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X-Ray Engine

X-Ray is the engine GSC Game World built in Kyiv for S.T.A.L.K.E.R. It ran all three games of the original trilogy from 2007 to 2009, and modders still build on it. For S.T.A.L.K.E.R. 2: Heart of Chornobyl, GSC moved to Unreal Engine 5.

History

GSC first announced S.T.A.L.K.E.R., then called Oblivion Lost, in November 2001. A pre-alpha build leaked to file-sharing networks in 2003 and showed off the engine before the game was done. Shadow of Chernobyl finally shipped on 20 March 2007, running on X-Ray with Direct3D 9 and Shader Model 3.0, a heavily modified ODE physics engine and A-Life, GSC’s own system that simulates the inhabitants of the Zone. Clear Sky (2008) used X-Ray 1.5 and gained DirectX 10 in patches, and Call of Pripyat (2009) used X-Ray 1.6 with DirectX 11 and tessellation.

The engine outlived the trilogy through modding. The source code of the Clear Sky version appeared on GitHub in 2014 under a licence that is not open source, and the community project OpenXRay builds on it. When a copyright claim took OpenXRay down in January 2024, GSC said on X that the project was allowed as a modding base and that the claim was not theirs; GitHub restored it two days later.

S.T.A.L.K.E.R. 2 was first shown running on Unreal Engine 4. In August 2021 GSC confirmed it had moved to Unreal Engine 5, tweeting: “Hey @UnrealEngine, feel free to mention we’re running on UE5.” The full story of that game is in the making of S.T.A.L.K.E.R. 2.

Games made with X-Ray Engine

3 games, oldest first. Each game links to the article that names its engine.

GameYearDeveloperEngine version
S.T.A.L.K.E.R.: Shadow of Chernobyl2007GSC Game WorldX-Ray Engine
S.T.A.L.K.E.R.: Clear Sky2008GSC Game WorldX-Ray 1.5
S.T.A.L.K.E.R.: Call of Pripyat2009GSC Game WorldX-Ray 1.6

At a glance

Developer
GSC Game World (Kyiv)
First game
S.T.A.L.K.E.R.: Shadow of Chernobyl (2007)
Last version
X-Ray 1.6 (2009)
Licence
In-house; source available to modders, not open source
Status
Retired by GSC; OpenXRay fork active

Sources

Checked .

  1. S.T.A.L.K.E.R.: Shadow of Chernobyl — Wikipedia
  2. S.T.A.L.K.E.R.: Clear Sky — Wikipedia
  3. S.T.A.L.K.E.R.: Call of Pripyat — Wikipedia
  4. S.T.A.L.K.E.R. 2: Heart of Chornobyl — Wikipedia
  5. S.T.A.L.K.E.R. game engine OpenXRay gets taken down on GitHub — gamingonlinux.com
  6. GitHub - OpenXRay/xray-16: Improved version of the X-Ray Engine, the game engine used in the world-famous S.T.A.L.K.E.R. game series by GSC Game World. Join OpenXRay! ;) — GitHub
  7. GitHub - OpenXRay/xray: X-Ray Engine 1.0 expansion. Original version was used in S.T.A.L.K.E.R.: Shadow of Chernobyl. — GitHub
  8. 'Stalker 2: Heart Of Chernobyl' is being developed in Unreal Engine 5 — NME
Image credits
  • X-Ray Engine logo — GSC Game World. Trademark of GSC Game World. Placed on a black square and converted to WebP