Shader "UltraCombos/Frozen/SpaceMapping"
{
	Properties
	{
		[PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}

		_StencilComp("Stencil Comparison", Float) = 8
		_Stencil("Stencil ID", Float) = 0
		_StencilOp("Stencil Operation", Float) = 0
		_StencilWriteMask("Stencil Write Mask", Float) = 255
		_StencilReadMask("Stencil Read Mask", Float) = 255

		_ColorMask("Color Mask", Float) = 15
	}

	SubShader
	{
		Tags
		{
			"Queue" = "Transparent"
			"IgnoreProjector" = "True"
			"RenderType" = "Transparent"
			"PreviewType" = "Plane"
			"CanUseSpriteAtlas" = "True"
		}

		Stencil
		{
			Ref[_Stencil]
			Comp[_StencilComp]
			Pass[_StencilOp]
			ReadMask[_StencilReadMask]
			WriteMask[_StencilWriteMask]
		}

		Cull Off
		Lighting Off
		ZWrite Off
		ZTest[unity_GUIZTestMode]
		//Blend OneMinusSrcColor One//SrcAlpha One // SrcAlpha OneMinusSrcAlpha
		Blend One Zero
		ColorMask[_ColorMask]

		Pass
		{
			Name "Default"
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma target 2.0

			#include "UnityCG.cginc"
			#include "UnityUI.cginc"

			struct appdata_t
			{
				float4 vertex   : POSITION;
				float2 texcoord : TEXCOORD0;
				UNITY_VERTEX_INPUT_INSTANCE_ID
			};

			struct v2f
			{
				float4 vertex   : SV_POSITION;
				//fixed4 color : COLOR;
				float2 texcoord  : TEXCOORD0;
				float4 worldPosition : TEXCOORD1;
				UNITY_VERTEX_OUTPUT_STEREO
			};

			fixed4 _TextureSampleAdd;
			float4 _ClipRect;

			v2f vert(appdata_t IN)
			{
				v2f OUT;
				UNITY_SETUP_INSTANCE_ID(IN);
				UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
				OUT.worldPosition = IN.vertex;
				OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);
				OUT.texcoord = IN.texcoord;

				return OUT;
			}

			sampler2D _MainTex;

			float4x4 homography[3];
			float3 homo_space;
			float2 texture_size;

			fixed4 frag(v2f IN) : SV_Target
			{
				//half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
				//color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);

				const float3 space = homo_space;
				const float2 clipped_size = texture_size;

				float2 uv = float2(IN.texcoord.x, 1 - IN.texcoord.y);
				float2 pos = uv * clipped_size;

				if (pos.y <= space.z)
				{
					if (pos.x < space.z || pos.x > space.z + space.x)
					{
						pos = float2(0, 0);
					}
					else
					{
						float4 homo_pos = mul(homography[0], float4(pos, 0, 1));
						pos = homo_pos.xy / homo_pos.w;
					}
				}
				else if (pos.x <= space.z)
				{
					float4 homo_pos = mul(homography[1], float4(pos, 0, 1));
					pos = homo_pos.xy / homo_pos.w;
				}
				else if (pos.x >= space.z + space.x)
				{
					float4 homo_pos = mul(homography[2], float4(pos, 0, 1));
					pos = homo_pos.xy / homo_pos.w;
				}

				uv = pos / clipped_size;
				uv = float2(uv.x, 1 - uv.y);
				half4 color = any(length(pos)) ? tex2D(_MainTex, uv) : float4(0, 0, 0, 1);

				//uv = float2(IN.texcoord.x, 1 - IN.texcoord.y);
				//color = half4(uv, 0, 1);
				//color = tex2D(_MainTex, IN.texcoord);

				return color;
			}
			ENDCG
		}
	}
}