Unity shader学习之屏幕后期处理效果之高度雾，重建world pos方法2

这里使用一种更高效地从深度纹理中重建世界坐标的方法。

首先计算摄像机的视锥体的四条射线向量进行线性插值，插值后的值便是该像素在世界空间坐标下到摄像机的方向。

然后通过与深度值相乘即可得到摄像机位置到该像素的向量，加上摄像机的位置则是该像素在世界空间中的位置。

转载请注明出处：https://www.cnblogs.com/jietian331/p/9443343.html

c#代码：

 using UnityEngine;

 public class HighFog2 : PostEffectRenderer
 {
     [SerializeField]
     Color m_fogColor = Color.white;
     [Range(0f, 1f)]
     [SerializeField]
     float m_fogDensity = 0.9f;
     [SerializeField]
     float m_fogPosY = 0.1f;
     [SerializeField]
     float m_fogDisappearHeight = ;

     protected override string ShaderName
     {
         get { return "Custom/Study/HighFog2"; }
     }

     protected override void OnRenderImage(RenderTexture src, RenderTexture dest)
     {
         float fov = base.SelfCamera.fieldOfView;
         float near = base.SelfCamera.nearClipPlane;
         Transform camT = base.SelfCamera.transform;

         float halfFOV = fov * Mathf.PI / 360f;
         float toTopDis = near * Mathf.Tan(halfFOV);
         float toRightDis = toTopDis * (Screen.width / Screen.height);
         Vector3 toTop = camT.up * toTopDis;
         Vector3 toRight = camT.right * toRightDis;
         Vector3 toCenter = camT.forward * near;
         Vector3 topLeft = (toCenter + toTop - toRight) / near;
         Vector3 topRight = (toCenter + toTop + toRight) / near;
         Vector3 bottomLeft = (toCenter - toTop - toRight) / near;
         Vector3 bottomRight = (toCenter - toTop - toRight) / near;

         Matrix4x4 matrix = Matrix4x4.identity;
         matrix.SetRow(, bottomLeft);
         matrix.SetRow(, bottomRight);
         matrix.SetRow(, topLeft);
         matrix.SetRow(, topRight);

         base.Mat.SetMatrix("_CameraRays", matrix);
         base.Mat.SetColor("_FogColor", m_fogColor);
         base.Mat.SetFloat("_FogDensity", m_fogDensity);
         base.Mat.SetFloat("_FogPosY", m_fogPosY);
         base.Mat.SetFloat("_FogDisappearHeight", m_fogDisappearHeight);
         base.OnRenderImage(src, dest);
     }
 }

shader:

 Shader "Custom/Study/HighFog2"
 {
     Properties
     {
         _MainTex ("Texture", 2D) = "white" {}
     }

     SubShader
     {
         Pass
         {
             ZTest Always
             ZWrite Off
             Cull Off

             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag

             #include "UnityCG.cginc"

             struct appdata
             {
                 float4 vertex : POSITION;
                 float2 uv : TEXCOORD0;
             };

             struct v2f
             {
                 float2 uv : TEXCOORD0;
                 float4 vertex : SV_POSITION;
                 float3 ray : TEXCOORD1;
             };

             sampler2D _MainTex;
             sampler2D _CameraDepthTexture;
             uniform float4x4 _CameraRays;
             uniform float4 _FogColor;
             uniform float _FogDensity;
             uniform float _FogPosY;
             uniform float _FogDisappearHeight;

             v2f vert (appdata v)
             {
                 v2f o;
                 o.vertex = UnityObjectToClipPos(v.vertex);
                 o.uv = v.uv;

                 int index;
                 if(v.vertex.x < 0.5 && v.vertex.y < 0.5)
                 {
                     index = ;
                 }
                 else if(v.vertex.x > 0.5 && v.vertex.y < 0.5)
                 {
                     index = ;
                 }
                 else if(v.vertex.x > 0.5 && v.vertex.y > 0.5)
                 {
                     index = ;
                 }
                 else
                 {
                     index = ;
                 }
                 o.ray = _CameraRays[index].xyz;

                 return o;
             }

             fixed4 frag (v2f i) : SV_Target
             {
                 fixed4 col = tex2D(_MainTex, i.uv);

                 float d = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, i.uv));
                 float3 worldPos = _WorldSpaceCameraPos + i.ray * d;

                 float fogWeight;
                 if(worldPos.y < _FogPosY)
                 {
                     fogWeight = ;
                 }
                 else if(worldPos.y > _FogPosY + _FogDisappearHeight)
                 {
                     fogWeight = ;
                 }
                 else
                 {
                     fogWeight =  - (worldPos.y - _FogPosY) / _FogDisappearHeight;
                 }

                 return lerp(col, _FogColor, fogWeight * _FogDensity);
             }

             ENDCG
         }
     }

     Fallback Off
 }

效果图如下：