unity 模型颜色渐变shader

Shader "Law/Car" {
    Properties{
        _MainColor("MainColor",color) = (1,1,1,1)
        _Color("Color",color) = (1,1,1,1)
        _Center("Center",range(-4.1,2.1)) = 0
        _R("R",range(0,1)) = 0.2
        _Glossiness("Smoothness", Range(0,1)) = 0.5
        _Metallic("Metallic", Range(0,1)) = 0.0
    }
        SubShader{
            Tags{ "RenderType" = "Opaque" }
 
            CGPROGRAM
            #pragma surface surf Standard vertex:vert
         
        fixed4 _Color;
        fixed4 _MainColor;
        float _Center;
        half _Glossiness;
        half _Metallic;
        float _R;
        sampler2D _MainTex;
 
        struct Input {
            float2 uv_MainTex;
            float4 vertex;
        };
 
        void vert(inout appdata_full v,out Input o)
        {
            o.uv_MainTex = v.texcoord.xy;
            o.vertex = v.vertex;
        }
         
 
        void surf (Input IN, inout SurfaceOutputStandard o) {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex);
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
 
            float d = IN.vertex.x - _Center;//该点距离中心点的距离，有正负
            float s = abs(d);
            d = d / s;    //取符号，正表示在上，负表示在下
            float f = s / _R;
            f = saturate(f);
            d *= f;
            d = d / 2 + 0.5;
              
            o.Albedo *= lerp(_MainColor, _Color, d)*2;
        }
        ENDCG
    }
    FallBack "Diffuse"
}