Shader "CrispyPin/diffuse"
{
	Properties
	{
		[NoScaleOffset]
		_LastFrame ("Render texture", 2D) = "white" {}
		[NoScaleOffset]
		_Noise ("Noise", 2D) = "white" {}
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag

			#include "UnityCG.cginc"

			#define WIDTH 256

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

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

			texture2D _LastFrame;
			sampler2D _Noise;

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

			float3 source_pixel(uint2 p, float2 uv, float2 rand_offset) {
				const uint dir = tex2D(_Noise, uv + _Time.xy + rand_offset).r * 4.0;
				if (dir == 0) {
					p.x += 1;
				} else if (dir == 1) {
					p.x -= 1;
				} else if (dir == 2) {
					p.y += 1;
				} else if (dir == 3) {
					p.y -= 1;
				}
				return _LastFrame[p];
			}

			float4 frag (v2f i) : SV_Target {
				if(_ProjectionParams.z > 1) discard;

				const uint2 p = i.uv * WIDTH;

				float red = _LastFrame[p].r - (1./255.);
				float green = _LastFrame[p].g - (1./255.);
				float blue = _LastFrame[p].b - (1./255.);

				if (red <= 0) {
					red = source_pixel(p, i.uv, float2(0.34, 0.89)).r;
				}
				if (green <= 0) {
					green = source_pixel(p, i.uv, float2(0.43, 0.19)).g;
				}
				if (blue <= 0) {
					blue = source_pixel(p, i.uv, float2(0.03, 0.39)).b;
				}
				// if (_LastFrame[p].r > 0) {
				// 	float pixel = _LastFrame[p].r - (1./255.);
				// 	return float4(pixel, pixel/2., 0, 1);
				// }


				// return float4(source.r - 0.02, 0, 0, 1);
				return float4(red, green, blue, 1);
			}
			ENDCG
		}
	}
}