spatial-design

# Spatial Design (visionOS) The design rules that make a visionOS app comfortable instead of exhausting — distilled from Apple's spatial-design sessions (WWDC23–26). Widget-specific rules live in `visionos/widgets`; custom immersive-environment production and budgets live in `immersive-environments.md`. ## When This Skill Activates - Designing or reviewing a visionOS app, window, volume, or immersive space - "Users say it's tiring / uncomfortable / hard to hit controls" - Porting an iPad app and deciding what should become spatial - Adding hover effects, custom gestures, environments, or spatial audio - Choosing a video experience format (spatial, 180°, 360°, wide-FOV, Apple Immersive) ## The prime directive: find the key moment Don't window a 2D app. Identify the one thing only possible on visionOS — the "key moment" — and build around it. Immersion has three approaches, and full immersion is not mandatory: full environments · integration with real surroundings (scene sensing) · meaningful audio. ## Layout & ergonomics - **Wide beats tall** — layouts match the human field of view; turning the head left/right is easier than up/down. Center = primary content; edges = secondary, infrequent actions. - Default placement sits along the natural line of sight, a bit **further than arm's reach**; extended reading goes farther out, centered and slightly below eye line. - **Design in points, not meters** — dynamic scale keeps windows legible at any distance (they scale up as they move away). Never fixed scale for UI; keep custom UI facing the viewer. - **Depth is hierarchy, used sparingly** — "prefer subtle depth" (a modal pushes its parent back). Keep text flat; 3D text is hard to read at an angle. - **Glass, never solid** window backgrounds — solid colors block the world, don't adapt to lighting, and "can feel constricting." Elements on glass use vibrancy + white text/symbols; system colors over custom (they're calibrated for legibility). Brand color goes in backgrounds or whole buttons, not glyphs. - Typography runs **heavier than iOS**: body = medium (vs regular), titles = bold (vs semibold), slightly increased tracking. Avoid small/lightweight custom fonts. - Component specs: vertical tab bar fixed left, **≤6 items**, expands on gaze · ornaments overlap the window's bottom edge **by 20pt**, borderless buttons inside · sheets appear centered at the parent's Z while the parent dims and pushes back · nested corners concentric (outer radius = inner + padding). - SwiftUI spatial layout: stacks default to `.back` depth alignment — switch to `.front` when content should read toward the viewer; `rotation3DLayout` (not `rotation3DEffect`) when rotation must affect layout; `SpatialContainer`/`spatialOverlay` for shared 3D space; `scaledToFit3D()` for models. ## Input: eyes target, hands confirm - **Every interactive element gets ≥60pt of total target area** (≈2.5°, ~4.4cm at 1m) — the element can be smaller if surrounding spacing makes up the difference. Standard buttons: 44pt + ≥8pt clearance; stacked buttons ≥16pt apart; list rows 4pt padding so hover effects don't overlap. - Keep interactive content **at one depth** — frequent focus-depth changes cause eye strain. - Eye-target shapes: circles, pills, rounded rectangles; no sharp edges or thick outlines; center text/glyphs with generous padding. - **Every interactive element needs a hover effect — and only interactive elements get one** (never read-only data). Hover runs out-of-process: gaze stays private until a gesture. - Hover rules (WWDC24/25): keep it subtle (a 5% scale is the reference); short delays prevent flicker (reveal effects: ~0.8s in / 0.2s out); effects start from a visible element — no invisible hotspots; high-traffic controls (toolbars, table cells) use ONLY the standard highlight; keep an anchoring element static; respect Reduce Motion (swap for cross-fade). - Standard gesture language first (pinch = tap, pinch-drag = scroll, two-hand zoom/rotate). Custom gestures must be explainable, repeatable without fatigue, distinct from system gestures, and false-positive-tested; map them to real-world actions. - Prefer **interaction at a distance** (eyes target, hands rest in lap) for long sessions; direct touch is for up-close manipulation — compensate for missing tactility (raise buttons, brighten as the finger approaches, snap state + spatial sound on contact). - Look-to-scroll only in reading/browsing surfaces, never scan-and-pick lists; auto-hiding controls should persist while looked at. ## Motion & visual comfort (the failure