Unity3D使用Shader实现腐蚀消失

Shader "XM/CorrosionEffect" {
 Properties {
 _Color ("Color", Color) = (1,1,1,1)
 _MainTex ("Albedo (RGB)", 2D) = "white" {}
 _Glossiness ("Smoothness", Range(0,1)) = 0.5
 _Metallic ("Metallic", Range(0,1)) = 0.0
 _ClipMaskTex ("Clip Mask", 2D) = "white" {}
 _ClipGray ("Clip Alpha", Range(0.0,1.0)) = 0.0
 _ClipLineSize ("Clip Line Size", Range(0,1)) = 0.0
 _ClipLineColor("Clip Line Color", Color) = (1,1,1,1)
 }
 SubShader {
 Tags { "RenderType"="Opaque" }
 LOD 200

 CGPROGRAM
 // Physically based Standard lighting model, and enable shadows on all light types
 #pragma surface surf Standard fullforwardshadows

 // Use shader model 3.0 target, to get nicer looking lighting
 #pragma target 3.0

 sampler2D _MainTex;
 sampler2D _ClipMaskTex;

 struct Input {
  float2 uv_MainTex;
 };

 half _Glossiness;
 half _Metallic;
 fixed4 _Color;
 fixed _ClipGray;
 fixed _ClipLineSize;
 fixed4 _ClipLineColor;

 void surf (Input IN, inout SurfaceOutputStandard o) {
  fixed4 m = tex2D (_ClipMaskTex, IN.uv_MainTex);
  fixed gray = Luminance(m.rgb);
  if(gray >= _ClipGray)
  {
  clip(-1);
  }

  fixed4 c;
  if(gray >= _ClipGray - _ClipLineSize)
  {
  c = _ClipLineColor;
  }
  else
  {
  // Albedo comes from a texture tinted by color
  c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
  }

  o.Albedo = c.rgb;

  // Metallic and smoothness come from slider variables
  o.Metallic = _Metallic;
  o.Smoothness = _Glossiness;
  o.Alpha = c.a;
 }
 ENDCG
 }
 FallBack "Diffuse"
}