Diegetic UI
The interface exists inside the 3D world, not as an overlay. When UI belongs to the space, immersion stays intact.
What is it?
Diegetic UI is a concept from game design (pioneered by Valve in Half-Life 2, Dead Space by EA) where interface elements exist within the narrative world rather than floating on top as HUD overlays. In AR/VR, this means UI is anchored to objects, surfaces, or spatial positions in the environment. Researchers like Steve Benford (University of Nottingham) formalized this for mixed reality contexts. The key insight: when an interface 'belongs' to the space, users maintain presence and immersion. When it floats as an overlay, it breaks the spatial contract and increases cognitive switching cost.
When to use it
When designing AR/VR interfaces where immersion matters. When building spatial computing experiences (Quest, Vision Pro). When the tension between 'interface that imposes itself' and 'interface that belongs to the space' needs resolution.
How to do it
Audit your current UI: list every element and classify it as diegetic (exists in-world), spatial (anchored to world but not narrative), or HUD (screen-fixed overlay).
For each HUD element, ask: could this information live on an in-world object? A label on a product, a status indicator on a device, a menu on a surface.
Design the spatial anchor: where in the 3D space does this UI element 'live'? What object or surface hosts it?
Test readability at different distances and angles. Diegetic UI must remain legible without breaking the spatial metaphor.
Pro tips
Not everything should be diegetic. Critical system alerts (low battery, safety warnings) can stay as HUD overlays. The goal is intentional placement, not dogmatic removal of all overlays.
Dead Space's health bar on the character's spine is the canonical example: game-critical information delivered diegetically. Find your equivalent.
In AR retail (like Fittingbox), the virtual try-on frame IS diegetic UI — it exists on the user's face, not as a floating panel. This is why it feels natural.