Rewind an animation in A-Frame

问题

I have an a-video somewhere in my scene. When I click a + button next to it, it triggers an animation to scale it up. It also makes visible a - button in order to scale it back to its original size.

I managed to make the upsizing part without too many issues, but can't find a way to reverse the animation, to make the a-video return to its original scale.

Here is what I have so far (adapted for briefness):

<a-video animation="property: scale; to: 20 20 20; dur: 200; dir: alternate; startEvents: startplay" src="#myvid" id="avideo"></a-video>
<a-image src="#play" onclick="document.getElementById('avideo').emit('startplay')"></a-image>
<a-image src="#pause" onclick="????"></a-image> <!-- is it possible to play the animation rewind here since I specified dir: alternate on #avideo? -->

The upscaling animation works fine, but I can't find how to trigger the rewinding part as described in the comments.

I'm fairly new to AFrame, it's probably something simple, but an answer could help rookies like me.

Thank you

回答1:

I'd try doing it with a second animation:

one does what you want
the other returns from the current state to the "original" state.

Lets say with a setup somewhat similar to yours

<a-sphere animation__play="property: scale; from: 1 1 1; to: 5 5 5; dur: 2000; dir: alternate; startEvents: play-anim; pauseEvents: pauseA-anim; stopEvents: stop-anim; loop: true"
          animation__rewind="property: scale; to: 1 1 1; easing: linear; startEvents: rewind-anim"
          animation-manager>
</a-sphere>

The animation-manager will be a custom component containing all the logic:

// custom component declaration
AFRAME.registerComponent("animation-manager", {
  // called upon initialization
  init: function() {
     // manage pressing the play image / button
     playBtn.addEventListener("click", e => this.el.emit("play-anim"));
     
     // manage the rewind image / button
     rewindBtn.addEventListener("click", e => {
       // set the current scale as the "starting point"
      this.el.setAttribute("animation__rewind", "from", this.el.getAttribute("scale"))
      
      // pause the current animation
      this.el.emit("pause-anim")
      // play the rewind animation
      this.el.emit("rewind-anim")
    })
  }
})

Check it out here.

来源：https://stackoverflow.com/questions/65022619/rewind-an-animation-in-a-frame

标签

javascript

aframe

webvr