Shader "Custom/Opacue"
{
    Properties
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _Threshold("Cutout threshold", Range(0,1)) = 0.1
        _Softness("Cutout softness", Range(0,0.5)) = 0.0
    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue" = "Transparent" }
        LOD 100

        ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha

        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;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _Threshold;
            float _Softness;

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

            fixed4 frag(v2f i) : SV_Target
            {
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);
                col.a = smoothstep(_Threshold, _Threshold + _Softness,
                    0.333 * (col.r + col.g + col.b));
                return col;
            }
            ENDCG
        }
    }
}