iOS 14 change in performance cost of SCNNode creation

This might be caused by the shader compiler performance bug in SceneKit in iOS 14. Shader compilation when adding nodes to a scene can be 100x slower in iOS 14 than in iOS 13. See https://developer.apple.com/forums/thread/659856 for more about this.

You can use the Xcode Instruments tool with the SceneKit profiling template to profile your app to take a look at the shader compile times. After you start then stop an Instruments SceneKit recording session, tap SceneKit Application > Frames above the lower window pane and change it to Events. Then type "compile" in the Input Filter control to limit the list to shader compile events. Normal (i.e., iOS 13) compile times for our app are around 1-2 ms but in iOS 14, compile times may be more like 100-200 ms.

Even if shader compiling is not your problem, Instruments may give you some insight into what else may be going on.

I ended up removing my SCNNodes instantiations finding another way to handle my situation, but I have also found that I have problems modifying a node's transform while a UIKit animation is running. It seems to cause a one-second delay in my fps every second or so, even when the node in question is not visible. I tried out the SceneKit profiling as you suggested, but at least with my current setup I am not seeing any compile events, and no clear other culprits in the event durations.