bug: collision breaks on tab switch

[neomodulo]

Describe the bug
This happens in the brand new unmodified 2D starter project. Works fine normally, but when I switch to another tab for a few seconds and come back, the little alien guy has fallen through the floor and the death barrier.

To Reproduce
Steps to reproduce the behavior :

1. Make a new starter project fibbo init 2d [project-name]
2. Run it npm run dev
3. Open the localhost link in your browser and switch to another tab for about 10 seconds.
4. Alien falls forever.

Expected behavior
Staying on the platform?

Screenshots
Image

Desktop (please complete the following information):

• Browser: Floorp (Firefox fork)
• Version: 11.21.0
• OS: Linux Mint 22

[Gugustinette]

Hey !

Yes this is a known bug, switching tab (and sometimes just waiting) can break the collisions.
It must have something to do with Rapier collision system.

This is top priority issue, thanks for opening it ! 👍

[Gugustinette]

Pinning some discutions I had with @doppl3r on dimforge Discord

The requestAnimationFrame calls are "paused in most browsers when running in background tabs".

Stepping the physic world by Date.now() - lastFrameTime might make objects go through each other when re-opening a tab that was inactive for too long (as the resulting delta will move the objects "very fast").

Using a Web Worker for running the simulation might help.

[Gugustinette]

Decided to not use a web worker, as it is basically impossible to reliably and efficiently sync the scene's data across multiple worker + main thread 30 times per second.

Doing everything in a single web worker is technically achievable however (as in react-three-offscreen) but :

• It is pretty hard and time consuming to maintain
• It won't enable direct observability over the scene in the main thread
  • This is required for devtools
  • More generally, it make accessing the scene's data harder (through async calls,...)

For the sake of this issue, I'll keep it simple and make it so the simulation doesn't run when the tab is inactive, and ignore the time that passed.
I'll also try to add a bit more control over the refresh rate (by creating a "pipeline" system) so the simulation can run slower than the rendering or main game loop.