Source (game engine)

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Source engine

Developer(s)	Valve Corporation
Stable release	Protocol 37, Build 3679 / December 5, 2008
Written in	C++
Platform	Microsoft Windows, Playstation 3, Xbox, Xbox 360
License	Proprietary
Website	http://source.valvesoftware.com/

The Source engine is a 3D game engine developed by Valve Corporation. The engine supports Microsoft Windows (32-bit and 64-bit), Xbox, Xbox 360, and PlayStation 3.

It debuted in June 2004 with Counter-Strike: Source and shortly thereafter Half-Life 2. Other games using the engine range from the sandbox style of Garry's Mod to the First Person Fighter Zeno Clash.

Contents 1 Notable technology 2 Modularity and notable upgrades 2.1 AI Director 3 Future technology 3.1 Source Filmmaker 3.2 Image-Based Rendering 4 Origins 5 Criticism 5.1 Toolset 5.2 Programming 6 Valve Developer Community 7 Licensed Source games 7.1 Mods 8 Papers 9 See also 10 References

[edit] Notable technology

For a more complete list, see Source Engine Features at the Valve Developer Community.

• Direct3D rendering from 6 (available but unsupported), to 9 with DirectX 10 hardware (referred to by the engine as "9.8")^[1]
  • OpenGL ES on Playstation 3.^{[citation needed]}
• High dynamic range rendering (HDR). It was the first major instance of Source's modularity in use, with the release of Half-Life 2: Lost Coast.
• Lag-compensating network communications^[2]
• Network-enabled and bandwidth-efficient physics engine^[3]. Source uses a heavily tweaked version of the Havok physics engine^[4].
• Multiprocessor support (any number of cores)^[5]
• Facial animation system: A full range of human and non-human facial movements, based on Professor Paul Ekman's Facial Action Coding System. It works in tandem with lip-syncing, which is auto-generated and localizable^[6]. Facial animation already had two upgrades since the release of Half-Life 2.
• Blended skeletal animation system^[7], including inverse kinematics^[8]
• Full-screen motion blur.
• Dynamic lighting and shadowing^[9][10]
• Alpha to coverage^[11] edge smoothing for foliage etc.^[12]
• Significant source code access for mod teams^[13]
• Network- or internet-distributed map compiler^[14]

[edit] Modularity and notable upgrades

Source was created to evolve incrementally as technology moved onwards, as opposed to the backwards compatibility-breaking "version jumps" of its competitors. This becomes especially relevant when considering Source's links to Steam, as the latter's automatic updates allow new versions of the former to 'pollinate' a user base to all intents and purposes instantaneously.

In practice however, there have been occasional breaks in this chain of compatibility. The release of Half-Life 2: Episode One and The Orange Box both introduced new versions of the engine that could not be used to run older games or mods without the developers performing upgrades to code and, in some cases, content. But both times the work required to move from the older version to the newer was significantly less than what one might have come to expect from other engines - where such an action may well not even be possible without total re-development.

Feature	Date of release	First use	Description
High dynamic range rendering	September 29, 2005	Day of Defeat: Source Half-Life 2: Lost Coast	Simulation of brightness values beyond computer monitors' actual range.
Facial animation 2	June 1, 2006	HL2: Episode One	Increased the details of facial expressions at close range.[15]
Soft particles	October 10, 2007	Team Fortress 2 HL2: Episode Two	Artist-driven and multiprocessor-optimised particles. Techniques are used to prevent particles being 'clipped' by 3D geometry.[citation needed]
Full-screen motion blur	October 10, 2007	Orange Box games	Not the same as the "cinematic" blur used to render Valve's various trailers; only appears when the camera is moved at high speed (e.g. spinning or falling).[16]
Facial animation 3	October 10, 2007	Team Fortress 2 HL2: Episode Two	Hardware accelerated on modern video cards for "feature film and broadcast television" quality.[17]
Dynamic lighting and shadowing	October 10, 2007	HL2: Episode Two	New texture-projecting dynamic lighting and shadow mapping system. Used primarily for Ep2's flashlight shadows.[18][10]
Landscape and flora rendering	October 10, 2007	HL2: Episode Two	Internal optimisations for the compiling and drawing of large open areas, and the addition of support for Alpha to coverage[11] on raster images (e.g. leaves).
Cinematic physics	October 10, 2007	HL2: Episode Two	Not actually a feature of the engine – a common misconception. Cinematic "physics" are actually pre-calculated animations created with Maya plug-in Blast Code.[19]
Multiprocessor optimizations	October 10, 2007	Orange Box games	Unlocked faster processing on systems with multiple CPUs or CPU cores, including the Xbox 360 and PlayStation 3 consoles.[10][20]On the PC this feature was experimental and unstable [21], Left 4 Dead brought improved support.[22]
Physics-animation blending	October 10, 2007	Team Fortress 2 HL2: Episode Two	Support for bone joints to be physically simulated on an otherwise pre-animated model. Used for flexible clothing and hair, wings, belt items, blubber, etc.
Post processing effects	November 18, 2008	Left 4 Dead	Dynamic color correction and filters like contrast, sharpening, film grain and vignetting. Used to draw the players attention, affect mood, or emulate a certain visual style[23][24]
Rendering and AI improvements	November 18, 2008	Left 4 Dead	Improvements to rendering and AI calculation to allow much larger number of characters to be rendered at once[23]

