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UE 4.26 Collision Issues

I am working on a game that’s basically VR squash. I decided to try it on Unreal Engine 4.26, hoping that I could be out of the prototype-ish phase by around the time it left preview.

I was going to submit this as an issue, but I get 500 Internal Server Error on both Firefox and Edge so I assume the issue reporter is down.

When I attempted to make a box on my hand hit the ball, I would get two different, wrong behaviours:

  • If the ball stopped bouncing and just stayed put, it would not interact with the bat. I tried doing Print String blueprint statements, but nothing was written.
  • If the ball was still bouncing, then it would interact with the bat… but weirdly. Like it would be shifted to the side, but its direction of travel may or may not be redirected. One time I hit the ball from the left… and it still moved forward, just kind-of sidestepped to the right. Not even smoothly… like it was just teleporting 10 centimeters to its right, but smoothly traveling forward.

Thankfully there wasn’t much logic, and most of it was C++, so I was able to drop it into a 4.25 project. In the 4.25 project, it seems like the ball can be hit just fine. Granted the specific object hierarchy will be different, but that’s mostly because I did a bunch of fiddling while I was trying to diagnose the 4.26 problem. First attempt worked on 4.25.

Is Chaos intentionally different from PhysX? Or is this a symptom of a bug?

I am working on a powered ragdolls project and when I tried the 4.26 preview with Chaos… it was indeed chaos.

I don’t know if Chaos right and I was doing something wrong that worked with PhysX. But it was definitely different. Instead of standing up straight their bodies ended up curled into a donut and they were leaning around. I don’t know if the constraints all changed or the physics force units or how the mass/inertia was calculated. I quickly downshifted right back to 4.25, leave that battle for another day.

If you need 4.26+ then I think you can switch it back to PhysX. Not sure the exact steps. Maybe you have to rebuild UE4 from source.

Guys .26 is in Preview. You shouldn’t be expecting it to work at all - let alone for it to be able to just convert a project and have it work fine.
Wait until the final release before putting a lot of work into it.

That said. The constraints are all changed/work differently. They need to be selected and re-aligned to the bones (reset or snap button). The colliding bodies seem to always collide and cause issues at this time - perhaps exactly because the notes say that Ragdolls aren’t ready yet.

Physics are modular, you can try to disable the Chaos plugins and the engine may default back to physx, however I would search on the actual topic of disabling it…

Additionally, Let’s bother our community manager:
@VictorLerp
I also received a 500 Internal server error when submitting a report, I did however get an email confirming it was received. Could you please let whoever is in charge of that know they need to fix it?

I’m well aware that it’s preview. That’s why I’m discussing it. It might be a bug, which I could help them find before release. (And if it’s an intentional change of behaviours then they might want to know for documentation purposes too.)

The issue with that is the fact they liekly already know, given the release notes do not state we currently have physX parity… but I am sure they would welcome the report anyway, I wasn’t telling you not to report it…