MouseMoveTracker.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace OVROSX {
	class MouseMoveTracker {

		private float baseV = 0.0f;
		private float diffV = 0.0f;
		private float baseH = 0.0f;
		private float diffH = 0.0f;
		private bool moving;
		private Vector2 movingOrigin;
		private float screenShorterRaidus;
		private UnityEngine.KeyCode triggerKeyCode;

		public MouseMoveTracker(UnityEngine.KeyCode keyCode) {
			screenShorterRaidus = Mathf.Min(Screen.width, Screen.height) / 2.0f;
			triggerKeyCode = keyCode;
		}

		public void Update() {

			if (moving) {

				Vector2 current = new Vector2(Input.mousePosition.x, Input.mousePosition.y); 

				Vector2 diff = current - movingOrigin;

				float diffX = Mathf.Clamp(diff.x, screenShorterRaidus*-1, screenShorterRaidus);
				float diffY = Mathf.Clamp(diff.y, screenShorterRaidus*-1, screenShorterRaidus);

				diffV = Mathf.Asin(diffY / screenShorterRaidus);
				diffH = Mathf.Acos(diffX / screenShorterRaidus) - 90 * Mathf.Deg2Rad;

				diffV *= -1;
				diffH *= -1;

				if (Input.GetMouseButtonUp(0)) {

					moving = false;

					baseV += diffV;
					baseH += diffH;

					diffV = 0;
					diffH = 0;

				}

			} else {

				if (Input.GetKey(triggerKeyCode) && Input.GetMouseButtonDown(0)) {

					moving = true;

					diffV = 0;
					diffH = 0;

					movingOrigin = new Vector2(Input.mousePosition.x, Input.mousePosition.y);

				}

			}

		}

		public Quaternion GetOrientation() {
			float v = (baseV + diffV) * Mathf.Rad2Deg;
			float h = (baseH + diffH) * Mathf.Rad2Deg;
			return Quaternion.Euler(v, h, 0.0f);
		}

	}
}