| Source | |
|---|---|
 | |
| Developer | Valve |
| Initial release | October 2004; 21 years ago (2004-10) |
| Repository | source-sdk-2013 onGitHub |
| Written in | C++ |
| Middleware | Havok |
| Predecessor | GoldSrc |
| Successor | Source 2 |
| License | Proprietary |
| Website | developer |
Source is a 3Dgame engine developed byValve. It debuted as the successor toGoldSrc in 2004 with the releases ofHalf-Life: Source,Counter-Strike: Source, andHalf-Life 2. Valve used Source in many of their games in the following years, includingTeam Fortress 2,Counter-Strike: Global Offensive,Dota 2, and thePortal andLeft 4 Dead franchises. Other notable third-party games using Source include most games in theTitanfall franchise,Vampire: The Masquerade – Bloodlines,Dear Esther,The Stanley Parable andGarry’s Mod. Valve released incremental updates to Source until succeeded bySource 2 in 2015.
Source distantly originates from theGoldSrc engine, itself a heavily modified version ofJohn Carmack'sQuake engine with some code from theQuake II engine. Carmack commented on his blog in 2004 that "there are still bits of earlyQuake code inHalf-Life 2".[1] Valve employee Erik Johnson explained the engine'snomenclature on the Valve Developer Community:[2]
When we were getting very close to releasingHalf-Life (less than a week or so), we found there were already some projects that we needed to start working on, but we couldn't risk checking in code to the shipping version of the game. At that point weforked off the code inVSS to be both
/$Goldsrcand/$Src. Over the next few years, we used these terms internally as "Goldsource" and "Source". At least initially, the Goldsrc branch of code referred to the codebase that was currently released, and Src referred to the next set of more risky technology that we were working on. When it came down to showHalf-Life 2 for the first time atE3, it was part of our internal communication to refer to the "Source" engine vs. the "Goldsource" engine, and the name stuck.
Source was developed part-by-part from this fork onwards, slowly replacing GoldSrc in Valve's internal projects[3] and, in part, explaining the reasons behind its unusually modular nature. Valve's development of Source since has been a mixture of licensedmiddleware and in-house-developed code. Older versions of Source useBink Video for video playback,[4] however more recent releases of the Source engine useWebM videos for menu backgrounds,Full Motion Videos, and splash screens.[5].
Source was created to evolve incrementally with new technology, as opposed to thebackward compatibility-breaking "version jumps" of its competitors. Different systems within Source are represented by separate modules which can be updated independently. WithSteam, Valve can distribute these updates automatically among its many users. In practice, however, there have been occasional breaks in this chain of compatibility. The release ofHalf-Life 2: Episode One andThe Orange Box both introduced new versions of the engine that could not be used to run older games ormods without the developers performing upgrades to code and, in some cases, content.[6] Both cases required markedly less work to update its version than competing engines.
The Source 2006 branch was the term used for Valve's games using technology that culminated with the release ofHalf-Life 2: Episode One.HDR rendering andcolor correction were first implemented in 2005 usingDay of Defeat: Source, which required the engine's shaders to be rewritten.[7] The former, along with developer commentary tracks, were showcased inHalf-Life 2: Lost Coast.Episode One introducedPhong shading and other smaller features.Image-based rendering technology had been in development forHalf-Life 2,[8] but was cut from the engine before its release. It was mentioned again byGabe Newell in 2006 as a piece of technology he would like to add to Source to implement support for much larger scenes that are impossible with strictlypolygonal objects.[9]
The Source 2007 branch represented a full upgrade of the Source engine for the release ofThe Orange Box. An artist-driven, threadedparticle system replaced previouslyhard-coded effects for all of the games within.[citation needed] An in-process tools framework was created to support it, which also supported the initial builds ofSource Filmmaker. In addition, the facial animation system was made hardware-accelerated on modern video cards for "feature film and broadcast television" quality.[10] The release ofThe Orange Box on multiple platforms allowed for a largecode refactoring, which let the Source engine take advantage of multiple CPU cores.[11] However, support on the PC was experimental and unstable[12] until the release ofLeft 4 Dead.[13] Multiprocessor support was later backported toTeam Fortress 2 andDay of Defeat: Source.[14] Valve created theXbox 360 release ofThe Orange Box in-house, and support for the console is fully integrated into the main engine codeline. It includes asset converters, cross-platform play andXbox Live integration.[15] ThePlayStation 3 release was outsourced toElectronic Arts, and was plagued with issues throughout the process.Gabe Newell cited these issues when criticizing the console during the release ofThe Orange Box.[16]
The Left 4 Dead branch is an overhaul of many aspects of the Source engine through the development of theLeft 4 Dead series. Multiprocessor support was further expanded, allowing for features like split screen multiplayer, additional post-processing effects, event scripting withSquirrel, and the highly-dynamicAI Director. The menu interface was re-implemented with a new layout designed to be more console-oriented. This branch later fueled the releases ofAlien Swarm andPortal 2, the former released with source code outlining many of the changes made since the branch began.Portal 2, in addition, served as the result of Valve taking the problem of porting to PlayStation 3 in-house, and in combination withSteamworks integration creating what they called "the best console version of the game".[17]
