Inconsistent Scenekit Framerate

Inconsistent SceneKit framerate

Unfortunately it looks like SceneKit (and SpriteKit) are in evolutionary stages of development, at the expense of those using them.

This problem is definitely on all devices, and the following frameworks, that I know of:

• SceneKit
• SpriteKit
• Metal

Even using OpenGL instead of Metal in the game frameworks the problem still exists, with no less consistency.

It looks to be an attempt by iOS to fix the frame rate at 40fps if iOS determines there's an issue maintaining a steady 60fps.

I think the cause of the drop to 40fps is iOS not being very good at interpreting "problems", and doing performance sampling over too short of a period at an unstable point in the app's launch, given many false positives for problems that aren't there once iOS itself has actually settled down and let the app/game run without hindrance.

The default template with the jetFighter shouldn't ever have trouble running at 60fps. So it only makes sense that this framerate cap "feature" would become active if the polling by iOS to determine when to cap the game loop at 40fps is done too early in the launch, for too short of a time. This means any interruption in the first few frames of the game causes iOS to cap it at 40fps, pre-emptively thinking the game won't/can't maintain 60fps.

Ironically, iOS is probably the cause of the hiccups it's detecting at the launch of the game that cause it to then consider the app unable to maintain a stable 60fps.

BUT I AM SPECULATING!

This is based on observation, not any known facts on the matter. But it's consistent with what I'm seeing happening and the only reasonable explanation I have so far.

The "good news" is iOS is not sampling only once and leaving it. It samples the game spasmodically, and after interruptions like jumping out to the home screen and back into the app.

For example: it's possible to cause a resampling of the framerate by iOS, and cause it to jump from 40 to 60, or 60 to 40, simply by starting Quicktime screenCapture whilst your device is connected. Apparently this (and a few other actions) will cause iOS to test the running app for its framerate consistency, again, then iOS adjusts according to its findings, again.

And, after an arbitrary amount of time, it scans again. If you leave the JetFighter template running for a while, you'll also see that eventually iOS does another test of the framerate consistency, and often determines that it's now stable enough at 60fps to put it back up to 60fps, despite having initially decided it should only run at 40fps.

I say all of this because I've watched a thing called "renderer" in the stats on the device deliberately taking up exactly the right amount of extra time in each gameloop to force 40fps, even when there's nowhere near enough other things going on to make that necessary.

It occurs to me that Apple is working on variable frame rate technology as per their statements about the iPad Pro, and the iOS features to support that have been (seemingly) implemented ahead of the release of the screen technology, and badly and oddly testing running apps to determine when to forcibly roll them down to slower frame rates.

Given that 40fps is an odd number not equally dividing into the default refresh rate of current devices at their 60fps refresh rate, it's likely the iPad Pro is capable of 120Hz screen refresh if they're so interested in 40fps.

When capturing from current iPads, if it's framerate locked at 40fps by iOS I'm seeing a 2:1:2:1:2:1 frame sequence that's how you'd make 40fps on a 60Hz refreshing device.

Which is in no way ideal. You wouldn't ever want to see this on a 60Hz screen because it's annoying, visually, even for people with insensitive eyes.

Possibly this variable framerate technology permits true 40fps on the new iPhones, I don't know. Haven't seen anything tested yet, but it does seem odd that something likely only truly possible on the iPad Pro is causing this issue on everything at the moment.

Low Framerate in SceneKit

The issue was that Physics was being called on every frame, then performing some logic. The player was hitting the floor, used to center the block, every frame. I changed the contact bit mask and all the issues went away.

Major iOS9 performance issues with Sprite Kit

It seems the majority of iOS9 issues are addressed in the latest iOS9.2 beta & Xcode 7.2 beta.

Thank you Apple for finally addressing the problem. Too bad I spent 2 months working on work-arounds.

I've been posting on Apple's forums, submitting bugs and communicating with a support technician. It's a shame that at no point did Apple offer any clarity over what issues they were aware of, and what the Sprite Kit team were addressing.

Still, at least it seems the majority of Sprite Kit issues are now resolved, and a career change is no longer necessary :]

Scenekit Error: Inconsistency in scene graph found in C3DNode finalize - clueless

I have encounted this error when my code was trying to remove nodes on a background thread, so I recommend checking that you are on the main thread with Thread.isMainThread when debugging to ensure you are on the main thread. Something like SCNAction.run(block) actually launches your code in a background thread, which is where I encountered this error. Basically the background thread removed from parent while at the same time the main thread was trying to do something with the node, which cause the scene graph to change before the node finished its process.

run actions in SceneKit Editor

what you see is the view jittering even though actions are running – that's a bug in SceneKit. As a workaround you can temporarily add a particle system or physics body in your scene to prevent the view from jittering.

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