2D Array with Grid

Question

I have created a program using turtle graphics to draw different shapes. There is a discrete grid underneath, 5x5, on top of the 400px by 400px JFrame. It wraps around top/bottom and left/right in case the shapes go over.

What I now need to do is add a 2d array that creates a 400x400 array of 0s. If a turtle moves through any pixels (corresponding to a point in the 2d array), the 0 needs to be changed to a 1. What is the best way to go about this? We're eventually working up to the functionality of Conway's Game of Life.

Answer 1

In my view the best way to go about this would be to keep track of the turtle's position (X & Y), direction with double variables, and then use basic trigonometry to calculate the next 'pixel' that the the tutrtle hits. I assume you're going to be runnibg this code using a timer or loop, so it could look something like this:

//This code is somehwere in your program
class Turtle
{
     private double x;
     private double y;
     private double direction; //direction in radians
    public double getX() {
        return x;
    }
    public void setX(double x) {
        this.x = x;
    }
    public double getY() {
        return y;
    }
    public void setY(double y) {
        this.y = y;
    }
    public double getDirection() {
        return direction;
    }
    public void setDirection(double direction) {
        while(direction > Math.PI * 2)
        {
            direction -= Math.PI * 2;
        }
        while(direction < 0)
        {
            direction += Math.PI * 2;
        }
        this.direction = direction;
    }
}

private static final int GRID_WIDTH = 400;
private static final int GRID_HEIGHT = 400;


private Turtle myTurtle = new Turtle();
private boolean[][] grid = new boolean[GRID_WIDTH][GRID_HEIGHT];
JFrame myJFrame = new JFrame();
private Graphics gridImage = myJFrame.getGraphics();

private void initialise()
{
    for(int y = 0; y < GRID_HEIGHT; y++)
    {
        for(int x = 0; x < GRID_WIDTH; x++)
        {
            grid[x][y] = false;
        }
    }

    gridImage.setColor(Color.BLACK);
    gridImage.fillRect(0, 0, GRID_WIDTH, GRID_HEIGHT);
    gridImage.setColor(Color.white);
}

//This code would be inside the loop or timer callback function
private void myMainFunction()
{
    double newX, newY;
    double deltaX, deltaY;

    deltaX = Math.cos(myTurtle.getDirection());
    deltaY = Math.sin(myTurtle.getDirection());

    newX = myTurtle.getX() + deltaX;
    newY = myTurtle.getY() + deltaY;

    if(newX < 0)
    {
        newX += GRID_WIDTH; 
    }
    else if(newX > GRID_WIDTH)
    {
        newX -=  GRID_WIDTH;    
    }

    if(newY < 0)
    {
        newY += GRID_HEIGHT; 
    }
    else if(newY > GRID_HEIGHT)
    {
        newY -=  GRID_HEIGHT;   
    }

    grid[(int)Math.floor(newX)][(int)Math.floor(newY)] = true;

    gridImage.fillRect((int)Math.floor(newX), (int)Math.floor(newY), 1, 1);
    myJFrame.update(gridImage);

    myTurtle.setX(newX);
    myTurtle.setY(newY);
}