recursion - sierpinskys triangle - HELP!!

hi!

i have to write a gui window, which draws sierpinskys triangle recursively, i have one main class:

package triangleMod;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Point;
 
import javax.swing.JFrame;

public class Main extends Frame{
   
    static Point a;
    static Point b;
    static Point c;
    static Triangle tryAngle;
    static JFrame frame;
   
 
    private static final long serialVersionUID = 1L;
 
    //frame setup taken from:
    //http://java.sun.com/docs/books/tutorial/uiswing/examples/components/FrameDemoProject/src/components/FrameDemo.java
    private static void createAndShowGUI() {
        //Create and set up the window.
        frame = new JFrame("Fractal: Sierpinski's Triangle");
        a = new Point(0, 443);
        b = new Point(512, 443);
        c = new Point(256, 0);
        tryAngle = new Triangle(a, b, c);
       
        tryAngle.setPreferredSize(new Dimension(514, 446));
        //frame.add(tryAngle);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        frame.getContentPane().add(tryAngle);
 
        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }
 
    public static void main(String[] args) {
           //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

AND MORE IMPORTANT: the triangle class with the recursion

package triangleMod;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Point;
 
class Triangle extends Component{
 
    private static final long serialVersionUID = 1L;
 
    //A, B, C initial triangle-points, assigned in the constructor
    private Point A, B, C;
    //points for the 3 new inner triangles in the current recursive step
    private Point A1, B1, C1, A2, B2, C2, A3, B3, C3;
 
    public Triangle(Point a, Point b, Point c){
        this.A = a;
        this.B = b;
        this.C = c;
        }
   
    //helper var for recursion termination
    int i= 300;
   
    //draws fractal
    public void drawFractal(Graphics g, Point a, Point b, Point c){
       
        /**
         * draw outer triangle
         **/
       
        //AB
        g.drawLine(a.x, a.y, b.x, b.y);
        //AC
        g.drawLine(a.x, a.y, c.x, c.y);
        //BC
        g.drawLine(b.x, b.y, c.x, c.y);
       
        /**
         * Points of the 3 new triangles get assigned
         **/
       
        //lower left triangle coordinates
        A1 = new Point(A.x, A.y);
        B1 = new Point(c.x, b.y);
        C1 = new Point((a.x+c.x)/2, (c.y+a.y)/2);
       
        //lower right triangle coordinates
        A2 = new Point(c.x, b.y);
        B2 = new Point(B.x, B.y);
        C2 = new Point((c.x+b.x)/2, (c.y+a.y)/2);
       
        //upper triangle coordinates
        A3 =  new Point((a.x+c.x)/2, (c.y+a.y)/2);
        B3 = new Point((c.x+b.x)/2, (c.y+a.y)/2);
        C3 = new Point(C.x, C.y);
       
        /**
         * draw inner reversed triangle
         **/
       
        //AB
        g.drawLine(A3.x, A3.y, B3.x, B3.y);
        //AC
        g.drawLine(A3.x, A3.y, A2.x, A2.y);
        //BC
        g.drawLine(B3.x, B3.y, A2.x, A2.y);
       
        /**
         * rekusive method calls for the three new triangles
         **/
       
    //termination condition not set correctly, helper var i used for testing
        while (i-->0) {           
           
            drawFractal(g, A1, B1, C1);
            //drawFractal(g, A2, B2, C2);
            //drawFractal(g, A3, B3, C3);
           
        }
    }
 
    public void paint(Graphics g){
        drawFractal(g, A, B, C);
    }
}

THE PROBLEM:

as you see, in the whle loop i commented two of the recursive calls out, if I just have one of the 3 calls (no matter which one of the three), it works, the triangles in that direction are drawn. but if I have two or three of the recursive call, it does not work, it's not drawing the triangles i want. the three recursive calls seem to affect each other in a way i don't want.

i just don't get each of the recursive drawing just the triangles they do draw, when i just have the one recursive call in the while loop. i thought it should work, as i have separated, always newly defined points for A1, B1, C1 and so on...

maybe i am misunderstanding how the java stack recursion works, can anyone maybe test my code and give any help??

would really be cool, thanks a lot

btw: i know that the condition in the while loop is not the right recirsive base condition, but i didn't think about the right one yet and just used it like it is there for testing, i want to fix that if my method principally works correct

Just another cross poster. And an ambitious one, at that.
http://www.java-forums.org/threads-synchronization/14036-recursion-sierpinskys-triangle-help.html
http://forums.sun.com/thread.jspa?threadID=5353545
http://forums.java.net/jive/thread.jspa?messageID=320623
http://www.daniweb.com/forums/post752824.html

@db: what's your/the problem with that?

sorry, i didn't know, that it's not ok, to post on several forums! i thought posting in different categories in one forum is not ok, but why not in different forums??

i do not mean to spam or something, i am just looking for help!!

are there the same people watching all java-forums anyway?? in this case, i can of course just post in one forum.

i do not understand, why using different forums parallel is not liked! maybe someone can explain that to me! and besides, i'd still be happy for just some help with my problem..

Hi Rob and welcome to Javaranch,

As Darryl alludes to, please BeForthrightWhenCrossPostingToOtherSites

Onto your question...

Here's my hint to help you track this down. Output the variables everytime the recursive loop is called, can you spot what's happening?

