for 
Microsoft Windows. It is part of 
DirectX.
GoldSrc engines ships with a software renderer, OpenGL and initially, Direct3D 6, prior to it being removed in 2013 after SteamPipe update. Unlike OpenGL (since detail textures support was added in 2004 with the release of CS:CZ) and like the Software renderer, it doesn't seems to have issues with overbright lighting. Also in 
James Bond 007: Nightfire, this game used Direct3D 8 instead.
Source mainly used Direct3D 9 (Shader Model 2) renderer, which later was upgraded to support Shader Model 3.0 (in all games since 
), but offers backward compatibility with older GPUs using DirectX feature levels as low as DX8 (or DX7, DX6 in previous version of Source). 
Left 4 Dead engine branch requires GPUs with Direct3D 9.0/DX9.0c (Shader Model 3.0) support in order to run.
Some third-party engine branch like 
Titanfall branch and 
Strata Source use Direct3D 11 instead. As of 2024, nearly all of Valve games also added support for Vulkan renderer on Windows, using DXVK to translates D3D9 to Vulkan. Enabling Vulkan translation will require the "-vulkan" launch option (except in Portal with RTX and upcoming Half-Life 2 RTX).
Source 2 mainly uses Direct3D 11, but also has options to use the Vulkan renderer.
GoldSrc Direct3D
Direct3D 6
Features
- Colored lighting - Quake simply had monotone lighting
- Transparent textures - Glass can now be used in maps
- Texture Filtering - Quake (GLQuake) simply Texture Filtering
- Detailed textures
Direct3D 8
Direct3D 8 only on 
Counter-Strike (Xbox)
Features
- Dynamic iris simulation - automatically adjust brightness, similar to HDR Rendering (only in )
Source Direct3D
- Primarily runs on Direct3D 9.0. Some third-party engine branches use Direct3D 11 or 12.
- Prior to Left 4 Dead engine branch, Source supports DirectX compatibility levels for older graphics card (such as DirectX 8 level card) that only support some, but not all DX9 features (or works poorly when run on DirectX 9 level).
- Support Shader Model 2.0 (and 3.0 after Source 2006).
- In CS:GO and Source 2013, has support for D3D9Ex (also known as Windows Aero DirectX extensions), which can improve performance on some GPUs. Windows Vista (or later) only.
- See Source page for features.
Source 2 Direct3D
- Runs on Direct3D 11
- Shader Model 5.0
- See Source 2 page for features.
See also
- DirectX Versions - list of DirectX feature levels
- OpenGL
- Vulkan, another graphics API, successor to OpenGL.
- Software renderer