Source/en






Source is a 3D game engine created by
Valve in 2004, and is the successor to
GoldSrc. Source has been used by Valve, third-party companies, and (much like GoldSrc) countless community mods by people around the globe. Today, it has largely been replaced by the
Source 2 engine for first-party usage since 2015, but it's still being commonly used today by modders and some third-party companies, and it's still regularly being maintained with engine and security updates.



Contents
Renderer
- Version 3.0 (and below) shaders

- Anti-aliasing support
- Source is the first Valve engine to support anti-aliasing, prior to MSAA (4X) being added to GoldSrc in 2013.
- MSAA is the traditional anti-aliasing method, works by samples (renders) each pixel multiple times at different locations within the frame and averages the samples to produce the final pixel value. It is commonly used in most older video games, including all Source engine games. Up to 8x MSAA (or 6x MSAA in Source 2004) is supported. Older GPUs (such as pre-Maxwell Nvidia cards) also support CSAA.
- FXAA is also supported in CS:GO engine branch. Unlike MSAA, FXAA has less performance hit than most other AA methods due to it being a post-processing effect, which meant that it can be unofficially added to older Source engine games (or even other video games, other engines and other applications in general), using software such as ReShade, or even built-in via the graphics driver settings, and unlike MSAA, FXAA and other post-processing method will affect transparent textures, however, due to it's nature, this makes FXAA looks worse than many other AA methods as it's appear to blur the image, plus it does not reconstruct the pixel which was missing due to lack of an traditional anti-aliasing.
- TAA is a modern AA method commonly used in most modern games, superseded the MSAA method for anti-aliasing, it works by combining information from past frames and the current frame to remove jaggies in the current frame. However, as mentioned, TAA combines information from past and current frames can cause blurring and ghosting effect while in motion, more noticeable with low FPS. In Source engine case, it is only available in few games such as
Apex Legends.
Tip:If the game is running in 4K resolution or above, or by downscaling 4K to 1080p or lower, the need for anti-aliasing is greatly reduced.
- Bump mapping and Normal mapping on models and the world
- Author shaders with HLSL
- Cube and environment mapping
- Phong shading for models
- Dynamic lights, vertex lighting and lightmaps, many light types including flickering, pulsing etc.
- HDR (in all games since
) and SDR/LDR (not in
and later) lighting
- Water with refraction, real-time world reflections and fresnel effects
- Water also supports flow mapping (in all games since
)
- Water also supports flow mapping (in all games since
- Advanced particle systems that can emit sprites or models
- Render-to-texture shadows allow for a large number of characters per scene
- Occluder entities for visibility blocking
- Indoor/Outdoor environments
- Deformable terrain
- 3D Skyboxes extend the horizon and add parallax on distant objects
- Dynamically rendered organics (grass, trees, etc.)
- Subdivision surfaces, diffuse & specular bump maps
- Real-time radiosity lighting
- Real-time cascaded shadow mapping that comes from the skybox (in all games since
)
- Effects include but are not limited to: particles, beams, volumetric smoke, sparks, blood, & environmental effects like fog and rain
- Scalability
- DX8-DX9 hardware supported (DX6-DX9 with modifications and fixed-function shaders)
- DX11 and later are also supported on some third-party branches.







