Immersive tech jargon decoded: XR, passthrough, 6DoF and spatial computing

Immersive technology invented a vocabulary almost overnight, and half of it is borrowed from games, optics and robotics. A product page may boast a headset with “6DoF inside-out tracking, colour passthrough, 110 degree FOV and 90 hertz refresh”. It reads like a spell. Each part, however, answers a simple question about how the headset sees you and how you see the world.

This article translates those parts, and the terms around building and running immersive experiences.

The umbrella terms

• XR (extended reality). The umbrella term for VR, AR and MR.
• VR (virtual reality). A fully digital world that replaces what you see.
• AR (augmented reality). Digital information overlaid on the real world, often through a phone.
• MR (mixed reality). Digital objects that sit in your space and react to it, such as hiding behind a real sofa.
• Spatial computing. A label for computing that understands and uses the space around you, with apps placed in your room.
• Metaverse. A loose term for shared, persistent virtual worlds. It has meant many things, so ask what is being described.
• Immersion and presence. Immersion is how much of your senses the system occupies. Presence is the feeling of being there.

How the headset knows where you are

• Tracking. Measuring the position and movement of your head, hands and controllers.
• 3DoF (three degrees of freedom). The device tracks only rotation, so you can look around but not move through space.
• 6DoF (six degrees of freedom). It tracks rotation and position, so you can walk, lean and duck. This is the standard for modern headsets.
• Inside-out tracking. Cameras on the headset watch the room to work out where it is. No external equipment is needed.
• Outside-in tracking. Sensors placed around the room track the headset. It can be very precise, with more setup.
• SLAM. Simultaneous localisation and mapping: building a map of the space and locating yourself in it at the same time.
• Hand tracking. Using cameras to follow your bare hands, without controllers.
• Eye tracking. Following where you look, for interaction and efficiency.
• Room-scale and guardian. Using a defined play area, with boundaries that warn you before you hit something.
• Anchor. A fixed point in the real world to which a virtual object is attached.

How it shows you the world

• Display and resolution. The screens in front of your eyes. More pixels per degree makes things sharper, particularly text.
• FOV (field of view). How wide the picture is, measured in degrees. Wider feels more natural. Human vision spans roughly 200 degrees horizontally, and headsets typically offer around 100.
• Refresh rate. How many times per second the picture is redrawn, in hertz. Higher is smoother and usually more comfortable.
• Latency (motion to photon). The delay between moving and seeing the result. Low latency prevents the world from appearing to swim.
• IPD (interpupillary distance). The distance between your pupils. Headsets adjust to match, for clarity and a correct sense of scale.
• Lenses. Optics that bend the screen image into a wide view. Fresnel and pancake designs differ in clarity and thickness.
• Passthrough. Cameras show the real world on the headset’s screens, so you can see your surroundings, and mixed reality becomes possible.
• See-through (optical) displays. Transparent lenses onto which digital light is projected, common in smart glasses.
• Foveated rendering. Drawing in full detail only where you are looking, to save computing power.
• Standalone and tethered. Standalone headsets have their own computer. Tethered ones connect to a PC.
• Haptics. Touch feedback, such as vibration in a controller or glove.
• Spatial audio. Sound that appears to come from a particular place around you.

Building the experience

• Engine. Software for building interactive 3D worlds. Unity and Unreal are the best known.
• WebXR. A web standard that allows VR and AR experiences to run in a browser, without an app.
• OpenXR. A standard that lets one application run on many headsets.
• SDK. A toolkit of ready-made code for a device or platform.
• Asset. Any piece of content, such as a 3D model, a texture or a sound.
• Polygon count. The number of triangles in a model, which affects speed.
• LOD (level of detail). Simpler versions of objects shown at a distance.
• Baked lighting. Light and shadow calculated in advance, instead of in real time, to save power.
• Shader. A small program that decides how a surface looks.
• Frame rate and frame budget. How many pictures per second, and how long each has to be drawn.
• Locomotion. How the user moves around: walking, teleporting or smooth movement.
• Interaction model. How people select, grab and manipulate objects.
• Digital twin. A 3D model connected to live data about a real place or object.
• Capture. Recording real places for 3D use, by photogrammetry, laser scanning or Gaussian splatting.

Comfort and safety words

• Motion sickness (cybersickness). Discomfort when what you see disagrees with what your balance senses.
• Vignette. Narrowing the view during movement to reduce discomfort.
• Vergence-accommodation conflict. A mismatch between where your eyes point and where they focus, which can cause eye strain.
• Presence break. A moment that reminds you that it is not real, such as a glitch or a lost tracking.
• Seated and standing modes. Experiences designed for different postures.
• Accessibility. Design that works for people with different abilities, for example subtitles and seated options.

Translating a product page

“6DoF inside-out tracking, colour passthrough, 110 degree FOV and 90 hertz refresh.” In plain words: the headset follows your movement in all directions using its own cameras, shows you the real room in colour when you want it, gives you a fairly wide view and redraws the picture 90 times a second for smooth motion. The question to ask is whether those features suit your users and your use.

Buzzword traps

• “Photorealistic.” Realistic to whom, and on what device? Ask to see it run on the target hardware.
• “Immersive.” Does it actually add value over a normal screen?
• “The metaverse.” Which platform, who owns it and who will use it?
• “AI-powered XR.” What does the AI do, concretely?
• “Hologram.” Usually a 3D effect on a screen or headset, not a free-floating image.

Questions to ask before you build or buy

• Who will use it, on which device, and for how long at a time?
• Is a headset needed, or would a browser or phone do?
• How will it be kept up to date, and who is responsible?
• How many people can use it at once, and how are headsets managed and cleaned?
• How will we measure whether it worked?

Frequently asked questions

What is the difference between passthrough and AR glasses?

Passthrough headsets show the real world through cameras and screens. AR glasses let you see the real world directly through transparent lenses, with digital light added. Each has strengths and limits.

Is 6DoF always needed?

For walking, reaching and natural interaction, yes. For watching 360 degree video, 3DoF is enough.

What refresh rate should I aim for?

Aim for the highest stable rate your devices support, often 72 to 120 hertz. A steady rate matters more than a high but unstable one.

Will these terms change?

Yes, quickly. Treat product names as temporary, and learn the concepts underneath.

Behind every piece of immersive jargon is a plain question: how does it know where I am, how does it show me the world and how does it feel to use? Ask those, and the specification sheets start to read like ordinary English.