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Lambda1VR is a port / mod of the Xash3D-FWGS Half-Life Engine for the Oculus Quest adding 6DoF weapon support and OpenGLES2.0 rendering.

Xash3D is a game engine, aimed to provide compatibility with Half-Life Engine, 
as well as to give game developers well known workflow and extend it.
Read more about Xash3D on ModDB:


The easiest way to install this on your Quest is using SideQuest, a PC desktop app designed to simplify sideloading apps and games ( even beat saber songs on quest ) on Standalone Android Headsets like Oculus Quest and Oculus Go. It supports drag and drop for installing APK files!

Download the latest version of SideQuest here:

Once you have installed Lambda1VR you will need to copy the game assets from a legally owned half-life install. Details below.


This is solely an engine port/mod, no game assets are included whatsoever. YOU MUST LEGALLY OWN HALF-LIFE IF YOU WISH TO PLAY IT IN VR USING LAMBDA1VR.

The original half-life can be purchased on Steam:

PLEASE NOTE: Half-life: Source is not compatible.

Copying the Full Game files to your Oculus Quest

Before attempting to start Lambda1VR you need to do the following:

  • Create a folder on your Quest called "xash"
  • Locate the install of half-life on your PC, if installed from Steam then it will be somewhere like C:/Program Files (x86)/Steam/steamApps/common/HalfLife/
  • Copy the entire folder "valve" to the newly created "xash" folder on the Quest (This will take a long time)
  • (optional) Copy the contents of the valve_hd folder into the valve folder now on your Quest (this gives you some nicer models). If you are a Mac user please read this post, otherwise you will get a crash:

Save Games File

Save game files are stored on the internal memory of your quest in the xash/valve folder. This means that if you uninstall/reinstall Lambda1VR all the saves are retained. If you change headset just make sure you copy {quest}/xash/valve/save to the new Quest. Any update will not affect any of your save game files.


Before you ask... YES!, the crowbar has to be swung in real life to smash stuff! (except in multi-player, you still have to press the trigger I'm afraid).

Left-handed people

Add the following cvar to your config.cfg file: vr_control_scheme "10"

If left handed players wish to mirror the weapons to avoid seeing the gaps in some of the weapon models then set the following cvar in config.cfg: vr_mirror_weapons "1"

Button / Controller Mappings (Primary configuration)


You can get quick access to the crowbar by reaching behind (so the controller is obscured) and then holding down the grip trigger, this will then auto-switch to the crowbar whilst the grip trigger remains held down. As soon as you release the grip you will switch back to the weapon you had selected previously. This is an excellent way to quickly smash boxes/vents etc without the hassle of cycling through the weapon selector for the crowbar.


This is the primary/default button mapping, an alternative configuration that might suit smooth turn locomotion players will be coming soon..

Dominant Hand Controller
Orientation/Position Weapon Orientation/Position
Trigger Fire Primary / Secondary
Grip (Hold) Enable secondary fire
Grip (Quick Click) Reload
Click Thumbstick Use (action)
Thumbstick Left/Right Turn
Thumbstick Up/Down Select Weapon (Fire to accept new weapon)
A / X (depending on dominant hand controller) Crouch*
B / Y (depending on dominant hand controller) Jump

* If you physically crouch in real life, then when the proper duck mechanic is triggered in-game you will see a HUD indicator in the top-right of the view

Off-hand Controller
Thumbstick Move/Strafe
Menu Button Menu
X / A (depending on off-hand controller) Flashlight on/off
Y / B (depending on off-hand controller) Toggle screen mode for cut-scenes (Show multi-player score table in multi-player games)
Orientation/Position Flashlight Orientation/Position
Trigger Hold down to run)
Grip (hold) Weapon Stabilise (hold to remain active)*
Click Thumbstick Enable/Disable Laser Aim

* Weapon stabilisation has a deadzone when the two controllers are less than 15cm from each other to prevent screwing up two-handed aiming with the Glock etc

Command Line Parameters

It is possible to supply command line parameter to the xash engine (and the Lambda1VR wrapper) using the commandline.txt file. The following command line parameters are supported by Lambda1VR (for a list of command line params supported by the Xash3D engine please see the Xash3D documentation):

for example you might use:

xash3d -log --supersampling 1.5 --msaa 2

Which will set super sampling to 1.5 and msaa to 2.

