The Source engine, developed by Valve Corporation, debuted with Counter-Strike: Source in summer 2004, and later in November with Half-Life 2. The Source engine is a successor to the GoldSrc engine, which is in turn built off of the now open source Quake Engine. John Carmack commented in 2004 that "there are still bits of early Quake code in Half-Life 2."
The engine is modular by design, allowing new technology to be implemented during the development of each Valve-developed game.
Initial release of the engine. Levels are built with brushes, primitives that can be textured and lit. All brush, model, entity and light data is compiled into a single file with the extension .bsp, using binary space partitioning. This method allows for less powerful computers to run enclosed areas at an acceptable performance as few calculations for the world are done during operation.
High dynamic range lighting was introduced in Day of Defeat: Source prior to its official demonstration in Lost Coast. It simulated the aperture of a camera to create lighting effects beyond a monitor's actual range. This required all lighting code to be rewritten.
Improved facial animation system, AI routines and shaders. Rim highlighting was first seen here.
Many additions added in this version. Among those are soft particle effects, hardware accelerated facial animation and multi-processor support for the Xbox 360 and Playstation 3. Multi-processor support for the PC was unstable until the later release of Left 4 Dead.
Many additions added in this version. Among those are improved multi-processor support of the PC, physics-based animation for clothes and hair and improved AI path finding. Lighting allowed self-shadowing normal maps and many post-processing effects were added, such as film grain, dynamic colour correction and vignetting.
An increase in the variation and number of effects seen by the player, but within the more limiting memory constraints of the Xbox 360. Improvements to the render of water were also added, allowing for hints of water movement.
Introduction of real-time depth-of-field shader and an experimental tile-based level generator called TileGen.
An improvement on the shadow mapping technology, sound operations for the dynamic music, blob particles for the rendering and correct spreading of paint / gels and the ability to project video onto different materials.
The Source SDK is a software development kit for creating maps and mods for the Source engine. It has a variety of tools and utilities.
is the tool used to access animations and choreography sequences. It allows the user to create or edit facial animations, gestures and movement which can be blended together. Lip syncing can be done using extracted phenomes from a spoken .wav file.
is a tool that allows users to view any model in a Source engine directory. It can view animations, bones and attachment points as they would appear in engine.
is the tool with which maps are created for the Source engine. Maps are created as .vmf files and compiled into .bsp files. All rendering data is contained within this file, including visibility and lighting.