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A head-mounted display places a visual display and viewing optics on the user's head. In an immersive virtual reality system, head tracking supplies the viewing pose and the renderer updates the scene accordingly. Separate eye views can provide binocular depth cues; motion-dependent views also change as the head translates or rotates.

For example, when a viewer leans sideways, a nearby virtual post should shift against a distant wall by more than the wall shifts. This requires tracking position as well as orientation. The two eye views also need distinct view transforms. WebXR exposes poses and per-view projections so an application can construct these images, while the device handles its particular display arrangement.^[ref]

Virtual reality presents an interactive simulated environment whose sensory output responds to a user's actions and viewpoint. A head-mounted display commonly renders a separate view for each eye and tracks head pose. For a rigid world point $p$, the current view transform maps $p$ into eye coordinates before perspective projection; updating that transform as the head moves makes stationary simulated objects appear fixed in the surrounding space.

The latency between movement and the corresponding displayed view matters: stale head pose makes the scene appear to lag behind the observer. Tracking, rendering, display timing and input handling therefore form one feedback loop. A simple experiment is to turn the head while viewing a virtual grid: incorrect orientation updates make the grid move with the head instead of remaining anchored. WebXR exposes per-frame viewer poses and eye views through explicit reference spaces, illustrating how a graphics application connects simulated geometry to tracked physical motion.^[ref]

WebXR is the Web interface for accessing tracked views and input associated with virtual reality and augmented-reality devices. A session supplies animation frames; the application obtains the viewer pose relative to a reference space and renders the views described for that frame. A head-mounted display commonly supplies separate views for the two eyes.^[ref]

For example, a virtual cube fixed one metre in front of the initial viewpoint must be transformed differently as the viewer turns or moves. Updating only the picture's projection while ignoring the tracked position makes the cube move incorrectly. Reference spaces give these poses a defined coordinate meaning; they are part of the application's spatial model rather than an interchangeable screen size.

The World Wide Web Consortium develops Web standards through technical groups and a public review process. Its specifications can define computational behavior precisely: WebXR describes tracked poses and views, while the CSS color specification defines color values and their interpretation. Such documents distinguish an interface's semantics from the particular browser or device implementing it. A document's stated publication status also matters; a draft records work in progress rather than silently implying a completed recommendation.^[ref][ref]