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Setting up XR

Introduction to the XR system in Godot

Godot provides a modular XR system that abstracts many of the different XR platform specifics away from the user. At the core sits the XRServer which acts as a central interface to the XR system that allows users to discover interfaces and interact with the components of the XR system.

Each supported XR platform is implemented as an XRInterface. Supported interfaces register themselves with the XRServer and can be queried with the find_interface method on the XRServer. When the desired interface is found it can be initialised by calling initialize on the interface.

Warning

A registered interface means nothing more than that the interface is available, if the interface is not supported by the host system, initialization may fail and return false. This can have many reasons and sadly the reasons differ from platform to platform. It can be because the user hasn't installed the required software, or that the user simply hasn't plugged in their headset. You as a developer must thus react properly on an interface failing to initialize.

Due to the special requirements for output in XR, especially for head mounted devices that supply different images to each eye, the XRServer in Godot will override various features in the rendering system. For stand-alone devices this means the final output is handled by the XRInterface and Godot's usual output system is disabled. For desktop XR devices that work as a second screen it is possible to dedicate a separate Viewport to handle the XR output, leaving the main Godot window available for displaying alternative content.

Note

Note that only one interface can be responsible for handling the output to an XR device, this is known as the primary interface and by default will be the first interface that is initialized. Godot currently thus only supports implementations with a single headset. It is possible, but increasingly uncommon, to have a secondary interface, for example to add tracking to an otherwise 3DOF only device.

There are three XR specific node types that you will find in nearly all XR applications:

  • XROrigin3D represents, for all intents and purposes, the center point of your play space. That is an oversimplified statement but we'll go into more detail later. All objects tracked in physical space by the XR platform are positioned in relation to this point.

  • XRCamera3D represents the (stereo) camera that is used when rendering output for the XR device. The positioning of this node is controlled by the XR system and updated automatically using the tracking information provided by the XR platform.

  • XRController3D represents a controller used by the player, commonly there are two, one held in each hand. These nodes give access to various states on these controllers and send out signals when the player presses buttons on them. The positioning of this node is controlled by the XR system and updated automatically using the tracking information provided by the XR platform.

There are other XR related nodes and there is much more to say about these three nodes, but we'll get into that later on.

Prerequisites for XR in Godot 4

While in Godot 3 most things worked out of the box, Godot 4 needs a little more setup. This is mainly due to the more advanced nature of the Vulkan renderer. There are many rendering features in Vulkan the XR system uses that aren't enabled by default. They are very easy to turn on, simply open up your project settings and tick the XR shaders tickbox in the XR section:

../../_images/xr_shaders.png

Warning

As Godot 4 is still in development, many post process effects have not yet been updated to support stereoscopic rendering. Using these will have adverse effects.

Note

Godot also has the choice between a desktop and mobile Vulkan renderer. There are a number of optimisations added to the mobile renderer that benefit XR applications. You may wish to enable this even on desktop.

OpenXR

OpenXR is a new industry standard that allows different XR platforms to present themselves through a standardised API to XR applications. This standard is an open standard maintained by the Khronos Group and thus aligns very well with Godots interests.

The Vulkan implementation of OpenXR is closely integrated with Vulkan, taking over part of the Vulkan system. This requires tight integration of certain core graphics features in the Vulkan renderer which are needed before the XR system is setup. This was one of the main d