Bug Stutter / Frame Pacing issues after upgrading to 2021.3

After the Upgrading project from Unity 2020.3.4 (URP 10.4.0) to Unity 2021.3.10 (URP 12.1.7), we are experiencing a stutter/frame pacing issue that had not been there before the upgrade. The stutter is noticeable when the player is using smooth locomotion and also visible on animated moving objects. The issue is only noticeable on Quest vr builds. With Steam VR the issue does not appear present.

We’ve been able to reduce the issue by switching to 72h. But there is still a stutter every one to two seconds. We’v e discovered that if we try to change the refresh rate with the OVRManager call the issue will get worse until the headset is put to sleep and woken back up.

OVRManager.display.displayFrequency = 80;


OVR metrics have no visible stutters and appear smooth.


When running with the profiler the issue gets worse and the spikes show as OculusRuntime.WaitToBeginFrame.

What We’ve tried and hasn’t had an impact

• Upgrading the Oculus Integration 3.2.2 (Package Manager)
  
  
• Upgrading the Oculus SDK to v47 (Asset Store)
  
  
• Switched Oculus to use the OpenXR back end
  
  
• Tested on OpenGLES and Vulken
  
  
• Test builds with Late Latching, Phase Sync, and Optimized Frame Pacing
  
  
• Tested on 2021.3.1. 2021.3.14, 2021.3.15, 2021.3.16

Steps to reproduce:

• Open a new URP project in 2021.3.10
  
  
• Make a simple animation of a moving shape
  
  
• Download the Oculus Integration and SDK
  
  
• Put OVR camera prefab in scene
  
  
• Add a simple script that changes the refresh rate on launch
  
  • OVRManager.display.displayFrequency = 90;
• Change Quality settings to performant
  
  
• Make an android Quest build and test on device

 

Bug report submitted


CASE IN-30623

 

Here are those stutters when looked at in the profiler

 

Looking at the profiler, you're on the edge of obtaining 90fps, so once you hit 89fps the framerate will vsync back to 45.
Generally XRUpdate is GPU related.

Do you still see the spike if you set the fps to 72?


Default URP is not optimized for VR. There are optimisation to be done, disabling SSAO is the first of many

 

Does a deep profile of "EarlyUpdate.XRUpdate" come up as "OculusRuntime.WaitToBeginFrame"? I find that even on simple test projects that it's like Oculus' runtime has Phase Sync on regardless of the Unity setting and often overshoots. Worst part is, I have no control over it and no way to turn it off.

Phase Sync
https://developer.oculus.com/documentation/unity/enable-phase-sync/

Related "By Design" Bug Report?
https://issuetracker.unity3d.com/issues/xr-sdk-oculus-earlyupdate-dot-xrupdate-spikes-inconsistently

 

It's not a performance issue.
If you ADB command to set refresh rate to 90, then sleep-cycle the headset, the stutters stop happening. Then ADB command to change the refresh to 72, without letting the headset go to sleep, and the stutters will come back. At a perfect interval.

It'll happen with any refresh rate change, with every version of Unity 2021 I've tested. Didn't happen in Unity 2020.

 

Then make a repro project and make a bug report.
If there are no well documented bug reports there won't be fixes

 

Thanks for the responses!

The stutters get worse with the profiler attached so not 100% those spikes in the profiler are related to the original issue and not just from over head from the profiler itself.

@DevDunk Yeah still see it at 72hz, attached a image. But still this spike could just be from the profiler over head.

@ScottCoconut Yup, on deep profile they read as OculusRuntime.WaitToBeginFrame. Intersting are you also seeing this just on 2021.3?

 

@LianneUnityXR thanks for looking into this. Reeeeaaaallly hoping to not have to move back to 2020 but I haven't been able to find a solution to these frame pacing/stutter issues.

@kayke thanks for putting in a bug report and for sending me the repo project. I'm definitely seeing the same issue and have tried everything under the sun to fix it without luck (in the repo project and with our company's product).

Here's a MQDH/Perfetto report of what I'm seeing in a simple project with a couple animated lines. Before and after the frames shown here, I'm getting 80fps pretty solidly but then I get frames like these on semi-regularly that make the whole VR experience feel stuttery/bad. If OculusRuntime forcing a kind of Phase Sync is the issue, I'd love an option to turn it off and give Swappy a chance to do its thing. If it's more of a frame pacing issue, I'm not really sure where to start as I've exhausted what feels like all combinations of all related settings exposed to me.

 

Just an update on our end. We may have found part of the issue.
We ran some test on deltaTime and were getting some values that were matching the pattern of stutters that were experiencing. When we changed some of our systems over to use our own custom deltaTime the consistent stutter was gone.

