Unity3D使用Shader实现腐蚀消失

本片shader实现的效果是模型腐蚀消失，且腐蚀的边缘大小可以调、颜色可调。效果图如下：

设置面板如下：

使用时需要给ClipMask参数给一张噪点图，设置合适的cliplinesize和cliplinecolor，然后调整clipalpha就可以了。

原理是通过获取噪点图上对应的颜色，转换成灰度，然后用灰度与clipalpha对比，如果大于则被剪裁掉。

shader实现如下：

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"
}

来源：https://blog.csdn.net/u012741077/article/details/53469215