[edit] AI Director

During the development of Left 4 Dead Valve created a new artificial intelligence technology they dubbed The Director.^[25] The Director is used to procedurally generate a different experience for the players each time the game is played. It monitors individual players' performance and how well they work together as a group to pace the game, determining the number of zombies that attack the player and the location of boss infected encounters based on information gathered. Besides pacing, the Director also controls some video and audio elements of the game to set a mood for a boss encounter or to draw the players' attention to a certain area.^[26].

A much simpler version of the A.I. Director was already used for some key battles in Half-Life 2: Episode Two^[27].

Valve calls the way the Director is working "Procedural narrative" because instead of having a difficulty level which just ramps up to a constant level, the A.I. analyze how the players fared in the game so far, and try to add subsequent events that would give them a sense of narrative.^[28]

Valve is looking for ways to apply the Director in their future games to make pacing and difficulty more dynamic. It will also be made available to mod makers through a Source SDK update following the release of Left 4 Dead. ^[29]

[edit] Future technology

[edit] Source Filmmaker

The tool used to create Team Fortress 2's "Meet the Team" videos as well as Left 4 Dead's introduction videos is the Source Filmmaker, an application that runs inside the engine. It allows users to record themselves many times over in the same scene, creating the illusion of many participants, as well as supporting a wide range of cinematographic effects and techniques such as motion blur, Tyndall effects, Dynamic Lighting, and depth of field. (Motion blur has now been added to the games themselves, though only when the view is moving at high speeds—not per-object as in the film-maker.) This tool is expected to be released to the public upon release of the final "Meet the Team" video.^{[citation needed]}

[edit] Image-Based Rendering

Image-based rendering technology had been in development for Half-Life 2^[30] but was cut from the engine before its release. It was mentioned again by Gabe Newell in 2006 as a piece of technology he would like to add to his company's engine, in order for them to support far larger scenes than are possible with strictly polygonal objects.^[31]

[edit] Origins

Source distantly originates from the GoldSrc engine, itself a heavily modified version of John D. Carmack's original Quake engine, as is explained by Valve employee Erik Johnson on the Valve Developer Community:^[32]

When we were getting very close to releasing Half-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 we forked off the code in VSS to be both $/Goldsrc and /$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 show Half-Life 2 for the first time at E3, 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^[33] and explaining in part the reasons behind its unusually modular nature. Valve's development of Source since has been a mixture of licensed middleware (Havok Physics, albeit heavily modified, and MP3 playback) and in-house-developed code.

John Carmack commented on his blog in 2004 that "there are still bits of early Quake code in Half-Life 2"^[34] and numerous development interfaces are similar to Quake's, at least at a high level.

[edit] Criticism

[edit] Toolset

The Source SDK tools are criticised for being outdated and difficult to use.^[35] A large number of the tools, including those for texture and model compilation, require varying levels of text-editor scripting from the user before they are executed at the command line with sometimes quite lengthy console commands.^[36] This obtuseness was cited by the University of London when they moved their exploration of professional architectural visualisation in computer games to Bethesda Softworks' Gamebryo-based Oblivion engine after a brief period with Source.^[37] Third-party tools provide GUIs,^[38] but are not supported by Valve.

