v0.18.0 introduces major bugs with collisions with sleeping bodies spamming collisionEnd indefinitely

[fishmongr]

Upgraded from v0.17.1 to latest to hopefully see some performance upgrades. Verified performance is pretty much the same but there is a nasty bug introduced if you have Engine enableSleeping true. Bodies that collide with sleeping bodies will have Matter.Events.on collisionEnd spammed indefinitely until you restart the server. It's pretty easy to reproduce.

This issue will likely happen more frequently than expected to anyone using Engine enableSleeping true as it's quite difficult to manually manage sleeping bodies when you want and not have the lib auto sleep everything including static bodies, this is due to sleepThreshold=-1 being so difficult to set in a manner that sticks, but that is an unrelated older usability issue.

[liabru]

Hey thanks for reporting, I'll look into this but if you happen to have a minimal example please do share.

Is there anything visible other than just that event getting too many calls?

[fishmongr]

Unfortunately I don't have a minimal example to share at the moment but if you have any difficulty reproducing the issue I can try to elaborate or generate an example. My implementation is running in Node as the back-end for a Phaser game. As soon as I move the player over a static asset (created for example with Bodies.rectangle(x, y, width, height, { label: 'wall', isStatic: true }); the onCollisionStart fires like normal and then on exiting the overlap the onCollisionEnd triggers at 60fps indefinitely until moving back onto the item. It starts again when exiting the overlap. The problem goes away when rolling back to 0.17.1.

I created an implementation level fix in our game by ensuring our static bodies do not unintentionally get converted to sleeping by the global Engine config, by setting newBody.sleepThreshold = -1 and found it avoids the issue for static game elements like walls but for elements that need to be destroyed on collision the issue occurs again. This is because we recycle destroyed physic bodies into a recommended reuse Pool with sleep enabled (to avoid game stutter with MatterJS having to rebuild index internally every time an object is added or removed). This causes the onCollisionEnd spam to start again for those items as they are removed on onCollisionStart and put to sleep.

[fishmongr]

@liabru if you have any consulting hours to spare we'd be happy to pay an hourly rate for you to review the integration of MatterJS in our game as we're working on performance optimizations for it. We have it set up in docker so pretty easy to get set up locally with it.

[tropicalpudding]

@liabru I have also been seeing this bug the past few days. In my instance I have a game where when a body collides with another particular static body, the first body will be set to sleeping then removed after a set amount of time. What I am noticing is that the collide end event will continue to fire even after the body is removed from the world. I set up a code pen to demonstrate:

https://codepen.io/tropicalpudding/pen/LYzgaXK

[liabru]

Thanks for the info both and @tropicalpudding for providing that example.

I've a preliminary fix for it here if you'd like to try it out and help review, that would be much appreciated: #1079

[fishmongr]

@liabru thanks for the quick patch! I tested it just now and unfortunately am still seeing the collisionEnd event getting triggered indefinitely after a collision exit. I also noticed CPU load for our test scenario, 10,000 completely static sleeping bodies and 1 active body goes from 20-30% load on v17.0.1 to average 40% load with this patch version.