Source Engine

Lore & Background

Source distantly originates from the GoldSrc engine, itself a heavily modified version of John Carmack's Quake engine with some code from the Quake II engine. Carmack commented on his blog in 2004 that 'there are still bits of early Quake code in Half-Life 2'. Valve employee Erik Johnson explained the engine's nomenclature on the Valve Developer Community: '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 and, in part, explaining the reasons behind its unusually modular nature. Valve's development of Source since has been a mixture of licensed middleware and in-house-developed code. Older versions of Source use Bink Video for video playback, however more recent releases of the Source engine use WebM videos for menu backgrounds, Full Motion Videos, and splash screens.

In Their Own Story

The server room hummed at 2 a.m., rows of idle machines breathing cold air into the dark. A junior network engineer pulled up the dedicated-server console for the night's first stress test—two hundred simulated soldiers dropping into a rain-slicked urban map, each one a stream of physics queries hitting the Havok solver. The first wave of bodies collided with a chain-link fence; the metal groaned, bent, and tore in ragged strips. A crate slid three meters across wet concrete before stopping. Somewhere in the particle buffer, a muzzle flash bloomed and died in four frames. The engineer watched the tick rate hold steady, exhaled, and typed a single line into the log: "Source holding. All systems nominal." Outside the window, the city was empty, but inside the engine, a hundred lives were already arguing over the last cover position.

Reader's Guide

Source was created to evolve incrementally with new technology, as opposed to the backward compatibility-breaking 'version jumps' of its competitors. Different systems within Source are represented by separate modules which can be updated independently. With Steam, 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 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. Both cases required markedly less work to update its version than competing engines. Key branches include Source 2006 (culminating with Half-Life 2: Episode One, introducing HDR rendering, color correction, and Phong shading), Source 2007 (full upgrade for The Orange Box, adding a threaded particle system, hardware-accelerated facial animation, and multi-core CPU support), the Left 4 Dead branch (overhaul with multiprocessor support, split-screen multiplayer, event scripting with Squirrel, and the AI Director), and OS X, Linux, and Android support (ports using OpenGL and Simple DirectMedia Layer, with game code made public to mod developers in 2013). Source 2 was announced at the Game Developers Conference in March 2015, stated to be free for developers with support for Vulkan and a new in-house physics engine called Rubikon. Dota 2 was ported to Source 2 in an update called Dota 2 Reborn, first released as an opt-in beta in June 2015 and officially replacing the original client in September 2015, making it the first game to use the engine. The engine had succeeded Source by the late 2010s.

Did You Know?

• Source distantly originates from the GoldSrc engine, itself a heavily modified version of John Carmack's Quake engine with some code from the Quake II engine.
• The name 'Source' came from internal Valve communication referring to the next set of risky technology, as opposed to the 'Goldsource' branch of the currently released code.
• Source 2 was first announced at the Game Developers Conference in March 2015 and debuted with Dota 2 Reborn in September 2015.
• The Left 4 Dead branch introduced the highly-dynamic AI Director and event scripting with Squirrel.