CODEWITHSUNDEEP
unity-game-engineprojectile
Alex
Alex

Reputation: 1262

Trajectory of projectile slightly off Unity2D

I have a simple cannon I am trying to program to shoot a projectile. I have 4 game objects:

My code for the cannon object is below:

public class cannon: MonoBehaviour
{ 
    public float power = 1.0f;
    public Transform projectile;

    void Update()
    {
        if (Input.GetButtonDown("Fire1"))
        {
            Transform bullet;
            Vector2 pos = transform.GetChild(0).position;
            bullet = Instantiate(projectile, pos, Quaternion.identity);
            Rigidbody2D bullet_rb = bullet.GetComponent<Rigidbody2D>();
            bullet_rb.AddForce(pos * power);
        }
    }
}

Everything seems to work okay, until I looked at the trajectory of the projectiles when the cannon is aimed directly along the x-axis. There is still a small y component to the applied force, which I didn't expect and do not desire.

Here's a gif:

enter image description here

What could be causing this behavior?

Upvotes: 1

Views: 278

Answers (1)

CosmicGiant
CosmicGiant

Reputation: 6441

The force you're adding is pos (times a scalar power)... The position of your cannon is above zero on the y axis, so that's why it launches with a y offset. I'm assuming it has an x offset too, just less noticeable, because the base (tank) is centered at x while it's above center in the y. Try moving the whole tank setup off away from the scene root; you'll probably see a huge spike in the force of the projectile, because of this error of using pos.

What you want is a vector representing a pure direction instead. One that is also normalized (magnitude of one). In this case, either right (forward in 2d) or up, from the perspective of the rotating tip or cannon.

Upvotes: 2

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