o3de/Gems/DiffuseProbeGrid/Code/Source/Render/DiffuseProbeGridTextureReadback.h

/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */
#pragma once

#include <Atom/RHI/ScopeProducer.h>
#include <Atom/RPI.Public/Pass/AttachmentReadback.h>
#include <Atom/RPI.Public/Pass/Pass.h>
#include <DiffuseProbeGrid/DiffuseProbeGridFeatureProcessorInterface.h>

namespace AZ
{
    namespace Render
    {
        class DiffuseProbeGrid;

        enum class DiffuseProbeGridReadbackState
        {
            Idle,
            Initializing,
            Irradiance,
            Distance,
            ProbeData,
            Complete
        };

        //! This class contains functionality necessary to read back the DiffuseProbeGrid textures, which
        //! allows them to be saved as assets to run the DiffuseProbeGrid in non-realtime mode.
        class DiffuseProbeGridTextureReadback final
        {
        public:
            DiffuseProbeGridTextureReadback(DiffuseProbeGrid* diffuseProbeGrid);
            ~DiffuseProbeGridTextureReadback() = default;

            void BeginTextureReadback(DiffuseProbeGridBakeTexturesCallback callback);
            void Update(const AZ::Name& passName);
            void FrameBegin(AZ::RPI::Pass::FramePrepareParams& params);

            bool IsIdle() const { return m_readbackState == DiffuseProbeGridReadbackState::Idle; }

        private:

            DiffuseProbeGrid* m_diffuseProbeGrid = nullptr;
            DiffuseProbeGridReadbackState m_readbackState = DiffuseProbeGridReadbackState::Idle;
            AZStd::shared_ptr<AZ::RPI::AttachmentReadback> m_attachmentReadback;
            DiffuseProbeGridBakeTexturesCallback m_callback;

            AZ::RPI::AttachmentReadback::ReadbackResult m_irradianceReadbackResult;
            AZ::RPI::AttachmentReadback::ReadbackResult m_distanceReadbackResult;
            AZ::RPI::AttachmentReadback::ReadbackResult m_probeDataReadbackResult;

            // number of frames to delay before starting the texture readbacks, this allows the textures to settle
            static constexpr int32_t DefaultNumInitializationFrames = 50;
            int32_t m_remainingInitializationFrames = DefaultNumInitializationFrames;
        };
    }   // namespace Render
}   // namespace AZ