Shader "Custom/GroundCircle"
{
Properties {
        _Color("Color", Color) = (1,1,1,1)
        _MainTex("Albedo (RGB)", 2D) = "white" {}
        
        _Center("Center", Vector) = (0,0,0,0)//圆的中心
        _Radius("Radius", Float) = 0.5//圆的半径
        _RadiusColor("Radius Color", Color) = (1,0,0,1)//圆的颜色
        _RadiusWidth("Radius Width", Float) = 2//圆的宽度
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200
        
        CGPROGRAM

        #pragma surface surf Standard fullforwardshadows
 
        #pragma target 3.0
 
        sampler2D _MainTex;
        fixed4 _Color;
 
        float3 _Center;
        float _Radius;
        fixed4 _RadiusColor;
        float _RadiusWidth;
 
        struct Input {
            float2 uv_MainTex;
            float3 worldPos;
        };
 
        void surf(Input IN, inout SurfaceOutputStandard o) {
            float d = distance(_Center, IN.worldPos);
            if (d > _Radius && d < _Radius + _RadiusWidth)
                o.Albedo = _RadiusColor;
            else
                o.Albedo = tex2D(_MainTex, IN.uv_MainTex).rgb;
        }
        ENDCG
    } 
    FallBack "Diffuse"
}