C++ Programming in Unreal Engine 5

# CHAPTER 6

C++ Programming in Unreal Engine 5 #

1. Introduction #

2. Learning Objectives #

• Understand the relationship between C++ and Blueprints (The Base Class concept).

• Create a new C++ Actor class in the UE5 editor.

• Understand the .h (Header) and .cpp (Source) file structure.

• Utilize the UPROPERTY and UFUNCTION macros to expose code to Blueprints.

• Write basic gameplay logic inside the Tick function.

3. The Blueprint-C++ Relationship #

• The Golden Rule: C++ handles the heavy logic and math (The Brains). Blueprints handle the visual setup, components, and art references (The Body).

• The Workflow: A programmer writes a C++ class called AWeapon. The designer creates a Blueprint child of AWeapon, assigns the 3D model of a shotgun, and sets the "Damage" variable to 50 in the editor.

4. Anatomy of an Unreal C++ Class #

1. 1. The Header File (.h): The "Table of Contents." This is where you declare your variables and functions.

1. 2. The Source File (.cpp): The "Implementation." This is where you write the actual logic (what the functions do).

5. Unreal Macros: UPROPERTY and UFUNCTION #

• UPROPERTY: Placed above a variable in the .h file.

• UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="Stats")

• *Result:* The variable can now be edited in the Details panel and used in Blueprint graphs.

• UFUNCTION: Placed above a function.

• UFUNCTION(BlueprintCallable, Category="Actions")

• *Result:* Designers can now call this C++ function as a visual node in Blueprints!

6. Code and Automation Examples #

#pragma once
#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "MyFloatingActor.generated.h"

UCLASS()
class MYGAME_API AMyFloatingActor : public AActor
{
    GENERATED_BODY()
    
public: 
    AMyFloatingActor(); // Constructor

    // Expose this variable to the UE5 Editor
    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="Float Settings")
    float FloatSpeed;

protected:
    virtual void BeginPlay() override;

public: 
    virtual void Tick(float DeltaTime) override;
};

Example: The Source Logic (.cpp)

#include "MyFloatingActor.h"

AMyFloatingActor::AMyFloatingActor()
{
    PrimaryActorTick.bCanEverTick = true; // Allow the Tick function to run
    FloatSpeed = 20.0f; // Default value
}

void AMyFloatingActor::BeginPlay()
{
    Super::BeginPlay();
}

void AMyFloatingActor::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);
    
    // Move the actor upwards every frame
    FVector NewLocation = GetActorLocation();
    NewLocation.Z += FloatSpeed * DeltaTime; 
    SetActorLocation(NewLocation);
}

7. Visual Learning: The C++ to Blueprint Pipeline #

[ C++ Header (.h) ] ---> Declares: UPROPERTY(EditAnywhere) float Health;
        |
     (Compiles)
        v
[ Unreal Editor ]   ---> 'Health' appears in the Details Panel!
        |
  (Designer Edits)
        v
[ C++ Source (.cpp) ] -> Uses the designer's new Health value in combat logic.

8. Best Practices #

• Use DeltaTime: If you move an object in the Tick() function by adding 1 unit of distance every frame, a player running the game at 120 FPS will move twice as fast as a player running at 60 FPS. Always multiply movements by DeltaTime (the time passed since the last frame) to ensure consistent speeds across all hardware.

9. Common Mistakes #

• Forgetting to Compile: If you change C++ code in Visual Studio/Rider and just press 'Play' in Unreal, nothing will happen. You must compile the code (using the Live Coding icon in UE5 or hitting Ctrl+Alt+F11) before the engine registers the changes.

10. Mini Project: Expose a Variable to the Editor #

1. 1. In the Content Browser, right-click -> New C++ Class. Select Actor. Name it ACubeSpinner.

1. 2. Open the .h file. Under public:, type:

1. 3. Save, go back to Unreal, and hit the "Compile" (Live Coding) button.

1. 4. Drag your new ACubeSpinner from the C++ Classes folder into the Viewport.

1. 5. Look at the Details Panel. You will see a new category called "Rotation" with your SpinSpeed variable ready to be edited!

11. Practice Exercises #

1. 1. Define the difference between the .h file and the .cpp file in Unreal Engine programming.

1. 2. Why is the UPROPERTY(EditAnywhere) macro considered a crucial bridge between Programmers and Level Designers?

12. MCQs with Answers #

13. Interview Questions #

• Q: Explain the ideal architectural relationship between C++ and Blueprints in a AAA game studio. Which system handles what tasks?

• Q: Walk me through the syntax and purpose of UPROPERTY(EditAnywhere, BlueprintReadWrite). What does each parameter inside the parenthesis actually do?

• Q: What is the purpose of GENERATED_BODY() at the top of an Unreal C++ class?

14. FAQs #

15. Summary #

16. Next Chapter Recommendation #