WaterFlush/Assets/Art/ThirdPart/Calm Water/Scripts/ImageEffect/UnderWaterFog.cs

using System;
using UnityEngine;

[ExecuteInEditMode]
[RequireComponent (typeof(Camera))]
[AddComponentMenu ("Image Effects/Rendering/UnderWater Fog")]
public class UnderWaterFog : MonoBehaviour
{

	public Color fogColor = Color.white;
	[Tooltip("Fog top Y coordinate")]
	public float height = 1.0f;
	[Range(0.001f,10.0f)]
	public float heightDensity = 2.0f;
	[Tooltip("Push fog away from the camera by this amount")]
	public float startDistance = 0.0f;

	public Shader fogShader = null;
	private Material fogMaterial = null;


	void OnEnable (){
		CheckResources ();
	}


	public bool CheckResources ()
	{

		if (fogShader == null) {
			fogShader = Shader.Find ("Hidden/UnderWaterFog");
		}

		if (fogMaterial == null) {
			fogMaterial = new Material (fogShader);
		}


		bool isSupported = true;

		if (!SystemInfo.SupportsRenderTextureFormat (RenderTextureFormat.Depth))
		{
			return false;
		}


		GetComponent<Camera>().depthTextureMode |= DepthTextureMode.Depth;

		return isSupported;
	}


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

		Camera cam = GetComponent<Camera>();
		Transform camtr = cam.transform;
		float camNear = cam.nearClipPlane;
		float camFar = cam.farClipPlane;
		float camFov = cam.fieldOfView;
		float camAspect = cam.aspect;


		Matrix4x4 frustumCorners = Matrix4x4.identity;

		float fovWHalf = camFov * 0.5f;

		Vector3 toRight = camtr.right * camNear * Mathf.Tan (fovWHalf * Mathf.Deg2Rad) * camAspect;
		Vector3 toTop = camtr.up * camNear * Mathf.Tan (fovWHalf * Mathf.Deg2Rad);

		Vector3 topLeft = (camtr.forward * camNear - toRight + toTop);
		float camScale = topLeft.magnitude * camFar/camNear;

		topLeft.Normalize();
		topLeft *= camScale;

		Vector3 topRight = (camtr.forward * camNear + toRight + toTop);
		topRight.Normalize();
		topRight *= camScale;

		Vector3 bottomRight = (camtr.forward * camNear + toRight - toTop);
		bottomRight.Normalize();
		bottomRight *= camScale;

		Vector3 bottomLeft = (camtr.forward * camNear - toRight - toTop);
		bottomLeft.Normalize();
		bottomLeft *= camScale;

		frustumCorners.SetRow (0, topLeft);
		frustumCorners.SetRow (1, topRight);
		frustumCorners.SetRow (2, bottomRight);
		frustumCorners.SetRow (3, bottomLeft);

		var camPos= camtr.position;
		float FdotC = camPos.y-height;
		float paramK = (FdotC <= 0.0f ? 1.0f : 0.0f);

		fogMaterial.SetColor ("_Color", fogColor);
		fogMaterial.SetMatrix ("_FrustumCornersWS", frustumCorners);
		fogMaterial.SetVector ("_CameraWS", camPos);
		fogMaterial.SetVector ("_HeightParams", new Vector4 (height, FdotC, paramK, heightDensity*0.5f));
		fogMaterial.SetVector ("_DistanceParams", new Vector4 (-Mathf.Max(startDistance,0.0f), 1.0f, 0, 0));

		var sceneMode= RenderSettings.fogMode;
		var sceneDensity = heightDensity;//RenderSettings.fogDensity;
		var sceneStart= RenderSettings.fogStartDistance;
		var sceneEnd= RenderSettings.fogEndDistance;
		Vector4 sceneParams;
		bool  linear = (sceneMode == FogMode.Linear);
		float diff = linear ? sceneEnd - sceneStart : 0.0f;
		float invDiff = Mathf.Abs(diff) > 0.0001f ? 1.0f / diff : 0.0f;
		sceneParams.x = sceneDensity * 1.2011224087f; // density / sqrt(ln(2)), used by Exp2 fog mode
		sceneParams.y = sceneDensity * 1.4426950408f; // density / ln(2), used by Exp fog mode
		sceneParams.z = linear ? -invDiff : 0.0f;
		sceneParams.w = linear ? sceneEnd * invDiff : 0.0f;
		fogMaterial.SetVector ("_SceneFogParams", sceneParams);
		fogMaterial.SetVector ("_SceneFogMode", new Vector4((int)sceneMode,0 , 0, 0));

		CustomGraphicsBlit (source, destination, fogMaterial, 0);
	}

	static void CustomGraphicsBlit (RenderTexture source, RenderTexture dest, Material fxMaterial, int passNr)
	{
		RenderTexture.active = dest;

		fxMaterial.SetTexture ("_MainTex", source);

		GL.PushMatrix ();
		GL.LoadOrtho ();

		fxMaterial.SetPass (passNr);

		GL.Begin (GL.QUADS);

		GL.MultiTexCoord2 (0, 0.0f, 0.0f);
		GL.Vertex3 (0.0f, 0.0f, 3.0f); // BL

		GL.MultiTexCoord2 (0, 1.0f, 0.0f);
		GL.Vertex3 (1.0f, 0.0f, 2.0f); // BR

		GL.MultiTexCoord2 (0, 1.0f, 1.0f);
		GL.Vertex3 (1.0f, 1.0f, 1.0f); // TR

		GL.MultiTexCoord2 (0, 0.0f, 1.0f);
		GL.Vertex3 (0.0f, 1.0f, 0.0f); // TL

		GL.End ();
		GL.PopMatrix ();
	}
}