写一个unity虚线shader

以下是一个简单的Unity虚线shader示例：

Shader "Custom/DashedLine" {
    Properties {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Texture", 2D) = "white" {}
        _DashSize ("Dash Size", Range(0.01, 0.1)) = 0.05
        _GapSize ("Gap Size", Range(0.01, 0.1)) = 0.05
    }

    SubShader {
        Tags {"Queue"="Transparent" "RenderType"="Transparent"}

        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct appdata {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            float _DashSize;
            float _GapSize;

            v2f vert (appdata v) {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            sampler2D _MainTex;
            float4 _Color;

            fixed4 frag (v2f i) : SV_Target {
                float2 repeat = float2(1.0, 1.0);
                float2 pos = i.uv * repeat;
                float2 d = fmod(pos / _DashSize, 2.0);
                float2 g = fmod(pos / _GapSize, 2.0);
                float2 col = fmod((pos - _GapSize / 2.0) / _DashSize, 2.0);
                col = step(1.0, col) * step(d.x, 1.0 - d.y) * step(g.x, 1.0 - g.y);
                return tex2D(_MainTex, i.uv) * _Color * col.xxxx;
            }
            ENDCG
        }
    }
    FallBack "Diffuse"
}

该shader可以在材质上应用，使用一张白色纹理可以实现虚线效果。其中Dash Size和Gap Size属性控制虚线和间隔的大小，Color属性控制虚线的颜色。