Unity Shader Fog霧氣效果

最近想做個galgame用到了霧氣效果，自己動手實現了下，現在分享給大家
效果圖：

可以調節的是光照強度和裸露半徑。
實現很簡單，直接看代碼應該就能理解，不能理解說明還需努力。

Shader "Custom/FogShader" 
{
    Properties 
    {
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
         br("Br", Float) = 4
         r("R",Float)=0.42
    }
    SubShader
    {
        Tags { "Queue"="AlphaTest" "IgnoreProjector"="True" "RenderType"="TransparentCutout" }
        Pass
            {

            Tags { "LightMode"="ForwardBase" }
            Blend SrcAlpha OneMinusSrcAlpha
                  
                CGPROGRAM

                sampler2D _MainTex;
                half br;
                float r;

                #pragma vertex vert
                #pragma fragment frag
                #include "Lighting.cginc"

                struct v2f
                {
                    float4 pos : SV_POSITION; 
                    half2  uv : TEXCOORD0;    
                };

                v2f vert(appdata_img v)
                {
                    v2f o;
                    o.pos = UnityObjectToClipPos(v.vertex);
                    o.uv = v.texcoord;
                    return o;
                }

                int isOutside(half2 uv)
                {
                   return  step(r*r,(uv.x-0.5)*(uv.x-0.5)+(uv.y-0.5)*(uv.y-0.5));
                }
               
                fixed4 frag(v2f i) : SV_Target
                {
                    float k=0.707106-r;
                    fixed4 renderTex = tex2D(_MainTex, i.uv);
                    int a=isOutside(i.uv);
                    float d=sqrt((i.uv.x-0.5)*(i.uv.x-0.5)+(i.uv.y-0.5)*(i.uv.y-0.5))-r; 
                    return fixed4(renderTex.xyz,1-renderTex.a*br*d/k)*a+renderTex*(1-a);
                }
                    ENDCG
        }
    }

    FallBack Off
}