UE5 Chaos Vehicles

Hi, thx for giving this early access, love you Epic.

Here the first result of my test with Chaos Vehicles Plugin.

Just create the project with the Vehicles Advanced (BluePrint), answer yes when Unreal 5 ask for updating the project on start.
And hit play … The car land on the floor, the suspension still are working, the camera inside outside, the sound etc…
But, the wheels do not turn left and right and the car do not move at all.

I have two computers desktop (not laptop) and i do the same on both.
It is simply never working in my older computer (as describe upper).
It is working in my new computer, but with no constant behaviour (see below).

On the new computer:

  • The same project can work or not work during the same session. Escape and retry to play can randomly make it work.
  • The car can also suddenly stop working during the play.
  • The front wheels stop rolling at some point during the decelerate (not brake) at some range speed even if they can turn left and right.
  • The torque have some loose of power.
  • The reverse as brake option can simply not work on some car and work on other.
  • The car can freeze in the air during a high jump and just fall straight way.

Not really chaos related but it happens to.

  • The sound stop playing at high speed.


Just to add in info:
UE4.26 chaos preview3 work seamly on my both computers.

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can you add the specs of your pc’s as i get the same issue of the little buggy not moving
my specs
i7 7700
GTX 960
Ram 64gb

My old computer :
i7 8700
16 go ram
gtx 1060 6gb

Again, UE 4.26 is obviously little heavy on this pc but it is working and the version chaos preview 3 work fine too.

so how did you get it to work, still can’t get the vehicle to move


I don’t get it working with my old computer, UE5 Chaos Vehicles plugin simply don’t work, the car never move.
And to be precise, i was just add the info to confirm this pc can handle chaos because it is working fine with UE 4.26 Chaos preview 3.
And even 4.26 the credibility of the behaviour is matter of taste i can say.

UE 5 early access Chaos Vehicles plugin work only with my more recent computer, but with all the strange behaviours described in the first post.

That’s it, i have stop to try, Chaos Vehicles plugin is not ready yet to do any relevant vehicles gameplay, except for totally inaccurate gameplay can be cool. :slight_smile:

Hi all,

I don’t know if that can solve your problem, but you too the vehicle is not moving, go to the plugins management, uncheck “chaosVehiclePlugin”, restart, go back to plugin management and check again “chaosVehiclePlugin” and restart. Et Voila! For me it work at least.


I have try and unfortunately this do not make it working on my old computer.

thanks but it didn’t work for me
please post your computer specs so that we can compare what works and what doesn’t

I have some more data.

I am trying to debug this to find out why the vehicle doesn’t move and I had a breakpoint in the car initialisation. Looked through the block of code and couldn’t see anything wrong, so hit F5 to continue.

And suddenly everything worked. The car actually was pretty good , which was a surprise.

Removed the breakpoint, and everything was broken again.

So my guess it’s a thread timing issue

Oh and by the way, don’t try to disable the chaos vehicle plugin. Makes the editor crash

I am also receiving issues with Vehicles(But custom vehicle using physics constraint)
It seems as if the constraints (angular and linear) does not lock It is always on free.
Do you think it is also part of thread timing issues?

I am digging into what is going on.
Chaos seems to run on it’s own core and “talks” to the various game components by async callbacks.

I am working on the theory that these callbacks are not happening which would match what you are seeing

I have found one thing that needs further research

The system has auto-brake. So when the speed is less than V and you aren’t accelerating, the brakes come on.

At the moment when you accelerate, the braking value goes to 0
When you release the accelerator, the braking value goes to -0

Which obviously isn’t correct

So the -0 was a totally different bug.

What I am seeing is that the vehicle component is throwing async inputs at chaos, and chaos is NEVER supplying any output

The chaos vehicle component processes the async que and moves objects about, but they are all empty

/* READ OUTPUT DATA - Access the async output data from the Physics Thread */
void UChaosVehicleMovementComponent::ParallelUpdate(float DeltaSeconds)
	if (const FChaosVehicleAsyncOutput* CurrentOutput = static_cast<FChaosVehicleAsyncOutput*>(CurAsyncOutput))

That if statement is NEVER true

This sound good, nice investigation.
And this trigger me a question.
Why this problem seem to affect only older computer ?

Because UE5 Chaos Vehicle.
Don’t work with my older computer.
i7 8700
16 go ram
gtx 1060 6gb

But, work with my more recent computer.
i7 10700k
32 go ram
rtx 3070

Good question.

I use a Intel Xeon Silver 4114 because it has loads of cores with hyperthreading. I get about 2200 threads.

When building UE4 games this reduces a full build and package data down to around a hour.

I only have a 1080 graphics card on board because I like to stay behind the curve. If my game renders at 60Hz on a 1080 it will be fast as a very fast thing on a newer GPU

Anyway , I will keep digging

I have found what is happening, just not got a fix for it yet.

I can prove I am correct though.

Press W before the car settles and everything works, wait till the car settles and it never does.

So my assumption is that the physics simulation is sleeping, but the code in ChaosVehicleMovementComponent that handles waking the vehicle is called but cannot wake the vehicle

 Warning: CurAsyncOutput cleared
[2021.06.21-08.49.24:116][203]LogClass: Warning: CurAsyncOutput set
[2021.06.21-08.49.24:116][203]LogClass: Warning: ParallelUpdate called
[2021.06.21-08.49.24:117][203]LogClass: Warning: ParallelUpdate PVehicleOutput->EngineRPM 1200.000488 ,PVehicleOutput->EngineTorque 0.000000 , PVehicleOutput->TransmissionRPM 136.705460
[2021.06.21-08.49.24:117][203]LogClass: Warning: CurAsyncOutput cleared
[2021.06.21-08.49.24:275][204]LogClass: Warning: ParallelUpdate called
[2021.06.21-08.49.24:275][204]LogClass: Warning: CurAsyncOutput cleared
[2021.06.21-08.49.24:406][205]LogClass: Warning: ParallelUpdate called
[2021.06.21-08.49.24:407][205]LogClass: Warning: CurAsyncOutput cleared
[2021.06.21-08.49.24:521][206]LogClass: Warning: ParallelUpdate called

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Got a solution




void UChaosVehicleMovementComponent::ProcessSleeping(const FControlInputs& ControlInputs)

And it works

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Thanks Paul can you some how push this to the Epic guys, personnally i don’t really want to go the github+compile route so i’ll have to wait for a update on the launcher version if it doesn’t take to long

This is what I did to fix it. I added “Wake all Rigid Bodies” to the throttle. This stopped the problem.


Could you explain where to add this line specifically? I am not a pro in ue so a step by step explanation would be nice. :slight_smile:

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