Oversized bounding boxes for example models

Questions
1

I’m not sure if this is specific to animated models or not, but I’ve only seen it with animated examples such as
three.js/Horse.glb at 50380bd1b84a1c1fbd3bb7e41769c21f01f3b60f · mrdoob/three.js · GitHub and
three.js/Flamingo.glb at 50380bd1b84a1c1fbd3bb7e41769c21f01f3b60f · mrdoob/three.js · GitHub and
but not three.js/PrimaryIonDrive.glb at 50380bd1b84a1c1fbd3bb7e41769c21f01f3b60f · mrdoob/three.js · GitHub

Drop a model such as Horse.glb into three.js / editor and its bounding box is much bigger than it needs to be. This is problematic when I’m using @donmccurdy’s three-to-cannon package to build physics objects from Three objects. I’ve imported the models in Blender and don’t see any stray points. The models are insanely large; could it be some sort of scale/precision issue?

I do see that three.js docs says “The function may result in a larger box than strictly necessary.” Is that the problem? Any way to fix?

2

These models use morph target animation. Bounding box computation for such meshes honor the maximum extend of all morph targets (which is a critical requirement so raycasting or view frustum culling properly work).

3

Thanks @Mugen87, now that I know it’s morph targets causing this (and now that I’m learning about them), I see other posts/issues about this. I see https://jsfiddle.net/q4sjbLuk/ https://jsfiddle.net/qosuLyhf/ where you implement AABB for skinned meshes…is there a way to compute a smaller AABB for any Object3D? For my needs (approximate physics simulation) it doesn’t need to be perfect; it could just use the extent of the object when it first loads or something.

4

You could temporarily remove all morph target attributes, compute the AABB and the add them back to the geometry.

1 Like
5

That seems to be doing the trick, thanks! Here’s my function that removes/restores morphAttributes:

toggleMorphAttributes(obj, restore) {
  obj.traverse(c => {
    if (c.geometry) {
      if (restore) {
        c.geometry.morphAttributes =
          c.geometry.userData.morphAttributes || {};
        delete c.geometry.userData.morphAttributes;
      } else {
        c.geometry.userData.morphAttributes = c.geometry.morphAttributes;
        c.geometry.morphAttributes = {};
      }
      c.geometry.boundingBox = null;
    }
  });
}