// This file is part of the FidelityFX SDK.
//
// Copyright (c) 2022-2023 Advanced Micro Devices, Inc. All rights reserved.
//
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// of this software and associated documentation files (the "Software"), to deal
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// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// THE SOFTWARE.

#ifndef FFX_FSR2_DEPTH_CLIP_H
#define FFX_FSR2_DEPTH_CLIP_H

FFX_STATIC const FfxFloat32 DepthClipBaseScale = 4.0f;

FfxFloat32 ComputeDepthClip(FfxFloat32x2 fUvSample, FfxFloat32 fCurrentDepthSample)
{
    FfxFloat32 fCurrentDepthViewSpace = GetViewSpaceDepth(fCurrentDepthSample);
    BilinearSamplingData bilinearInfo = GetBilinearSamplingData(fUvSample, RenderSize());

    FfxFloat32 fDilatedSum = 0.0f;
    FfxFloat32 fDepth = 0.0f;
    FfxFloat32 fWeightSum = 0.0f;
    for (FfxInt32 iSampleIndex = 0; iSampleIndex < 4; iSampleIndex++) {

        const FfxInt32x2 iOffset = bilinearInfo.iOffsets[iSampleIndex];
        const FfxInt32x2 iSamplePos = bilinearInfo.iBasePos + iOffset;

        if (IsOnScreen(iSamplePos, RenderSize())) {
            const FfxFloat32 fWeight = bilinearInfo.fWeights[iSampleIndex];
            if (fWeight > fReconstructedDepthBilinearWeightThreshold) {

                const FfxFloat32 fPrevDepthSample = LoadReconstructedPrevDepth(iSamplePos);
                const FfxFloat32 fPrevNearestDepthViewSpace = GetViewSpaceDepth(fPrevDepthSample);

                const FfxFloat32 fDepthDiff = fCurrentDepthViewSpace - fPrevNearestDepthViewSpace;

                if (fDepthDiff > 0.0f) {

#if FFX_FSR2_OPTION_INVERTED_DEPTH
                    const FfxFloat32 fPlaneDepth = ffxMin(fPrevDepthSample, fCurrentDepthSample);
#else
                    const FfxFloat32 fPlaneDepth = ffxMax(fPrevDepthSample, fCurrentDepthSample);
#endif
                    
                    const FfxFloat32x3 fCenter = GetViewSpacePosition(FfxInt32x2(RenderSize() * 0.5f), RenderSize(), fPlaneDepth);
                    const FfxFloat32x3 fCorner = GetViewSpacePosition(FfxInt32x2(0, 0), RenderSize(), fPlaneDepth);

                    const FfxFloat32 fHalfViewportWidth = length(FfxFloat32x2(RenderSize()));
                    const FfxFloat32 fDepthThreshold = ffxMax(fCurrentDepthViewSpace, fPrevNearestDepthViewSpace);

                    const FfxFloat32 Ksep = 1.37e-05f;
                    const FfxFloat32 Kfov = length(fCorner) / length(fCenter);
                    const FfxFloat32 fRequiredDepthSeparation = Ksep * Kfov * fHalfViewportWidth * fDepthThreshold;

                    const FfxFloat32 fResolutionFactor = ffxSaturate(length(FfxFloat32x2(RenderSize())) / length(FfxFloat32x2(1920.0f, 1080.0f)));
                    const FfxFloat32 fPower = ffxLerp(1.0f, 3.0f, fResolutionFactor);
                    fDepth += ffxPow(ffxSaturate(FfxFloat32(fRequiredDepthSeparation / fDepthDiff)), fPower) * fWeight;
                    fWeightSum += fWeight;
                }
            }
        }
    }

    return (fWeightSum > 0) ? ffxSaturate(1.0f - fDepth / fWeightSum) : 0.0f;
}

FfxFloat32 ComputeMotionDivergence(FfxInt32x2 iPxPos, FfxInt32x2 iPxInputMotionVectorSize)
{
    FfxFloat32 minconvergence = 1.0f;

    FfxFloat32x2 fMotionVectorNucleus = LoadInputMotionVector(iPxPos);
    FfxFloat32 fNucleusVelocityLr = length(fMotionVectorNucleus * RenderSize());
    FfxFloat32 fMaxVelocityUv = length(fMotionVectorNucleus);

    const FfxFloat32 MotionVectorVelocityEpsilon = 1e-02f;

    if (fNucleusVelocityLr > MotionVectorVelocityEpsilon) {
        for (FfxInt32 y = -1; y <= 1; ++y) {
            for (FfxInt32 x = -1; x <= 1; ++x) {

                FfxInt32x2 sp = ClampLoad(iPxPos, FfxInt32x2(x, y), iPxInputMotionVectorSize);

