ARCore demo builds and deploys but shows no AR (black background, no tracking) on device

[CharHeap]

I was able to successfully build the plugin using the godot-cpp branch 4.4, and I can also build and deploy the demo project without errors.

However, I’m not seeing any actual AR functionality on the device:

• The app launches, but only shows a black background (no camera passthrough)
• Camera permissions are requested and granted
• The 3D scene does not move with the device (no tracking / AR behavior at all)
• UI elements (checkboxes) appear but don’t have any effect
• The app remains responsive, but nothing AR-related seems to initialize

Environment

• Godot: built against godot-cpp branch 4.4

• Plugin: latest from repo (no modifications)

• Device: Lenovo tablet (previously used successfully with WebXR)

• Android target SDK:

  • Tried SDK 31 (works but shows device warning)
  • Also tested with higher target SDK 34 (same behavior)

Questions

• Can you confirm that the demo project is currently expected to work?
• If so, what behavior should I expect (e.g. camera passthrough, tracking)?
• On which devices has this been tested successfully?

At the moment, I’m unsure whether this is:

• a device compatibility issue
• a missing setup step
• or a problem with the current plugin/demo state

Currently unable to debug further: when using deploy with remote debug, the app gets stuck on Godot’s boot splash. This seems expected, as I have not yet built the plugin stub for my host OS (Windows), as described in the README. I plan to do that next in order to capture any errors that may currently be occurring silently.

Any guidance would be appreciated.

[thomascrow01]

feel like I've had a similar issue before but don't quite remember, otherwise probably test one of the google ar core sample apps if you haven't https://developers.google.com/ar/develop/samples, I know google ar core has issues on certain devices despite what's listed on their list of compatible devices

also keep in mind that portrait mode isn't properly implemented for this repo

otherwise what version of gradle are you using?

[CharHeap]

Thanks for the quick reply. I will try the google ar core samples next week to check if it's the device.

I also tried the fork from tGautot (supposedly has portrait?) but it was the same (and UI etc. was initially set to not visible and had to remove the custom path in the export template..). I am also trying to use it in landscape.

Not sure which version of gradle I used, will report back here on tuesday. Which version should I be using? And does it make a difference? The build seemed to run just fine.

Again, thanks for your quick reply. Also, if you have an example stub plugin which would allow to deploy with remote debug it would help a lot.

[thomascrow01]

the camera feed from ar core on tGautot's branch doesn't work properly on Godot 4.5+ so gotta stick to 4.4 (something about using the camera feed texture in a shader, no idea)

I personally use java 17.0.13-tem which works for me for compiling both the plugin and project within the Godot editor

[CharHeap]

I used Godot 4.4 in all my tests. So you are able to get this branch running with Godot 4.4? Or could you maybe publish a working fork? I also found a recent linkedin post where someone talked about having to fix the black background and other issues. They did however not think of publishing their fixes or making a pull request unfortunately.

[CharHeap]

Environment

• Java: 17.0.15-tem
• Gradle: 8.9

Resolution
The issue was resolved by adding:

custom_api_file=../thirdparty/godot_cpp_extension_api/extension_api.json

to the scons command.

Without this parameter, the default extension_api lacks the Godot functions required for the background renderer. While switching to a newer godot-cpp branch or commit resolves the build errors, this broke the plugin quietly for me (no AR nor background as I described initially).

The working approach was:

• Leave the existing godot-cpp branch/commit unchanged
• Use the custom API file during the build process

Suggestion
This requirement should be documented in the README.