Rotate Angle Axis

December 02, 2017

UE4 Version: 4.18.3

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

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'll learn how to use the RotateAngleAxis function. Start by creating a new C++ actor class and call it RotateAngleAxis. In the header file we'll create two float variables and two FVector variables and make them EditAnywhere so we can edit them later inside the editor. Below is the final header file code.

RotateAngleAxis.h

#pragma once

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

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

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
ARotatingAngleAxis::ARotatingAngleAxis()
{
 	// 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 inside the Tick function. For this example we are going to use a fixed vector point, so every frame we want to set our fixed location by setting our NewLocation to a fixed FVector.

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. We will print to the screen the RotateValue and AngleAxis variables to see the values in real time.

Finally, set the actor's location with SetActorLocation to our NewLocation. To learn more about the RotateAngleAxis function from the Unreal Engine 4 documentation you can click here.

Tick function

// Called every frame
void ARotatingAngleAxis::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);

	FVector NewLocation = FVector (0,0,800);

	AngleAxis += DeltaTime * Multiplier;

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

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

	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, FString::Printf(TEXT("RotateValue: %s"), *RotateValue.ToString()));	
	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Green, FString::Printf(TEXT("AngleAxis: %f"), AngleAxis));

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

	SetActorLocation(NewLocation, 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. Below is the final .cpp file.

RotatingAngleAxis.cpp

#include "RotatingAngleAxis.h"

// Sets default values
ARotatingAngleAxis::ARotatingAngleAxis()
{
 	// 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 ARotatingAngleAxis::BeginPlay()
{
	Super::BeginPlay();	
	
}

// Called every frame
void ARotatingAngleAxis::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);

	FVector NewLocation = FVector (0,0,800);

	AngleAxis += DeltaTime * Multiplier;

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


	FVector myCharacter = GetWorld()->GetFirstPlayerController()->GetPawn()->GetActorLocation();

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

	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, FString::Printf(TEXT("RotateValue: %s"), *RotateValue.ToString()));	
	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Green, FString::Printf(TEXT("AngleAxis: %f"), AngleAxis));

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

	SetActorLocation(NewLocation, false, 0, ETeleportType::None);
	
}

Author

Harrison McGuire

Harrison McGuire