Rendering multiple objects with different textures, vertex buffers, and uniform values in Vulkan

My background is in OpenGL and I'm attempting to learn Vulkan. I'm having a little trouble with setting up a class so I can render multiple objects with different textures, vertex buffers, and UBO values. I've run into an issue where two of my images are drawn, but they flicker and alternate. I'm thinking it must be due to presenting the image after the draw call. Is there a way to delay presentation of an image? Or merge different images together before presenting? My code can be found here, I'm hoping it is enough for someone to get an idea of what I'm trying to do: https://gitlab.com/cwink/Ingin/blob/master/ingin.cpp

Thanks!

If You think it's a problem with presentation, then read this (and the following) tutorials: software.intel.com/en-us/articles/…
– Ekzuzy
Sep 2 at 8:12

But it seems that You synchronize rendering and presentation correctly. Is there any error message generated by Validation Layers?
– Ekzuzy
Sep 2 at 8:20

1 Answer
1

You call render twice per frame. And render calls vkQueuePresentKHR, so obviously the two renderings of yours alternate.

render

vkQueuePresentKHR

You can delay presentation simply by delaying vkQueuePresentKHR call. Let's say you want to show each image for ~1 s. You can simply std::this_thread::sleep_for (std::chrono::seconds(1)); after each render call. (Possibly not the bestest way to do it, but just to get the idea where your problem lies.)

vkQueuePresentKHR

std::this_thread::sleep_for (std::chrono::seconds(1));

render

vkQueuePresentKHR does not do any kind of "merging" for you. Typically you "merge images" by simply drawing them into the same swapchain VkImage in the first place, and then present it once.

vkQueuePresentKHR

VkImage

drawing in the same vkImage as separate renderpasses won't work because he clears the color attachment as the load op.
– ratchet freak
Sep 2 at 10:56

@ratchetfreak Speaking generally. I assume things that has to be done for this to work will be done. E.g. having single renderpass for this. I hope my A is just sufficient for the OP to discard some of his wrong assumptions and preconceptions.
– krOoze
Sep 2 at 14:39

@krOoze Thanks for the answer, do you mean having a separate renderpass just for clearing and then another one without clearing to draw the objects? I'm also not sure that will 100% work since I'm trying to use the MVP to translate the image to different coordinates, and it seems that the uniform data is linked to the image being drawn.
– Cody Wink
Sep 2 at 17:54

@CodyWink I meant single renderpass for everything in the above comment as an example. But that is an implementation detail; many ways to achieve the same...
– krOoze
Sep 2 at 20:21

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