Shader "Hidden/TextureCombinerShader"
{
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			// make fog work
			#pragma multi_compile_fog
			
			#include "UnityCG.cginc"

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

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

			sampler2D _TextureR;
			sampler2D _TextureG;
			sampler2D _TextureB;
			sampler2D _TextureA;
			half4 _TexturesGiven;
			half4 _InvertedTextures;
			float _DefaultValue;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = v.uv;
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the textures
				fixed4 colR = tex2D(_TextureR, i.uv);
				fixed4 colG = tex2D(_TextureG, i.uv);
				fixed4 colB = tex2D(_TextureB, i.uv);
				fixed4 colA = tex2D(_TextureA, i.uv);

				fixed R = abs(_InvertedTextures.x - colR.r * colR.a);
				fixed G = abs(_InvertedTextures.y - colG.r * colG.a);
				fixed B = abs(_InvertedTextures.z - colB.r * colB.a);
				fixed A = abs(_InvertedTextures.w - colA.r * colA.a);

				fixed4 texCol = fixed4(R,G,B,A);
				fixed4 col = lerp(texCol, _DefaultValue , (1 - _TexturesGiven));
				return col;
			}
			ENDCG
		}
	}
}