modes) - **Depth cues must agree** — size, blur, occlusion, shadow, texture density. Conflicts cause double vision and fatigue. Beware repeating patterns (eyes lock onto different repeats). - **Vection**: large moving content that fills the view reads as self-motion → discomfort. Make big moving content semitransparent so passthrough anchors the viewer. - **Avoid oscillations around 0.2 Hz** (one cycle per 5s); if unavoidable, low amplitude + semitransparency, and honor Reduce Motion with an oscillation-free alternative. - **No head-locked content**; if unavoidable: small, central, far — or lazy-follow. - Camera motion inside windows: keep the content horizon level with the real horizon; slow, predictable focus of expansion inside the field of view; never fast pure rotations — cut with a quick fade instead. Avoid close-range fly-bys. - Moving the user or the scene: fade out during motion, fade back when settled. Design stationary-first — the system fades immersive content when people move. - Eyes rotate most comfortably downward and left/right; upward/diagonal fixation is for brief interactions only. Slow dark→bright transitions (allow adaptation). ## Spatial sound as a design material - Two layers: **point-source emitters** (positioned, room-matched reverb is automatic) + **looping ambient surround beds**. Even a windowed app may fill the room with a soundscape. - Randomize repeats — pitch, amplitude, sample choice, position, timing. Nothing loops audibly from the same spot. - Mix with distance: a few dB down AND pushed farther away = background. - Use direction to steer attention (footsteps from the left before an entrance); attach multiple emitters to characters (feet omnidirectional, mouth directional). - UI sounds: subtle — heard constantly. Match character/timing to the visual transitions. ## Interactive experiences (from Encounter Dinosaurs) Adapt to the real room (portal up to 4m across in big rooms; set-distance + dimmed passthrough in tiny ones) · open small and welcoming, onboard that content reacts to people · use head position for eye contact (proximity signals interactivity; averted attention signals not) · consistent interaction rules — inconsistency shatters immersion · pace emotion with low-relief breaks (nonstop interaction physically exhausts) · gentle in-world boundaries over hard failures · accessibility is spatial too: VoiceOver, Dwell, captions, audio descriptions, Dynamic Type. ## Video format decision guide | You want | Use | |---|---| | Flat storytelling | 2D/3D/spatial video, windowed or docked (3D needs expanded) | | "Being there," forward-facing | Stereo 180° (half-equirectangular) | | Look-anywhere | 360° (equirectangular 2:1, typically mono) | | Action-cam POV | Wide-FOV APMP (120–180°, parametric lens projection) | | Premium cinematic immersion | Apple Immersive Video (8160×7200/eye @ 90fps, up to 210°×180°) | Comfort rule: immersive playback puts the head where the camera was — high-motion scenes auto-reduce immersion (QuickLook/AVKit/RealityKit); encode stereo as MV-HEVC, never side-by-side. APMP formats never play inline. ## Scene behavior defaults Prefer scene restoration (windows come back where placed); disable only for transient/welcome windows (`restorationBehavior(.disabled)`, `defaultLaunchBehavior(.suppressed)`). Adapt volumes to walls/tables via surface snapping info (authorization required). Handle Digital Crown recentering (`onWorldRecenter`). Progressive immersion with an aspect ratio is a comfort lever for vertical/high-motion content. ## Output Format Spatial design review: ``` Area | Finding | Comfort/ergonomic rule violated | Fix ``` ordered: comfort violations (motion/depth/head-lock) first — they end sessions; then input targets; then layout polish. Route environment production to `immersive-environments.md`, widgets to `visionos/widgets`. ## References - https://developer.apple.com/videos/play/wwdc2023/10072/ (Principles of spatial design) - https://developer.apple.com/videos/play/wwdc2023/10076/ (Spatial user interfaces) - https://developer.apple.com/videos/play/wwdc2023/10073/ (Spatial input) - https://developer.apple.com/videos/play/wwdc2023/10078/ (Vision and motion) - https://developer.apple.com/videos/play/wwdc2024/10086/ (Design great visionOS apps) - https://developer.apple.com/videos/play/wwdc2025/303/ (Hover interactions) - https://developer.apple.com/videos/play/wwdc2025/304/ (Video experiences) - https://developer.apple.com/design/human-interface-guidelines/designing-for-visionos - Related: `visionos/widgets`, `design/animation-patterns`