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. In 
James Bond 007: Nightfire, a heavily modified GoldSrc game, it used Direct3D 8 instead. With the Half-Life 25th Anniversary Update, all GoldSrc games also uses Direct3D 9 but only for startup videos when software renderer is used.
Source primarily used Direct3D 9, initially Shader Model 2.0, which later was upgraded to support Shader Model 3.0 (in all games since 
as of 2005), but offers backward compatibility with older GPUs (that predates DirectX 9) using DirectX feature levels as low as DirectX 8 (or DirectX 7 and 6 in previous version of Source before Orange Box branch). 
Left 4 Dead engine branch requires GPUs with 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 third-party wrapper 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 (boots up to Vulkan, using RTX Remix's own copy of DXVK which was then translated again to (or outputted as) Direct3D 12), and in Team Fortress 2 branch games which boots to Vulkan by default on Linux).
Source 2 primarily uses Direct3D 11, and previously provided support for Direct3D 9, 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 is used only on 
Counter-Strike (Xbox) and James Bond 007: Nightfire.
Features
- Dynamic iris simulation - automatically adjust brightness, similar to HDR Rendering (only in )
Direct3D 9
Since Half-Life 25th Anniversary Update, Direct3D 9 is used to display startup videos when software renderer is used.
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 (or feature level,
dxlevelfor short) 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). - After Left 4 Dead branch, the DirectX level system (
dxlevel, or feature level system) alongside support for DirectX 8 GPUs (which uses Direct3D 9 with DirectX level system) has been deprecated in favor of automatic CPU & GPU model & performance detection (viacpu_levelandgpu_level), and it's console command "mat_dxlevel" was hidden by default and marked as launcher-only, meaning that the command can be only changed via command line argument (attempting to enter the command in the console normally would result in "Unknown command"), but using VScript or SourceMod server plugin, or by usingmat_infoinstead, it is revealed that Left 4 Dead branch (aswell as Portal 2 branch and the original release of Dota 2, but not CS:GO) runs ondxlevel 100(DirectX level 10.0), however the actual renderer is still being rendered in Direct3D 9. The Source engine never officially support Direct3D 10 given Direct3D 9 is still sufficient, according to Valve (Doug Lombardi). - In all games since Source Multiplayer (since 2011)[1], Source 2013 and Counter-Strike: Global Offensive, also support D3D9Ex (labeled as Windows Aero DirectX extensions in game options), which can improve performance on some GPUs, and reduces CPU usage up to 40%. It also improves Alt + Tab ⇆ and windowed mode support. Requires Windows Vista or later. Can be disabled using
-nod3d9ex(-disable_d3d9exfor CS:GO).
Bug:Despite Valve claiming that the issue has been fixed,[1] you cannot disable D3D9Ex (Windows Aero DirectX extensions) via in-game Advanced Video Options. Valve later eventually removed the D3D9Ex toggle in Team Fortress 2 branch.
- Prior to Left 4 Dead engine branch, Source supports DirectX compatibility levels (or feature level,
- Support Shader Model 2.0 (and 3.0 after updates to Source 2004 since Day of Defeat: Source).
- Shader Model 5.0 and 6.0 if Direct3D 11 or 12 is used.
- Support for both forward, deferred and clustered rendering pipelines.
- Source primarily uses the forward renderer, while Dota 2, as well as some third-party Source games (,
, etc.) use the deferred renderer (shading or lighting). - Deferred rendering is a rendering technique that allows games to render many dynamic lights with little performance impact. Deferred rendering is commonly used in most modern titles (this include some third-party Source games). Dota 2 is the only official Source game to use this technique.
- Other titles such as Portal 2: Community Edition also use the Clustered shading technique, resulting in similar lighting performance as the deferred renderer (both clustered, forward & deferred), but unlike deferred, clustered works with both forward & deferred rendering pipelines.
- Source primarily uses the forward renderer, while Dota 2, as well as some third-party Source games (
- LDR (SDR) and HDR (in all games since
) rendering
- HDR rendering (High Dynamic Range rendering) is introduced with the release of Day of Defeat: Source (and Half-Life 2: Lost Coast a month later), running on updated version of Source 2004. HDR rendering is the process of generating computer graphics scenes using lighting calculations done in high dynamic range (HDR). It works by automatically adjust exposure and "blooming" colors above 100% brightness into neighboring areas, mimicking the way cameras and even eyes handle light exposure, then collapsing the image into SDR color range (tonemapping), resulting an image appears to have higher color saturation, more bloom and improved contrast while still technically being limited by the SDR color range. Assets such as skyboxes have HDR versions with higher color range (16 or 32-bits/channel) than LDR skyboxes (8-bits/channel RGB).
- LDR rendering (or SDR rendering) is the old way the game was rendered, using standard dynamic range lighting. It has been deprecated since Left 4 Dead engine branch. This does not apply to some games such as the original release of Dota 2, for example, which always use LDR.
Risk of Confusion:Not to be confused with "HDR display output", which can display HDR images (including HDR rendering) natively on HDR monitors, resulting in higher brightness & more color range and contrast than a SDR monitor is capable of, and can significantly reduce or eliminate tonemapping. The Source engine, using Direct3D 9 by default, doesn't support native HDR output to HDR-capable displays, except in 
Apex Legends on consoles (PlayStation 5 and Xbox Series X/S only).
- See Source page for more features.
Source 2 Direct3D
- Runs on Direct3D 11
- Available in all Source 2 games except s&box.
- Previously also support Direct3D 9 in Dota 2 (Reborn) before it was dropped in 2021.
- Shader Model 5.0
- Multithreaded rendering
- 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
External links
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