Finding rotation of Child. Why is there no absoluteRotation or locallyRotate methods?

Questions
1

I’m trying to set the position and rotation of an object to be equal to another object that has a parent.

For position I use: object1.locallyTranslate(object2.absolutePosition);

But this isn’t an option for rotation so I have to use the world matrix?

I googled some and tried doing:

var tempWorldMatrix = object2.getWorldMatrix();
object1.rotationQuaternion = tempWorldMatrix .decompose.rotation;

No luck though. Is there a simple standard way people get local rotation in world space? Thanks!

2

decompose does not work that way it requires parameters for the decomposition to be stored in. See Babylon.js Playground

As usual please supply a simple playground showing your code and what is wrong when asking a question. You will usually get a quicker answer, for one reason it is far easier for a replier to add a correction to a PG than to construct one and so more likely to get a response.

4 Likes
3

Thank you for the help. I will make a Playground next time.

I turned your solution into the function below and it worked. I originally asked because I was surprised there wasn’t a built in solution like object.absoluteRotation.

let getChildRotation = function(child){ //return the rotation of a child of a parent object by using a temporary World Matrix
    var scale = new BABYLON.Vector3(0, 0, 0);
    var rotation = new BABYLON.Quaternion();
    var translation = new BABYLON.Vector3(0,0,0);

    var tempWorldMatrix = child.getWorldMatrix();
    tempWorldMatrix.decompose(scale, rotation, translation);
    return rotation;
}