Running some tests it appears that after you change the hz with OVR, Time.deltaTime is off until the headset is sleep cycled.

We still see an intermittent stutter every ~5 seconds, but the consistent stutter appears to be directly linked to deltaTime.

 

Interesting, I thought they fixed deltatime issues in a recent LTS

 

Glad to here you found your main issue @kayke! But also pretty alarming that such a low level thing as delta time could be giving erroneous results. Especially since there is plenty of Unity code that relies on it that we don't have access to, like animations.

 

A seemingly related thread. The most recent posts point to a regression in some of the deltaTime improvements dependent on platform.

https://forum.unity.com/threads/tim...-vsync-camerafollow-and-jitter.430339/page-11

 

Hi, all. Did anyone happen to find any solution or bypass, except for moving to 2020? Is there a chance that the fix is coming anytime soon? Really struggling with the same issue

 

Here is a relevant datapoint:

This thread here has people losing their mind about Time.deltaTime being unstable. It was started in 2016:
https://forum.unity.com/threads/time-deltatime-not-constant-vsync-camerafollow-and-jitter.430339/

A fix was introduced in 2020.

 

@immersification haven't heard back from Unity on when/if a fix is planned.

I was able to work around the issue by implementing our own delta time. I used the system stopwatch class to track time and used

Code (CSharp):

1. stopwatch.ElapsedMilliseconds

to extrapolate delta time.

 

@kayke thanks a lot! We're going to try this. Almost got our brains melted with this

 

Just for reference the bug has been confirmed by Unity and there is a page for it on the issue tracker.

https://issuetracker.unity3d.com/is...dot-waittobeginframe-when-the-player-is-built

 

I'm very interested in this issue, where can I download this project, I want to do a test.

 

Looks like they are going to ignore 2020 and 2021 because of a compilation error in the submission.

 

Thanks a lot for investigating this further, it's probably related to a performance problem with 2021 LTS that keeps popping up every now and then. I've been stuck in 2020 LTS for too long due to this but I might give it a try again using your workaround!

EDIT: from the bug tracker page:

Not sure what this means, considering you found the issue in a 2021 version.

 

I'm running into the same problem, only using URP in Unity version 2021.3.18f, I've already tried with older versions 16f and 17f.

It also occurs with App Space Warp.

I thought I was going crazy, anyone suggest a solution? A hug to everyone and thanks.

In 2021.3.19f the problem continues.*

 

The solution is to mass vote on the issue on the issuetracker

 

This tutorial is based on the great work done by @DevDunk which you can see in you and a thousand apologies for not having put a reference before, the basic difference with this one is the implementation of the URP that I do from the manifest.json unlike @DevDunk which perform an installation, I'm not sure that it will solve the problem but in the initial tests it seems to be so.

TUTORIAL @DevDunk

Hi guys, I think I have found a possible solution.

First, I apologize for my English since it is practically nil, I will try to develop all the steps that I have taken and I hope that it works for you, it is doing quite well for me except for some initial flickering, but then it looks fluid.

I'm not an expert either, so if you see something outrageous please don't take it into account.

Create project with normal Unity 2021.3.19f WITHOUT URP, I load it like this for fear that later there will be residues from the initial installation of the URP that comes by default with Unity and that is not the one we need.




Once the typical project is compiled, we move to the Android platform, install XR Plug-in Management and when finished we select Oculus tabs.The XR Plug-in Management>>>Oculus settings would be as follows.



Now we are going to download Oculus Integration in my case I am using v49, when it is installed in the dialog boxes select OpenXR and the typical, update, restart, etc...

In the project you can start marking assets and with the right button press Show in Explorer or go to your project folder and in Packcages you will find two .json files, open the one called manifest.json and it should look like in the image, adding the dependencies that are checked.



You can find it at the following link in the Oculus documentation. https://developer.oculus.com/documentation/unity/unity-asw/

Once those lines have been entered, click save and the Unity project will begin to compile the new packages.

When finished we have to configure the graphic themes for URP, we have to create a URP Asset, in the folder that we want (I organize everything in my own way, I will not be the one to say how to follow an order =op), press the right button Create >>>Rendering>>>URP Asset (whit Universal Renderer) as it is in the image.



In the Quality configuration, use the one you want, I recommend this, but surely someone can give ideas for a better result.




It only lets me upload five images I continue with the post.

 

CONTINUE ->

Clicking on the Asset Render Pipeline we configure as indicated in the image. It is how I have it but as I have already told you, I am sure that you have better ideas.



