Should I always use a fence in rendering

[guijiangheng]

I see non consistent fence usage across some vulkan tutorials which confuse me a lot. For example, triangle.cpp wait for fence while rendering a frame, but vulkanscene.cpp didn't. I think there will be multiple command buffer runs on the GPU concurrently if not wait on fence, Why not wait fence can works correctly.

[SaschaWillems]

Yes, using multiple fences to wait for command buffer completion is the proper way. The samples that don't use fences work because they use other means of synchronization like vkDeviceWaitIdle or vkQueueWaitIdle, which you should not use in practice.

So to sum it up:

• Uses fences (per command buffer)
• Use multiple uniform buffers per command buffer in flight
• Don't use heavy sync functions like vkDeviceWaitIdle or vkQueueWaitIdle

We may update the API samples to use better sync in the future, but that's not a small task. Those samples are mainly meant to showcase how to use a certain part of the API, so synchronization is secondary in those.