Rotate a Vector FRotator to FVector - to turn and look at character

Development Programming & Scripting C++
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1

I have an Actor that is a cube, and a thrid view character player that I control around.

I’m trying to convert an FRotator to a FVector so that I can turn the Actor to look towards the Character.

I get error at compilation time, it states that I can’t convert rotation to vector position, but I have seen other examples where people do this in Unreal Engine. I must be missing something, Is it some include ? that I did not add, I looked at the includes to see dependencies but I could not find anything.

Error Message:

**cannot convert argument 1 from 'FVector' to 'FRotator'or the operator cannot be called**

I also get:
 No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

I tried different modes.
For example the CCP of my Cube actor sort of NPC part that is suppose to look at the Character.

//Get the location of the character, works fine it gets the location on world of x,y,z of the character.
 FVector CharacterPosition3D = GetWorld()->GetFirstPlayerController()->GetPawn()>GetActorLocation();

//Get Actor Rotation of the cube actor.
FRotator Rotation = GetActorRotation();

//Convert FRotator to FVector, Rotate the Vector Position of the actor towards the character by rotating the vector. 

FVector NewVector = Rotation.RotateVector(CharacterPosition3D);

//Turn The actor towards the Character
SetActorRotation(NewVector);

I get cannot convert Rotation to Vector , operation not supported.

I also tried directly with:

FVector NewVector = GetActorRotation().RotateVector(CharacterPosition3D);

and I eliminated the Rotation variable. Still the same error.

Also did a test to make sure it’s not the components, and added manual values,

FVector SomeVariable = FRotator(30.f, 40.f, 0.f).RotateVector(FVector(20.f,  20.f,  20.f));

Same error, it cannot convert Frotator to FVector, I looked for includes to see if this .RotateVector is tied up to some include somewhere to some library header but I could not find anything.

2

Looks like that’s how it should work. Are you sure that’s the error that you’re getting, and that it goes to that line?

3

Error points to line with: SetActorRotation(NewVector);

It’s fine until here, it’s when it tries to put it in practice I guess, the newvector with it’s values it got from the conversion to rotate the vector.

I also tried to add SetActorRotation(NewVector, ETeleportType::None);
I added some includes
#include “Math/Rotator.h”
#include “Math/Quat.h”

But it does not work and I get the same errors.
These are the two errors that pop up in my message log, they point to the same line

**cannot convert argument 1 from 'FVector' to 'FRotator'or the operator cannot be called**

** No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called**

Edit:
I think I understand my mistake. I’m trying to rotate an FVector with a SetActorRotation, that is the problem, FVector NewVector is not an FRotator, and the conversion happens at FVector NewVector, it is distorted there as a vector, so I guess I have to find a way to set it in another way.

How do you set a rotated vector, if I use SetActorLocation it just teleports it to the player.

4

ah, right, I was concentrating on the Rotating the Vector part.

You want SetActorRotation(NewVector.Rotation());

5

Yeah but I don’t want to use the built in function Rotation()
I already have a working example with it that is functional.

The conversion function that works is this:
FVector NewVector = (Character - ActorLocationCube).Rotation();

I sort of want to elaborate on my own, Rotation() is not a C++ function, it’s part of the unreal system. Basicly the Rotation() function converts Fvector Location to Rotation, so Rotation points to location. Then I just set the rotation and add (NewVector) without anything.

Problem is that this function does the job of what I’m trying to do manually.

I feel like a gifter.

      FVector ActorLocation  = GetActorLocation();
      FVector Character = GetWorld()->GetFirstPlayerController()->GetPawn()->GetActorLocation();
      FRotator RotateValue = (Character - ActorLocation).Rotation();
      SetActorRotation(RotateValue)

Anyone who wants this, it works. The Cube will be rotated at you with it’s face towards when the game starts.

I want to do this without Rotation();
Or at least understand how Rotation(); works, what is inside of this function.
If you want to learn C++ I guess you will want to do that so you are not in the dark with what you use.

6

You do have access to the source code

FRotator FVector::ToOrientationRotator() const
{
	FRotator R;

	// Find yaw.
	R.Yaw = FMath::Atan2(Y,X) * (180.f / PI);

	// Find pitch.
	R.Pitch = FMath::Atan2(Z,FMath::Sqrt(X*X+Y*Y)) * (180.f / PI);

	// Find roll.
	R.Roll = 0;

#if ENABLE_NAN_DIAGNOSTIC || (DO_CHECK && !UE_BUILD_SHIPPING)
	if (R.ContainsNaN())
	{
		logOrEnsureNanError(TEXT("FVector::Rotation(): Rotator result %s contains NaN! Input FVector = %s"), *R.ToString(), *this->ToString());
		R = FRotator::ZeroRotator;
	}
#endif

	return R;
}
7

You sure it’s the Rotation() function ?

It says ToOrientationRotator()

Interesting anyway I will take a look at this function.

8

yeah they renamed it years ago, left the old one as a call to it

FRotator FVector::Rotation() const
{
	return ToOrientationRotator();
}

https://github.com/EpicGames/UnrealEngine/blob/release/Engine/Source/Runtime/Core/Private/Math/UnrealMath.cpp

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9

Thanks I will be looking at it to see what I can deduce from :sweat_smile: it

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