How can I launch a ball given an angle in degrees and a magnitude?

Question

I'm making a little bullet hell game for fun. Here is what is supposed to happen: I launch a big ball and it goes on for n seconds until it explodes into many smaller balls. These smaller balls are launched into different directions based on the angle intervals I want in the for loop. I was wondering how can I take a degree angle and a magnitude and turn it into a Vector2 so I can change the velocity of each.

So far I have t$$anonymous$$s code:

 void Explode()
     {
         Vector2 spawnLoc = rigidbody2d.position;
         Debug.Log("Exploded");
         for (int i = 0; i < 360; i += 45) //spawn 8 balls and launch in 45deg intervals
         {
             Vector2 direction = degToVec2(i);
             GameObject smallBall = Instantiate(ball, spawnLoc, Quaternion.identity);
             smallBall.GetComponent<Rigidbody2D>().velocity = direction;
         }
         Destroy(gameObject);
     }

and the function:

 Vector2 degToVec2(int degree)
     {
         float x = Mathf.Cos(degree);
         float y = Mathf.Sin(degree);
         Vector2 vector = (new Vector2(x,y).normalized)*speed;
         Debug.Log(vector);
         return vector;
     }

I almost got it right but its not exactly what I want because the angle of 1 or 2 balls launched goes above 360 degrees. I'm pretty sure its because of the way i'm trying to find x and y.

Answer 1

Best Answer

Answer by BastianUrbach · Nov 12, 2019 at 08:33 AM

Mathf.Sin and Mathf.Cos use radians, not degrees. You should multiply degree with Mathf.Deg2Rad. Also, the .normalized is unnecessary, vector already has a length of 1.

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Major_Lag · Nov 12, 2019 at 06:58 PM 0

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Silly me, for some reason using radians didn't even cross my mind. Thank you.

Answer 2

Answer by Captain_Pineapple · Nov 12, 2019 at 08:48 AM

Hey there,

in general your mistake is common one: you did not read the documentation ;) Mathf.Cos does not take degree but radians as input. so multiply by 3.141/180.0 and you are good to go.

a way to make your code a bit more smooth:

    void Explode(int count)
     {
         Vector2 spawnLoc = rigidbody2d.position;
         Debug.Log("Exploded into " + count + " parts");
         float angleInc = 6.282f / count;
         for (int i = 0; i < count; i++) 
         {
             Vector2 direction = new Vector2(Mathf.Cos(angleInc * i),Mathf.Sin(angleInc * i))*speed;
             GameObject smallBall = Instantiate(ball, spawnLoc, Quaternion.identity);
             smallBall.GetComponent<Rigidbody2D>().velocity = direction;
         }
         Destroy(gameObject);
     }

also you need to read into object pooling. Always instantiating and destroying objects will lead to a performance issue sooner or later.

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Major_Lag · Nov 12, 2019 at 07:00 PM 0

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Thank you for the responce. You are also right that my problem was I wasn't using radians. I like your code cleanup too, I will consider it.

How can I launch a ball given an angle in degrees and a magnitude?

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