using UnityEngine;
using System.Collections;

[ ExecuteInEditMode]
[RequireComponent (typeof(Camera))]
[AddComponentMenu ("Image Effects/Rendering/Screen Space Ambient Obscurance")]
class ScreenSpaceAmbientObscurance : PostEffectsBase {
	[Range (0,3)]	
	public float intensity = 0.5f;
	[Range (0.1f,3)]	
	public float radius = 0.2f;
	[Range (0,3)]
	public int blurIterations = 1;
	[Range (0,5)]
	public float blurFilterDistance = 1.25f;
	[Range (0,1)]
	public int downsample = 0;

	public Texture2D rand = null;
	public Shader aoShader= null;

	private Material aoMaterial = null;	

	public override bool CheckResources (){	
		 CheckSupport (true);
		
		aoMaterial = CheckShaderAndCreateMaterial (aoShader, aoMaterial);
		
		if (!isSupported)
			ReportAutoDisable ();
		return isSupported;			
	}

	void OnDisable (){
		if(aoMaterial)
			DestroyImmediate (aoMaterial);
		aoMaterial = null;
	}
	
	[ImageEffectOpaque]
	void OnRenderImage ( RenderTexture source ,   RenderTexture destination  ){	
		if (CheckResources () == false) {
			Graphics.Blit (source, destination);
			return;
		}

		Matrix4x4 P = GetComponent<Camera>().projectionMatrix;
		var invP= P.inverse;
		Vector4 projInfo = new Vector4
	        ((-2.0f / (Screen.width * P[0])), 
	         (-2.0f / (Screen.height * P[5])),
	         ((1.0f - P[2]) / P[0]), 
	         ((1.0f + P[6]) / P[5]));

		aoMaterial.SetVector ("_ProjInfo", projInfo); // used for unprojection
		aoMaterial.SetMatrix ("_ProjectionInv", invP); // only used for reference
		aoMaterial.SetTexture ("_Rand", rand); // not needed for DX11 :)
		aoMaterial.SetFloat ("_Radius", radius);
		aoMaterial.SetFloat ("_Radius2", radius*radius);
		aoMaterial.SetFloat ("_Intensity", intensity);
		aoMaterial.SetFloat ("_BlurFilterDistance", blurFilterDistance);

		int rtW = source.width;
		int rtH = source.height;

		RenderTexture tmpRt  = RenderTexture.GetTemporary (rtW>>downsample, rtH>>downsample);
		RenderTexture tmpRt2;

		Graphics.Blit (source, tmpRt, aoMaterial, 0);

		if (downsample > 0) {
			tmpRt2 = RenderTexture.GetTemporary (rtW, rtH);
			Graphics.Blit(tmpRt, tmpRt2, aoMaterial, 4);
			RenderTexture.ReleaseTemporary (tmpRt);
			tmpRt = tmpRt2;

			// @NOTE: it's probably worth a shot to blur in low resolution 
			//  instead with a bilat-upsample afterwards ...
		}
		
		for (int i = 0; i < blurIterations; i++) {
			aoMaterial.SetVector("_Axis", new Vector2(1.0f,0.0f));
			tmpRt2 = RenderTexture.GetTemporary (rtW, rtH);
			Graphics.Blit (tmpRt, tmpRt2, aoMaterial, 1);
			RenderTexture.ReleaseTemporary (tmpRt);

			aoMaterial.SetVector("_Axis", new Vector2(0.0f,1.0f));
			tmpRt = RenderTexture.GetTemporary (rtW, rtH);
			Graphics.Blit (tmpRt2, tmpRt, aoMaterial, 1);
			RenderTexture.ReleaseTemporary (tmpRt2);
		}

		aoMaterial.SetTexture ("_AOTex", tmpRt);		
		Graphics.Blit (source, destination, aoMaterial, 2);

		RenderTexture.ReleaseTemporary (tmpRt);
	}	
}