Materials System
- Instead of traditional textures, Source defines sets of materials that specify what the object is made from and the texture used for that object. A material specifies how an object will fracture when broken, what it will sound like when broken or dragged across another surface, and what that object's mass and buoyancy are. This system is much more flexible than other texture-only systems
- Materials can interact with objects or NPCs, such as mud or ice for vehicles to slide/lose traction on
Multiplayer Network Code
- Time- and gamer-tested by millions of gamers around the world
- Support for both LAN-based multiplayer and Internet-based multiplayer games
- Prediction analysis for interpolating collision/hit detection
- Optimizations for high-latency, high-packet-loss 56k connections
Advanced Characters
- Detailed and believable characters
- Realistic eyes
- Focus on player/object, not simply parallel views
- Proper eye bulge for realistic eye reflections
- Simulated musculature provides outstanding emotions, speech, and body language
- Language independent speech, characters can speak naturally in many languages
- Skeletal/bone system for animation
- Layered animation system can synthesize complex animations out of several pieces
Physics
- Uses Havok physics engine, licensed from Havok Group (now acquired by Microsoft)
- More responsive world with realistic interactions
- Sounds & graphics follow from physics
- AI characters can interact with physically simulated objects
- Ropes/cables, machines, constraint systems, ragdoll physics
- Can be controlled by level design
- Kinematic animated bone followers
- Custom procedural physics controllers
- Vehicles
- Wheels slip and skid
- Realistic suspensions with springs on each wheel
- Realistic leaning during acceleration/deceleration and turning
- Individually tunable parameters such as horsepower, gearing, max speed, shift speed, tire material, tire friction, spring tension/dampening, etc.
- Multiple players in a vehicle in multiplayer
- Hovercraft support for cheaper simulation
Advanced AI
- I/O system allows level designers to control AI
- Sophisticated navigation: characters that run, fly, jump, crouch, climb stairs and ladders, and burrow underground
- AI senses things using sight, sound, and smell
- AI relationships determine friend/foe status of other entities
- Battle AI allows squads of AI characters to operate together, know when to advance, retreat, lay cover fire, etc.
Sound System
- 7.1, 5.1 surround sound, 4 speaker surround
Bug:On system running Windows Vista and later, due to the game engine using DirectSound and older version of Miles Sound System, the game may output only 5.1 surround despite 7.1 selected or 7.1 audio may not work properly without custom
dsound.dll
(such as Creative Alchemy, DSOAL or IndirectSound). This issue is not affected by some third-party games, such asTitanfall 2,
Apex Legends.
Note:Some Source games (such as
Alien Swarm,
Portal 2 and
Counter-Strike: Global Offensive) may not include options to enable 7.1 surround sound without using console commands.
- High-quality 3D spatialization
- Custom software DSP
- Automatic DSP based on environmental geometry
- Microsoft ADPCM-compressed WAV files
- 16-bit 44.1 KHz (CD Quality), stereo wave data with all features
Warning:48 KHz audio (DVD Quality) is not supported by default. Not to be confused with 44.1 KHz, which is the CD Quality audio.
- MP3 decompression (requires Miles license)
- Support for audio streaming on any wave [Clarify]
- Real-time wave file stitching [Clarify]
- Pre-authored Doppler effect encoded waves
- Pre-authored distance variant encoded waves
- Commentary system
UI
- Server browser — Displays all active game servers and allows a player to choose which one to participate on. Players can filter and sort server lists in order to speed up the display and selection of a server.
- VGUI — Valve's custom GUI interface mimics most of the Windows controls but is rendered using the Source engine for both in game and out of game uniform UI display. Some features:
- Panorama (in all games since
) — Introduced in 2018, Valve's new Custom GUI interface that resembles modern web design and authoring (HTML5/CSS/JS). Using
.XML
and JavaScript files, developers can create dynamic and clean huds and menus and even high-quality in-game intractable panels.
Programming
- All code written in C/C++ using Visual Studio .NET 2003 and later. Easily and quickly derive new entities from existing base classes
- Internal context sensitive performance monitoring system
- Graphics performance measurement tools built into the engine
- Modular code design (via DLLs) allows swapping out of core components for easy upgrading or code replacement
- VScript scripting system allows using external coding languages, such as Squirrel and Lua, in maps to create more complex systems (in all games since
) (also in
)
Tools
HLFaceposer
- Facial expression tool used to craft speech and emotions
Valve Hammer Editor
- WYSIWYG World editor
- Create world brushes
- Terrain editor
- Place detailed world models and AI NPCs
- Set navigation points/paths for NPCs
- Place triggers, clip brushes, logic, etc.
- Allows level designer to hook up I/O between entities to control AI within the game
Half-Life Model Viewer
- Full model previewer
- Rotate models in any direction
- Set up hit boxes
- View physics hull
- View normals
- Wireframe, shaded or textured view modes
- Studiomdl
- Model compiler
- VBSP, VRAD, VVIS, VMPI
- Map compilation tools (bsp, lighting and visibility)
- VMPI — distributed compilation tool allowing level compiles to be spread across many PCs greatly reducing compile times
- Exporters
- XSI, Max and Maya
.smd
exporters for exporting 3D models
- XSI, Max and Maya
Products using Source 