                FfxFloat32x2 fMotionVector = LoadInputMotionVector(sp);
                FfxFloat32 fVelocityUv = length(fMotionVector);

                fMaxVelocityUv = ffxMax(fVelocityUv, fMaxVelocityUv);
                fVelocityUv = ffxMax(fVelocityUv, fMaxVelocityUv);
                minconvergence = ffxMin(minconvergence, dot(fMotionVector / fVelocityUv, fMotionVectorNucleus / fVelocityUv));
            }
        }
    }

    return ffxSaturate(1.0f - minconvergence) * ffxSaturate(fMaxVelocityUv / 0.01f);
}

FfxFloat32 ComputeDepthDivergence(FfxInt32x2 iPxPos)
{
    const FfxFloat32 fMaxDistInMeters = GetMaxDistanceInMeters();
    FfxFloat32 fDepthMax = 0.0f;
    FfxFloat32 fDepthMin = fMaxDistInMeters;

    FfxInt32 iMaxDistFound = 0;

    for (FfxInt32 y = -1; y < 2; y++) {
        for (FfxInt32 x = -1; x < 2; x++) {

            const FfxInt32x2 iOffset = FfxInt32x2(x, y);
            const FfxInt32x2 iSamplePos = iPxPos + iOffset;

            const FfxFloat32 fOnScreenFactor = IsOnScreen(iSamplePos, RenderSize()) ? 1.0f : 0.0f;
            FfxFloat32 fDepth = GetViewSpaceDepthInMeters(LoadDilatedDepth(iSamplePos)) * fOnScreenFactor;

            iMaxDistFound |= FfxInt32(fMaxDistInMeters == fDepth);

            fDepthMin = ffxMin(fDepthMin, fDepth);
            fDepthMax = ffxMax(fDepthMax, fDepth);
        }
    }

    return (1.0f - fDepthMin / fDepthMax) * (FfxBoolean(iMaxDistFound) ? 0.0f : 1.0f);
}

FfxFloat32 ComputeTemporalMotionDivergence(FfxInt32x2 iPxPos)
{
    const FfxFloat32x2 fUv = FfxFloat32x2(iPxPos + 0.5f) / RenderSize();

    FfxFloat32x2 fMotionVector = LoadDilatedMotionVector(iPxPos);
    FfxFloat32x2 fReprojectedUv = fUv + fMotionVector;
    fReprojectedUv = ClampUv(fReprojectedUv, RenderSize(), MaxRenderSize());
    FfxFloat32x2 fPrevMotionVector = SamplePreviousDilatedMotionVector(fReprojectedUv);

    float fPxDistance = length(fMotionVector * DisplaySize());
    return fPxDistance > 1.0f ? ffxLerp(0.0f, 1.0f - ffxSaturate(length(fPrevMotionVector) / length(fMotionVector)), ffxSaturate(ffxPow(fPxDistance / 20.0f, 3.0f))) : 0;
}

void PreProcessReactiveMasks(FfxInt32x2 iPxLrPos, FfxFloat32 fMotionDivergence)
{
    // Compensate for bilinear sampling in accumulation pass

    FfxFloat32x3 fReferenceColor = LoadInputColor(iPxLrPos).xyz;
    FfxFloat32x2 fReactiveFactor = FfxFloat32x2(0.0f, fMotionDivergence);

    float fMasksSum = 0.0f;

    FfxFloat32x3 fColorSamples[9];
    FfxFloat32 fReactiveSamples[9];
    FfxFloat32 fTransparencyAndCompositionSamples[9];

    FFX_UNROLL
    for (FfxInt32 y = -1; y < 2; y++) {
        FFX_UNROLL
        for (FfxInt32 x = -1; x < 2; x++) {

            const FfxInt32x2 sampleCoord = ClampLoad(iPxLrPos, FfxInt32x2(x, y), FfxInt32x2(RenderSize()));

            FfxInt32 sampleIdx = (y + 1) * 3 + x + 1;

            FfxFloat32x3 fColorSample = LoadInputColor(sampleCoord).xyz;
            FfxFloat32 fReactiveSample = LoadReactiveMask(sampleCoord);
            FfxFloat32 fTransparencyAndCompositionSample = LoadTransparencyAndCompositionMask(sampleCoord);

            fColorSamples[sampleIdx] = fColorSample;
            fReactiveSamples[sampleIdx] = fReactiveSample;
            fTransparencyAndCompositionSamples[sampleIdx] = fTransparencyAndCompositionSample;

            fMasksSum += (fReactiveSample + fTransparencyAndCompositionSample);
        }
    }

    if (fMasksSum > 0)
    {
        for (FfxInt32 sampleIdx = 0; sampleIdx < 9; sampleIdx++)
        {
            FfxFloat32x3 fColorSample = fColorSamples[sampleIdx];
            FfxFloat32 fReactiveSample = fReactiveSamples[sampleIdx];
            FfxFloat32 fTransparencyAndCompositionSample = fTransparencyAndCompositionSamples[sampleIdx];

            const FfxFloat32 fMaxLenSq = ffxMax(dot(fReferenceColor, fReferenceColor), dot(fColorSample, fColorSample));
            const FfxFloat32 fSimilarity = dot(fReferenceColor, fColorSample) / fMaxLenSq;

