Shader "PengLu/ImageEffect/Unlit/GaussianBlur" {
	Properties {
		_MainTex ("Base (RGB)", 2D) = "white" {}

	}
	
	CGINCLUDE

		#include "UnityCG.cginc"

		sampler2D _MainTex;
				
		uniform half4 _MainTex_TexelSize;
		uniform float _blurSize;
	
		// weight curves

		static const half curve[4] = { 0.0205, 0.0855, 0.232, 0.324};  
		static const half4 coordOffs = half4(1.0h,1.0h,-1.0h,-1.0h);

		struct v2f_withBlurCoordsSGX 
		{
			float4 pos : SV_POSITION;
			half2 uv : TEXCOORD0;
			half4 offs[3] : TEXCOORD1;
		};


		v2f_withBlurCoordsSGX vertBlurHorizontalSGX (appdata_img v)
		{
			v2f_withBlurCoordsSGX o;
			o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
			
			o.uv = v.texcoord.xy;
			half2 netFilterWidth = _MainTex_TexelSize.xy * half2(1.0, 0.0) * _blurSize; 
			half4 coords = -netFilterWidth.xyxy * 3.0;
			
			o.offs[0] = v.texcoord.xyxy + coords * coordOffs;
			coords += netFilterWidth.xyxy;
			o.offs[1] = v.texcoord.xyxy + coords * coordOffs;
			coords += netFilterWidth.xyxy;
			o.offs[2] = v.texcoord.xyxy + coords * coordOffs;

			return o; 
		}		
		
		v2f_withBlurCoordsSGX vertBlurVerticalSGX (appdata_img v)
		{
			v2f_withBlurCoordsSGX o;
			o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
			
			o.uv = v.texcoord.xy;
			half2 netFilterWidth = _MainTex_TexelSize.xy * half2(0.0, 1.0) * _blurSize;
			half4 coords = -netFilterWidth.xyxy * 3.0;
			
			o.offs[0] = v.texcoord.xyxy + coords * coordOffs;
			coords += netFilterWidth.xyxy;
			o.offs[1] = v.texcoord.xyxy + coords * coordOffs;
			coords += netFilterWidth.xyxy;
			o.offs[2] = v.texcoord.xyxy + coords * coordOffs;

			return o; 
		}	

		half4 fragBlurSGX ( v2f_withBlurCoordsSGX i ) : SV_Target
		{
			half2 uv = i.uv;
			
			half4 color = tex2D(_MainTex, i.uv) * curve[3];
			
  			for( int l = 0; l < 3; l++ )  
  			{   
				half4 tapA = tex2D(_MainTex, i.offs[l].xy);
				half4 tapB = tex2D(_MainTex, i.offs[l].zw); 
				color += (tapA + tapB) * curve[l];
  			}

			return color;

		}	
					
	ENDCG
	
	SubShader {
	  ZTest Off  ZWrite Off Blend Off



	Pass {
		ZTest Always
		
		
		CGPROGRAM 
		
		#pragma vertex vertBlurVerticalSGX
		#pragma fragment fragBlurSGX
		
		ENDCG
		}	
		

	Pass {		
		ZTest Always
		
				
		CGPROGRAM
		
		#pragma vertex vertBlurHorizontalSGX
		#pragma fragment fragBlurSGX
		
		ENDCG
		}	
	}	

	FallBack Off
}