Solving a geometric problem.

[Chris Patuzzo]

Hi there, I'm new to these forums.

I was hoping to get some help with writing a method to solve a geometric problem in Java.

The problem goes something like this:

A tank stands in a random location of a field surrounded by a fence. It fires a projectile at a random bearing. Find where it hits the fence.

We already know these values:

fieldWidth
fieldHeight
tankX
tankY
bearing

I hoped the structure could be something like this:

class CoOrdinate {
  private double x;
  private double y;

  public coOrdinate(double x, double y) {
    this.x = x;
    this.y = y;
  }

  public double getX() {
    return x;
  }

  public double getY() {
    return y;
  }
}

class Projectile {
  private double fieldWidth = 500;
  private double fieldHeight = 1000;
  private double tankLocation = new CoOrdinate(50, 810);
  private double bearing = 165; //Between 0 and 359
  
  public CoOrdinate getHitCoOrdinate() {
    //Find the co-ordinate it hits at.
    return hitCoOrdinate;
  }
}

I'm not so good at maths or geometry so I was hoping someone could help me write the method to solve this problem.

Thanks a lot for your time.

[WingedPanther]

Are you familiar with trigonometry? Your answer to that will determine how much detail I go into.

[Chris Patuzzo]

Yes, I've studied maths and further maths at A level. I'm familiar with it, but I may be a little rusty.

[Chris Patuzzo]

I had a think and I thought that a simpler way of thinking of the problem is in the scenario of a pool table where you're trying to find where it hits the side on the first bounce (assuming there's no pockets and the balls has a radius of 1).

[WingedPanther]

If you convert your angle into radians, and take the tangent, then you're looking for the intersection of the line: y - posY = tan(angle)*(x-posX) with the walls. You should have an intersection with two walls, the correct wall will be determined by the angle (firing up/down or left/right)