Parameter Values Desription
supersampling 0.1 upwards (default: 1.25) Sets the super (or under) sampling value
msaa 1, 2, 4 (default: 4) Sets the MSAA anti-aliasing value
cpu 1-4 (default: 2) Sets the CPU scaler
gpu 1-4 (default: 3) Sets the GPU scaler

Things to note / FAQs

  • Your screen name (for multi-player) can be set in the config.cfg file
  • FPS counter can be enabled in the Video Options menu
  • Weapon recoil is disabled by default.. if you want a more authentic experience it can be enabled with the cvar: vr_weapon_recoil 1
  • If the player height is messed up. Try reseting the view by holding the home button for 2 seconds. After that go into the main menu and back into the game.
  • After changing files in xash/vale folder, often the device needs to be restarted for the game to use the changed files.

Known Issues

  • Application crashes when you complete the Hazard Course
  • No way to enter text
  • Positional tracking doesn't really work on multi-player servers (unless you run your own server and set the following cvar: sv_accelerate 10000), it sort of works if you hold down the "run" trigger, but it isn't very good
  • Lambda1VR will crash if you haven't copied the half-life game assets to the right location, no warning, just crash
  • Complaint when you exit that the app did not shutdown properly (or crashed or something).. since you are quitting this wasn't considered serious enough to hold up the release, but will be fixed in a future update
  • The edges of some textures are still corrupting when the flashlight shines on them

Future To-Dos

  • Text entry / Virtual Keyboard - Frustratingly the Quest virtual keyboard isn't available through the native SDK :(


You need the following:

  • Android Developer Studio
  • Android SDK API level 24
  • Latest Android Native Development Kit
  • Oculus Mobile SDK 1.24.0
  • The Lambda1VR folder should be below VrSamples in the extracted SDK
  • Create a file in the root of the extracted Oculus Mobile SDK that contains the ndk.dir and sdk.dir properties for where your SDK/NDK are located (see Gradle documentation regarding this)
  • To build debug you will need a android.debug.keystore file placed in the following folder: oculus_sdk_dir/VrSamples/Lambda1VR/Projects/Android

Alternatively you can use the docker image created by BrainSlugs83 which can be found here:


I would like to thank the following teams and individual for making this possible:

  • Baggyg - My long-time VR friend whose roles in this have been varied and all helpful, also the creator of excellent websites/artwork/assets for this mod and more recently becoming something of a MilkShape guru
  • The Xash3D team / Uncle Mike
  • GLE4ES without which this wouldn't have worked at all:
  • Max Vollmer for their 2017 Half-Life VR mod, of which I used and modified the 6DoF weapons code for this mod, the original code for which can be seen here:
  • The SideQuest team - For making it easy for people to install this
  • for the weapon models that were used in the first couple of releases
  • Please go to for a full list of credits for weapon models used in the current version

Notice of Non-Affiliation and Disclaimers

Lambda1VR is not affiliated, associated, authorized, endorsed by, or in any way officially connected with Valve Corporation, or any of its subsidiaries or its affiliates. Lambda1VR is an unofficial port of the Xash3D-FWGS engine, which was originally written by Uncle Mike as a fully compatible open-source GoldSrc engine alternative, more details on that extraordinary project can be found here: However this port (Lambda1VR) is not affiliated, associated, authorized, endorsed by, or in any way officially connected with the Xash3D team. This port was developed using the now deprecated Xash3D port found here:


Lambda1VR is covered by the GPL 3.0 license which is inherited from the Xash3D-FWGS project. The HLSDK sub-repository and associated works (which include the original 6DoF weapons code by Max Vollmer) are in a separate repository wholly covered with the Valve Corporation Half Life 1 SDK LICENSE (