Alt + マウス右クリックでカメラを動かす.cs

using UnityEngine;
using System.Collections;

// Alt + マウス右クリックでカメラを動かす

public class MouseCamera : MonoBehaviour {

	float oldMouseX = 0;
	float oldMouseY = 0;
	float mouseX = 0;
	float mouseY = 0;
	public float speedX = 1.0f;
	public float speedY = 1.0f;

	bool isMousePressed = false;

	void Update () {
		if (Input.GetMouseButtonDown (0)) {
			isMousePressed = true;
			oldMouseX = Input.GetAxis ("Mouse X");
			oldMouseY = Input.GetAxis ("Mouse Y");
		}
		if (Input.GetMouseButtonUp (0)) {
			isMousePressed = false;
		}

		// マウス押してる時にしか動かさない
		if (!isMousePressed) {
			return;
		}

		if (Input.GetKey(KeyCode.LeftAlt) || Input.GetKey(KeyCode.RightAlt)) {
			var mouseX = Input.GetAxis ("Mouse X");
			var mouseY = Input.GetAxis ("Mouse Y");

			var diffX = mouseX - oldMouseX;
			var diffY = mouseY - oldMouseY;

			this.transform.Rotate (new Vector3 (-diffY * speedY, diffX * speedX, 0));
		}
	}
}