Introduction

Note: This documentation is for the old 0.2.0 version of A-Frame. Check out the documentation for the current 0.7.0 version

Primitives alias A-Frame entities and map HTML attributes to component properties. They are a convenience layer on top of the core API and are meant to:

  • Ease us into the concept of the entity-component-system pattern.
  • Provide a more familiar interface with HTML attributes mapping to only a single value.
  • Pre-compose useful components together with prescribed defaults to create semantic building blocks out-of-the-box.

A-Frame ships with a handful of primitives for common use cases such as displaying basic geometric primitives, 3D models, and media assets.

Example

Here is an assortment of various primitives in use:

<a-scene>
<!-- Using the asset management system for better performance. -->
<a-assets>
<a-asset-item id="fox-obj" src="fox.obj"></a-asset-item>
<a-asset-item id="fox-mtl" src="fox.mtl"></a-asset-item>
<img id="texture" src="texture.png">
<video id="video" src="video.mp4"></video>
</a-assets>
<a-camera fov="80"><a-cursor></a-cursor></a-camera>
<a-box src="#texture" depth="2" height="5" width="1"></a-sky>
<a-image src="fireball.jpg"></a-image>
<a-video src="#video">
<a-obj-model src="#fox-obj" mtl="#fox-mtl"></a-obj-model>
<a-sky color="#432FA0"></a-sky>
</a-scene>

How They Work

To create a wide red box using the primitives API, we could write:

<a-box color="red" width="3"></a-box>

Once attached, this will expand to:

<a-box color="red" width="3" geometry="primitive: box; width: 3" material="color: red"></a-box>

Thus, it is equivalent to:

<a-entity geometry="primitive: box; width: 3" material="color: red"></a-entity>

Under the hood, we see that primitives extend <a-entity> as a custom element while providing some defaults. It defaults the geometry.primitive property to box. And it maps (i.e., proxies) the HTML width attribute to the underlying geometry.width property and the HTML color attribute to the underlying material.color property.

Primitives are Entities

Since primitives extends <a-entity>s, operations that can be done upon entities can be done upon primitives. These operations include:

  • Positioning, rotating, and scaling
  • Attaching additional components to define additional appearance, behavior, or functionality
  • Applying animations
  • Specifying mixins

Primitives are Helpers

Note that primitives are a helper layer on top of A-Frame’s core API. Thus it is still extremely valuable to grasp the following:

  • How the rest of the system works under the hood
  • How to compose and configure components onto entities
  • How to use the asset management system

If you haven’t already, we heavily recommend skimming through the rest of the documentation.

Reading the Documentation for Individual Primitives

The following documentation pages for individual primitive elements will:

  • Describe what the primitive does in practice
  • Describe roughly how the primitive is composed
  • Describe which component properties the attributes proxy the value to (e.g., color maps to material.color, meaning the color property of the material component)
  • Describe any techniques or caveats

A lot of the primitives represent geometric meshes (i.e., shapes with an appearance). Thus, many of them inherit the common mesh attributes. So while attributes such as color or src are not listed in the attributes table for primitives such as <a-box> or <a-plane>, they are there. Remember to refer to common mesh attributes table when noted.