Shader "Hidden/HDRenderLoop/SkyHDRI"
{
    SubShader
    {
        Pass
        {
            ZWrite Off
            ZTest LEqual
            Blend One Zero

            HLSLPROGRAM
            #pragma target 5.0
            #pragma only_renderers d3d11 // TEMP: unitl we go futher in dev

            #pragma vertex Vert
            #pragma fragment Frag

            #include "Common.hlsl"
            #include "CommonLighting.hlsl"
        
            TEXTURECUBE(_Cubemap);
            SAMPLERCUBE(sampler_Cubemap);
            float4 _SkyParam; // x exposure, y multiplier, z rotation

            struct Attributes
            {
                float3 positionCS : POSITION;
                float3 eyeVector : NORMAL;
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float3 eyeVector : TEXCOORD0;
            };

            Varyings Vert(Attributes input)
            {
                // TODO: implement SV_vertexID full screen quad
                Varyings output;
                output.positionCS = float4(input.positionCS.xy, UNITY_RAW_FAR_CLIP_VALUE
                    , 1.0);
                output.eyeVector = input.eyeVector;

                return output;
            }

            float4 Frag(Varyings input) : SV_Target
            {
                float3 dir = normalize(input.eyeVector);

                // Rotate direction
                float phi = DegToRad(_SkyParam.z);
                float cosPhi, sinPhi;
                sincos(phi, sinPhi, cosPhi);
                float3 rotDirX = float3(cosPhi, 0, -sinPhi);
                float3 rotDirY = float3(sinPhi, 0, cosPhi);
                dir = float3(dot(rotDirX, dir), dir.y, dot(rotDirY, dir));

                return ClampToFloat16Max(SAMPLE_TEXTURECUBE_LOD(_Cubemap, sampler_Cubemap, dir, 0) * exp2(_SkyParam.x) * _SkyParam.y);
            }

            ENDHLSL
        }

    }
    Fallback Off
}