What does the term 'XR' mean?

As with the WebXR API spec, this document uses the acronym XR to refer to the spectrum of hardware, applications, and techniques used for Virtual Reality, Augmented Reality, and other related technologies. Examples include, but are not limited to:

• Immersive or augmented environments used for education, gaming, multimedia, 360⁰ content and other applications.
• Head mounted displays, whether they are opaque, transparent, or utilise video passthrough.
• Mobile devices with positional tracking.
• Fixed displays with head tracking capabilities.

The important commonality between them being that they all offer some degree of spatial tracking with which to simulate a view of virtual content as well as navigation and interaction with the objects within these environments.

Terms like "XR Device", "XR Application", etc. are generally understood to apply to any of the above. Portions of this document that only apply to a subset of these devices will be indicated as appropriate.

Definitions of Virtual Reality

Virtual Reality definitions vary but converge on the notion of immersive computer mediated experiences. They involve interaction with objects, people and environments using a range of controls. These experiences are often multi-sensory and may be used for educational, therapeutic or entertainment purposes.

Definitions of Augmented Reality

Augmented Reality definitions vary but converge on the notion of computer mediated interactions involving overlays on the real world. These may be informational, or interactive depending on the application.

Immersive Environment challenges

Some of the many challenges with immersive environments accessibility (and also gaming) include the use of extremely complex input devices, control schemes that require a high degree of precision, timing and simultaneous action; ability to distinguish subtle differences in busy visual and audio information, having to juggle multiple complex goals and objectives [[web-adapt]].

There are also currently very useful accessibility guidelines available that are specific to gaming [[game-a11y]].

XR and Supporting Multimodality

Modality relates to modes of sense perception such as sight, hearing, touch and so on. Accessibility can be thought of as supporting multi-modal requirements and the transformation of content or aspects of a user interface from one mode to another that will support various user needs.

Considering various modality requirements in the foundation of XR means these platforms will be better able to support accessibility related user needs. There will be many modality aspects for the developer and/or content author to consider:

NOTE: XR authors and content designers will also need access to tools that support the multimodal requirements listed below.

The following Inputs and Outputs can be considered modalities that should be supported in XR environments.

Various Input Modalities

The following are example of some of the diverse input methods used by people with disabilities. NOTE: In many real world applications these input methods may be combined.

• Speech - this is where a users voice is the main input. Using a range of voice commands a user should be able to navigate in an XR environment, interact with the objects in that environment using their voice alone.
• Keyboard - this is where the keyboard alone is the users main input. A user should be able to navigate in an XR environment, interact with the objects in that environment using the keyboard alone.
• Switch this is where a since button Switch alone is the users main input. A user should be able to navigate in an XR environment, interact with the objects in that environment using a Switch alone. This switch may be used in conjunction with an Assistive Technology scanning application within the XR environment that allows them to select directions for navigation, macros for communication and interaction.
• Gesture - this is where gesture based controllers are the main input and can be used to navigate in an XR environment, interact with the objects in that environment make selections using their voice alone.
• Eye Tracking - this is where eye tracking applications is the main input. Using a range of voice commands a user should be able to navigate in an XR environment, interact with the objects in that environment using these eye tracking applications.

Various Output Modalities

The following are a list of outputs that can be available to a user to help them understand, interact with and 'sense' feedback from an XR application. Some of these are in common use on the Web and other exploratory (such as Olfactory and Gustatory.)

• Tactile - this is using the sense of touch, or commonly referred to as haptics.
• Visual - this is using the sense of sight, such as 2D and 3D graphics.
• Auditory - this is using the sense of sound, such as rich spatial audio, surround sound.
• Olfactory - this is the sense of smell.
• Gustatory - this is the sense of taste.

XR controller challenges

As mentioned there are a range of input devices that may be used. Supporting these controllers requires an understanding of what they are and how they work. There are a variety of alternative gaming controls that may be very useful in XR environments and applications. For example the XBOX Adaptive Controller.

