//Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Conversion/CubemapToEquirectangularGnomic" {

	Properties{
		  _MainTex("Cubemap (RGB)", CUBE) = "" {}
		  _EquiRotation("Rotation X", Float) = 1.0
		  _EquiRotationY("Rotation Y", Float) = 1.0
		  _FOVScale_X("FOV X", Float) = 0.45
		  _FOVScale_Y("FOV Y", Float) = 0.1
	}

		Subshader{
			Pass {
				ZTest Always Cull Off ZWrite Off
				Fog { Mode off }

				CGPROGRAM
					#pragma vertex vert
					#pragma fragment frag
					#pragma fragmentoption ARB_precision_hint_fastest

		#include "UnityCG.cginc"

		#define PI    3.141592653589793
		#define TWOPI 6.283185307179587
		#define PI_2  1.570796326794897

		struct v2f {
			float4 pos : POSITION;
			float2 uv : TEXCOORD0;
		};

		samplerCUBE _MainTex;
		float _EquiRotation;
		float _EquiRotationY;
		float _FOVScale_X;
		float _FOVScale_Y;


		v2f vert(appdata_img v)
		{
			v2f o;
			o.pos = UnityObjectToClipPos(v.vertex);
			o.uv = v.texcoord.xy;
			return o;
		}

		fixed4 frag(v2f i) : COLOR
		{

			float2 q = i.uv;

		
			float2 cp = (float2(PI + _EquiRotation,PI_2) * 2.0 - 1.0) * float2(PI, PI_2);  // [-PI, PI], [-PI_2, PI_2]
    
			// Convert screen coord in gnomonic mapping to spherical coord in [PI/2, PI]
			
			float2 convertedScreenCoord = (q.xy * 2.0 - 1.0) * float2(_FOVScale_X, _FOVScale_Y) * float2(PI, PI_2); 
			float x = convertedScreenCoord.x;
			float y = convertedScreenCoord.y;
    
			float rou = sqrt(x * x + y * y);
			float c = atan(rou); 
			float sin_c = sin( c );
			float cos_c = cos( c );  
    
			float lat = asin(cos_c * sin(cp.y) + (y * sin_c * cos(cp.y)) / rou);
			float lon = cp.x + atan2(x * sin_c, rou * cos(cp.y) * cos_c - y * sin(cp.y) * sin_c);
    

			
			lat = (lat / PI_2 + 1.0) * 1.0; 
			lon = (lon / PI + 1.0) * 0.5; //[0, 1]


			float2 final = float2(lon, lat) * float2(TWOPI, PI);

			final.x = final.x;
			final.y = final.y + _EquiRotationY;

			float3 unit = float3(0,0,0);

			unit.x = sin(final.y) * sin(final.x) * -1;
			unit.y = cos(final.y * -1);
			unit.z = sin(final.y) * cos(final.x) * -1;

			return texCUBE(_MainTex, unit);
		}
	ENDCG
}
	}
		Fallback Off
}