In April 2010, Valve released all of their major Source games onOS X, coinciding with the release of the Steam client on the same platform. Valve announced that all their future games would be released simultaneously for Windows and Mac.[18][19] The first of Valve's games to support Linux wasTeam Fortress 2, the port released in October 2012 along with the closed beta of the Linux version of Steam. Both the OS X and Linux ports of the engine take advantage ofOpenGL and are powered bySimple DirectMedia Layer.[20] During the process of porting, Valve rearranged most of the games released up toThe Orange Box into separate, but parallel "singleplayer" and "multiplayer" branches. The game code to these branches was made public to mod developers in 2013, and they serve as the current stable release of Source designated for mods. Support for Valve's internal Steam Pipe distribution system as well as theOculus Rift are included.[21] In May 2014,Nvidia released ports ofPortal andHalf-Life 2 to theirTegra 4-based Androidhandheld game consoleNvidia Shield.[22]
Source 2 was announced by Valve as the successor to Source at theGame Developers Conference in March 2015.[23] There, Valve stated that it would be free to use for developers, with support for theVulkan graphical API, as well as using a new in-housephysics engine called Rubikon.[24][25] In June 2015, Valve announced thatDota 2, originally developed with Source, would be ported over to Source 2 in an update calledDota 2 Reborn.[26][27]Reborn was first released to the public as an opt-in beta update that same month before officially replacing the original client in September 2015, making it the first game to use the engine.[28][29] The engine had succeeded Source by the late 2010s.
Source SDK is thesoftware development kit for the Source engine, and contains many of the tools used by Valve to develop assets for their games. It comes with several command-line programs designed for special functions within the asset pipeline, as well as a few GUI-based programs designed for handling more complex functions. Source SDK was launched as a free standalone toolset through Steam, and required a Source game to be purchased on the same account. Since the release ofLeft 4 Dead in late 2008, Valve began releasing "Authoring Tools" for individual games, which constitute the same programs adapted for each game's engine build. AfterTeam Fortress 2 became free-to-play, Source SDK was effectively made open to all Steam users. When some Source games were updated to Source 2013, the older Source SDKs were phased out. The three applications mentioned below are now included in the install of each game.[citation needed]
There are three applications packaged in the Source SDK: Hammer Editor, Model Viewer, and Face Poser. The Model Viewer is a program that allows users to view models and can be used for a variety of different purposes, including development. Developers may use the program to view models and their corresponding animations, attachment points, bones, and so on. Face Poser is the tool used to access facial animations and choreography systems. This tool allows one to editfacial expressions, gestures and movements for characters,lip sync speech, and sequence expressions and other acting cues and preview what the scene will look like in the game engine.[30]
The Hammer Editor, the engine's officiallevel editor, uses rendering and compiling tools included in the SDK to create maps using thebinary space partitioning (BSP) method. Level geometry is created with 3D polygons calledbrushes; each face can be assigned atexture which also defines the properties of the surface such as the sounds used for footsteps.[31] Faces can also be converted into a displacement allowing for more natural shapes such as hills to be created.
Scenery objects or complex geometry can be imported as separate 3D models from the game directory. These models can also be used as physics objects or interactive props. The editor also features an in-depth logicI/O system that can be used to create complex interactive elements. Signals to trigger different responses or change the state of an entity can be sent between entities such as buttons,NPCs, intangible trigger brushes, and map props.
TheSource Dedicated Server (SRCDS) is a standalone launcher for the Source engine that runs multiplayer game sessions without requiring a client. It can be launched through Windows or Linux and can allow for custom levels and assets. Most third-party servers additionally runMetamod:Source and SourceMod, which together provide a framework on top of SRCDS for custom modification of gameplay on existing titles.[32][33]
Source Filmmaker (SFM) is a 3D animation application that was built from within the Source engine.[34] Developed by Valve, the tool was originally used to create movies forDay of Defeat: Source andTeam Fortress 2. It was also used to create some trailers for Source Engine games. SFM was released to the public in 2012.
In June 2016, Valve released the Destinations Workshop Tools, a set of freevirtual reality (VR) creation tools running using the Source 2 SDK.[35]
In June 2005, Valve opened the Valve Developer Communitywiki. It replaced Valve's static Source SDK documentation with a fullMediaWiki-powered community site.[36]
Valve staff have occasionally produced professional and/or academic papers for various events and publications, includingSIGGRAPH,Game Developer Magazine andGame Developers Conference, explaining various aspects of Source engine's development.[37]
In addition to the games listed above,Titanfall,Titanfall 2, andApex Legends use a custom engine derived from Source. It has been significantly modified to the point whereTitanfall 2's lead engineer claimed of this engine that "there's not a lot of Source left".[41]
Chris Green: The Source engine supports a wide variety of shaders. The refraction shader on the window here requires us to copy the scene to a texture, refract it, and then apply it the window surface. To fully support HDR, every shader in the engine needed to be updated, so this refraction shader was improved to the support the full range of contrast.
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