I added some print-statements as suggested, here's the changed class:

package triangleMod;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Point;
 
class Triangle extends Component{
 
private static final long serialVersionUID = 1L;
 
//A, B, C initial triangle-points, assigned in the constructor
private Point A, B, C;
//points for the 3 new inner triangles in the current recursive step
private Point A1, B1, C1, A2, B2, C2, A3, B3, C3;

//debug helpers
private String str1 = "recursive Call1", str2 = "recursive Call2", str3 = "recursive Call3";
 
public Triangle(Point a, Point b, Point c){
this.A = a; 
this.B = b; 
this.C = c;
}

//helper var for recursion termination
int i= 300;

//draws fractal
public void drawFractal(Graphics g, Point a, Point b, Point c, String debugStr){

System.out.println(debugStr + ": " + "a.x: " + a.x +  ", " + "b.x: " + b.x + ", " + "c.x: " + c.x);
System.out.println(debugStr + ": "  + "a.y: " + a.y + ", " + "b.y: " + b.y + ", " + "c.y: " + c.y);
System.out.println();

/**
 * draw outer triangle
 **/

//AB
g.drawLine(a.x, a.y, b.x, b.y);
//AC
g.drawLine(a.x, a.y, c.x, c.y);
//BC
g.drawLine(b.x, b.y, c.x, c.y);

/** 
 * Points of the 3 new triangles get assigned
 **/

//lower left triangle coordinates
A1 = new Point(A.x, A.y);
B1 = new Point(c.x, b.y);
C1 = new Point((a.x+c.x)/2, (c.y+a.y)/2);

//lower right triangle coordinates
A2 = new Point(c.x, b.y);
B2 = new Point(B.x, B.y);
C2 = new Point((c.x+b.x)/2, (c.y+a.y)/2);

//upper triangle coordinates
A3 =  new Point((a.x+c.x)/2, (c.y+a.y)/2);
B3 = new Point((c.x+b.x)/2, (c.y+a.y)/2);
C3 = new Point(C.x, C.y);

/** 
 * draw inner reversed triangle
 **/

//AB
g.drawLine(A3.x, A3.y, B3.x, B3.y);
//AC
g.drawLine(A3.x, A3.y, A2.x, A2.y);
//BC
g.drawLine(B3.x, B3.y, A2.x, A2.y);

/**
 * rekusive method calls for the three new triangles
 **/

//termination condition not set correctly, helper var i used for testing
while (i-->0) {

drawFractal(g, A1, B1, C1, str1);
drawFractal(g, A2, B2, C2, str2);
drawFractal(g, A3, B3, C3, str3);

}
}
 
public void paint(Graphics g){
drawFractal(g, A, B, C, "");
}
}

the prints start with:

then the following print comes very often with the same values:

and then i get alternating prints for the recursive calls 2 and 3 with changing values like:

recursive Call2: a.x: 0, b.x: 512, c.x: 0
recursive Call2: a.y: 443, b.y: 443, c.y: 442
 
recursive Call3: a.x: 0, b.x: 256, c.x: 256
recursive Call3: a.y: 442, b.y: 442, c.y: 0
 
recursive Call2: a.x: 256, b.x: 512, c.x: 256
recursive Call2: a.y: 442, b.y: 443, c.y: 221
 
recursive Call3: a.x: 256, b.x: 384, c.x: 256
recursive Call3: a.y: 331, b.y: 331, c.y: 0
 
recursive Call2: a.x: 256, b.x: 512, c.x: 320
recursive Call2: a.y: 331, b.y: 443, c.y: 165
 
recursive Call3: a.x: 288, b.x: 416, c.x: 256
recursive Call3: a.y: 248, b.y: 248, c.y: 0
 
recursive Call2: a.x: 256, b.x: 512, c.x: 336
recursive Call2: a.y: 248, b.y: 443, c.y: 124
 
recursive Call3: a.x: 296, b.x: 424, c.x: 256
recursive Call3: a.y: 186, b.y: 186, c.y: 0
 
recursive Call2: a.x: 256, b.x: 512, c.x: 340
recursive Call2: a.y: 186, b.y: 443, c.y: 93
 
recursive Call3: a.x: 298, b.x: 426, c.x: 256
recursive Call3: a.y: 139, b.y: 139, c.y: 0
 
recursive Call2: a.x: 256, b.x: 512, c.x: 341
recursive Call2: a.y: 139, b.y: 443, c.y: 69
...

I am now even more confused, about this order in which the recursive calls happen and have no clue about what and where i coded wrong...

OK, this is a good step forward!

Now think about:

1.) The _scope_ of the variables that you have declared
1.b) When you change their value
1.c) What you chagne that value to

The print outs that you now have will help you see this.

E.g. Are the variables going to get overridden each time the recursive call is made? Or are they Kept intact? Do they need to be reset?

If there is too much "noise" start by commenting out 2 of the variables so you're only dealing with one point of the triangle, you should see a pattern emerge...

the prints are still hard to interpret for me! i don't get, why recursive call1 is executed so often before then call2 and call3 are coming alternately...

the scope of my A1, B1, C1 is class-wide, as I declared them as fields.. but as I asign new Point objects to them in every execution of the method, thats probably not necessarry.

the mentioned declarations of new points to the labels A1, A2 ,A3 are the only places I change values or not? thats what I want, but i am not sure, if i'm right here..! I thought, that if I just make new points in every call, with adjusting the parameter points to points for the next 3 smaller triangles, i can just call the method again 3 times with my new points and in that recursive call new points are created for the next 3 triangles...

I now tried to define my points A1, B1, C1... within the method, it actually does change the gui pic and the print methods (but not correctly again), which i don't understand, because, I define new points, whenever the method is calles, why does it matter, if I declare the labels inside or outside the method, because, if I assign new points to the labels anyway, the scope should not matter anymore (obviously it does!)

my main lack of understanding is, why a single recursive call in the while loop works correctly for the triangles it has to draw, but calling all 3 makes crap for all of them...

huh, hard to keep overview all the relations here...