virtualx-engine/thirdparty/amd-fsr2/shaders/ffx_fsr2_postprocess_lock_status.h

// This file is part of the FidelityFX SDK.
//
// Copyright (c) 2022-2023 Advanced Micro Devices, Inc. All rights reserved.
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#ifndef FFX_FSR2_POSTPROCESS_LOCK_STATUS_H
#define FFX_FSR2_POSTPROCESS_LOCK_STATUS_H

FfxFloat32x4 WrapShadingChangeLuma(FfxInt32x2 iPxSample)
{
    return FfxFloat32x4(LoadMipLuma(iPxSample, LumaMipLevelToUse()), 0, 0, 0);
}

#if FFX_HALF
FFX_MIN16_F4 WrapShadingChangeLuma(FFX_MIN16_I2 iPxSample)
{
    return FFX_MIN16_F4(LoadMipLuma(iPxSample, LumaMipLevelToUse()), 0, 0, 0);
}
#endif

#if FFX_FSR2_OPTION_POSTPROCESSLOCKSTATUS_SAMPLERS_USE_DATA_HALF && FFX_HALF
DeclareCustomFetchBilinearSamplesMin16(FetchShadingChangeLumaSamples, WrapShadingChangeLuma)
#else
DeclareCustomFetchBicubicSamples(FetchShadingChangeLumaSamples, WrapShadingChangeLuma)
#endif
DeclareCustomTextureSample(ShadingChangeLumaSample, Lanczos2, FetchShadingChangeLumaSamples)

FfxFloat32 GetShadingChangeLuma(FfxInt32x2 iPxHrPos, FfxFloat32x2 fUvCoord)
{
    FfxFloat32 fShadingChangeLuma = 0;

#if 0
    fShadingChangeLuma = Exposure() * exp(ShadingChangeLumaSample(fUvCoord, LumaMipDimensions()).x);
#else

    const FfxFloat32 fDiv = FfxFloat32(2 << LumaMipLevelToUse());
    FfxInt32x2 iMipRenderSize = FfxInt32x2(RenderSize() / fDiv);

    fUvCoord = ClampUv(fUvCoord, iMipRenderSize, LumaMipDimensions());
    fShadingChangeLuma = Exposure() * exp(FfxFloat32(SampleMipLuma(fUvCoord, LumaMipLevelToUse())));
#endif

    fShadingChangeLuma = ffxPow(fShadingChangeLuma, 1.0f / 6.0f);

    return fShadingChangeLuma;
}

void UpdateLockStatus(AccumulationPassCommonParams params,
    FFX_PARAMETER_INOUT FfxFloat32 fReactiveFactor, LockState state,
    FFX_PARAMETER_INOUT FfxFloat32x2 fLockStatus,
    FFX_PARAMETER_OUT FfxFloat32 fLockContributionThisFrame,
    FFX_PARAMETER_OUT FfxFloat32 fLuminanceDiff) {

    const FfxFloat32 fShadingChangeLuma = GetShadingChangeLuma(params.iPxHrPos, params.fHrUv);

    //init temporal shading change factor, init to -1 or so in reproject to know if "true new"?
    fLockStatus[LOCK_TEMPORAL_LUMA] = (fLockStatus[LOCK_TEMPORAL_LUMA] == FfxFloat32(0.0f)) ? fShadingChangeLuma : fLockStatus[LOCK_TEMPORAL_LUMA];

    FfxFloat32 fPreviousShadingChangeLuma = fLockStatus[LOCK_TEMPORAL_LUMA];

    fLuminanceDiff = 1.0f - MinDividedByMax(fPreviousShadingChangeLuma, fShadingChangeLuma);

    if (state.NewLock) {
        fLockStatus[LOCK_TEMPORAL_LUMA] = fShadingChangeLuma;

        fLockStatus[LOCK_LIFETIME_REMAINING] = (fLockStatus[LOCK_LIFETIME_REMAINING] != 0.0f) ? 2.0f : 1.0f;
    }
    else if(fLockStatus[LOCK_LIFETIME_REMAINING] <= 1.0f) {
        fLockStatus[LOCK_TEMPORAL_LUMA] = ffxLerp(fLockStatus[LOCK_TEMPORAL_LUMA], FfxFloat32(fShadingChangeLuma), 0.5f);
    }
    else {
        if (fLuminanceDiff > 0.1f) {
            KillLock(fLockStatus);
        }
    }

    fReactiveFactor = ffxMax(fReactiveFactor, ffxSaturate((fLuminanceDiff - 0.1f) * 10.0f));
    fLockStatus[LOCK_LIFETIME_REMAINING] *= (1.0f - fReactiveFactor);

    fLockStatus[LOCK_LIFETIME_REMAINING] *= ffxSaturate(1.0f - params.fAccumulationMask);
    fLockStatus[LOCK_LIFETIME_REMAINING] *= FfxFloat32(params.fDepthClipFactor < 0.1f);

    // Compute this frame lock contribution
    const FfxFloat32 fLifetimeContribution = ffxSaturate(fLockStatus[LOCK_LIFETIME_REMAINING] - 1.0f);
    const FfxFloat32 fShadingChangeContribution = ffxSaturate(MinDividedByMax(fLockStatus[LOCK_TEMPORAL_LUMA], fShadingChangeLuma));

    fLockContributionThisFrame = ffxSaturate(ffxSaturate(fLifetimeContribution * 4.0f) * fShadingChangeContribution);
}

#endif //!defined( FFX_FSR2_POSTPROCESS_LOCK_STATUS_H )