Ar Vr Xr

AR / VR / XR (Reality Tech)

Use this skill when the user is building or debugging:

• AR (camera passthrough overlays)
• VR (fully immersive)
• XR/MR (mixed reality, spatial computing)
• WebXR/OpenXR, Quest/Vision Pro/PCVR
• Unity/Unreal/Web (Three.js, Babylon.js, A-Frame)

First Questions (Only Ask What Blocks Progress)

Ask up to 3:

1. Target platform: Web (WebXR) or native (OpenXR via Unity/Unreal)?
2. Target device(s): Quest, Vision Pro, PCVR (SteamVR), mobile AR (ARKit/ARCore), other?
3. Interaction + locomotion: hands, controllers, gaze, roomscale, smooth locomotion, teleport?

If the user does not know yet, default to:

• WebXR + Three.js for a fast prototype
• Teleport locomotion + snap-turn for comfort

Workflow

1. Define the experience mode and constraints.

   • AR vs VR vs MR
   • Required capabilities: 3DoF/6DoF, plane detection, meshing, hand tracking, anchors

2. Establish world scale and coordinate conventions early.

   • 1 unit = 1 meter (recommended)
   • Choose a single "up" axis and stick to it end-to-end

3. Build a vertical slice (minimum shippable loop).

   • Tracking + session start
   • One interaction (grab/select)
   • One UI surface (menu, tooltip, reticle)

4. Budget performance from day 1.

   • Stable frame time beats peak quality
   • Reduce draw calls, overdraw, shader cost, and texture bandwidth

5. Enforce comfort defaults.

   • Avoid sustained acceleration
   • Prefer teleport and snap-turn
   • Keep UI readable and at comfortable depth

6. Treat privacy and sensors as first-class.

   • Camera/mic permissions, spatial maps, room meshes, biometrics
   • Minimize collection, document clearly, store locally when possible

WebXR Quickstart (Three.js)

import * as THREE from 'three';
import { VRButton } from 'three/examples/jsm/webxr/VRButton.js';

const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(70, window.innerWidth / window.innerHeight, 0.01, 100);
const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.xr.enabled = true;
document.body.appendChild(renderer.domElement);
document.body.appendChild(VRButton.createButton(renderer));

const light = new THREE.HemisphereLight(0xffffff, 0x444444, 1.0);
scene.add(light);

const floor = new THREE.Mesh(
  new THREE.PlaneGeometry(10, 10),
  new THREE.MeshStandardMaterial({ color: 0x222222 })
);
floor.rotation.x = -Math.PI / 2;
scene.add(floor);

renderer.setAnimationLoop(() => {
  renderer.render(scene, camera);
});

Notes:

• WebXR requires HTTPS (or localhost).
• To target AR: request an immersive-ar session and handle hit-test/anchors (framework-specific).

OpenXR Notes (Unity/Unreal)

• Unity: prefer XR Plugin Management + OpenXR plugin; use XR Interaction Toolkit for baseline interaction.
• Unreal: use the OpenXR plugin; validate input mappings per device.

When debugging native XR:

• Confirm runtime: OpenXR runtime (SteamVR, Oculus, WMR) and version
• Validate action bindings and controller profiles
• Verify frame timing on-device, not just in editor

Comfort Checklist

• Keep horizon stable; avoid camera bob unless user opts in
• Use snap-turn (30-45 deg) by default
• Teleport is the safest default locomotion
• Avoid "forced" motion tied to animations
• UI: large text, high contrast, avoid depth conflict (z-fighting)

Performance Checklist

• Measure on target device (Quest/Vision Pro/PCVR), not only desktop
• Reduce: draw calls, transparent layers, dynamic shadows, post-processing
• Prefer baked lighting where possible
• Stream assets with progressive quality (LOD), avoid blocking loads

Device Profile: Varjo XR-4

If the target device is Varjo XR-4 Series, use varjo-xr-4 for runtime/tracking/refresh-rate specifics.

Interleave With New Skills (plurigrid/asi PRs #61-64)

Use these as building blocks:

• visual-design: spatial UI readability, typography, contrast, layout
• svelte-components / sveltekit-structure / sveltekit-data-flow: WebXR shells, menus, settings, content pipelines
• browser-navigation: XR web debugging and reproducible repro steps
• bandwidth-benchmark: asset streaming, scene/texture delivery constraints
• threat-model-generation + security-review: sensors, permissions, privacy, on-device data
• jepsen-testing: correctness thinking for multi-user/shared-state XR backends

Jepsen For Shared-State XR

Use jepsen-testing when your experience includes a backend claim about correctness under faults (multiplayer rooms, shared anchors, inventories, authoritative physics, replicated scene graphs).

XR-specific intake:

• Define the surface: websocket RPC, REST/gRPC, realtime relay, or a persistence API.
• Define acknowledged for XR ops (e.g., "spawn confirmed", "anchor committed", "inventory write ok").
• Pick a checkable property per primitive:
• Room membership/presence: no phantom joins, monotonic session state.
• Object transforms: no lost acknowledged updates; no impossible readbacks.
• Anchors/placements: placement does not disappear after an ok, unless explicitly deleted.

Faults worth testing:

• Partitions between clients and relay/region.
• Process kill/restart of relay, authoritative host, or storage layer.
• Clock skew if you use timestamps for conflict resolution.

Minimization tip:

• Reduce to 1-2 rooms, 2-3 objects, and a single nemesis schedule until the violation is explainable.

Example Prompts This Skill Should Handle

• "Build a WebXR VR scene with teleport and grab interactions"
• "Port this Unity project to OpenXR and fix controller bindings"
• "Optimize this Quest app to hit stable 72/90 fps"
• "Design a spatial settings UI that stays readable in passthrough"
• "Threat-model an AR app that uses camera + spatial mapping"
• steamvr-tracking for Lighthouse/base station setup- xr-color-management for sRGB/P3/Rec.2020 pipeline issues

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