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Very important physics issue not fixed since 2016?

First off, amazing software, thank you!

This physics issue has not been fixed since 2016!!! And is likely what’s causing a lot of the issues with physics, yet it’s such a simple fix.

It says it was fixed long time ago - July 2016. It is not? Could you provide repro steps?

a lot of the issues with physics

Anything specific?

If you set the DragCoefficient to a higher value than the original, it will produce the effect of accelerating when the vehicle is moving back. What’s happening is the opposite of drag effect is applied. So to fix this when the vehicle is moving backwards, the drag coefficient needs to be negative.

Drag coefficient is not accounted for when vehicle velocity is negative (moving back), it speeds up instead of being slowed

This is in Unreal Engine 5 Chaos Physics

I’ve seen this effect of accelerating off the level in other instances, it is likely that if drag is fixed it would slow those down instead of accelerating them off, so once this is fixed it seems will fix alot of the issues.

You’re then talking about a regression of a 5yo bug in another engine. Pretty sure that’d need to be reported as a new issue:

https://epicsupport.force.com/unrealengine/s/?language=en_US

Nice catch, btw.


But this is not Chaos right? The current system will be completely replaced afaik (someone corrects me) so fixing something in a system that will not exist in half a year is probably not very high on a priority list.

Just because epic and Nvidia are parting ways (and nvidia doesn’t seem too interested in maintaining their gameworks/physx stuff) doesn’t mean it isn’t important.

Still, it’s usually better to implement physx via library as if it wasn’t part of the engine.
This would become needed as soon as chaos actually makes it into the launcher releases.

As far as fixing the issue. You could actually modify all of the behaviors in a CPP project.
The vehicle classes are engine side files too. So modifying the base cpp stuff would affect changes into any instance you later generate.

If this is indeed a regression, you can track it on git.