AnnotationScaler.cs

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

public class AnnotationScaler : MonoBehaviour {

    public GameObject arrow1;
    public GameObject arrow2;

    public float maxScale = 15f;
    public float minScale = 0.5f;

    private bool reScale = false;
    private Vector3 rescaleDirection;

    public void rescaleAnnotation(BaseEventData eventData) {
        PointerEventData data = eventData as PointerEventData;
        if (data.button != PointerEventData.InputButton.Left) {
            return;
        }
        rescaleDirection = Vector3.Scale(arrow1.transform.localPosition,arrow1.transform.localPosition).normalized;
        reScale = true;
    }

    public void stopRescale(BaseEventData eventData) {
        PointerEventData data = eventData as PointerEventData;
        if (data.button != PointerEventData.InputButton.Left) {
            return;
        }
        reScale = false;
    }

    private void rescaleMesh() {
        InputDevice inputDevice = InputDeviceManager.instance.currentInputDevice;
        Plane intersectPlane = new Plane ();
        float dist = 0f;
        Ray intersectRay = inputDevice.createRay ();
        //Move Ray to CameraCenter
        intersectRay.origin = inputDevice.getEventCamera ().transform.position;

        //update plane
        Vector3 camAnnoVec = (intersectRay.origin - this.transform.position);
        Vector3 globalDir = this.transform.TransformDirection (rescaleDirection);
        Vector3 planeVec = Vector3.Cross (globalDir, camAnnoVec);
        Vector3 normal = Vector3.Cross (globalDir, planeVec);
        normal.Normalize ();

        intersectPlane.SetNormalAndPosition (normal, this.transform.position);

        if (intersectPlane.Raycast (intersectRay, out dist)) {
            Vector3 intersectPoint = intersectRay.GetPoint (dist);
            //intersectPoint is Local
            intersectPoint = this.transform.InverseTransformPoint (intersectPoint);

            //reduce to point on scale direction
            intersectPoint = Vector3.Scale (intersectPoint, rescaleDirection);
            //Intersect Point always Positiv
            intersectPoint = Vector3.Scale (intersectPoint, intersectPoint.normalized);
            Vector3 newScale = (intersectPoint.normalized * intersectPoint.magnitude) * 2;

            if (newScale.magnitude > maxScale || newScale.magnitude < minScale) {
                return;
            }

            arrow2.transform.localPosition = 0.5f * newScale + newScale.normalized;
            arrow1.transform.localPosition =  -1f * arrow2.transform.localPosition;

            Vector3 actScale = this.GetComponentInParent<Annotation> ().getMeshScale ();
            //Add scale only in one Direction
            newScale = actScale - Vector3.Scale (actScale, rescaleDirection) + newScale;


            this.GetComponentInParent<Annotation> ().rescaleMesh (newScale);


        }

    }

    public void Start() {
        Vector3 scale = this.GetComponentInParent<Annotation> ().getMeshScale ();
        Vector3 rescaleDir = Vector3.Scale(arrow1.transform.localPosition,arrow1.transform.localPosition).normalized;
        scale = Vector3.Scale (rescaleDir, scale);
        arrow2.transform.localPosition = 0.5f * scale + scale.normalized;
        arrow1.transform.localPosition =  -1f * arrow2.transform.localPosition;
    }

    public void Update() {
        this.transform.rotation = this.GetComponentInParent<Annotation>().myAnnotationMesh.transform.rotation;
        if(reScale) {
            rescaleMesh ();
        }
    }
}