Aframe: size of model

Question

When using a model as a source to an entity, say gltf, is there a way we know the original size? Since the scale attribute works on relative size, it seems to be a trial an error to fit the model to our desired size. I tried using the geometry.getComputingBox() of the mesh of the model but it returns null. Wondering if there is a component that is available that lets us specify the scale in absolute terms.

Answer 1

Ah, figured it out.

var model = this.el.object3D;
var box = new THREE.Box3().setFromObject( model );
var size = box.getSize();

gives you the size. then using the above any desired size can be set.

Created a simple component that can be conveniently used

AFRAME.registerComponent('resize', {
  schema: {
    axis: {
      type: 'string',
      default: 'x'
    },
    value: {
      type: 'number',
      default: 1
    }
  },
  init: function() {
    var el = this.el;
    var data = this.data;
    var model = el.object3D;
    el.addEventListener('model-loaded', function(e) {
      var box = new THREE.Box3().setFromObject( model );
      var size = box.getSize();
      var x = size.x;
      var y = size.y;
      var z = size.z;
      if(data.axis === 'x') {
        var scale = data.value / x;
      }
      else if(data.axis === 'y') {
        var scale = data.value / y;
      }
      else {
        var scale = data.value / z;
      }
      el.setAttribute('scale', scale + ' ' + scale + ' ' + scale);
    });
  }
});

And it can be used as to proportionately resize the model with x axis length as 0.5

<a-entity resize='axis:x; value:0.5' gltf-model='#model`></a-entity>

Answer 2

(This would have come as a comment but as I don't have enough rep points this is coming as an answer.)

I found that the model doesn't have a size directly after the model-loaded event listener so I trigger the rescale from the update method. Funnily enough though if you don't have the model-loaded event listener then the size of the model will be 0 even after the first update is fired. This is my variant of the above code with the difference being that the dimension is set in meters:

const AFRAME = window.AFRAME;

/*
* Scales the object proportionally to a set value given in meters.
*/

AFRAME.registerComponent('natural-size', {
  schema: {
    width: {
      type: "number",
      default: undefined // meters
    },
    height: {
      type: "number",
      default: undefined // meters
    },
    depth: {
      type: "number",
      default: undefined // meters
    }
  },

  init() {
    this.el.addEventListener('model-loaded', this.rescale.bind(this));
  },

  update() {
    this.rescale();
  },

  rescale() {

    const el = this.el;
    const data = this.data;
    const model = el.object3D;

    const box = new THREE.Box3().setFromObject(model);
    const size = box.getSize();

    if ( !size.x && !size.y && !size.z ) {
      return;
    }

    let scale = 1;

    if ( data.width ) {
      scale = data.width / size.x;
    } else if( data.height ) {
      scale = data.height ( size.y);
    } else if( data.depth ) {
      scale = data.depth / size.y;
    }

    el.setAttribute('scale', `${scale} ${scale} ${scale}`);

  },

  remove() {
    this.el.removeEventListener('model-loaded', this.rescale);
  }

});

Then:

<a-entity natural-size='width:0.72' gltf-model='#model`></a-entity>

Answer 3

box.getSize has changed, I combined what I found here with what I found in another answer and noticed in the console to produce a more minimalist answer just to determine the size itself of a model:

    getDimensions(object3d) {
        // e.g., object3d = document.querySelector('#goban').object3D
        var box = new THREE.Box3().setFromObject( object3d );
        var x = box.max.x - box.min.x 
        var y = box.max.y - box.min.y 
        var z = box.max.z - box.min.z 

        return {x,y,z}
    }