Shader "Hidden/PostProcessing/DeferredFog"
{
    HLSLINCLUDE

        #pragma multi_compile __ FOG_LINEAR FOG_EXP FOG_EXP2

    //  Start: LuxWater
        #pragma multi_compile __ LUXWATER_DEFERREDFOG

        #if defined(LUXWATER_DEFERREDFOG)
            sampler2D _UnderWaterMask;
            float4 _LuxUnderWaterDeferredFogParams; // x: IsInsideWatervolume?, y: BelowWaterSurface shift, z: EdgeBlend

            inline float DecodeFloatRG( float2 enc ) {
                float2 kDecodeDot = float2(1.0, 1/255.0);
                return dot( enc, kDecodeDot );
            }
        #endif
    //  End: LuxWater

        #include "../StdLib.hlsl"
        #include "Fog.hlsl"

        TEXTURE2D_SAMPLER2D(_MainTex, sampler_MainTex);
        TEXTURE2D_SAMPLER2D(_CameraDepthTexture, sampler_CameraDepthTexture);

        #define SKYBOX_THREASHOLD_VALUE 0.9999

        float4 Frag(VaryingsDefault i) : SV_Target
        {
            half4 color = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoordStereo);

            float depth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture, i.texcoordStereo);
            depth = Linear01Depth(depth);
            float dist = ComputeFogDistance(depth);
            half fog = 1.0 - ComputeFog(dist);

        //  Start: LuxWater
            #if defined(LUXWATER_DEFERREDFOG)
                half4 fogMask = tex2D(_UnderWaterMask, UnityStereoTransformScreenSpaceTex(i.texcoordStereo));
                float watersurfacefrombelow = DecodeFloatRG(fogMask.ba);

            //  Get distance and lower it a bit in order to handle edge blending artifacts (edge blended parts would not get ANY fog)
                float ldist = (watersurfacefrombelow - depth) + _LuxUnderWaterDeferredFogParams.y * _ProjectionParams.w;
            //  Fade fog from above water to below water
                float fogFactor = saturate ( 1.0 + _ProjectionParams.z * _LuxUnderWaterDeferredFogParams.z * ldist ); // 0.125 
            //  Clamp above result to where water is actually rendered
                fogFactor = (fogMask.r == 1) ? fogFactor : 1.0;
            //  Mask fog on underwarter parts - only if we are inside a volume (bool... :( )
                if(_LuxUnderWaterDeferredFogParams.x) {
                    fogFactor *= saturate( 1.0 - fogMask.g * 8.0);
                    if (ldist < -_ProjectionParams.w * 4 && fogMask.r == 0 && fogMask.g < 1.0) {
                        fogFactor = 1.0;
                    }
                }
            //  Tweak fog factor
                fog *= fogFactor;
            #endif
        //  End: LuxWater         

            return lerp(color, _FogColor, fog);
        }

        float4 FragExcludeSkybox(VaryingsDefault i) : SV_Target
        {
            half4 color = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoordStereo);

            float depth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture, i.texcoordStereo);
            depth = Linear01Depth(depth);
            float skybox = depth < SKYBOX_THREASHOLD_VALUE;
            float dist = ComputeFogDistance(depth);
            half fog = 1.0 - ComputeFog(dist);

        //  Start: LuxWater
            #if defined(LUXWATER_DEFERREDFOG)
                half4 fogMask = tex2D(_UnderWaterMask, UnityStereoTransformScreenSpaceTex(i.texcoordStereo));
                float watersurfacefrombelow = DecodeFloatRG(fogMask.ba);

            //  Get distance and lower it a bit in order to handle edge blending artifacts (edge blended parts would not get ANY fog)
                float ldist = (watersurfacefrombelow - depth) + _LuxUnderWaterDeferredFogParams.y * _ProjectionParams.w;
            //  Fade fog from above water to below water
                float fogFactor = saturate ( 1.0 + _ProjectionParams.z * _LuxUnderWaterDeferredFogParams.z * ldist ); // 0.125 
            //  Clamp above result to where water is actually rendered
                fogFactor = (fogMask.r == 1) ? fogFactor : 1.0;
            //  Mask fog on underwarter parts - only if we are inside a volume (bool... :( )
                if(_LuxUnderWaterDeferredFogParams.x) {
                    fogFactor *= saturate( 1.0 - fogMask.g * 8.0);
                    if (ldist < -_ProjectionParams.w * 4 && fogMask.r == 0 && fogMask.g < 1.0) {
                        fogFactor = 1.0;
                    }
                }
            //  Tweak fog factor
                fog *= fogFactor;
            #endif
        //  End: LuxWater 

            return lerp(color, _FogColor, fog * skybox);
        }

    ENDHLSL

    SubShader
    {
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            HLSLPROGRAM

                #pragma vertex VertDefault
                #pragma fragment Frag

            ENDHLSL
        }

        Pass
        {
            HLSLPROGRAM

                #pragma vertex VertDefault
                #pragma fragment FragExcludeSkybox

            ENDHLSL
        }
    }
}