English for XR and Spatial Computing Developers: visionOS, AR/VR Vocabulary

A New Vocabulary for a New Dimension

Spatial computing — the category that encompasses augmented reality (AR), virtual reality (VR), and mixed reality (MR) — has introduced a rich vocabulary that many developers are encountering for the first time. Apple’s visionOS platform, Meta’s Quest ecosystem, and web standards like WebXR have each contributed terms. Whether you are building for headsets or exploring the space conceptually, this vocabulary guide will help you read documentation, follow conference talks, and discuss spatial development in English.

Core Spatial Computing Terms

Reality Spectrum

The reality spectrum describes the range from fully physical to fully virtual environments.

Virtual Reality (VR) — a fully immersive computer-generated environment that replaces the physical world entirely. The user cannot see the real world while in VR.

Augmented Reality (AR) — digital content overlaid onto a view of the physical world. The user remains visually present in their real environment.

Mixed Reality (MR) — an experience where digital and physical elements interact in real time. Digital objects can be occluded by physical ones and respond to the physical environment.

Extended Reality (XR) — an umbrella term covering all of the above: VR, AR, and MR.

Passthrough

Passthrough is the technology that shows the user a camera-based feed of the real world through a headset, enabling mixed reality experiences on devices that do not use transparent lenses. On Apple Vision Pro, passthrough is called EyeSight externally and provides the foundation for the immersive environment system.

“We use passthrough mode for the productivity app so users can interact with virtual panels while remaining aware of their physical surroundings.”

Spatial UI

Spatial UI refers to user interface elements positioned in three-dimensional space rather than on a flat screen. Spatial UI requires thinking about depth, scale, gaze direction, and physical reach.

“In spatial UI design, you need to consider not just where a panel is on screen, but at what depth it sits, how large it appears at that distance, and whether it is within the user’s comfortable reach zone.”

Anchor

An anchor is a reference point in physical or virtual space to which digital content is attached, ensuring it remains stable relative to the real world as the user moves.

World anchor — ties content to a fixed position in the physical world. “The floor plan overlay is attached to a world anchor so it remains aligned to the building structure as the user walks around.”

Image anchor — detects a specific image in the camera feed and attaches content to it. Used for experiences triggered by posters, product packaging, or printed markers.

Plane anchor — attaches content to a detected horizontal or vertical surface, such as a table or wall.

visionOS-Specific Vocabulary

visionOS is Apple’s operating system for the Apple Vision Pro headset. It introduces several platform-specific concepts.

Volume — in visionOS, a bounded 3D container for SwiftUI content that floats in the user’s space. Volumes behave like windows but have depth. “We package the 3D product viewer as a volume so users can position it anywhere in their space.”

Immersive Space — a visionOS scene type that gives the app full control of the user’s environment, replacing the passthrough view with a custom 3D world.

Ornament — a UI element in visionOS that is positioned relative to a window but appears to float in space beside it, like a toolbar that accompanies a 2D window in three-dimensional space.

RealityKit — Apple’s framework for rendering and animating 3D content, used on both visionOS and iOS/macOS AR. “RealityKit handles physics simulation, material rendering, and animation blending for the spatial scene.”

Reality Composer Pro — Apple’s tool for building and previewing spatial scenes, USDZ assets, and particle effects.

Hand tracking — the capability of a spatial computing device to detect and track the position and pose of the user’s hands without requiring a physical controller. “In the hands-free navigation mode, hand tracking allows users to select items with a pinch gesture.”

Eye tracking — tracking the direction of the user’s gaze for interaction. On Vision Pro, eye tracking combined with hand gestures is the primary input method. “The interface responds to eye tracking — whatever the user is looking at is highlighted, and a pinch gesture confirms the selection.”

WebXR Vocabulary

WebXR is the browser API that enables AR and VR experiences on the web, without a native app.

Session — a WebXR session represents an active AR or VR experience. Sessions can be immersive-vr, immersive-ar, or inline.

Reference space — the coordinate system used in a WebXR session. Common types: viewer (relative to the headset), local (relative to where the session started), and bounded-floor (a room-scale tracked space).

Hit testing — the process of determining where a ray from the camera or controller intersects with a real-world surface, used to place virtual objects on physical surfaces. “We use hit testing to let users tap a real surface to place a virtual furniture item.”

Five Example Sentences

1. “The product visualisation app runs in passthrough mode so customers can see how a piece of furniture would look in their physical room while the virtual model is positioned by a surface anchor.”
2. “We designed the spatial UI with all interactive elements at arm’s reach depth — placing them too far away felt unnatural and reduced interaction accuracy.”
3. “On visionOS, we use a volume for the 3D model viewer and a standard window for the catalogue list, allowing users to browse and view simultaneously.”
4. “Hand tracking on the Quest 3 is sufficiently precise for fine-grain manipulation, but we still provide controller-based alternatives for tasks requiring sustained accuracy.”
5. “The WebXR session is initialised as immersive-ar and uses hit testing to detect horizontal surfaces, allowing the user to anchor the virtual object on any table or floor in the room.”

Keeping Up With the Space

Spatial computing vocabulary is evolving quickly. Apple’s developer documentation, the WebXR Device API specification, and conference talks from WWDC and AWE (Augmented World Expo) are excellent sources for authentic English in this domain. The terminology is still stabilising — you will sometimes see the same concept referred to differently across platforms, which is a normal feature of a rapidly maturing field.