The interface of Valve's Hammer Editor, the SDK's world-creation tool, has not changed significantly since its initial release for GoldSrc and the original Half-Life in 1998.

Before the Valve Developer Community Wiki was opened the SDK's user documentation was limited.^[39]

[edit] Programming

Unlike most modern game engines, Source requires all program code to be written in C++. This can be contrast with the Unreal engine and its UnrealScript language, which allows code to be written as discrete "mutators" and distributed piecemeal. The closest Source comes to this is server plug-ins in multiplayer games that can be installed by administrators — those aside, even the smallest change to a game's behaviour requires source code access and the creation of a different, and quite possibly incompatible, version of the game's binaries.

In response to this, several Source engine games and mods, starting with Garry's Mod and including Fortress Forever, GoldenEye: Source and Smod, have implemented the Lua scripting language. These implementations are not available in either the consumer or licensee SDKs however, and as a result the development communities that have formed around each (which have sometimes created entire games within games) cannot migrate to the Source engine in general.

[edit] Valve Developer Community

On June 28, 2005, Valve opened the Valve Developer Community Wiki. VDC replaced Valve's static Source SDK documentation with a full MediaWiki-powered community site; within a matter of days Valve reported that "the number of useful articles nearly doubled". These new articles covered the previously undocumented Counter-Strike: Source bot (added by the bot's author, Mike Booth), Valve's NPC AI, advice for mod teams on setting up source control, and more.

[edit] Licensed Source games

Valve

Counter-Strike: Source

Day of Defeat: Source

Half-Life 2

Half-Life 2: Deathmatch

Half-Life 2: Episode One

Half-Life 2: Episode Two

Half-Life 2: Lost Coast

Half-Life Deathmatch: Source

Half-Life: Source

Left 4 Dead

Left 4 Dead 2

Portal

Team Fortress 2

Other developers

The Crossing^[40]

Dark Messiah of Might and Magic

E.Y.E [1]

Garry's Mod

Mabinogi: Heroes

Nuclear Dawn [2] [3]

Postal III^[41]

Salvation

SiN Episodes

Sting: The Secret Operations

The Ship

They Hunger: Lost Souls

Vampire: The Masquerade – Bloodlines

Zeno Clash

Untitled Threewave Software game^[42]

Kuma Reality Games

DinoHunters

Dogfights: The Game

The History Channel's ShootOut! The Game

The Kill Point: Game

Kuma\War 2

Education and research

VR Worlds 2 [4]

[edit] Mods

See also: Category:Source engine mods

[edit] Papers

Valve staff infrequently produce papers for various events and publications, including SIGGRAPH, Game Developer Magazine and Game Developers Conference, explaining various aspects of Source's development. They are aimed at professional audiences and often discuss complex concepts. They are listed on Valve's corporate website.

[edit] See also

Wikimedia Commons has media related to: Zeno Clash

• First-person shooter engine
• Game engine
• Source SDK

[edit] References

v • d • e Video game technology by the Valve Corporation Content delivery Steam  · Steamworks Game engines GoldSrc  · Source Third-party modifications GoldSrc modifications  · Source modifications Other topics Half-Life TV  · Source Software Development Kit  · Valve Anti-Cheat

v • d • e Source engine games Valve Half-Life series Half-Life 2 · Half-Life 2: Deathmatch · Half-Life Deathmatch: Source · Half-Life: Source · Half-Life 2: Lost Coast · Half-Life 2: Episode One · Half-Life 2: Episode Two · Half-Life 2: Episode Three Other Counter-Strike: Source · Day of Defeat: Source · Left 4 Dead · Left 4 Dead 2 · Portal · Team Fortress 2 Kuma The DinoHunters · Dogfights: The Game · The History Channel's ShootOut! The Game · The Kill Point: Game · Kuma\War 2 Other The Crossing · Dark Messiah of Might and Magic · E.Y.E. · Garry's Mod · Mabinogi Heroes · Nuclear Dawn · Postal III · Salvation · SiN Episodes · Sting: The Secret Operations · The Ship · They Hunger: Lost Souls · Vampire: The Masquerade – Bloodlines · VR Worlds 2 · Zeno Clash