Issues with rotating a group in place

Questions
,
1

Hi,

I am having a hard time rotating a Group that contains GLTF model in place.
The idea is to create a Group like following:

        const group = new THREE.Group();
        group.matrixAutoUpdate = false;
        this.scene.add(group);

Then add a GLTF model into it:

        // Load and center the model
        const gltf = await loadGLTF('scene.gltf');
        gltf.scene.scale.set(0.0010, 0.0010, 0.0010);

        const box = new THREE.Box3().setFromObject(gltf.scene );
        const center = box.getCenter( new THREE.Vector3() );

        gltf.scene.position.x += ( gltf.scene.position.x - center.x );
        gltf.scene.position.y += ( gltf.scene.position.y - center.y );
        gltf.scene.position.z += ( gltf.scene.position.z - center.z );
        gltf.scene.position.z -= 0.5;
        group.add(gltf.scene);

When group is created and object added I want to it to be positioned in a predefined position and rotated based on Quaternion in-place. I tried everything and for some reason couldn’t combine these two operations (ThreeJs r143).
My last attempt was following:

     // Translate group to the center to rotate it
    const trnslate = new THREE.Matrix4().transpose().toArray();
    group.matrix.set(...trnslate);
    group.updateMatrix();
    // Perform rotation
    group.setRotationFromQuaternion(estimateResult.rotationQuaternion);
    group.updateMatrix();
    // Translate rotated group to the new position
    const position = new THREE.Vector3(npos[0], npos[1], npos[2]);
    const trnslateBack = new THREE.Matrix4().setPosition(position).transpose().toArray();
    group.matrix.set(...trnslateBack);
    group.updateMatrix();

Rotation works, however, translation doesn’t. I am pretty sure I am missing something very basic, but for some reason I cannot understand what exactly is wrong.
I also tried to update position by passing a new vector to it using group.position.set(npos[0], npos[1], npos[2]) it didn’t work either. Even manually created matrix didn’t work properly.

Whenever I apply rotation, the object just flies around instead of being rotated in place.

2

Its possible the object center is not the same as the group center.
Perhaps using the Bounding Box Helper might help visualize the objects center

3

You were right! I aligned them and everything started working perfectly! I knew I was missing something basic :smile: