question on desiredImageCount being set to minImageCount instead of maxImageCount in Vulkan swapchain creation

[Ryu613]

hi everyone，
I'm currently learning Vulkan and exploring the Filament source code. I noticed that in most cases, desiredImageCount is typically set to maxImageCount when creating a swap chain. However, in the following code snippet, it is set to minImageCount when desiredImageCount exceeds maxImageCount:

code reference link

Is this intentional due to specific design considerations, or is it potentially an oversight? I would appreciate any insights into the reasoning behind this choice.

Thank you!

[Ryu613]

in this code condition, choose minImageCount or maxImageCount are the same.
ref: https://github.com/KhronosGroup/Vulkan-Samples/blob/main/samples/performance/hpp_swapchain_images/README.adoc

[poweifeng]

in this code condition, choose minImageCount or maxImageCount are the same. ref: https://github.com/KhronosGroup/Vulkan-Samples/blob/main/samples/performance/hpp_swapchain_images/README.adoc

The reference you gave is a good start.

Too many swapchain images will cause perceived input latency (I'm rendering frame n based on the current input, but frame n won't appear on screen until time n+m where m is the number of swapchain images).

Too few swapchain images will stall the presentation queue because frames are not yet eready.

The current code has a heuristic of minCount + 1. If there's a need, we can make this a configurable value.