CODEWITHSUNDEEP
javaandroidprojectile
Meowxiik
Meowxiik

Reputation: 13

Calculating bullet speed

I need to calculate X and Y speed for bullet (bullet will move every "update" by these), so i have following

public int[] getXandYSpeed(int pointOfOriginX, int pointOfOriginY, int aimToX, int aimToY){
  int[] coords = new int[2];
  aimToX = aimToX - pointOfOriginX;
  aimToY = aimToY - pointOfOriginY;

  while((aimToX + aimToY) > 5){
    aimToX = aimToX/2;
    aimToY = aimToY/2;
  }

  coords[0] = aimToX;
  coords[1] = aimToY;
  return coords;

But, this is not really accuare and bullet have like random speed(if final in final loop is aimToX plus AimToY equals 6 so (each is 3) so final speed will be x=1 and y=1, and if final loop equals four than it will end like x=2 and y=2, and thats making difference)

So, question is, how to make it better?

Upvotes: 1

Views: 200

Answers (1)

Dave
Dave

Reputation: 888

if you want the bullet to travel at a constant speed at any angle, you really want something more like this. Also the comments about using double from @JSlain are spot on, they will be much more accurate even if you have to round out the values when you draw/render the bullet

public double[] getSpeed(int sx, int sy, int ex, int ey)
{
    double dx = ex - sx;
    double dy = ey - sy;

    double theta = Math.atan2(dy, dx); //get the angle your bullet will travel

    int bulletSpeed = 5; //how fast your bullet can go.

    double[] speeds = new double[2];

    speeds[0] = Math.cos(theta) * bulletSpeed;
    speeds[1] = Math.sin(theta) * bulletSpeed;

    return speeds;
}

Upvotes: 1

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