Aframe Webxr

A-Frame WebXR Skill

When to Use This Skill

• Build VR/AR experiences with minimal JavaScript
• Create cross-platform WebXR applications (desktop, mobile, headset)
• Prototype 3D scenes quickly with HTML primitives
• Implement VR controller interactions
• Add 3D content to web pages declaratively
• Build 360° image/video experiences
• Develop AR experiences with hit testing

Core Concepts

1. Entity-Component-System (ECS)

A-Frame uses an entity-component-system architecture where:

• Entities are containers (like <div> in HTML)
• Components add functionality/appearance to entities
• Systems provide global functionality

<!-- Entity with components -->
<a-entity
  geometry="primitive: box; width: 2"
  material="color: red; metalness: 0.5"
  position="0 1.5 -3"
  rotation="0 45 0">
</a-entity>

Primitives are shortcuts for common entity + component combinations:

<!-- Primitive (shorthand) -->
<a-box color="red" position="0 1.5 -3" rotation="0 45 0" width="2"></a-box>

<!-- Equivalent entity-component form -->
<a-entity
  geometry="primitive: box; width: 2"
  material="color: red"
  position="0 1.5 -3"
  rotation="0 45 0">
</a-entity>

2. Scene Setup

Every A-Frame app starts with <a-scene>:

<!DOCTYPE html>
<html>
  <head>
    <script src="https://aframe.io/releases/1.7.1/aframe.min.js"></script>
  </head>
  <body>
    <a-scene>
      <!-- Entities go here -->
      <a-box position="-1 0.5 -3" color="#4CC3D9"></a-box>
      <a-sphere position="0 1.25 -5" radius="1.25" color="#EF2D5E"></a-sphere>
      <a-cylinder position="1 0.75 -3" radius="0.5" height="1.5" color="#FFC65D"></a-cylinder>
      <a-plane position="0 0 -4" rotation="-90 0 0" width="4" height="4" color="#7BC8A4"></a-plane>
      <a-sky color="#ECECEC"></a-sky>
    </a-scene>
  </body>
</html>

The scene automatically injects:

• Default camera (position: 0 1.6 0)
• Look controls (mouse drag)
• WASD controls (keyboard movement)

3. Camera Systems

Default Camera (auto-injected if none specified):

<a-entity camera="active: true" look-controls wasd-controls position="0 1.6 0"></a-entity>

Custom Camera:

<a-camera position="0 2 5" look-controls wasd-controls="acceleration: 50"></a-camera>

Camera Rig (for independent movement and rotation):

<a-entity id="rig" position="0 0 0">
  <!-- Camera for head tracking -->
  <a-camera look-controls></a-camera>

  <!-- Movement applied to rig, not camera -->
</a-entity>

VR Camera Rig with Controllers:

<a-entity id="rig" position="0 0 0">
  <!-- Camera at eye level -->
  <a-camera position="0 1.6 0"></a-camera>

  <!-- Left hand controller -->
  <a-entity
    hand-controls="hand: left"
    laser-controls="hand: left">
  </a-entity>

  <!-- Right hand controller -->
  <a-entity
    hand-controls="hand: right"
    laser-controls="hand: right">
  </a-entity>
</a-entity>

4. Lighting

Ambient Light (global illumination):

<a-entity light="type: ambient; color: #BBB; intensity: 0.5"></a-entity>

Directional Light (like sunlight):

<a-entity light="type: directional; color: #FFF; intensity: 0.8" position="1 2 1"></a-entity>

Point Light (radiates in all directions):

<a-entity light="type: point; color: #F00; intensity: 2; distance: 50" position="0 3 0"></a-entity>

Spot Light (cone-shaped beam):

<a-entity light="type: spot; angle: 45; intensity: 1.5" position="0 5 0" rotation="-90 0 0"></a-entity>

5. Materials and Textures

Standard Material:

<a-sphere
  material="color: #FF0000; metalness: 0.5; roughness: 0.3"
  position="0 1 -3">
</a-sphere>

Textured Material:

<a-assets>
  <img id="woodTexture" src="wood.jpg">
</a-assets>

<a-box material="src: #woodTexture" position="0 1 -3"></a-box>

Flat Shading (no lighting):

<a-plane material="shader: flat; color: #4CC3D9"></a-plane>

6. Animations

Property Animation:

