Flickering on Touch

[ShikiGami]

Describe the bug
This is a horrible bug that has made the prospect of using this imposible, in which each time you touch the screen or remove your finger from the screen, in AR mode, the whole scene will flicker, meaning, for a mili second every single GameObject and UI element will disappear and then comeback, giving you this flickering illusion when touching the screen.

To Reproduce

• Create a project in Unity 6, using URP and the new Input System.
• Import WebXR-exporter, interactions and the samples.
• Compile the project
• Test on an android smartphone with chrome
• Get into AR mode
• Touch the screen and there it is

Expected behavior
There shouldn't be any flickering

Unity info (please complete the following information):

• Editor version: 6000.0.60f1
• WebXR package version: 0.22.1
• WebXR Interactions version: 0.22.0
• Git or OpenUPM: OpenUPM
• Using old components (like the Desert sample) or Input System + XR Interaction Toolkit: Yes, but the same effect happens without this sample.
• Built-in render pipeline or URP: URP

Smartphone (please complete the following information):

• Device: Pixel 8a
• OS: Android 16
• Browser: Chrome 141

[De-Panther]

Does it happen in this sample?
https://de-panther.github.io/unity-webxr-export/Build

And in this?
https://immersive-web.github.io/webxr-samples/anchors.html

Can you share your project + your build?

Thanks

[ShikiGami]

It doesn't happen in those builds; it happens when you build it from scratch in a new Unity 6 project.
I've tried with both samples, my own stuff, and everything flickers when entering in AR mode, doesn't matter how you call AR mode, if from the HTML button or from inside the app.
Also, when going in VR, the flickering comes with a red flash of light.
Funny thing is, even though it does recognize the touch movement, it doesn't flicker on movement, just when touching and when releasing.

Here is an example: https://shikinobuhisa.com/webxrtest/

[De-Panther]

Weird. It doesn't happen in other Unity 6 projects I tested.
Please share your project.

[ShikiGami]

There is absolutely nothing special about the project. I literally just created yet again another new project in Unity 6000.0.60f1, followed the instructions to start, with the sample, compiled, and put it on my web server, and exactly the same result.

https://1drv.ms/u/c/bae472a1906efbfe/EUpcgN4KzDFHoHZc9IVZBbABu_A_U7Xy5OlThOhP_kTPcg?e=1aIUrw

I'm not completely sure but I think this is related. I seem to get this warning when going into AR or VR mode
[.WebGL-0x3754061a4400] GL_INVALID_OPERATION: glDrawArrays: Active draw buffers with missing fragment shader outputs.

[ShikiGami]

I did some regression tests, and compiling the same project with 6000.0.23f1 gives me the expected outcome, but with 6000.0.60f1 I'm getting the flickering

[De-Panther]

Thanks.
I'll have to investigate what changed in that Unity version and see if it's something that can be solved.

[hint1122]

I experienced the same issue. I'm using version 2022.3.14f1, and I've tested WebXR versions 0.16, 0.22, and the sample 0.20 version from GitHub. After confirming the sample worked properly and cross-checking with my project, I found that manually adjusting the frame rate caused flickering. Once I commented out that part of the code, the flickering stopped

[cefoot]

@hint1122 can you be more specific? I do not adjust the framerate (at least not that I'm aware of and there is no code calling Application.targetFrameRate) What exactly did help you removing the flickering?
Thanks in advance ;)

[hint1122]

@cefoot Sorry, I just checked now because I was pressed for time with the work schedule. As mentioned above, I only confirmed that the issue is always reproduced when the frame is manually adjusted. It wasn’t in the previous project, and in the current project I only commented out the code where I had added Application.targetFrameRate = 30;.

[yubbit]

I've been running into this as well. It looks like this bug begins to occur starting with 6000.0.50f1. It seems to occur when XRData.SendTouchEvent is called on lines 594 or 598, where an invalid call to glDrawElements is made which causes the screen to flicker. This seems to be the relevant error:

build.framework.js:1293  WebGL: INVALID_FRAMEBUFFER_OPERATION: drawElements: Cannot render to a XRWebGLLayer framebuffer outside of an XRSession animation frame callback.
_glDrawElements @ build.framework.js:1293
$func69382 @ build.wasm:0x17c9e9d
$func69053 @ build.wasm:0x17a5bc6
$func69198 @ build.wasm:0x17b7ef3
$func70097 @ build.wasm:0x1830b65
$func70125 @ build.wasm:0x183905e
$func75456 @ build.wasm:0x1a0cd3c
$func75456 @ build.wasm:0x1a0cdb1
$func72023 @ build.wasm:0x194d968
$dynCall_v @ build.wasm:0x23d0ca8
(anonymous) @ build.framework.js:1293
_JS_CallAsLongAsNoExceptionsSeen @ build.framework.js:1293
$func72022 @ build.wasm:0x194909a
$func54148 @ build.wasm:0xf59cee
$dynCall_iiii @ build.wasm:0x23d0c4b
(anonymous) @ build.framework.js:1293
touchEventHandlerFunc @ build.framework.js:1293
jsEventHandler @ build.framework.js:1293
XRData.SendTouchEvent @ build.framework.js:137
XRManager.onInputSourceEvent @ build.framework.js:598

I could continue looking into this, but I'm a bit lost on what else to check.