And now we click on the other Asset Render that has been created for us (Universal Render Data) and leave it as in the image.



Again in Project Settings in Graphics we make sure that the Scriptable is loaded otherwise we put it, the configuration that you see here is like this in the example of Oculus App-Space Warp


And finally, under Graphics is URP Global Settings that should look like the following image.



All that remains is to activate the Space Warp App, create a script, and drag it to an object in the scene.

Code (CSharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5.  
6. public class EnableAppSpaceWarp : MonoBehaviour
7. {
8.     // Start is called before the first frame update
9.     void Start()
10.     {
11.         OVRManager.SetSpaceWarp(true);
12.     }
13. }

Now it only remains to compile, you can see that the FPS are at 36, at first it jumps a bit but it disappears quickly and I can see everything smoothly.

I leave conclusions in the next post.

 

If you look at the documentation what we are doing is implementing a URP created specifically by Oculus to use App Space Warp, we can create a material using Simple Lit for example and it shouldn't give any problems. In fact, you can use another type of material using, for example, a different Shader and you will see that the jumps occur again, in my scene I have objects with Simple Lit that I use from the oculus package and another from an Asset that I have downloaded and the strange movements they occur with the second while the rest of the scene I can walk and see without problems.

I leave you a video of what the test scene looks like.

The textures are 1024*1024 for the cliffs, the ground is 1025*1024 and the sky is 2048*2048

A hug and I hope I can help you a little.

The mountain that I see at the end is the one that gives me problems because of what I have told you, it is not visible in the video but in the glasses it is a flicker like the one that other colleagues comment. A curious thing is how the FPS is "maintained" at 36 except for a small drop at the end, however when you turn the "normal" FPS drops to 72, but in a second or two it recovers.

I almost forgot, I'm using mixed lights, and a bakend.

A hug to all.

 

It definitely doesn't work, I'm leaving the post if you don't care in case someone from Unity sees it and can indicate that it's being done wrong in case it's a bad configuration.

(I really want to cry...)



Android Logcat:

2023/02/25 09:50:35.004 16052 16219 Info VrApi FPS=45/90,Prd=28ms,Tear=0,Early=0,Stale=1,Stale2/5/10/max=0/0/0/1,VSnc=0,Lat=-3,Fov=0,CPU4/GPU=4/3,1478/490MHz,OC=FF,TA=0/0/0,SP=N/N/N,Mem=1804MHz,Free=3094MB,PLS=0,Temp=23.0C/0.0C,TW=2.00ms,App=3.17ms,GD=0.00ms,CPU&GPU=7.40ms,LCnt=2(DR0,LM0),GPU%=0.34,CPU%=0.12(W0.15),DSF=1.00,CFL=14.74/19.66

2023/02/25 09:50:35.004 16052 16219 Info VrApi ASW=90, Type=App E=0.011/0.261,D=0.000/0.000

A zero comma from learning Unreal

 

@ChescoRed make a bug report, you seem to have a good project for them to test on. Posting it here helps the community a bit, but doesn't guarantee unity staff looking at it

 

Can you ping unity to explore 2020 and 2021. They are ignoring it in your report dude to some compilation error in the project submission.

 

I am testing with Unity version 2021.2.19f and I use a Nukadelic version in the manifest.json and it seems to work fairly well.

- Unity Versión: Unity 2021.2.19 April 5, 2022 unityhub://2021.2.18f1/0c6e675195cf
-Nukadelic GitHub: https://github.com/nukadelic/unity-application-spacewarp

 

A similar issue just landed a fix in the latest 2021.3.20
https://issuetracker.unity3d.com/is...atime-values-arent-stable-on-specific-devices

 

Hello @DevDunk , I have done the tests on the 20f a plane, a URP cube and the most basic configuration and I still have the problem of image stuttering when I move the player.

 

Hello everyone, there is a new update of 2021LTS, specifically 2021.3.21 where I just carried out tests and in principle the blinking problem when you use URP has disappeared, greetings to all.

 

This issue has been driving me crazy and preventing me from launching my game (developing for VR quest platform). I noticed this problem in 2021.3.15f1 and I tried updating my project to latest LTS 2021.3.25f1. It seems like my game runs very smooth for about 10mins and then slowly the stuttering sets in to where its very noticeable and really effects the gameplay. If i quit the game and then start playing again Its goes back to being smooth until after another 10 mins or so. Anyone know a fix or work around for this?

 

Is the framerate still stable if you check the profiler and or OVRMetrics?
If so, if it's reproducable, please make a bug report.