Strata Source
Strata Source (more informally known as Strata, and formerly known as the Chaos Engine) is a third-party 
Source engine branch using licensed code. It is a modified version of the 
CS:GO engine branch that combines the features of both CS:GO and the 
Portal 2 engine branch, along with many improvements that bring Source close to modern standards. This engine branch was first released publicly with the launch of 
Portal: Revolution, and is still in active development.
Features
Feature list from the Strata Source Wiki
New since the CS:GO engine branch:
- Native Direct3D 11 renderer
- Replaces Direct3D 9 renderer, and adds some new features that previous version of Direct3D doesn't have.
- Vulkan renderer on Linux, using DXVK to convert DX11 calls to Vulkan
- 64-bit executable
- Game runs on 64-bit on all platforms; 32-bit and Mac OS support has been dropped. 64-bit allows better performance and allows the game to access more than 4GB of RAM.
- PBR shaders
Introduces a new 
PBR shader that attempts to create realistic reactions to light
- Ported Portal 2 engine branch features
- Including but not limited to World Portals and Portal gun
- Expanded map limits (128k x 128k x 128k) via BSP v25 and increased entity cap
- Backwards compatible
- Compatible with BSP v19-21
- Compatible with
Source 2013 (and older) branch models - The model format found in games such as
is now supported. - WEBM video support, replacing older Bink videos
- Increased framerate, lower file sizes, and easier to author
- New v7.6 VTF version
- Adds support for the higher-quality ATI1N, ATI2N, BC6H, and BC7 texture compression formats, as well as lossless
deflate compression on top of existing image format, for reduced size. Better support for 4K textures[How?]. - Many improvements to Linux support
- Fully cross-platform engine tools and utils
- Improved MP3 support with addition of OGG (Vorbis, Opus, Speex and PCM supported) and FLAC audio formats
- Steam Audio
- Improved HRTF, environmental reflection effects, basic occulsion
- Many improvements to the
Hammer level editor, named 
Strata Hammer - Many code quality improvements (Refactors, cleanup, and C++20)
- Sentry crash report integration
Availability
The following titles run on the Strata Source branch:
Portal 2: Community Edition
Momentum Mod- Portal: Revolution (Uses older version of P2:CE as a base)
The source code for this branch is not available, however, authoring tools exist for each game, located in 
/bin/win64/.
See also
- Strata Source's Wiki
Mapbase, a mod for Source 2013 Singleplayer with similar goals
Alien Swarm Deferred- Strata Hammer
