Rotate Actor Around Player With Rotation

December 02, 2017

UE4 Version: 4.18.3

Github Link: https://github.com/Harrison1/unrealcpp/tree/master/RotateActorAroundWithRotation

For this tutorial we are using the standard first person C++ template with starter content. If you don't know how to add a new actor class to your project, please visit the Add C++ Actor Class post.

In this tutorial we will be rotating an actor around a set point in the game world with it always facing the origin. Start by creating a new C++ actor class and call it RotateActorAroundWithRotation. In the header file we'll create two float variables and two FVector variables and make them EditAnywhere so we can edit them later on inside the editor. Below is the final header file code.

RotateActorAroundWithRotation.cpp

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "RotateActorAroundWithRotation.generated.h"

UCLASS()
class UNREALCPP_API ARotateActorAroundWithRotation : public AActor
{
	GENERATED_BODY()
	
public:	
	// Sets default values for this actor's properties
	ARotateActorAroundWithRotation();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:	
	// Called every frame
	virtual void Tick(float DeltaTime) override;

	// declare our float variables
	UPROPERTY(EditAnywhere, Category = Movement)
	float AngleAxis;

	UPROPERTY(EditAnywhere, Category = Movement)
	FVector Dimensions;

	UPROPERTY(EditAnywhere, Category = Movement)
	FVector AxisVector;

	UPROPERTY(EditAnywhere, Category = Movement)
	float Multiplier;
	
};

In the .cpp let's start by setting some default values for our actor. I took some time playing around with the variables so I think my default should suffice to get us going, but feel free to change them to whatever you want.

default values

// Sets default values
ARotateActorAroundWithRotation::ARotateActorAroundWithRotation()
{
 	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;

	Dimensions = FVector (300, 0, 0);
	AxisVector = FVector (0, 0, 1);
	Multiplier = 50.f;

}

All of our logic is going to go in the Tick function. Every frame we want to set our fixed location by setting our NewLocation to a fixed FVector variable. In your game you might want to connect the NewLocation to another actor or at least make it EditAnywhere in the editor, but for this tutorial let's just set it and move on. Alternatively, you can set NewLocation to the player location so the actor always rotates around the player.

Next, we want to add to our AngleAxis variable which will indicate the degree around the point the actor should move to. We add DeltaTime multiplied by our Multiplier for smooth movement. If AngleAxis is greater than or equal to 360 we re-set the AngleAxis to 0.

Next, we'll set RotateValue by using the RotateAngleAxis functions from our Dimensions vector. This will return the amount of units needed to move the actor to its next location. Add RotateValue's X, Y, and Z values to our NewLocation variable accordingly. Next, we'll configure our new ration by makeing a FRotator value and setting the value to FRotator(0, AngleAxis, 0). Then we'll make a FQuat using the NewRotation value.

Finally, set the actor's location and rotation with SetActorLocationAndRotation to our NewLocation.

Tick function

// Called every frame
void ARotateActorAroundWithRotation::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	
	FVector NewLocation = FVector (0,0,400);

	// rotate around player
	// FVector NewLocation = GetWorld()->GetFirstPlayerController()->GetPawn()->GetActorLocation();
	
	AngleAxis += DeltaTime * Multiplier;

	if(AngleAxis >= 360.0f) 
	{
		AngleAxis = 0;
	}

	FVector RotateValue = Dimensions.RotateAngleAxis(AngleAxis, AxisVector);

	NewLocation.X += RotateValue.X;
	NewLocation.Y += RotateValue.Y;
	NewLocation.Z += RotateValue.Z;

	FRotator NewRotation = FRotator(0, AngleAxis, 0);
	
	FQuat QuatRotation = FQuat(NewRotation);

	SetActorLocationAndRotation(NewLocation, QuatRotation, false, 0, ETeleportType::None);

}

Compile the code. Drag and drop the new actor into the game world. Add a static mesh component to the actor. Now when you push play the actor will find and cirlce around the given vector point and always point towards the origin. Below is the final .cpp file.

RotateActorAroundWithRotation.cpp

#include "RotateActorAroundWithRotation.h"


// Sets default values
ARotateActorAroundWithRotation::ARotateActorAroundWithRotation()
{
 	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;

	Dimensions = FVector (300, 0, 0);
	AxisVector = FVector (0, 0, 1);
	Multiplier = 50.f;

}

// Called when the game starts or when spawned
void ARotateActorAroundWithRotation::BeginPlay()
{
	Super::BeginPlay();
	
}

// Called every frame
void ARotateActorAroundWithRotation::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	
	FVector NewLocation = FVector (0,0,400);

	// rotate around player
	// FVector NewLocation = GetWorld()->GetFirstPlayerController()->GetPawn()->GetActorLocation();
	
	AngleAxis += DeltaTime * Multiplier;

	if(AngleAxis >= 360.0f) 
	{
		AngleAxis = 0;
	}

	FVector RotateValue = Dimensions.RotateAngleAxis(AngleAxis, AxisVector);

	NewLocation.X += RotateValue.X;
	NewLocation.Y += RotateValue.Y;
	NewLocation.Z += RotateValue.Z;

	FRotator NewRotation = FRotator(0, AngleAxis, 0);
	
	FQuat QuatRotation = FQuat(NewRotation);

	SetActorLocationAndRotation(NewLocation, QuatRotation, false, 0, ETeleportType::None);

}

Author

Harrison McGuire

Harrison McGuire