Is it possible to do offscreen rendering without Surface in Vulkan?

Question

Similar to surfaceless context in OpenGL can we do it in Vulkan.

Answer 1

Sure it's even designed to do so from the start.

Instead of getting your images from a swapchain, create them and allocate and bind memory for it yourself.

Getting the result back will then require a copy into a host-visible readback buffer after the render.

Answer 2

SaschaWillems/Vulkan renderheadless.cpp example

It seems that Vulkan is designed to support offscreen rendering better than OpenGL.

This is mentioned on this NVIDIA overview: https://developer.nvidia.com/transitioning-opengl-vulkan

This is a runnable example that I just managed to run locally: https://github.com/SaschaWillems/Vulkan/tree/b9f0ac91d2adccc3055a904d3a8f6553b10ff6cd/examples/renderheadless/renderheadless.cpp

After installing the drivers and ensuring that the GPU is working I can do:

git clone https://github.com/SaschaWillems/Vulkan
cd Vulkan
git checkout b9f0ac91d2adccc3055a904d3a8f6553b10ff6cd
python download_assets.py
mkdir build
cd build
cmake ..
make -j`nproc`
cd bin
./renderheadless

and this immediately generates an image headless.ppm without opening any windows:

I have also managed to run this program an Ubuntu Ctrl + Alt + F3 non-graphical TTY, which further indicates it really does not need a screen.

Other examples that might be of interest:

• https://github.com/SaschaWillems/Vulkan/blob/b9f0ac91d2adccc3055a904d3a8f6553b10ff6cd/examples/screenshot/screenshot.cpp starts a GUI, and you can click a button to take a screenshot, and it gets saved to `screenshot
• https://github.com/SaschaWillems/Vulkan/blob/b9f0ac91d2adccc3055a904d3a8f6553b10ff6cd/examples/offscreen/offscreen.cpp render an image twice to create a reflection effect

Related: How to use GLUT/OpenGL to render to a file?

Tested on Ubuntu 20.04, NVIDIA driver 435.21, NVIDIA Quadro M1200 GPU.