Abstract
This document lists user needs and requirements for people with disabilities when using virtual reality or immersive environments, augmented or mixed reality and other related technologies (XR). It first introduces a definition of XR as used throughout the document, then briefly outlines some uses of XR. It outlines the complexity of understanding XR, introduces some technical accessibility challenges such as the need for multi-modal support, synchronization of input and output devices and customization. It then outlines accessibility related user needs for XR and suggests subsequent requirements. This is followed by related work that may be helpful in understanding the complex technical architecture and processes behind how XR environments are built and what may form the basis of a robust accessibility architecture.
This document is most explicitly not a collection of baseline requirements. It is also important to note that some of the requirements may be implemented at a system or platform level, and some may be authoring requirements.
Introduction
XR is an acronym used to refer to the spectrum of hardware, applications, and techniques used for virtual reality or immersive environments, augmented or mixed reality and other related technologies. This document is developed as part of a discovery into accessibility related user needs and requirements for XR. This document does not represent a formal working group position, nor does it currently represent a set of technical requirements that a developer or designer need strictly follow. It aims to outline the diversity of some current accessibility related user needs in XR and what potential requirements to meet those needs may be.
What does the term 'XR' mean?
As with the WebXR API spec and as indicated in the related WebXR explainer, this document uses the acronym XR to refer to the spectrum of hardware, applications, and techniques used for virtual reality or immersive environments, augmented or mixed reality and other related technologies. Examples include, but are not limited to:
- Immersive or augmented environments used for education, gaming, multimedia, 360° 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 and immersive environments
Virtual reality and immersive environment 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 and mixed reality
Augmented and mixed 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.
Understanding XR and Accessibility Challenges
Understanding XR itself presents various challenges that are technical. They include issues with a range of hardware, software and authoring tools. To make accessible XR experiences there is a need to understand interaction design principles, accessibility semantics and assistive technologies. However, these all represent 'basic' complexities that are in themselves substantial. To add to this, for many designers and authors they may neither know or have access to people with disabilities for usability testing. Neither may they have a practical way of understanding accessibility related user needs that they can build a solid set of requirements from. In short, they just may not understand what user needs they are trying to meet.
Some of the issues in XR, for example in gaming, for people with disabilities include:
- Over emphasis on motion controls. There are many motion controllers that emphasise using your body to control the experience. Some games with XR components may lock out traditional control methods when a VR headset is being used, and the user should always be able to use a range of input mechanisms.
3DOF and
6DOF may have their own specific mobility issues, for example
3DOF may have implications for people who have motor impairments that affect the use of one or both arms.
6DOF may have implications for people who are quadriplegic and for people that use a wheelchair or mobility aid for navigation where there is a need to move directionally in physical space or a higher emphasis on the lower extremity for movement.
- VR Headsets need the user to be a physical position to play. The user should not have to be in a particular physical position such as standing or sitting to play a game or perform some action. Or there should be ability to remap these 'physical positions' to other controls (such as using WalkinVRDriver).
- Games and hardware being locked to certain manufacturers. Consoles should allow full button remapping on standard game controllers - to different types of assistive technologies such as switches. These remapping preferences should be mobile, and transportable across a range of hardware devices and software.
- Gamification of VR forces game dynamics on the user. Some users may wish to just explore an immersive environment without the 'game', or any particular challenge.
- Audio design lacks spatial accuracy. Sound design needs particular attention and can be critical for a good user experience for people with disabilities. The auditory experience of a game or other immersive environment may 'be' the experience [[able-gamers]].
There are a range of disabilities that will need to be considered in making XR accessible. It is beyond the scope of this document to describe them all in detail. General categories or types of disabilities are:
- Auditory disabilities
- Cognitive disabilities
- Neurological disabilities
- Physical disabilities
- Speech disabilities
- Visual disabilities
A person may have one of these disabilities or a combination of several. User needs are presented here that may relate to several of these disabilities with a range of requirements that should be met by the author or the platform. For XR designers and authors understanding these needs is crucial when making XR environments accessible.
Some things designers and authors need to be aware of:
- Understanding specific diverse user needs and how they relate to XR.
- Successfully identifying modality needs that are not obvious - but still need to be supported.
- Suitable authoring tools that support accessibility requirements in XR.
- Using languages, platforms and engines that support accessibility semantics.
- Providing accessible alternatives for content and interaction.
- The provision of specific commands within the VR environment (e.g., to go directly to a specified location or to follow another user) which assist with navigation to support different modalities.
- The use of virtual assistive technologies (e.g., white cane via a haptic device) to provide non-visual feedback. The research identified that if the same audio cues associated with a real-world infrared white cane were used in immersive environment, users were able to effectively centre themselves in the middle of pathways and walk successfully through virtual doorways based on the same audio feedback as used in the equivalent real-world device [[maidenbaum-amendi]]
Immersive Environment challenges
Some of the challenges within immersive environments (and gaming) accessibility 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. XR authors and content designers will also need access to tools that support the multi-modal 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. In many real world applications these input methods may be combined.
- Speech - this is where a user's voice is the main input. Using a range of speech 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 user's 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 user's 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 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 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 user to remap keyboard inputs to control or interact with virtual environments. These powerful customizations 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 user's ability.
Customization of control inputs
Give 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 or different assistive technologies. A user may switch 'mode' of interaction or the tools used without degrading the user experience where they lose focus on a task and cannot return to it, or make unwanted input.