Products made by Valve
Year | Title | Co-developed with | Engine branch | Platforms | Notes |
---|---|---|---|---|---|
2004 |
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Turtle Rock Studios | ![]() ![]() |
PC: Windows, Mac, Linux | First game to use the Source engine. Remake of Counter-Strike. |
2004 |
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PC: Windows, Mac, Linux | Remaster of Half-Life. It is critically panned by most gamers since 2013 due to the huge amount of bugs that was introduced when the game was updated to ![]() ![]() |
|
2004 |
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PC: Windows, Mac, Linux Consoles: Original Xbox, Xbox 360, PlayStation 3 |
Sequel to Half-Life, and later Half-Life: Alyx. Included on ![]() The game was set 20 years after the event of Half-Life, takes place in the City 17, which is under Combine control. Prior to it's release, it was infamously leaked in Oct 2003, and Valve had to delay the game until Nov 2004. It is also the first game to require the installation of Steam in order to play. |
|
2004 |
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PC: Windows, Mac, Linux | Multiplayer component of Half-Life 2. | |
2005 |
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PC: Windows, Mac, Linux | Remake of Day of Defeat. | |
2005 |
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PC: Windows, Mac, Linux | Originally as part of Half-Life 2, which was cut at some point before it was released, and was developed after the leak happened but was ultimately cut, then later released in 2005 as a HDR lighting technology demo. It runs on a much newer engine which would soon later be called ![]() ![]() |
|
2006 |
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PC: Windows, Mac, Linux | Multiplayer component of Half-Life: Source. | |
2006 |
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PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3 |
The game is the sequel to Half-Life 2, and the story begins after the Citadel reactor core was destroyed, Gordon and Alyx both survived the explosion. When it's come to technical, it uses ![]() ![]() |
|
2007 |
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PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3 |
A sequel to Half-Life 2: Episode One. The City 17 has been destroyed, and the Citadel was partially collapsed, Gordon and Alyx has survived the train crash. The game largely take places in White Forest. Story aside, when it's come to technical, it uses the ![]() ![]() |
|
2007 |
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PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3, Nintendo Switch |
A completely new game and IP from Valve, set in the Half-Life universe, and take places in Aperture Laboratories. It is a puzzle-based shooter game, allowing you to create portals, that link to one another on any flat and large enough surface. In 2023, a unofficially remastered version of the game, ![]() Like the other two new games in The Orange Box package, it uses the ![]() |
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2007 |
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PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3 |
Sequel to , focusing on cartoon graphics unlike the pre-release footage/screenshots, which aimed to be more realistic. This is the last game, along with 2 other games as part of The Orange Box pack to use the engine branch that requires Half-Life 2 assets to operate. The console version of the game is no longer updated, as opposed to PC version of the game, which is frequently updated. |
|
2008 |
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Turtle Rock Studios (under Valve South) |
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PC: Windows, Mac Consoles: Xbox 360, PlayStation 3 |
A new multiplayer co-op game, with horror zombie theme. It use a new engine branch which does not requires Half-Life 2 assets in order to work, it also add many new features and introduced VPK. |
2009 |
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PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3 |
Originally was planned to be an update for Left 4 Dead, it was later released as standalone game. Like Left 4 Dead, it also runs on the same L4D branch, but much newer. Like TF2, the console version ( ![]() This game is also ported to the ![]() |
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2010 |
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PC: Windows | A new multiplayer co-op game, with horror zombie theme. It use a new engine branch which does not requires Half-Life 2 assets in order to work, it also add many new features and introduced VPK. A co-op alien shooter, which was a remake of the Unreal Tournament 2004 mod with the same name. It succeeded the ![]() |
|
2011 |
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PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3, Nintendo Switch (part of Portal Companion Collection) |
Has it's own engine branch, and once again, introduced new features and succeeded ![]() |
|
2012 |
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Hidden Path Entertainment | ![]() |
PC: Windows, Mac, Linux Consoles: Xbox 360, PlayStation 3 |
Sequel to Counter-Strike: Source, originally developed as a Xbox 360 port of Counter-Strike: Source before Valve eventually turned it into a new Counter-Strike game. Used the Source 1 engine until 2023, now uses the new Source 2 engine under the name ![]() Prior to being delisted, it was Free to Play on PC since 2018. |
2013 |
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Dota 2 engine branch (formerly) | PC: Windows, Mac, Linux | Formerly, now using Source 2 since 2015. | |
Year | Title | Co-developed with | Engine branch | Platforms | Notes |
Third-Party
Games, tool and mods made by third-party companies and mod teams.
Released
|
|
|
In development (Unreleased)
This section are for unreleased 3rd party games and tools that are in development, not publicly released, or is in Beta/Early Access.
Planned Release Date | Title | Developer(s) | Publisher(s) | Engine branch (currently) |
Platforms | Notes |
---|---|---|---|---|---|---|
Q4 2023 (upcoming) |
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Second Face Software | Second Face Software | ![]() |
PC: Windows, Linux | Due to the wishes of the engine branch developers, this mod cannot be released until ![]() |
TBA |
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KiwifruitDev | KiwifruitDev | ![]() |
PC: Windows, Linux | Not yet released, it was originally developed on ![]() ![]() ![]() |
TBA |
infestus | Team Infestus | Team Infestus | ![]() |
PC: Windows, Mac, Linux | Currently in closed beta |
TBA |
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Momentum Team | Momentum Team | ![]() |
PC: Windows, Linux | Currently in closed beta. Due to the wishes of the engine branch developers, this mod cannot be released until ![]() |
TBA |
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Fillip Victor | Fillip Victor | ![]() |
PC: Windows | |
TBA |
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Orbifold Studios | TBA | ![]() |
PC: Windows | |
TBA |
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P2:CE Team | P2:CE Team | ![]() |
PC: Windows, Linux | Currently in closed beta. |
TBA |
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LunchHouse Software | LunchHouse Software | ![]() |
PC: Windows |
More Third-party Source Engine games
See Also
External links

- Source Engine Tutorials https://www.sourcemodding.com/tutorials/source
- Tutorials for Source Engine https://gamebanana.com/tuts/games/35
- Tutorials - Source - Mod DB https://www.moddb.com/engines/source/tutorials
- GitHub Issues page - for engine bug reports.