医学CT效果shader

首先需要根据医院提供的数据生成Texture3D,然后在shader中使用内置函数tex3D进行3D纹理采样，最后通过lightCT封装的算法过滤颜色通道，只取单个通道。shader代码如下，效果如图。

Shader "Custom/CT"
{
   Properties
   {
       _Volume ("Texture3D", 3D) = "" {}
       _WindowWidth("WindowWidth",float) = 2000
       _WindowPos("NarrowPos",float) = 1000
       maxDataValue("DataMax",float) = 2000
       minDataValue("DataMin",float) = 0
   }

   SubShader
   {
       Tags { "RenderType"="Opaque" "Queue" = "Geometry" }
       LOD 100
       //ZWrite Off
       //ZTest Off
       Pass
       {
           CGPROGRAM
           #pragma vertex vert
           #pragma fragment frag
           #include "UnityCG.cginc"

#pragma multi_compile _ WHOLE

sampler3D _Volume;

float minDataValue;
float maxDataValue;

float _WindowWidth;
float _WindowPos;

           float lightCT(float a){
               float minV = saturate((_WindowPos - (_WindowWidth / 2) - minDataValue ) / (maxDataValue - minDataValue));
               float maxV = saturate((_WindowPos + (_WindowWidth / 2) - minDataValue ) / (maxDataValue - minDataValue));
               return saturate((a - minV)/(maxV - minV));
           }
           struct appdata
           {
               float4 vertex : POSITION;
           };

           struct v2f
           {
               float4 vertex : SV_POSITION;
               float3 worldPos : TEXCOORD0;
           };

           v2f vert (appdata v)
           {
               v2f o;
               o.vertex = UnityObjectToClipPos(v.vertex);
               o.worldPos = v.vertex;
               return o;
           }

           fixed4 frag (v2f i) : SV_Target
           {
               float4 col = float4(0, 0, 0, 0);
               float3 lpos =i.worldPos;
               float3 pos =float3(lpos.x, lpos.y , lpos.z+0.5);//做成屏幕特效的坐标调整
               col = tex3D(_Volume, float4(pos, 0));//采样3D纹理
               col.r = lightCT(col.r);   //CT图像生成算法过滤，此处取任意一个通道即可
               return float4(col.rrr,1);
           }
           ENDCG
       }
   }
}

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