Shader "Custom/LightRays"{
	Properties{
		_MainTex("Texture",2D)="white"{}
		_Color1("Color1",Color)=(0.1,1,1,1)
		_Color2("Color2",Color)=(0,0.46,1,0)
		_Speed("Speed",Range(0,5.0))=0.5
		_Size("Size",Range(1.0,30.0))=15.0
		_Skew("Skew",Range(-1.0,1.0))=0.5
		_Shear("Shear",Range(0.0,5.0))=1.0
		_Fade("Fade",Range(0.0,1.0))=1.0
		_Contrast("Contrast",Range(0.0,50.0))=1.0
	}
	SubShader{
        Tags{
        	"Queue"="Transparent"
        	"IgnoreProjector"="True"
        	"RenderType"="Transparent"
        	"PreviewType"="Plane"
        }
        Cull Off
        Lighting Off
        ZWrite Off
        Fog {Mode Off}
        Blend SrcAlpha OneMinusSrcAlpha
		Pass{
			CGPROGRAM
			#pragma vertex vert_img
			#pragma fragment frag

			#include "UnityCG.cginc"

			float4 permute(float4 x){
				return fmod(34.0*pow(x,2)+x,289.0);
			}

			float2 fade(float2 t){
				return 6.0*pow(t,5.0)-15.0*pow(t,4.0)+10.0*pow(t,3.0);
			}

			float4 taylorInvSqrt(float4 r){
				return 1.79284291400159-0.85373472095314*r;
			}

			#define DIV_289 0.00346020761245674740484429065744f

			float mod289(float x){
				return x-floor(x*DIV_289)*289.0;
			}

			#define REPEAT_Y 1000.0

			float PerlinNoise2D(float2 P){
				//Mirror the pattern on large Y number
				if(floor(P.y/REPEAT_Y)%2==0){
			  		P.y-=floor(P.y/REPEAT_Y)*REPEAT_Y;
				}else{
					P.y-=floor(P.y/REPEAT_Y)*REPEAT_Y;
					P.y=REPEAT_Y-P.y;
				}
				float4 Pi=floor(P.xyxy)+float4(0.0,0.0,1.0,1.0);
				float4 Pf=frac(P.xyxy)-float4(0.0,0.0,1.0,1.0);
				float4 ix=Pi.xzxz;
				float4 iy=Pi.yyww;
				float4 fx=Pf.xzxz;
				float4 fy=Pf.yyww;
				float4 i=permute(permute(ix)+iy);
				float4 gx=frac(i/41.0)*2.0-1.0;
				float4 gy=abs(gx)-0.5;
				float4 tx=floor(gx+0.5);
				gx=gx-tx;
				float2 g00=float2(gx.x,gy.x);
				float2 g10=float2(gx.y,gy.y);
				float2 g01=float2(gx.z,gy.z);
				float2 g11=float2(gx.w,gy.w);
				float4 norm=taylorInvSqrt(float4(dot(g00,g00),dot(g01,g01),dot(g10,g10),dot(g11,g11)));
				g00*=norm.x;
				g01*=norm.y;
				g10*=norm.z;
				g11*=norm.w;
				float n00=dot(g00,float2(fx.x,fy.x));
				float n10=dot(g10,float2(fx.y,fy.y));
				float n01=dot(g01,float2(fx.z,fy.z));
				float n11=dot(g11,float2(fx.w,fy.w));
				float2 fade_xy=fade(Pf.xy);
				float2 n_x=lerp(float2(n00, n01),float2(n10, n11),fade_xy.x);
				float n_xy=lerp(n_x.x,n_x.y,fade_xy.y);
				return 2.3*n_xy;
			}

			fixed4 _Color1;
			fixed4 _Color2;
			float _Speed;
			float _Size;
			float _Skew;
			float _Shear;
			float _Fade;
			float _Contrast;

			fixed4 frag(v2f_img i):SV_Target{
				fixed4 color=lerp(_Color1,_Color2,1-i.uv.y);
				fixed noisePos=i.uv.x;
				noisePos+=-0.5;
				noisePos*=_Size;
				noisePos+=(1-i.uv.y)*(_Size*_Skew);
				noisePos*=1/lerp(1,_Shear,1-i.uv.y);
				fixed val=PerlinNoise2D(float2(noisePos,_Time.y*_Speed))/2 + 0.5f;
				val=_Contrast*(val-0.5)+0.5;
				color.a*=lerp(val,val*i.uv.y,_Fade);
				color.a=clamp(color.a,0.0,1.0);
				return color;
			}
			ENDCG
		}
	}
}