Screen bounding box after rotate

Questions
1

Hi,
Trying to keep my 2d bounding box calculate at same angle but it seem the bounding box follow the first object even if i cloned the mesh and reset the Z angle to zero
any ideas !

controls.addEventListener("dragstart", function (event) {

            if (event.object) {

                AnimatorObject = event.object;

                AnimatorObject.rotation.z += MathUtils.degToRad(30);

                FakeAnimatorObject = AnimatorObject.clone();

                FakeAnimatorObject.rotation.z = 0;

                return;

            }

        });

let boundingBox2D = computeScreenSpaceBoundingBox(
    FakeAnimatorObject,
    Camera
);
2

Calling FakeAnimatorObject.updateMatrixWorld(); for the cloned mesh solved my problem
any explanation am new on threejs

3

I assume computeScreenSpaceBoundingBox() requires an up-to-date world matrix. The clone operation should actually copy the world matrix, too, so I’m a bit irritated that it does not work in the first place.

4

i even try to trick it without clone like that but still giving bounding box of the rotated mesh not the default angle (zero) , really confusing any explanation

AnimatorObject.rotation.z = 0;
let boundingBox2D = computeScreenSpaceBoundingBox(
    AnimatorObject,
    Camera
);
AnimatorObject.rotation.z = MathUtils.degToRad(30);
5

Well, after this line, the world matrix requires a re-computation. Otherwise it won’t honor the new transformation of the object.

6

is there is any preformance impact using updateMatrixWorld() in loop

7

That depends on the complexity of the scene graph. There are use cases where updateMatrixWorld() is a CPU hot spot.

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