using UnityEngine;
using System.Collections;

public class RenderFogPlane : MonoBehaviour {
	
	public Camera cameraForRay;
	private float CAMERA_ASPECT_RATIO = 1.33333f;
	private float CAMERA_NEAR;
	private float CAMERA_FAR;
	private float CAMERA_FOV;
	private Matrix4x4 frustumCorners;
	
	private Mesh mesh;
	private Vector2[] uv = new Vector2[4];
	
	void OnEnable()
	{
		GetComponent<Renderer>().enabled	= true;
		if(mesh == null)
			mesh = (GetComponent<MeshFilter>() as MeshFilter).sharedMesh;
		
		if(mesh != null)
		{
			uv[0] = new Vector2(1.0f,1.0f);
			uv[1] = new Vector2(0.0f,0.0f);
			uv[2] = new Vector2(2.0f,2.0f);
			uv[3] = new Vector2(3.0f,3.0f);
			mesh.uv = uv;
		}
		
		if(cameraForRay == null)
		{
			cameraForRay	= Camera.main;
			if(cameraForRay != null)
				transform.parent	= cameraForRay.transform;
				transform.localPosition	= new Vector3(0,0,0);
				transform.localRotation	= Quaternion.identity;
		}
		
		cameraForRay.depthTextureMode	= DepthTextureMode.Depth;
			
	}
	
	private bool Supported()
	{
		return (GetComponent<Renderer>().sharedMaterial.shader.isSupported && 
			SystemInfo.supportsImageEffects && 
			SystemInfo.supportsRenderTextures &&				
			SystemInfo.SupportsRenderTextureFormat(RenderTextureFormat.Depth));
	}
	
	private bool EarlyOutIfNotSupported()
	{
		if(!Supported())
		{
			enabled = false;
			return true;
		}
		
		return false;
	}
	
	private void OnDisable()
	{
		GetComponent<Renderer>().enabled = false;
		if(cameraForRay != null && cameraForRay.depthTextureMode != DepthTextureMode.None)
			cameraForRay.depthTextureMode	= DepthTextureMode.None;
	}
		

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () 
	{
		if(EarlyOutIfNotSupported())
		{
			enabled = false;
			return ;
		}
		
		if(!GetComponent<Renderer>().enabled)
			return ;
		
		frustumCorners	= Matrix4x4.identity;
		Ray ray;
		Vector4 vec;
		Vector3 corner;
		
		CAMERA_NEAR = cameraForRay.nearClipPlane;
		CAMERA_FAR	= cameraForRay.farClipPlane;
		CAMERA_FOV	= cameraForRay.fieldOfView;
		CAMERA_ASPECT_RATIO	= cameraForRay.aspect;
		
		float fovWHalf = CAMERA_FOV * 0.5f;
		
		Vector3 toRight = cameraForRay.transform.right * CAMERA_NEAR * Mathf.Tan(fovWHalf * Mathf.Deg2Rad) * CAMERA_ASPECT_RATIO;
		Vector3 toTop 	= cameraForRay.transform.up * CAMERA_NEAR * Mathf.Tan(fovWHalf * Mathf.Deg2Rad);
		
		Vector3 topLeft = cameraForRay.transform.forward * CAMERA_NEAR - toRight + toTop;
		float CAMERA_SCALE = topLeft.magnitude * CAMERA_FAR/CAMERA_NEAR;
		
		// correctly place transform first
		transform.localPosition 	= new Vector3(transform.localPosition.x,transform.localPosition.y,CAMERA_NEAR + 0.0001f);
		transform.localScale		= new Vector3((toRight * 0.5f).magnitude,1.0f,(toTop * 0.5f).magnitude);
		transform.localRotation		= Quaternion.Euler(new Vector3(270.0f,0.0f,0.0f));
		// write view frustum corner "rays"
		topLeft.Normalize();
		topLeft	*= CAMERA_SCALE;
		
		Vector3 topRight = cameraForRay.transform.forward * CAMERA_NEAR + toRight + toTop;
		topRight.Normalize();
		topRight *= CAMERA_SCALE;
		
		Vector3 bottomRight = cameraForRay.transform.forward * CAMERA_NEAR + toRight - toTop;
		bottomRight.Normalize();
		bottomRight *= CAMERA_SCALE;
		
		Vector3 bottomLeft = cameraForRay.transform.forward * CAMERA_NEAR - toRight - toTop;
		bottomLeft.Normalize();
		bottomLeft *= CAMERA_SCALE;
		
		frustumCorners.SetRow(0,topLeft);
		frustumCorners.SetRow(1,topRight);
		frustumCorners.SetRow(2,bottomRight);
		frustumCorners.SetRow(3,bottomLeft);
		
		GetComponent<Renderer>().sharedMaterial.SetMatrix("_FrustumCornersWS",frustumCorners);
		GetComponent<Renderer>().sharedMaterial.SetVector("_CameraWS",cameraForRay.transform.position);
	}
}