Drawing a Fractal Pattern composed of Circles Using Java

Question

I've been working on this project for last week and can't figure out how to fix it. I feel like I'm so close but can't spot my error! My assignment calls for me to draw circles along an imaginary line using the Java Graphics class. Draw a circle in the center with a radius of n. Then draw two circles with radius of n/2 whose endpoints intersect with the left and right arc of the circle.

I have been able to draw the 2nd step of two circles to the right and left of the first circle. However, my program is supposed to then draw four circles of the same size recursively. One circle to both the right and left side of the left circle AND one circle to both the right and left side of the right circle. Something is suspect with my code.

Any help would be greatly appreciated.

 package fractalcircles;

 import java.awt.*;
 import javax.swing.*;

 public class FractalCircles {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) 
{   //create a MyCanvas object
    MyCanvas canvas1 = new MyCanvas();

    //set up a JFrame to hold the canvas
    JFrame frame = new JFrame();
    frame.setTitle("FractalCircles.java");
    frame.setSize(500,500);
    frame.setLocation(100,100);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //add the canvas to the frame as a content panel
    frame.getContentPane().add(canvas1);
    frame.setVisible(true);
}//end main
 }//end class

 class MyCanvas extends Canvas
 {
public MyCanvas()
{} //end MyCanvas() constructor

//this method will draw the initial circle and invisible line
public void paint (Graphics graphics)
{
    int x1,x2,y1,y2; //future x and y coordinates
    int radius=125; //radius of first circle
    int xMid=250, yMid=250; //center point (x,y) of circle

    //draw invisible line
    graphics.drawLine(0,250,500,250);

    //draw first circle
    graphics.drawOval(xMid-radius,yMid-radius,radius*2,radius*2);


    //run fractal algorithm to draw 2 circles to the left and right
   drawCircles(graphics, xMid, yMid, radius);

}

void drawCircles (Graphics graphics, int xMid, int yMid, int radius)
{
    //used to position left and right circles
    int x1 = xMid-radius-(radius/2);
    int y1 = yMid-(radius/2);
    int x2 = xMid+radius-(radius/2);
    int y2= yMid-(radius/2);

    if (radius > 5)
    {
         //draw circle to the left
    graphics.drawOval(x1, y1, (radius/2)*2, (radius/2)*2);

    //draw circle to the right
    graphics.drawOval(x2, y2, (radius/2)*2, (radius/2)*2);
    }

    drawCircles (graphics, xMid, yMid, radius/2);  
}

Answer 1

Some adapted version using recursion... Draw the circle, then draw its 2 children by calling the same function again.

void drawCircles(Graphics graphics, int xMid, int yMid, int radius) {
    // end recursion
    if(radius < 5)
        return;

    // Draw circle
    graphics.drawOval(xMid - radius, yMid - radius, radius * 2, radius * 2);

    // start recursion
    //left
    drawCircles(graphics, xMid-radius, yMid, radius / 2);
    //right
    drawCircles(graphics, xMid+radius, yMid, radius / 2);
}

Answer 2

It looks to be like you only have one drawCircles call inside your drawCircles function. This can't be right because each time you draw a circle you need to call the recursive function twice. I see that you are drawing two circles, but that is actually backwards.

To get this to work, you need to draw one circle, and call the recursive function twice.

Here is what you need to change:

• Make it so that the drawCircle draws one circle, centered on the coordinates
• in drawCircle, call drawCircle twice, once with the left circle coords, once with the right

That should do it.

Answer 3

You are only drawing 1 circle from each side of the big circle. You need to change the code. I only write a short fix but don't tested. Good luck

void drawCircles (Graphics graphics, int xMid, int yMid, int radius)
{
//used to position left and right circles
int x1 = xMid-radius-(radius/2);
int x2 = xMid+radius-(radius/2);
int x3 = xMid+radius+(radius/2);
int x4 = xMid-radius+(radius/2);
int y = yMid-(radius/2);


if (radius > 5)
{
     //draw 4 circles
   graphics.drawOval(x1, y, (radius/2)*2, (radius/2)*2);
   graphics.drawOval(x2, y, (radius/2)*2, (radius/2)*2);
   graphics.drawOval(x3, y, (radius/2)*2, (radius/2)*2);
   graphics.drawOval(x4, y, (radius/2)*2, (radius/2)*2);
}

//left
drawCircles(graphics, xMid-radius, yMid, radius / 2);
//right
drawCircles(graphics, xMid+radius, yMid, radius / 2);  
}