            // Increase power for non-similar samples
            const FfxFloat32 fPowerBiasMax = 6.0f;
            const FfxFloat32 fSimilarityPower = 1.0f + (fPowerBiasMax - fSimilarity * fPowerBiasMax);
            const FfxFloat32 fWeightedReactiveSample = ffxPow(fReactiveSample, fSimilarityPower);
            const FfxFloat32 fWeightedTransparencyAndCompositionSample = ffxPow(fTransparencyAndCompositionSample, fSimilarityPower);

            fReactiveFactor = ffxMax(fReactiveFactor, FfxFloat32x2(fWeightedReactiveSample, fWeightedTransparencyAndCompositionSample));
        }
    }

    StoreDilatedReactiveMasks(iPxLrPos, fReactiveFactor);
}

FfxFloat32x3 ComputePreparedInputColor(FfxInt32x2 iPxLrPos)
{
    //We assume linear data. if non-linear input (sRGB, ...),
    //then we should convert to linear first and back to sRGB on output.
    FfxFloat32x3 fRgb = ffxMax(FfxFloat32x3(0, 0, 0), LoadInputColor(iPxLrPos));

    fRgb = PrepareRgb(fRgb, Exposure(), PreExposure());

    const FfxFloat32x3 fPreparedYCoCg = RGBToYCoCg(fRgb);

    return fPreparedYCoCg;
}

float EvaluateSurface(FfxInt32x2 iPxPos, FfxFloat32x2 fMotionVector)
{
    FfxFloat32 d0 = GetViewSpaceDepth(LoadReconstructedPrevDepth(iPxPos + FfxInt32x2(0, -1)));
    FfxFloat32 d1 = GetViewSpaceDepth(LoadReconstructedPrevDepth(iPxPos + FfxInt32x2(0, 0)));
    FfxFloat32 d2 = GetViewSpaceDepth(LoadReconstructedPrevDepth(iPxPos + FfxInt32x2(0, 1)));

    return 1.0f - FfxFloat32(((d0 - d1) > (d1 * 0.01f)) && ((d1 - d2) > (d2 * 0.01f)));
}
void DepthClip(FfxInt32x2 iPxPos)
{
    FfxFloat32x2 fDepthUv = (iPxPos + 0.5f) / RenderSize();
    FfxFloat32x2 fMotionVector = LoadDilatedMotionVector(iPxPos);

    // Discard tiny mvs
    fMotionVector *= FfxFloat32(length(fMotionVector * DisplaySize()) > 0.01f);

    const FfxFloat32x2 fDilatedUv = fDepthUv + fMotionVector;
    const FfxFloat32 fDilatedDepth = LoadDilatedDepth(iPxPos);
    const FfxFloat32 fCurrentDepthViewSpace = GetViewSpaceDepth(LoadInputDepth(iPxPos));

    // Compute prepared input color and depth clip
    FfxFloat32 fDepthClip = ComputeDepthClip(fDilatedUv, fDilatedDepth) * EvaluateSurface(iPxPos, fMotionVector);
    FfxFloat32x3 fPreparedYCoCg = ComputePreparedInputColor(iPxPos);
    StorePreparedInputColor(iPxPos, FfxFloat32x4(fPreparedYCoCg, fDepthClip));

    // Compute dilated reactive mask
#if FFX_FSR2_OPTION_LOW_RESOLUTION_MOTION_VECTORS
    FfxInt32x2 iSamplePos = iPxPos;
#else
    FfxInt32x2 iSamplePos = ComputeHrPosFromLrPos(iPxPos);
#endif

    FfxFloat32 fMotionDivergence = ComputeMotionDivergence(iSamplePos, RenderSize());
    FfxFloat32 fTemporalMotionDifference = ffxSaturate(ComputeTemporalMotionDivergence(iPxPos) - ComputeDepthDivergence(iPxPos));

    PreProcessReactiveMasks(iPxPos, ffxMax(fTemporalMotionDifference, fMotionDivergence));
}

#endif //!defined( FFX_FSR2_DEPTH_CLIPH )