While XR is the experience, the controller is king, and plays a critical part in overcoming some complexity as well as mediating issues that may relate to other challenges around usability and helping the user understand sensory substitution devices.

Controllers such as the XBOX Adaptive Controller and other switch type inputs allow the issuer to remapping keyboard inputs to control virtual environments. The powerful customisations may allow the user to "do that thing that is difficult" for them with ease. In conjunction with this controller, for example, users with limited mobility they can also simulate actions in the XR environment that they would not be able to physically perform. WalkinVRDriver is a good example of this where motion range, position and orientation can be set to the users ability.

Customisation of control inputs

Giving the user the ability to modify their input preference or use a variety of input devices. The remapping of keys used to control movement or interaction in virtual environments is not currently required by WCAG. It is nevertheless noted in the literature as desirable.

Using multiple diverse inputs simultaneously

A user with a disability may have several input devices. A user may switch 'mode' of interaction or the tools used and should be able to do so without degrading into a poor user experience where they lose focus on a task and cannot return to it, or make unforced errors, accidental input and so on.

Consistent tracking with multiple inputs

There may be tracking issues when switching input devices. A tracking issue is where the user may lose their focus or it can be modified in unpredictable or unwanted ways, this can cause loss of focus and potentially push the user to make unwanted inputs or choices.

Outputs sent to multiple devices will need to be synchronised.

Usability and affordances in XR

An XR application should have a high level of usability for someone with a disability who is using AT. Some challenges in translating interaction models may be:

• How can a user understand the affordance models used in XR interactions? Or can this be mediated by their own interaction preferences and controllers?
• What interactions are allowed or not allowed?
• How can an accessibility abstracted XR experience focussed on supporting a different modality, successfully interact with another?

User Needs definition

This document outlines various accessibility related 'user needs' for XR. These 'user needs' should drive accessibility requirements for XR and its related architecture. These come from people with disabilities who use Assistive Technology (AT) and wish to see the features described available within XR enabled applications.

User needs and requirements are often dependent on context of use. The following outline some accessibility user needs and requirements that may be applicable in immersive environments, augmented reality and 360⁰ applications.

These following are neither exhaustive, nor definitive but are presented in order to help orientate the reader towards understanding some broad user needs and how to meet them.

Immersive Semantics and customisation

• User Need 1: A user of Assistive Technology wants to navigate, identify locations, objects and interact within an immersive environment.
• REQ 1a: Navigation mechanisms must be intuitive with robust affordances. Navigation, location and object descriptions must be semantically accurate and identified in a way that is understood by assistive technology.
• REQ 1: Controls need to support alternative mapping, rearranging of position, resizing and sensitivity.

Motion agnostic interactions

• User Need 2: A mobility impaired user may want to interact with items in an immersive environment in a way that doesn't require particular bodily movement to perform any given action.
• REQ 2a: Allow the user performing an action in the environment, in a device independent way, without having to do so physically.
• REQ 2b: Ensure that all areas of the user interface can be accessed using the same input method.
• REQ 2c: Allow multiple input methods to be used at the same time.

Immersive Personalisation

• User Need 3: Users with cognitive and learning disabilities may need to personalise the immersive experience in various ways.
• REQ 3a: Support Symbol sets so they can be used to communicate and layered over objects and items to convey affordances or other needed information in way that can be understood according to user preference.
• REQ 3b: Allow the user to turn off of 'mute' non-critical environmental content such as animations, visual or audio content, or non-critical messaging.

Interaction and Target customisation

• User Need 4: A user with limited mobility may need to be able to hit a larger 'Target size' for a button or other controls in immersive environments.
• REQ 4a: Ensure fine motion control is not needed to activate an input.
• REQ 4b: Ensure hit targets are large enough with suitable spacing around them.
• REQ 4c: Ensure multiple actions or gestures are not required at the same time to perform any action.

Voice Commands

• User Need 5: A user with limited mobility may want to be able to use Voice Commands within the immersive environment, to navigate, interact and communicate with others in XR environments.
• REQ 5a: Ensure Navigation and interaction can be controlled by Voice Activation.

