Vulkan - draw texture directly without vertices and shaders

Question

Is it possible to draw texture (if it is with correct width, height and pixel format) directly to frame buffer without using vertices and shaders in Vulkan?

Torras

To downvoters: I guess he is looking for something close to OpenGL's glDrawPixels() / glDrawBuffer() in Vulkan API, which enabled direct draw to framebuffer. While drawing a full screen textured quad with no perspective projections and no ZBuffer write is the straight forward solution, it is still a valid question. – Bratislava

@NicolBolas Sorry, but you are very tough. Vulkan is terrible new and had a giant doc and huge structure to look at. It is not trivial in any way. And I guess the propose of StackOverflow is to build bridges between who knows and who don't know. – Bratislava

I agree with Alex here - there is a lot of documentation to look through, and if you haven't used Vulkan yet, and are reading the documentation to decide whether you want to use it, then you probably won't realise that the vkCmdCopy* commands are what you want. Most small samples show how to draw with indices and vertices, not direct texture copies. I have asked questions, which had sections in the documentation that could answer them, but I did not find them. – Buchner

Answer 1

You can do a vkCmdCopyImage to copy from your vkImage to a swapchain's vkImage provided the vkSurface supports being a TRANSFER_DST as by the supportedUsageFlags field from the result of vkGetPhysicalDeviceSurfaceCapabilitiesKHR.

Otherwise you need to do a fullscreen render and grab the color data from the input image as a sampled texture or input attachment.

Rhubarb

You can also use vkCmdBlitImage if you want scaling, filtering or format conversions as well. vkCmdCopyImage just straight up takes a copy of the memory, which isn't always useful. – Postrider

But note that this requires the source format to support the VK_FORMAT_FEATURE_BLIT_SRC_BIT and the destination format to support the VK_FORMAT_FEATURE_BLIT_DST_BIT. This may not always be the case, so if you're going to use a blit, check these first. – Blinker