bitECS - Some scene changes broken with "tried loading multiple nav mesh"

[mikemorran]

Description
We encountered this at last friday's meetup. Changing scenes to certain environments freezes the screen and we see a nav.js line 14 error "tried loading multiple nav meshes".

To Reproduce
Steps to reproduce the behavior:

1. Go to a room with new loader enabled
2. Attempt to change scenes to this url: https://hubs.mozilla.com/scenes/0MdfQwB/cloud-nine

Expected behavior
The scene change should complete without errors.

[takahirox]

Thanks for the problem report.

I tested and noticed that the problem may not be related to scene change. It seems to happen even without scene change.

I just created a room with the scene. The sceen freezes with the new loader enabled.

https://hubs.mozilla.com/aDWWsdL/favorite-perfumed-nation

From this code

https://github.com/mozilla/hubs/blob/e6e92b8291cf83db9df1c097725d15deb7974f10/src/systems/nav.js#L13-L16

I guess the console error happens if there are multiple nav meshes in a scene? But as the code indicates, nav.loadMesh() seems to release the old one as fallback so I'm not sure if it's the root cause of the freeze. We need more investigation.

[keianhzo]

It seems that it's actually related with an exception loading invalid particle images. It seems that Aframe caught those exceptions as we were are the same thing in the AFrame system. I've opened a PR to fix this.

[takahirox]

By the way @keianhzo what do you think of the console error? Does it happen because the scene has multiple nav meshes? If so, with the new loader multiple nav meshes in a scene is not accepted (while with the old loader they are accepted)?

[keianhzo]

There was actually a difference between how we were processing the nav-mesh in the old and new loader, I've opened a PR: #6326