Building with Basic HTML
Note: This documentation is for the old 0.3.0 version of A-Frame. Check out the documentation for the current 0.9.0 version
Let’s build a scene using A-Frame’s basic primitive HTML building blocks!
This sample Hello World scene starts with a box:
Just like with regular HTML elements, we can configure the element by setting
HTML attributes. Here, we define the color, width, height, depth of
<a-box> documentation to see the available attributes.
For flat displays, the default control scheme lets us look around by
click-dragging the mouse and move with the
WASD keys. Upon
entering VR, the default control scheme lets us look around with a VR
headset and, if room scale is possible, literally walk around.
A-Frame uses a right-handed coordinate system:
- Positive X-axis is “right”
- Positive Y-axis is “up”
- Positive Z-axis is pointing out of the screen towards us
The basic distance unit is defined in meters. When designing a scene for VR, it
is important to consider the real world scale of the objects we create. A box
height="100" may look normal on our computer screens, but in VR the
box will appear massive.
The basic rotational unit is defined in degrees. To determine the positive direction of rotation, use the right-hand rule. Point our thumbs down the direction of a positive axis, and the direction which our fingers curl around the positive direction of rotation.
The example above (assuming we are positioned on the origin looking down the negative Z-axis) will translate the box left/up/back, rotate the box to the right, stretch the box left-and-right and back-and-front, and shrink the box up-and-down:
We can apply an image texture to the box with an image or video using the
attribute. To make sure the color does not mix with the texture, we set the
background color to white:
It is best to cache the texture and block the scene from rendering until the texture has loaded. To do so we must move the texture into the asset management system by:
- Defining the asset as an
- Giving it an ID (
- Referring to the asset using the ID in selector format (
We can add an animation to the box using the built-in animation
system. We can place an
<a-animation> element as a child of the
entity to interpolate values. Let’s have the box rotate indefinitely to add
some motion to the scene:
To interact with the box via clicking or gazing, we can use a cursor which we place as a child of the camera such that it is fixed to the screen. When we don’t define a camera, the scene will inject a default camera, but in this case to add a cursor, we will need to explicitly define a camera.
Next we direct the animation to start when the cursor clicks the
box, using the animation’s
begin attribute. The cursor will emit the
click event on the box, and the animation will listen for it:
As an aside, a more advanced method would be to write a component that listens to an event and does whatever we want it to do:
We can then attach the component to the
<a-box color="#FFF" width="4" height="10" depth="2"
We can change how the scene is lit with
<a-light>. By default the
scene will inject an ambient light and a directional light (which acts like the
sun). Once we add lights of our own, however, the default lighting setup is removed:
Lastly, we can add a background to the scene using
background can be a color, a 360° image, or even a 360° video:
That is all it takes to create a very basic scene which places static objects in a 3D space using HTML. A good VR experience requires rich interaction and dynamic behavior. With the help of A-Frame components, we can build a more advanced scene.