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
Animations in A-Frame are defined by attaching an
<a-animation> element as a child of the entity to animate. The API is roughly based after the Web Animations specification.
As an introductory example, to define a 5-meter orbit on an entity about the Y-axis that takes 10 seconds, we can offset its position and animate the rotation of a parent entity. This animation starts with the initial rotation about the Y-axis of 0 degrees and goes around to 360 degrees. It’s defined with a duration of 10000 milliseconds, maintains the final value on each cycle of the animation, and loops indefinitely.
Many attributes and values are used to define animations. We’ll delve into more detail below:
|attribute||Attribute to animate. To specify a component attribute, use
|begin||Delay (in milliseconds) or event name to wait on before beginning animation.||0|
|direction||Direction of the animation (between
|dur||Duration in (milliseconds) of the animation.||1000|
|easing||Easing function of the animation. There are very many to choose from.||ease|
|fill||Determines effect of animation when not actively in play. One of
|from||Starting value.||Current value.|
|repeat||Repeat count or
|to||Ending value. Must be specified.||None|
A-Frame’s animation system can animate several possible categories of attributes.
A-Frame has several standard
vec3 components (i.e.,
scale). These components consist of three factors: X, Y, and Z. We can pass three space-delimited numbers to the
to attributes just as we would define them on an entity. In this case, the animation system will assume we are animating a
For example, if we want to animate an entity going from one spot to another, we can animate the
A-Frame has several standard components that accept a single boolean value. Boolean values can be “animated” as well by flipping the boolean at the end of each animation cycle.
For example, we can define an animation that toggles off the visibility of an entity after 5 seconds.
We can animate numeric attributes as well. For example, we can animate the intensity of the light primitive.
We can animate a certain property of a multi-property component. To do so, we select the component property using the dot syntax:
For example, to animate a cone’s top radius, we can select the
radiusTop value with
begin attribute defines when the animation should start playing.
This can either be a number, representing milliseconds to wait, or an event name to wait for. For example, we can define an animation that waits 2 seconds from when the animation is attached before scaling an entity.
Or we can define an animation that waits for the parent element to trigger an event named
fade before fading an entity.
direction attribute defines which way to animate between the starting value and the final value.
When an alternating direction is defined, the animation will go back and forth between the
to values like a yo-yo. Alternating directions only take affect when the animation is set to repeat.
|alternate||On even-numbered cycles, animate from
|alternate-reverse||On odd-numbered cycles, animate from
easing attribute defines the easing function of the animation, which defaults to
ease. There are too many easing functions to list, but we can implicitly explain what all of them are.
One possible value is
linear. And the basic easing functions are
Then there are additional groups of easing functions. Each group of easing functions are prefixed by the above basic easing functions. The groups of easing functions are
For example, the
cubic group of easing functions would consist of
fill attribute defines the effect of animation when not actively in play. Think of
fill as what values the animation sets on the entity before and/or after each animation cycle. Below are the possible values for
fill and their effects.
|backwards||Before the animation starts, set the starting value to the
|both||Combine the effects of both backwards fill and forwards fill.|
|forwards||After the animation finishes, the final value will stay at the
|none||Before the animation starts, set the starting value to the initial value. After the animation finishes, reset the value to the initial value.|
repeat attribute defines how often the animation repeats. We call each repeat of the animation a cycle. Repeat can either be a number that counts down on each animation cycle until it reaches
0 at which point the animation will end, or it can be set to
indefinite and the animation will loop continuously until the animation is manually removed or stopped.
<a-animation> element emits a couple of events.
|animationend||Emitted when the animation finishes. In case of repeats, emitted when the repeat count reaches
|animationstart||Emitted immediately when the animation begins playing.|