Physics Projectiles, Coroutines and Object Pooling (Unity)

z4gon
z4gon

Using Corotuines and Object Pools to instantiate projectiles, and Ribidbodies for simple physics.

References

Table of Content

Projectile: Bullet

  • For now, a simple component that has a Collider and a Rigidbody.
  • The Rigidbody will not be kinematic, to be able to use Velocity. And will ignore gravity, to follow a straight line.
1public float speed
2{
3    get { return rigidBody.velocity.z; }
4    set { rigidBody.AddForce(transform.forward * value, ForceMode.VelocityChange); }
5}
6private Rigidbody rigidBody;
7
8private void Awake()
9{
10    rigidBody = GetComponent<Rigidbody>();
11}

ObjectPool: Gun

  • This component will use the ObjectPool to store the Bullet game objects.
  • It will also define a Coroutine to periodically fire the gun, and shoot projectiles.

Properties

1public Bullet bulletPrefab;
2public float bulletsPerSecond;
3public float bulletSpeed;
4public int defaultBulletsPoolCapacity = 10;
5public int maxBulletsPoolSize = 20;
6private ObjectPool<Bullet> bulletsPool;
7private Coroutine shootCoroutine;

Initialize Object Pool

1void Awake()
2{
3    bulletsPool = new ObjectPool<Bullet>(
4        createFunc: CreatePooledBullet,
5        actionOnGet: OnGetBulletFromPool,
6        actionOnRelease: OnReleaseBulletToPool,
7        actionOnDestroy: OnDestroyBulletFromPool,
8        collectionCheck: true,
9        defaultCapacity: defaultBulletsPoolCapacity,
10        maxSize: maxBulletsPoolSize
11    );
12}

Object Pool Event Handlers

1private Bullet CreatePooledBullet() => Object.Instantiate(bulletPrefab, transform.position, transform.rotation);
2private void OnGetBulletFromPool(Bullet bullet) => bullet.gameObject.SetActive(true);
3private void OnReleaseBulletToPool(Bullet bullet) => bullet.gameObject.SetActive(false);
4void OnDestroyBulletFromPool(Bullet bullet) => Destroy(bullet.gameObject);

Shoot Projectiles

1public void StartShooting()
2{
3    shootCoroutine = StartCoroutine(Shoot());
4}
5
6public void StopShooting() => StopCoroutine(shootCoroutine);
7
8private IEnumerator Shoot()
9{
10    while (true)
11    {
12        var bullet = bulletsPool.Get();
13
14        if (bullet != null)
15        {
16            bullet.transform.position = transform.position;
17            bullet.transform.rotation = transform.rotation;
18            bullet.speed = bulletSpeed;
19        }
20
21        yield return new WaitForSeconds(1.0f / bulletsPerSecond);
22    }
23}

Player

  • The Player game object will react to player input, and shoot projectiles.
1public List<Gun> guns = new List<Gun>();
2
3public void OnShootAction(InputAction.CallbackContext context)
4{
5    if (context.performed)
6        StartShooting();
7    else if (context.canceled)
8        StopShooting();
9}
10
11private void StartShooting()
12{
13    foreach (var gun in guns)
14        gun.StartShooting();
15}
16
17private void StopShooting()
18{
19    foreach (var gun in guns)
20        gun.StopShooting();
21}

All the Pieces Together

Picture

Correcting Projectile Trajectory

  • Given the perspective of the camera, projectiles that are aligned to the direction of the player do not follow a straight line in the viewport.
  • This is a problem since the player won't be able to aim for enemies in the top left and right corners.

Picture

  • Using a Raycast again, to get the corresponding point at the top edge, we can make the Player to LookAt it.
  • This effectively makes the aiming dynamic, and keeps a straight like of projectiles in the viewport.
1public void OnPointerPosition(InputAction.CallbackContext context)
2{
3    ...
4
5    // look at
6    point = new Vector2(point.x, Screen.height);
7    ray = mainCamera.ScreenPointToRay(point);
8    if (boundaries.plane.Raycast(ray, out distance))
9    {
10        transform.LookAt(ray.GetPoint(distance), Vector3.up);
11    }
12}

Picture