Great, hopefully you can reproduce.  I'm thinking this might be thermal throttling by the OS (device gets warm) and it just handles things differently when it come to Metal.  Another easy way to see this is Application.targetFrameRate = 60; on an older device.

Hi,

Thank you for the video and project.

I tried reproducing it with an iPhone 11 (only iOS available today) and by increasing the count/texture I got the app to crash :). 730 Augmentations with shadows etc.

Tomorrow I will have my hands on an iPad Air, will retest and update the thread.

Thank you.

Vuforia Engine Support

Ok, found some time today.  Please keep me updated, this issue is important to us.  I didn't mention in the video but this is present in all devices tried and all vision modes.  If you need to replicate on a newer device, you'll have to make the graphics processing workload more intensive by duplicating things, ramping up to 60fps, or some other method.

Video explaining the bug:

https://www.dropbox.com/s/9dvxteow62dc009/Vuforia-Metal-Lag-Bug.mp4?dl=0

Unity project file (2019.3 f6)

https://www.dropbox.com/s/1mxq2wxihq2se6i/Vuforia-Metal-Lag-Bug.zip?dl=0

Thanks for checking this out, won't have time today, will provide a project tomorrow.  It was an iPad Air 2 (latest iOS) (non ARKit).   It also happens on an iPhone 8+ as well (but the load has to be much higher).  I've seen it with Unity 2018.4-2019.3 with Vuforia 8.3.8-8.6.7, but it may be exist outside of that. It happens in all modes: Platform_Fusion, Vuforia_Fusion and Vision_Only.

Hi,

If this is happening with Metal and not with OpenGLES3 than yes, I would tent to agree that this would be bug but visible only with lower end models or depending on the load.

Coming back to your your questions.

1. I believe you answered it with your Edit

2. As per our API documentation https://library.vuforia.com/content/vuforia-library/en/reference/unity/classVuforia_1_1VuforiaRenderer.html#abe4ffb36f5d6f70ef3612bb39cb41cfe

Query recommended rendering frame rate based on application hints. The target rendering frame rate of an AR or VR application is an important trade-off between optimal experience and device power usage. The choice is influenced by multiple parameters including device type, the active Trackers, the camera and/or sensor frame rates. Furthermore there are application specific trade offs to consider. These hints can be passed to the function as parameters (see FpsHint). For example, an application with animated content may need consistent 60 fps rendering even on a device that can only deliver poses at 30 fps. GetRecommendedFps considers the device parameters as well as the application specific hints and returns a recommended frame rate. The returned value can then be set via setTargetFps. Note that GetRecommendedFps may return different values tuned to the active CameraDevice.CameraDeviceMode and active Trackers. Thus it is recommended to call this API after the application has completed the camera and tracker setup as well as when an application transitions between modes (For example when transitioning between AR to VR modes)

Could you please provide me the unity project to quickly test the behavior?

Also I would be interested to know the device model being used? ( which Ipad version)

Thank you.

Vuforia Engine Support