<a-box
  position="0 1 -3"
  animation="property: rotation; to: 0 360 0; loop: true; dur: 5000">
</a-box>

Multiple Animations (use animation__* naming):

<a-sphere
  position="0 1 -3"
  animation__position="property: position; to: 0 3 -3; dir: alternate; loop: true; dur: 2000"
  animation__rotation="property: rotation; to: 360 360 0; loop: true; dur: 4000"
  animation__scale="property: scale; to: 1.5 1.5 1.5; dir: alternate; loop: true; dur: 1000">
</a-sphere>

Event-Based Animation:

<a-box
  color="blue"
  animation__mouseenter="property: scale; to: 1.2 1.2 1.2; startEvents: mouseenter"
  animation__mouseleave="property: scale; to: 1 1 1; startEvents: mouseleave"
  animation__click="property: rotation; from: 0 0 0; to: 0 360 0; startEvents: click">
</a-box>

7. Assets Management

Preload assets for better performance:

<a-scene>
  <a-assets>
    <!-- Images -->
    <img id="texture1" src="texture.jpg">
    <img id="skyTexture" src="sky.jpg">

    <!-- Videos -->
    <video id="video360" src="360video.mp4" autoplay loop></video>

    <!-- Audio -->
    <audio id="bgMusic" src="music.mp3" preload="auto"></audio>

    <!-- Models -->
    <a-asset-item id="tree" src="tree.gltf"></a-asset-item>

    <!-- Mixins (reusable component sets) -->
    <a-mixin id="redMaterial" material="color: red; metalness: 0.7"></a-mixin>
  </a-assets>

  <!-- Use assets -->
  <a-entity gltf-model="#tree" position="2 0 -5"></a-entity>
  <a-sphere mixin="redMaterial" position="0 1 -3"></a-sphere>
  <a-sky src="#skyTexture"></a-sky>
</a-scene>

8. Custom Components

Register custom components to encapsulate logic:

AFRAME.registerComponent('rotate-on-click', {
  // Component schema (configuration)
  schema: {
    speed: {type: 'number', default: 1}
  },

  // Lifecycle: called once when component attached
  init: function() {
    this.el.addEventListener('click', () => {
      this.rotating = !this.rotating;
    });
  },

  // Lifecycle: called every frame
  tick: function(time, timeDelta) {
    if (this.rotating) {
      var rotation = this.el.getAttribute('rotation');
      rotation.y += this.data.speed;
      this.el.setAttribute('rotation', rotation);
    }
  }
});

<a-box rotate-on-click="speed: 2" position="0 1 -3"></a-box>

Common Patterns

Pattern 1: VR Controller Interactions

Problem: Enable object grabbing and manipulation in VR

Solution: Use hand-controls and custom grab component

<a-scene>
  <!-- VR Camera Rig -->
  <a-entity id="rig">
    <a-camera position="0 1.6 0"></a-camera>

    <a-entity
      id="leftHand"
      hand-controls="hand: left"
      laser-controls="hand: left">
    </a-entity>

    <a-entity
      id="rightHand"
      hand-controls="hand: right"
      laser-controls="hand: right">
    </a-entity>
  </a-entity>

  <!-- Grabbable objects -->
  <a-box class="grabbable" position="-1 1.5 -3" color="#4CC3D9"></a-box>
  <a-sphere class="grabbable" position="1 1.5 -3" color="#EF2D5E"></a-sphere>
</a-scene>

<script>
AFRAME.registerComponent('grabbable', {
  init: function() {
    var el = this.el;

    el.addEventListener('triggerdown', function(evt) {
      console.log('Grabbed by', evt.detail.hand);
      el.setAttribute('color', 'green');
    });

    el.addEventListener('triggerup', function(evt) {
      el.setAttribute('color', 'blue');
    });

    el.addEventListener('gripdown', function(evt) {
      // Attach object to controller
      var controllerEl = evt.detail.controller;
      controllerEl.object3D.attach(el.object3D);
    });

    el.addEventListener('gripup', function(evt) {
      // Detach from controller
      var sceneEl = el.sceneEl.object3D;
      sceneEl.attach(el.object3D);
    });
  }
});

// Apply grabbable component
document.querySelectorAll('.grabbable').forEach(el => {
  el.setAttribute('grabbable', '');
});
</script>