// Space Scene Camera C# Script (version: 1.03)
// SPACE UNITY - Space Scene Construction Kit
// http://www.spaceunity.com
// (c) 2013 Stefan Persson

// DESCRIPTION:
// This script is attached to the Space Scene camera and it renders the space scene which is then used as a background
// to the main camera.

// INSTRUCTIONS:
// This script is attached to the SpaceCamera prefab. Normally you do not need to configure anything if you use the prefab.

// But just in case: It is important that the SpaceScene camera has a depth value lower than the main camera of the scene. 
// The rendering path should be set to "Forward" and the culling mask should be set to "DeepSpace" layer (if the DeepSpace 
// layer does not exist, create it manually and name it "DeepSpace" and it should show up - Unity does not export layer
// names which is why it goes missing.) It is also important that the Main Camera (or whatever camera you use) is set to a
// depth valua higher than the space camera and that the Clear Flags to Depth Only, and finally that the Culling Mask
// ignores the DeepSpace layer.

// PARAMETERS:
//   parentCamera	(reference to the parent (usually Main) camera so the space camera can rotate in sync)
//                  (if no camera is specified the script will assume and try to att mainCamera)
//   inheritFOV		(true/false if FOV (field of view) of space camera should change with the parent camera
//   relativeSpeed  (relative speed if you wish to travel through the space scene)
//                  (use with caution as you will go through planets and beyond nebulas unless you create boundaries yourself.)

// Version History
// 1.03 - Fixed deprecated code (changed Camera.mainCamera to Camera.main, and Camera.fov to Camera.fieldOfView)
// 1.02 - Prefixed with SU_SpaceSceneCamera to avoid naming conflicts.
// 1.01 - Initial Release.

using UnityEngine;
using System.Collections;

public class SU_SpaceSceneCamera : MonoBehaviour {
	// Reference to parent camera to sync rotation and FOV (field of view)
	public Camera parentCamera;
	// Whether or not SpaceCamera should change FOV if parent camera FOV is changed
	public bool inheritFOV = true;
	// Relative speed if you wish to move within the space scene, 
	// use with caution as you will go through planets and beyond nebulas unless you create boundaries yourself.
	public float relativeSpeed = 0.0f;
	
	// Private variables
	private Vector3 _originalPosition;
	private Transform _transformCache;
	private Transform _transformCacheParentCamera;

	// The space camera must have a reference to a parent camera so it knows how to rotate the background
	// This script allows you to specify a parent camera (parentCamera) which will act as reference
	// If you do not specify a camera, the script will assume you are using the main camera and select that as reference	
	void Start () {
		// Cache the transform to increase performance
		_transformCache = transform;
		
		if (parentCamera == null) {
			// No parent camera has been set, assume that main camera is used
			if (Camera.main != null) {
				// Set parent camera to main camera.
				parentCamera = Camera.main;							
			} else {				
				// No main camera found - throw a fit...
				Debug.LogWarning ("You have not specified a parent camera to the space background camera and there is no main camera in your scene. " +
								  "The space scene will not rotate properly unless you set the parentCamera in this script.");
			}
		}
		
		if (parentCamera != null) {
			// Cache the transform to the parent camera to increase performance
			_transformCacheParentCamera = parentCamera.transform;							
		}
		
		// Set the original position of the transform which is used for relative movement
		_originalPosition = _transformCache.position;
	}
	
	void Update () {		
		if (_transformCacheParentCamera != null) {
			// Update the rotation of the space camera so the background rotates		
			_transformCache.rotation = _transformCacheParentCamera.rotation;
			if (inheritFOV) GetComponent<Camera>().fieldOfView = parentCamera.fieldOfView;
			
			// Update the relative position of the space camera so you can travel in the space scene if necessary
			// Note! You will fly out of bounds of the space scene if your relative speed is high unless you restrict the movement in your own code.
			_transformCache.position = _originalPosition + (_transformCacheParentCamera.position * relativeSpeed);
		}
	}
}