Shader "Unlit/LUT"
{
	Properties
	{
        _MainTex ("Texture", 2D) = "white" {}
        _RedOverlay ("RedOverlay", 2D) = "white" {}
        _BlueOverlay ("BlueOverlay", 2D) = "white" {}
        _GreenOverlay ("GreenOverlay", 2D) = "white" {}
        _Greyscale ("GreyscaleOverlay", 2D) = "white" {}
        _GreyscalePower ("Greyscale Power", Range (0, 1)) = 1
	}
	SubShader
	{       

        Tags {"Queue"="Transparent" "IgnoreProjector"="True"}
        ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha
		LOD 100

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

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

			struct v2f
			{
				float2 uv : TEXCOORD0;
				UNITY_FOG_COORDS(1)
				float4 vertex : SV_POSITION;
			};

            sampler2D _MainTex;
            sampler2D _RedOverlay;
            sampler2D _BlueOverlay;
            sampler2D _GreenOverlay;
            sampler2D _Greyscale;
            float4 _MainTex_ST;
            float4 _RedOverlay_ST;
            float _GreyscalePower;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				UNITY_TRANSFER_FOG(o,o.vertex);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);
                fixed4 r = tex2D(_RedOverlay, i.uv*_RedOverlay_ST.xy);
                fixed4 g = tex2D(_BlueOverlay, i.uv);
                fixed4 b = tex2D(_GreenOverlay, i.uv);
                fixed4 gr = tex2D(_Greyscale, i.uv);

                fixed4 ret;

                r.a = col.r;
                r.rgb *= col.r;

                g.a = col.g;
                g.rgb *= col.g;

                b.a = col.b;
                b.rgb *= col.b;

                float4 sum = (r+g+b);
                sum.rgb = sum.rgb - float3(gr.a,gr.a,gr.a) * _GreyscalePower;
                sum.a += gr.a;
                return sum;
				// apply fog
				UNITY_APPLY_FOG(i.fogCoord, col);
			}
			ENDCG
		}
	}
}