AnnotationRotater.cs

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;

public class AnnotationRotater : MonoBehaviour {

    private GameObject meshPositionNode;
    private bool rotate;
    private Vector3 localRotationAxis;


    public void startRotate (BaseEventData eventData) {
        PointerEventData data = eventData as PointerEventData;
        if (data.button != PointerEventData.InputButton.Left) {
            return;
        }
        this.transform.GetChild (0).gameObject.SetActive (true);
        Vector3 localUp = this.transform.parent.InverseTransformDirection (this.transform.parent.forward);
        localRotationAxis = Vector3.Cross (localUp, this.transform.localPosition);


        rotate = true;
    }

    public void stopRotate (BaseEventData eventData) {
        PointerEventData data = eventData as PointerEventData;
        if (data.button != PointerEventData.InputButton.Left) {
            return;
        }
        this.transform.GetChild (0).gameObject.SetActive (false);
        rotate = false;
    }

    private void RotateObject () {
        InputDevice inputDevice = InputDeviceManager.instance.currentInputDevice;
        float dist = 0f;
        Plane intersectPlane = new Plane ();

        Vector3 normal = this.transform.parent.TransformDirection(localRotationAxis.normalized);
        intersectPlane.SetNormalAndPosition (normal, this.transform.parent.position);
        //Debug.DrawLine (this.transform.parent.position, this.transform.parent.position + normal);
        Ray intersectRay = inputDevice.createRay ();
        //Move Ray to CameraCenter
        intersectRay.origin = inputDevice.getEventCamera ().transform.position;
        if (intersectPlane.Raycast (intersectRay, out dist)) {
            Vector3 intersectPoint = intersectRay.GetPoint (dist);
            //intersectPoint local

            //Debug.DrawLine (this.transform.parent.position, this.transform.position);
            //Debug.DrawLine (this.transform.parent.position, intersectPoint);
            Vector3 posDir = this.transform.position - this.transform.parent.position;
            Vector3 intersectDir = intersectPoint - this.transform.parent.position;
            float angle = Vector3.Angle (posDir, intersectDir);

            //angle pos or neg ?
            if(Vector3.Dot(Vector3.Cross(posDir, intersectDir), normal) < 0) {
                angle =  -angle;
            }

            //Debug.Log (angle);
            this.GetComponentInParent<Annotation> ().rotateMesh(Quaternion.AngleAxis (angle, localRotationAxis));
        
        }
    }

    // Update is called once per frame
    void Update () {
        this.transform.parent.rotation = this.GetComponentInParent<Annotation>().myAnnotationMesh.transform.rotation;
        if(rotate) {
            RotateObject ();
        }
    }
}