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Portal 2 engine branch

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Portal 2 engine branch
In-game screenshot of Portal 2, running on Portal 2 engine branch.
In-game screenshot of Portal 2, running on Portal 2 engine branch.
Developer(s)
Release date(s)
April 18, 2011
Status
Actively updated (as of 2026)
SDK
Portal 2 Authoring Tools
Tools only, SDK Base & source code not available.
Forks
Titanfall branch Titanfall branch (heavily modified & completely rebuilt)
Successor
Improved shadow mapping in Portal 2.
Blob particles in Portal 2.

The Portal 2 engine branch Portal 2 engine branch was introduced with Portal 2 in 2011. It was forked from the Left 4 Dead engine branch between Left 4 Dead and Left 4 Dead 2 (starting off with the original Left 4 Dead),[1] with some elements (and new features) from L4D2 version of the Left 4 Dead branch then later Alien Swarm engine branch (which it succeeded) added when those games & branches were close to it's release during the development of Portal 2 and it's branch. It was superseded by the CS:GO engine branch. With the release of Portal 2, this marks the first time Source engine was ported to PlayStation 3, since the release of The Orange Box.

Note.pngNote: As of Counter-Strike 2's release, the Portal 2 engine branch is currently the latest standalone Source 1 branch (alongside Orange Box derived Team Fortress 2 branch) that is still being actively maintained by Valve.

Features

New since the Alien Swarm engine branch is:

Improved shadow mapping
The entity env_projectedtexture is significantly improved. Compared to previous implementations, it has higher default resolution, better edge filtering and support for the caching of shadows from static objects.
Video playback on materials
Added support to render Bink Video in-game on surfaces, used for elevator screens in Portal 2.
Blob particles
A particle renderer that renders blobs of liquid, used for paint gel in Portal 2. A similar blob particles system are originally present in Source 2007 Source 2007 or Source 2009 Source 2009, but was disabled in code.
World portals
World portals that can seamlessly link together separate parts of the world. This feature is exclusive to this engine branch.
Sound operators
For defining complex audio behaviour.
Finished water debris flow
The base texture water flow feature from the Alien Swarm engine branch has been finished, with flowed normals now distorting color lookup and the flow map's alpha channel controlling color map opacity.

Tools

Hammer Hammer new features
DotA Camera - restrict the camera to be in the DotA orientation and distance from the ground. Likely included because Valve was developing Dota 2 simultaneously with Portal 2, leading to this feature slipping into Portal 2's engine branch.

PS3 exclusive features

Official PS3 Support
PS3 is now officially supported by Valve. Unlike the PS3 port of The Orange Box The Orange Box, which was outsourced to Electronic Arts, Portal 2's PS3 port was developed in-house. Valve seemingly put more effort into making use of the PS3 hardware than EA did, allowing the game to achieve better performance by taking advantage of the SPE cores on the RSX processor.
Needless to say, this is not particularly useful to most modders though.
MLAA anti-aliasing
Post-processing effect used to reduce stair-step (aliasing) effect on geometry and transparent textures, while having less performance impact compared to MSAA.
Steam integration (Steamworks)
The PlayStation 3 version of Portal 2 features Steam integration. Achievements are synced with both PSN and Steam, and PS3 users were able to play cross-platform co-op with Steam friends. Steam services on PS3 were shut down in 2016, although as Steam itself obviously still exists, it is possible to restore this functionality on a modded PS3 using third party plugins.
PlayStation Move support
Portal 2 on PS3 supports PlayStation Move motion controller.

Availability and usage

The following titles run on the Portal 2 engine branch:

Source code and SDK Base for this branch is not available. However, authoring tools exist for custom content:

References

1. Confirmed by the Steam2 content delivery leak in August 30, 2026. The unfinished Portal 2 build from Jul 28, 2009, also known as the Corehub build, which was before the release of Left 4 Dead 2, was built on modified Left 4 Dead branch (L4D version) with Portal + few Half-Life 2 gamecode. The early Portal 2 build has protocol version 37. As Left 4 Dead in Jan 2009 later get's the protocol version updated from "37" to "38", it is assumed that the fork was occurred between the Left 4 Dead release (or before it's release) in 2008 up to Jan 2009. Said 2009 Corehub build also has Motel props textures with VTF 7.5, a VTF version which would eventually be released with Alien Swarm. Later by 2010, the 2010 build of Portal 2 has Left 4 Dead 2 menu UI, replacing the stock Source engine VGUI menu from Half-Life 2/Portal 1, suggesting that various L4D2 code were also ported over to the in-development Portal 2 branch..

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