download_from_gpu() [3/3]

MAYAFLUX_API void MayaFlux::Buffers::download_from_gpu	(	const std::shared_ptr< VKBuffer > &	source,
		void *	data,
		size_t	size,
		const std::shared_ptr< VKBuffer > &	staging = nullptr
	)

Download from GPU buffer to raw data (auto-detects host-visible vs device-local)

Parameters

source	Source GPU buffer
data	Destination data pointer
size	Size in bytes
staging	Optional staging buffer (created if needed for device-local)

Convenience wrapper over StagingUtils that:

• Auto-detects if buffer is host-visible or device-local
• Handles staging buffer creation if needed
• Copies data to destination pointer

Definition at line 459 of file StagingUtils.cpp.

{
    if (!source) {
        error<std::invalid_argument>(
            Journal::Component::Buffers,
            Journal::Context::BufferProcessing,
            std::source_location::current(),
            "download_from_gpu: source buffer is null");
    }
 
    if (size == 0) {
        return;
    }
 
    auto temp_target = std::make_shared<VKBuffer>(
        size, VKBuffer::Usage::STAGING, Kakshya::DataModality::UNKNOWN);
 
    auto buffer_service = Registry::BackendRegistry::instance()
                              .get_service<Registry::Service::BufferService>();
 
    if (!buffer_service) {
        error<std::runtime_error>(
            Journal::Component::Buffers,
            Journal::Context::BufferProcessing,
            std::source_location::current(),
            "download_from_gpu requires a valid buffer service");
    }
 
    buffer_service->initialize_buffer(temp_target);
 
    if (source->is_host_visible()) {
        download_host_visible(source, temp_target);
    } else {
        std::shared_ptr<VKBuffer> staging_buf = staging;
 
        if (!staging_buf) {
            staging_buf = create_staging_buffer(size);
        }
 
        download_device_local(source, temp_target, staging_buf);
    }
 
    auto temp_data = temp_target->get_data();
 
    if (temp_data.empty()) {
        error<std::runtime_error>(
            Journal::Component::Buffers,
            Journal::Context::BufferProcessing,
            std::source_location::current(),
            "download_from_gpu: failed to retrieve data from temporary buffer");
    }
 
    if (temp_data.size() > 1) {
        MF_ERROR(Journal::Component::Buffers, Journal::Context::BufferProcessing,
            "download_from_gpu: unexpected multiple data variants in temporary buffer. Only the first will be used.");
    }
 
    Kakshya::DataAccess accessor(
        const_cast<Kakshya::DataVariant&>(temp_data[0]),
        {},
        source->get_modality());
 
    auto [ptr, bytes, format_hint] = accessor.gpu_buffer();
 
    std::memcpy(data, ptr, std::min(size, bytes));
}

References MayaFlux::Journal::BufferProcessing, MayaFlux::Journal::Buffers, create_staging_buffer(), download_device_local(), download_host_visible(), MayaFlux::Registry::BackendRegistry::get_service(), MayaFlux::Kakshya::DataAccess::gpu_buffer(), MayaFlux::Registry::BackendRegistry::instance(), MF_ERROR, ptr, and MayaFlux::Kakshya::UNKNOWN.

Referenced by MayaFlux::Buffers::ShaderProcessor::download_bound(), MayaFlux::Buffers::ShaderProcessor::download_bound(), download_from_gpu(), download_from_gpu(), and download_to_view().

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