Rotate an object (model) with rotation of an another object (hand-VR)-CodePudding

I am making an object rotate with the rotation angle of the hand. It is working well and I am able to rotate the 3D model object. Unfortunately now I only want the object to rotate in its z-axis. I am trying to use Quaternion.Euler (0, 0, rot.eulerAngles.z); but does not work and the model rotates in all 3 axes. How do I fix it?

    public GameObject targetHand;

    [Header ("3D Model")]
    public GameObject powerSwitch;

    [Header ("Hand to 3D Model")]
    public float activationDistance;
    private Quaternion currentRot;
    private Vector3 startPos;
    private bool offsetSet;

    void Update () {

            if ((IsCloseEnough ())) {
                Rotate ();
            } else {
                offsetSet = false;
            }
        
    }
    void Rotate () {

        SetOffsets ();

        Vector3 closestPoint = Vector3.Normalize (targetHand.transform.position - powerSwitch.transform.position);
        var rot = Quaternion.FromToRotation (startPos, closestPoint);
        rot = Quaternion.Euler (0, 0, rot.eulerAngles.z); //Not working when I do this, why?
        powerSwitch.transform.rotation = rot * currentRot;

    }

    void SetOffsets () {
        if (offsetSet)
            return;

        startPos = Vector3.Normalize (targetHand.transform.position - powerSwitch.transform.position);
        currentRot = powerSwitch.transform.rotation;

        offsetSet = true;
    }

    bool IsCloseEnough () {
        if (Mathf.Abs (Vector3.Distance (targetHand.transform.position, powerSwitch.transform.position)) < activationDistance)
            return true;

        return false;
    }

CodePudding user response：

You want to clamp the rotation around that axis.

I have a few rotation extension methods like this to help.

public static class MyExtensions // Name it what you like I just use this
{
    public static Quaternion ClampRotationAroundZAxis(this Quaternion q)
    {
        if (!Mathf.Approximately(q.w, 0f))
        {
            q.x = !Mathf.Approximately(q.x, 0f) ? q.x /= q.w : q.x;
            q.y = !Mathf.Approximately(q.y, 0f) ? q.y /= q.w : q.y;
            q.z = !Mathf.Approximately(q.z, 0f) ? q.z /= q.w : q.z;
            q.w = 1f;
        }

        q.x = 0f;
        q.y = 0f;

        return q;
    }
}

// To Call it 
rotation.ClampRotationAroundZAxis();

Edit

You can get it to match it like this if I have them the correct way round otherwise swap order when setting the dir

Vector3 dir = (powerSwitch.transform.position - targetHand.transform.position).normalized;
Quaternion rot = Quaternion.LookRotation(dir, Vector3.up).ClampRotationAroundZAxis();
powerSwitch.transform.rotation = rot;

CodePudding user response：

Can not believe how simple it is.

To rotate things JUST .z axies you should keep other axies. Example :

Transform target;

transform.eulerAngles = new Vector3(transform.eulerAngles.x, transform.eulerAngles.y, target.eularAngles.z);

Just using targets z.