How to calculate the trajectory of bullet in Unity2D?

Question

I'm doing the 2D game with bullets moving in parabola, but before I shoot the projectile I want to be able to calculate its trajectory.

            float velocity = Mathf.Min(Mathf.Max(distance, 1), 2.5f);
        float cos = Mathf.Cos( (gameObject.transform.localEulerAngles.z + 90) * Mathf.Deg2Rad);
        float sin = Mathf.Sin( (gameObject.transform.localEulerAngles.z + 90) * Mathf.Deg2Rad);
        newGO.GetComponent<Rigidbody2D>().AddForce(velocity * new Vector3(cos, sin))

This code adds the rigidbody2d to my bullet (newGO). I try to count a point after 1 sec of flying using it:

Debug.Log(new Vector3(source.transform.position.x + velocity * 1 * cos, source.transform.position.y + velocity * sin * 1 + Physics2D.gravity.y * 0.5f * 1));

Unfortunately it doesn't return the correct result. What should I do? Thanks for help and sorry for my English.

"doesn't count correct" please explain what is incorrect about it. Say what you expect to get and show what you are actually getting. — Scott Chamberlain, May 13 '16 at 19:15
For example: bullet's x = 2.7, y = -1.14 after 1 sec, but my code returns (x,y)=(1.5, -4.9) — Pawelsar1, May 13 '16 at 19:20
Put information like that in your question by [editing it](http://stackoverflow.com/posts/37217689/edit) — Scott Chamberlain, May 13 '16 at 19:21
You're saying that you want to predict where will your projectile after a second? — ORParga, May 13 '16 at 19:23
@ScottChamberlain, "doesn't count correct" OP simply means in English "I get the wrong result". I wish I could speak a third language that well! — Fattie, May 13 '16 at 19:29
BTW @Pawelsar1 - that word in English is **calculate**. "I want to calculate it". Your English is great!! — Fattie, May 13 '16 at 19:38

score 2 · Accepted Answer · answered May 13 '16 at 20:50

I think being a projectile you should use Rigidbody2D.velocity to set the initial velocity of the projectile rather than Rigidbody2D.AddForce. (Although the documentation does not recommend)

This simple script predicts where the attached object will be in a time determined by the variable "timeLimit" and moves a "target" gameobject to that point.

public class Velocity : MonoBehaviour {

    public GameObject target;

    private float HoriInitialSpeed = 5;
    private float VertInitialSpeed = 5;
    private float timeLimit = 2;
    private float timeElapsed=0;

    void Start ()
    {
        float HoriPredict = HoriInitialSpeed * timeLimit;
        float VertiPredict = VertInitialSpeed* timeLimit + (0.5f * Physics2D.gravity.y * timeLimit * timeLimit);

        target.transform.Translate(HoriPredict, VertiPredict,0);
        GetComponent<Rigidbody2D>().velocity = new Vector2(HoriInitialSpeed, VertInitialSpeed);
    }

    void Update () {
        timeElapsed += Time.deltaTime;
        if(timeElapsed >= timeLimit)
        {
            //stop the bullet
            GetComponent<Rigidbody2D>().velocity = new Vector2(0, 0);
            GetComponent<Rigidbody2D>().gravityScale = 0;
        }
    }
}

Note: the bullet and the target must be in the same point inicially

@Joe Blow thnks master. --- Pawelsar1 I hope to play your game soon — ORParga, May 15 '16 at 13:16

How to calculate the trajectory of bullet in Unity2D?

1 Answers1