Build a Complete 3D Unity Game

# CHAPTER 20

Build a Complete 3D Unity Game #

1. Introduction #

2. Project Requirements #

• Environment: A walled 3D arena with baked lighting.

• Player: A CharacterController that moves via keyboard/joystick, with a camera follow script.

• Enemy AI: Zombies that spawn dynamically and use the NavMesh to chase the player.

• Combat/Interaction: Collecting glowing orbs to increase score, while avoiding enemies.

• UI: A Canvas displaying current score, health, and a "Game Over" screen.

• Game Flow: A Main Menu scene that transitions into the gameplay scene.

3. Step 1: The Environment and Lighting #

1. 1. The Arena: Create a large Plane for the floor and four Cubes for the walls. Create a Material (dark gray) and apply it to the floor.

1. 2. Navigation: Select the floor and walls, mark them as Static, and go to Window -> AI -> Navigation to Bake the NavMesh (ensure the blue grid appears).

1. 3. Lighting: Go to Window -> Rendering -> Lighting. Click Generate Lighting to bake the shadows of the walls onto the floor, saving performance.

4. Step 2: The Player Controller #

1. 1. The Avatar: Create a Capsule. Name it "Player". Tag it as "Player" in the Inspector. Add a CharacterController component.

1. 2. The Script: Create PlayerMovement.cs.

• Read Input.GetAxis for Horizontal and Vertical.

• Use Vector3 direction = new Vector3(h, 0, v).normalized;

• Apply gravity: velocity.y += -9.81f * Time.deltaTime;

• Move: controller.Move((direction * speed + velocity) * Time.deltaTime);

1. 3. The Camera: Attach a CameraFollow script to the Main Camera. Give it an offset of (0, 8, -6) and make it smoothly Lerp to the Player's position in LateUpdate().

5. Step 3: Enemy AI #

1. 1. The Zombie: Create a red Cylinder. Add a NavMeshAgent component. Set its speed to a value slightly slower than the player.

1. 2. The Script: Create EnemyAI.cs.

• In Start(), find the player: player = GameObject.FindGameObjectWithTag("Player").transform;

• In Update(), set the destination: agent.SetDestination(player.position);

1. 3. Make the Zombie a Prefab by dragging it into the Project window. Delete it from the scene.

6. Step 4: Game Manager and Spawning #

1. 1. The Manager: Create an Empty GameObject named GameManager.

1. 2. The Script: Create GameManager.cs.

• Hold public int score = 0; and a reference to the TextMeshProUGUI score text.

• Write a Coroutine (IEnumerator) to spawn enemies.

IEnumerator SpawnEnemies()
{
    while (true) // Infinite loop
    {
        yield return new WaitForSeconds(3.0f); // Wait 3 seconds
        // Pick a random location on the map
        Vector3 randomSpawn = new Vector3(Random.Range(-10, 10), 0, Random.Range(-10, 10));
        Instantiate(enemyPrefab, randomSpawn, Quaternion.identity);
    }
}

7. Step 5: Collectibles and UI #

1. 1. The Orb: Create a glowing Sphere. Set its Collider to Is Trigger. Tag it as "Coin".

1. 2. The Script: Create OrbPickup.cs.

• On OnTriggerEnter, check if the other object is the "Player".

• If true, call FindObjectOfType<GameManager>().AddScore(10);

• AudioSource.PlayClipAtPoint(pickupSound, transform.position);

• Destroy(gameObject);

1. 3. The UI: Create a Canvas. Add a TextMeshPro object anchored to the Top-Right for the Score. Add a full-screen Panel (hidden by default) for the Game Over screen.

8. Step 6: Game Over State #

1. 1. Open PlayerMovement.cs.

1. 2. Add an OnCollisionEnter method.

1. 3. If the player collides with an object tagged "Enemy":

• Call the GameManager to show the Game Over UI Panel.

• Stop the game: Time.timeScale = 0f;

1. 4. The Game Over panel should have a Button that calls SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex); to restart the game. (Remember to set Time.timeScale = 1f; in Start()).

9. Step 7: Publishing (The Build) #

1. 1. Create a MainMenu scene with a "Play" button.

1. 2. Open File -> Build Settings.

1. 3. Drag MainMenu (Index 0) and GameArena (Index 1) into the Scenes in Build list.

1. 4. Click Build and Run.

1. 5. The standalone .exe will launch. You can now click play, run around the arena, collect glowing orbs, and flee from the ever-increasing horde of pathfinding zombies.

10. Your Journey Continues #

Unity is an incredibly deep engine. From here, the path is yours. You can explore the Shader Graph to create stunning visual materials without writing code. You can learn Cinemachine for AAA camera cutscenes. You can dive into Netcode to build the next hit multiplayer shooter.

The most important thing you can do now is start a new project. Do not follow a tutorial. Try to build a simple game (like Pong or Flappy Bird) entirely from your own memory. You will get stuck. You will read the Unity Documentation. You will fix the bugs. That is how you become a professional Game Developer.

Course Complete.