Problem with FRotator functions

Development Programming & Scripting C++
1

Hi, I am making an Aircraft Simulator. I am facing a lot of problem with FRotator calculations.

To avoid gimbal lock when adding FRotators, I used this



		FRotator CurrentRot = GetActorRotation();
		FTransform RTrans(CurrentRot);
		RTrans.ConcatenateRotation(NewRot.Quaternion());
		SetActorRotation(RTrans.Rotator());

This works ok but there is a slight jerking action when the actor hits the gimbal lock and skips over it.

Oher than that, sometimes I want to change the Roll of the Aircraft when the Yaw changes(giving an tilting action when going sides). But when I change both at the same time, the pitch also changes.

Should I rewrite the whole system using Quaternion? Will that work?

2

Yes it will :slight_smile:

As the person who wrote the code you are posting above I can verify that STATEMENT REVISED, see here:

In my own multiplayer game which uses physics based skeletal mesh creatures as the playable unit, I found there is an additional issue with FRotator lockups, they happen even more frequently on clients than on the server!

I was getting by with FRotator until I started testing multiplayer, and then I realized I just had to go the Quaternion route.

Is your main unit a skeletal mesh?

Is it simulating physics or not?


**Spherical Interpolation**

I can highly recommend Slerp for your needs



```


//Quat.h

/** Spherical interpolation. Will correct alignment. Output is not normalized. */

static CORE_API FQuat Slerp( const FQuat &Quat1,const FQuat &Quat2, float Slerp );


```



My own game's development continues happily because I was able to make the switch to quaternion and all the lockup issues disappeared, even in multiplayer with multiple clients all tested on the same machine! :)

Rama
3

Thanks for the reply Rama.

Yup the code which I wrote was written by you https://answers.unrealengine.com/questions/46525/how-can-i-avoid-gimble-lock-when-adding-2-rotators.html.
It worked in nearly every case after that. But when making something which was needed to have much more rotational freedom like the aircraft simulator, it didn’t work perfectly.

I was confused if to use rotation matrices or quats.
I have never used quaternions. Lets see how it works out.

Edit… Did you replace the FRotator replication by a custom quat replication?

4

You can send FQuat over the network :slight_smile:



UFUNCTION(reliable, server, WithValidation)
void SERVER_SetGoalRotation(FQuat NewRot);

If you get a crash related to this though, make sure to set it to a local var before sending it into the Server function:

Answerhub

:slight_smile:

Rama