Shader "Polybrush/Simple Texture Blend"
{
    Properties
    {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Texture1 ("Texture 1 (RGB)", 2D) = "white" {}
        _Texture2 ("Texture 2 (RGB)", 2D) = "white" {}
        _Texture3 ("Texture 3 (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    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 _Texture1;
        sampler2D _Texture2;
        sampler2D _Texture3;

        struct Input
        {
            float2 uv_MainTex;
            float4 color : COLOR;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
            // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf (Input IN, inout SurfaceOutputStandard o)
        {
            fixed4 a = tex2D(_MainTex, IN.uv_MainTex);
            fixed4 b = tex2D(_Texture1, IN.uv_MainTex);
            fixed4 c = tex2D(_Texture2, IN.uv_MainTex);
            fixed4 d = tex2D(_Texture3, IN.uv_MainTex);

            fixed4 color = lerp(lerp(lerp(lerp(0, d, IN.color.a), c, IN.color.b), b, IN.color.g), a, IN.color.r);

            o.Albedo = color.rgb * _Color;
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = color.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}