A-Frame: How to define a mixin dynamically at runtime? - aframe

Question

A-Frame Mixins go into the <a-assets> element, which must be defined before the scene is rendered. This makes sense for pre-loading/caching images, videos etc, but it seems there should be a way to dynamically create and use mixins.
Just adding the mixin to <a-assets> at runtime does not seem to work. The recommendation for adding image assets at runtime is to inline the image source and set it on the material directly. Is there some similar way of defining/altering a mixin at runtime? Or do I just need to set the relevant properties on all the objects to which the mixin is applied (taking care to also account for properties having been set by other mixins later in the mixin chain or directly on the object itself)
Edit: It looks like aframe-asset-on-demand-component is designed to do this for image/video assets. Unclear if works for mixins, but it also hasn't been updated in a year. Is this a (semi-)officially recommended solution?

Answer 1

Sorry if I've misunderstood your question but I seem to be able to add mixins to the assets tag at runtime. A basic version would mean writing a component as follows;
// add assets at run time
AFRAME.registerComponent('addasset', {
init: function () {
var assets = document.getElementsByTagName('a-assets')[0]
var mixin = document.createElement('a-mixin')
mixin.setAttribute('id', 'makeitred')
mixin.setAttribute('material', 'color: red')
assets.appendChild(mixin)
},
});
And then attach that component to the scene as follows;
<a-scene addasset>
<a-assets>
</a-assets>
<a-cylinder
mixin="makeitred"
position="0 0.5 -3">
</a-cylinder>
</a-scene>
Here is a working glitch
To demonstrate how that could be added once the scene is running here is a version of the same component with a setTimeout to demonstrate how the mixin could be added later on.
// add assets at run time, delayed
AFRAME.registerComponent('addasset', {
init: function () {
setTimeout(function(){
var assets = document.getElementsByTagName('a-assets')[0]
var mixin = document.createElement('a-mixin')
var cylinder = document.getElementsByTagName('a-cylinder')[0]
mixin.setAttribute('id', 'makeitred')
mixin.setAttribute('material', 'color: red')
assets.appendChild(mixin)
cylinder.setAttribute('mixin', 'makeitred')
}, 2000);
},
});
and then the HTML in which the mixin attribute will be added later
<a-scene addasset>
<a-assets>
</a-assets>
<a-cylinder
position="0 0.5 -3">
</a-cylinder>
</a-scene>
Here is a glitch of that
And for the sake of exploration, here is the same set up but triggered by an example event. First the same component but with an event listener
// add assets at run time, triggered by event
AFRAME.registerComponent('addasset', {
init: function () {
document.addEventListener("testevent", function(){
var assets = document.getElementsByTagName('a-assets')[0]
var mixin = document.createElement('a-mixin')
var cylinder = document.getElementsByTagName('a-cylinder')[0]
mixin.setAttribute('id', 'makeitred')
mixin.setAttribute('material', 'color: red')
assets.appendChild(mixin)
cylinder.setAttribute('mixin', 'makeitred')
});
},
});
Then a component that emits an event for testing
// test event to trigger adding of mixin
AFRAME.registerComponent('testevent', {
init: function () {
var self = this.el
setTimeout(function(){
self.emit("testevent")
}, 3000);
},
});
Then the HTML, as before but including a test entity that emits an event
<a-scene addasset>
<a-assets>
</a-assets>
<a-cylinder
position="0 0.5 -3">
</a-cylinder>
<a-entity
testevent>
</a-entity>
</a-scene>
And here is a glitch for that
So you could mix those up, add the mixin to assets but delay/trigger on event the addition of properties or add the mixin to assets with properties but delay/trigger on event the setting of that attribute on your target elements.
I hope that helps