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javasimulationhexagonal-tiles

Hexagonal Grid (Flat Top) Distance Calculation

I have been working on creating a hexagonal (flat top) grid for a simulation I am working on. I have attempted to work out the distance between the hexagons, from a specified target hexagon.

The solution I have works for most of the time, apart from every odd column from the target hexagon north of the target is shifted up by 1. I know that sounds confusing but I have attached an image to explain what I mean:

hexagonal game grid

As you guys can see, the bottom half of the grid below the target hexagon and every other column above the target Hexagon is correct. I cannot understand why :S

Here is an explanation of the Axial & Cube Co-ords.

http://www.redblobgames.com/grids/hexagons/#coordinates

Here is the code responsible for converting the Axial Co-ords to Cube Co-ords.

public void setQR(int theQ, int theR){

    this.q = theQ;
    this.r = theR;

    this.x = this.q;
    this.z = this.r - (this.q - (this.q&1)) /2;
    this.y = -(this.x + this.z);
}

And heres the code for working out distance.

FYI, the Hexagons are created from a CentrePoint (CPx, CPy).

    private double distance = 0;

public double workOutDistance(Hexagon hexagon, HexagonFood target){

    double targetX = target.getCPX();
    double targetY = target.getCPY();

    double hexagonX = hexagon.getCPX();
    double hexagonY = hexagon.getCPY();

    double deltaX = (targetX-hexagonX)*-1;
    double deltaY = (targetY-hexagonY)*-1;

    double deltaXRadius = (deltaX/(SimField.hexSize)/1.5);
    double deltaYApothem = (deltaY/(SimField.hexSize/1.155)/2);

    hexagon.setQR((int)deltaXRadius, (int)deltaYApothem);


    ArrayList<Integer> coords = new ArrayList<>();

    coords.add(
    Math.abs(hexagon.getX() - target.getX())
    );

    coords.add(
    Math.abs(hexagon.getZ() - target.getZ())
    );

    coords.add(
    Math.abs(hexagon.getY() - target.getY())
    );

    System.out.println(coords);
    distance = Collections.max(coords);

    return distance;
}

Can anyone please tell me why this is happening ? Would be greatly appreciated.

EDIT:

After changing Int to Double as suggested by Tim, I get this.

https://i.sstatic.net/javZb.png

**

SOLUTION

**

after experimenting with the answers given, This small tweak solves the problem.

changing this..

public void setQR(int theQ, int theR){

    this.q = theQ;
    this.r = theR;

    this.x = this.q;
    this.z = this.r - (this.q - (this.q&1)) /2;
    this.y = -(this.x + this.z);
}

to this..

public void setQR(int theQ, int theR){

    this.q = theQ;
    this.r = theR;

    this.x = this.q;
    if (this.r>0){
        this.z = this.r - (this.q - (this.q&1))/2;
    }
    else {
        this.z = this.r - (this.q + (this.q&1))/2;
    }
    this.y = -(this.x + this.z);
}
Solution

  • You're casting a double to an int when calling setQR(); are you sure that's doing what you expect? Doubles use floating point math, so the number you'd expect to be 2.0 might actually be 1.999999989, which would then be rounded down to 1 when cast to an int.

    I'm also skeptical of the line that reads this.z = this.r - (this.q - (this.q&1)) /2;. You're adding 1 when the number is odd, which seems to be the failure case you're experiencing; I'd make sure that line is doing what you're expecting, too.

    If you're not stepping through this with a debugger and examining the values, you're doing it wrong.