Using viewer without a window

[trinhtuanlong]

Can I use vsg::Viewer without a window. I tried to setup instance, then create commandGraphs like:

auto commandGraph = vsg::CommandGraph::create(device, queueFamilyIndex)

, setup my viewer like:

vsg::ref_ptr<vsg::Viewer> createViewer(
    vsg::ref_ptr<vsg::Instrumentation> instrumentation,
    std::vector<vsg::ref_ptr<vsg::CommandGraph>> commandGraph) {
    auto viewer = vsg::Viewer::create();
    viewer->assignRecordAndSubmitTaskAndPresentation(commandGraph);
    viewer->assignInstrumentation(instrumentation);
    viewer->compile();
    return viewer;
}

Then in the main loop I tried:

	    data0->assign(pixelData, 0, sizeof(vsg::vec4), WIDTH, HEIGHT);
	    data0->properties.format = format_vk_in;
	    data0->properties.dataVariance =
		vsg::DYNAMIC_DATA_TRANSFER_AFTER_RECORD;
	    vkViewer->update();
	    vkViewer->recordAndSubmit();

But the API stopped at the first beginCommandBuffer:

Thread 0, Frame 0:
vkBindBufferMemory(device, buffer, memory, memoryOffset) returns VkResult VK_SUCCESS (0):
    device:                         VkDevice = 0x6261aa358e40
    buffer:                         VkBuffer = 0x6261aa228a70
    memory:                         VkDeviceMemory = 0x6261aa4126b0
    memoryOffset:                   VkDeviceSize = 0


Command terminated

My goal is to setup a VSG to do only compute and then Copy (currently with mappedData) without creating any window or camera in the process (so purely an image processing library to be used in another app). How do I do this? I tried to mimic the example in vsgcompute but the example is too minimal, for example would data transfer (dynamic data) still works without a viewer? Do I have to make an update traversal? What is the way to proceed in this case?

[robertosfield]

I haven't tried mixing just compute with TransferTask. You should be a able to instantiate the required components like TransferTask and call them directly, essentially do what the vsg::Viewer/RecordAndSubmitTask.

[trinhtuanlong]

Do I have to setup threading myself also? Can you point me to the part of Viewer setup that pertains to Swapchain so I can remove that part.

[robertosfield]

I'm afraid I don't have the bandwidth to guide you through this process, I simply have too many others tasks on my plate right now.

As I said I haven't tried to do what you are trying to do so far as my focus has been on the rendering side. So I simple haven't spent the time thinking through the possible approaches, or generalizations of the Viewer to make what you are doing easier. To help you I'd have to learn and spend time thinking about the topic, so I can't really provide a roadmap of what to do and what to tweak.