Colour changes

• User Need 6: Colour blind users may need to be able to customise the colours used in the immersive environment. This will help with understand affordances on various controls or where colour is used to signify danger or permission.
• REQ 6a: Provide customised high contrast skins for the environment to suit their particular luminosity and colour contrast requirements.

Magnification Context and resetting

• User Need 7: Screen magnification users may need to be able to check the context of their view in immersive environment.
• REQ 7a: Allow the screen magnification user to check the context of their view and track/reset focus as needed.

Critical Messaging and Alerts

• User Need 8: Screen magnification users may need to be made aware of critical messaging and alerts in immersive environments often without losing focus. They may also need to route these messages to 'second screens' (see REQ 1).
• REQ 8a: Ensure that critical messaging, or alerts have priority roles that can be understood and flagged to AT, without moving focus.

Gestural interfaces and interactions

• User Need 9: A blind user may wish to interact with a gestural interface, such as a virtual menu system, using gloves and a head set.
• REQ 9a: Using a virtual menu system - enable a self-voicing option and have each category, or item description spoken to them as they receive focus via a gesture or other input. As the blind user gestures to trigger both movement and interaction. The user may get more detail about items that are closer to them, if navigating a virtual store the user must be allowed to query and interrogate items and make selections.

Text description transformation

• User Need 10: A deaf or hard of hearing person, for whom English or any other written language, may not be their first language and may have a preference for signing of text alternatives or equivalents.
• REQ 10a: Allow object or item text descriptions to be presented to the user via a signing avatar.

Safe harbour controls

• User Need 11: People with Cognitive Impairments may be easily overwhelmed in Immersive Environments.
• REQ 11a: Allow the user to set a 'safe place' - quick key, shortcut or macro.

Immersive Time limits

• User Need 12: Users with cognitive impairments may be adversely affected by spending too much time in any immersive environment or experience, or may lose track of time.
• REQ 12a: Allow the user to set a time limit for any immersive session.

Reset Focus and orientation

• User Need 13: A screen magnification user or user with a cognitive disability or learning impairment may easily lose focus and be disorientated in immersive environments.
• REQ 13a: Ensure the user an reset and calibrate their orientation/view in a device independent way.
• REQ 13b: Ensure field of view in Immersive environments, are appropriate, and can be personalised - so users are not disorientated.

Routing to Second Screens

• User Need 14: A deaf-blind user communicating via a RTC application in XR may have sophisticated 'routing' requirements for various inputs and outputs. 
• REQ 14: Allow the user to route text output, alerts, environment sounds and audio to a braille or other devices.

Interaction Speed

• User Need 15: Users with physical disabilities or cognitive and learning disabilities may find some interactions too fast to keep up with or maintain.
• REQ 15a: Allow user to change speed at which they travel through an immersive environment, or can perform interactions.
• REQ 15b: Allow timings for interactions or critical inputs to be modified or extended.
• REQ 15c: Provide an XR angel or helper for the user with a cognitive or learning disability.
• REQ 15d: Provide clear start and stop mechanisms.

Avoiding sickness triggers

• User Need 16: Users with vestibular disorders, Epilepsy, and photo sensitivity may find some interactions trigger motion sickness and other affects.
• REQ 16a: Avoid interactions that trigger epilepsy or motion sickness and provide alternatives.
• REQ 16b: Ensure flickering images are at a minimum, will not trigger seizures (more than 3 times a second), or can be turned off or reduced.

Binaural Audio track alternatives

• User Need 17: Deaf and hard of hearing users may need binaural recordings of audio content in order to perceive it.
• REQ 17a: Provide alternative binaural audio recording tracks to emulate 3 dimensional sound forms in immersive environments.

Subtitling customisation

• User Need 18: Users with vision impairments may need to customise subtitles and other text in immersive environments.
• REQ 18a: Allow customisable context sensitive reflow of text and subtitled content in XR spaces. The suitable subtitling area may be smaller than what is required currently for television [[inclusive-seattle]]
.