How to get bone position in gltf-model

Questions
,
1

How would I go about getting the position of a bone or “node” (I guess) of a GLTF Model? I want to attach an object to a GLTF Model, but only have it follow one object in that GLTF. It has animations, so I want it to follow the object’s animation. (I know this is confusing) If you need the website or some code, feel free to ask! Thanks a ton!

2

I think you’ll be able to use something such as this

const boneWorldPos = new THREE.Vector3()

function animate() {
 bone.getWorldPosition(boneWorldPos)
 object.position.copy(boneWorldPos) 
}

This would get the world position of the bone and assign it to boneWorldPos which can then be copied to the position of your object…

3

How would I go about actually getting that bone’s position from the GLTF model’s bones? I know how to move objects to a position, but Im not sure how to actually get that bones position in the GLTF model (or node, I guess)

4

are you using plain three or r3f? in plain three you can do something like this…

let bone
const boneWorldPos = new THREE.Vector3()

gltfLoader.load( 'modelURL', function ( gltf ) {
 gltf.scene.traverse( function ( child ) {
  if(child.name === 'theNameOfTheBone'){
   bone = child
  }
 })
}

function animate() {
 bone.getWorldPosition(boneWorldPos)
 object.position.copy(boneWorldPos) 
}
5

I am using A-FRAME for this project. I will try to use that and form it around A-FRAME. would I still need the scene in gltf.scene.traverse... Or would I need to get the scene element? I just wanted to make sure, and then I will go ahead and try that.

6

im not sure how A-Frame works tbh.

you may be able to simplify it and use…

let bone = gltf.scene.getObjectByName('theNameOfTheBone')

essentially you just need to specify which bone you’re after and use bone.position, however the suggestion above to use bone.getWorldPosition(boneWorldPos) will return the absolute world position of the bone in question