Complexity needs to be managed and co-ordinated between different kinds of assistive technology in immersive environments. There is a platform level requirement to support multiple assistive technologies in a cohesive manner. This would allow combinations to be used in a co-ordinated way e.g where the users day-to-day AT, can be used with other AT that may be embedded in the environment already for example.
The REQ 5b: Voice activation also indicates potential issues with pairing multiple devices via bluetooth.
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 assistive technology. Some challenges in translating interaction models may be:
- How can a user understand the affordance models used in XR interactions? Can they be mediated by their own interaction preferences and models?
- What interactions are allowed or not allowed?
- How can an accessibility abstracted XR experience focussed on supporting a different modality, successfully interact with another?
- How can we ensure what happens in one modality, is update in another so various abstractions are not out of sync? e.g. synchronization of captions between real time text transcriptions and other alternatives such as symbols or AAC?
XR User Needs and Requirements
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 technologies 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 360° 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 customization
- 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 accurate and identified in a way that is understood by assistive technology.
- REQ 1b: Controls need to support alternative mapping, rearranging of position, resizing and sensitivity.
- REQ 1c: Objects that are important within any given context of time and place can be identified in a suitable modality.
- REQ 1d: Allow filtering and the ability to query items and their content for more details.
In an spatialized augmented reality environment a blind user may find a combination of text to speech and sonic symbols helpful. By using a combination of text to speech and sonic symbolism a blind user can do a self-guided tour of a given area using their smartphone. [[spatialized-navigation]]
Motion agnostic interactions
- User Need 2: A person with a physical disability 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.
Personalization involves tailoring aspects of the user experience to meet the needs and preferences of the individual user. W3C are working on various modules for web content that aim to support personalization and are exploring areas such as: [[personalization-semantics]] [[personalization-content]] [[personalization-requirements]]
- Expanding the accessibility information that may be supplied by the author.
- Facilitate preference driven individual personalization.
- Enable the author to specify key semantics needed to support users with cognitive impairments.
Interaction and target customization
- User Need 4: A user with limited mobility, or users with tunnel or peripheral vision may need a larger 'Target size' for a button or other controls.
- 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.
- REQ 4d: Support 'Sticky Keys' requirements such as serialization for various inputs when the user needs to press multiple buttons.
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.
- REQ 5a: Ensure Navigation and interaction can be controlled by Voice Activation.
- REQ 5b: Voice activation should preferably use native screen readers or voice assistants rather than external devices to eliminate the additional step needed to pair devices.
Color changes
- User Need 6: Color blind users may need to be able to customise the colors used in the immersive environment. This will help with understanding affordances of various controls or where color is used to signify danger or permission.
- REQ 6a: Provide customised high contrast skins for the environment to suit their particular luminosity and color 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 environments.
- REQ 7a: Allow the screen magnification user to check the context of their view and track/reset focus as needed.
- REQ 7b: Where it makes sense (such as in menus) interface elements can be enlarged and the menu reflowed to enhance the usability of the interface up to a certain magnification requirement.
There are customisation approaches such as the automatic generation of user interfaces as demonstrated in the SUPPLE project, which adapt to the different challenges the user may face, such as vision, motor control and other user preferences and abilities. A generated UI can make multiple adaptations for different user needs at the same time. This is achieved by generating a UI, or several - after testing a persons ability using an algorithm to learn their preferences. [[supple-project]]
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 a 'second screen' (see REQ 14 Second Screen).
- 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.
- REQ 9a: Support touch screen accessibility gestures (e.g. swipes, flicks and single, double or triple taps with 1, 2 or 3 fingers). See REQ 14 Second Screen.
- REQ 9b: Using a virtual menu system - enable a self-voicing option and have each category, or item description, spoken as they receive focus via a gesture or other input. As the blind user gestures to trigger both movement and interaction they may get more detail about items that are closer to them. The user must be allowed to query and interrogate these items and make selections.
- REQ 9c: Allow for the re-mapping of gestures to associate different actions with different input types or gestures. This may be a virtual switch that can map to new macros on the fly. This will allow the user to change defaults and employ gestures to carry out new actions offered by the immersive environment as required.
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.
Second screen
- User Need 14: A deaf-blind user communicating via a RTC application in XR may have sophisticated 'routing' requirements for various inputs and outputs and the need to manage same.
- REQ 14a: Allow the user to route text output, alerts, environment sounds or audio to a braille or other second screen device.
- REQ 14b: Ensure that the user can manage the flow of critical messaging, or content to display on a second screen.
- REQ 14c: Support touch screen accessibility gestures (e.g. swipes, flicks and single, double or triple taps with 1, 2 or 3 fingers) on a second screen device to allow the user to navigate menus and interact.
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 users 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. This may be triggered when doing teleportation or other movements in XR.
- 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.
Spatial audio tracks and alternatives
- User Need 17: Deaf and hard of hearing users may need spatialized audio content with audio description in order to perceive it.
- REQ 17a: Provide spatialized audio content and audio descriptions to emulate three dimensional sound forms in immersive environments.
Captioning, Subtitling and Text: Support and customization
- User Need 18: Users with vision impairments may need to customise captions, subtitles and other text in XR environments.
- REQ 18a: Provide support for captioning and subtitling of multimedia content.
- REQ 18b: Allow customisable context sensitive reflow of captions, subtitles and text content in XR environments. The suitable subtitling area may be smaller than what is required currently for television [[inclusive-seattle]].
Mono audio option
- User Need 19: Users with hearing loss in just one ear may miss information in a stereo or binaural soundscape.
- REQ 19a: Allow mono audio sound to be sent to both headphones so that the user can perceive the whole soundscape through either ear. [[mono-ios]].