Computer Science Canada

Polygon Class
Author:  batman [ Fri Nov 03, 2006 6:05 pm ]
Post subject:  Polygon Class
Alright, so im trying to work on a polygon class but im having troubles with it. I know how to do a rectangle class, a circle class but im kinda confused about polygons. I have no clue how to do a polygon class. I ve done all ta i could. Can someone help me draw a polygon?????????
I think have to set the coordinates so the center is at 0,0 so some of te coordinates are negative. I need help fixing my code.


code:

import java.awt.*;


public class Polygon
{
    int x, y; // centre of object
    public int width;
    public int height;
    Color c;
    public Polygon (int initialX, int initialY, int initialHeight)
    {
        x = initialX;
        y = initialY;
        height = initialHeight;
        width = height / 2;
        c = Color.BLUE;
    }


    public Rect (int initialX, int initialY, int initialHeight, Color initialColor)
    {
        x = initialX;
        y = initialY;
        height = initialHeight;
        width = height / 2;
        c = initialColor;
    }


    public void setPosition (int newX, int newY)
    {
        x = newX;
        y = newY;
    }


    public void setHeight (int newHeight)
    {
        height = newHeight;
        width = height / 2;
    }

    public void draw (Graphics g)
    {
        int drawX = x - width / 2;
        int drawY = y - height / 2;

        g.setColor (c);
        g.fillPolygon (drawX, drawY, width, height);
    }
}


Author:  Booya [ Fri Nov 03, 2006 6:10 pm ]
Post subject: 
I think there is somethin wrong with ur code when you are trying to draw the polygon at the end. A polygon has six coordinates not 4. How u fix this im not sure because im newbe.
Author:  ericfourfour [ Sat Nov 04, 2006 1:10 am ]
Post subject: 
Actually, a polygon as more than 2 sides a hexagon has 6. Your polygon should be made up of triangles though. That way it will be easier to deal with collisions.
Author:  Dan [ Sun Nov 05, 2006 2:41 pm ]
Post subject: 
A polygon is any shape made up of at least 3 lines that conect to each other. Java has a bulit in polygon class that can show you how it is done.

The easyest way to make a polygon is to take a 2d array of x and y quardents and then draw line segnements between the points. Then join the last x and y to the first x and y to complet the shape.
Author:  Clayton [ Mon Nov 06, 2006 8:49 am ]
Post subject: 
ie, in Turing the code would look something like this:

Turing:

procedure Polygon (x,y : array 1 .. * of int, clr : int)
    for i : 1 .. upper (x) - 1
        Draw.Line (x(i),y(i), x(i + 1), y(i + 1), clr)
    end for
    Draw.Line (x(upper(x)),y(upper(y)),x(1),y(1),clr)
end Polygon
Author:  ericfourfour [ Mon Nov 06, 2006 4:54 pm ]
Post subject: 
Well, if you wanna save yourself a Draw.Line use this.

code:
type coord :
    record
        x, y : real
    end record
proc polygon (pos : array 0 .. * of coord, clr : int)
    for id1 : 0 .. upper (pos)
        var id2 := (id1 + 1) mod (upper (pos) + 1)
        Draw.Line (round (pos (id1).x), round (pos (id1).y), round (pos (id2).x), round (pos (id2).y), clr)
    end for
end polygon


To get the second id just add one to the first id and then get the remainder between that and the amount of positions.

code:
second id = (first id + 1) mod (amount of positions)


I think (I'm not completely sure) in Java it would be:

code:
id2 = (id1 + 1) % pos.length
Author:  gsquare567 [ Tue Nov 07, 2006 11:19 pm ]
Post subject: 
what you have to do is make an array of the x's and y's and then they'll pair up when you drawPolygon.. eg.
code:

// should give you a diamond =D
int[] x = {-2, 0, 2, 0};
int[] y = {0, 2, 0, -2};
g2d.setColor(new Color(Color.Blue));
g2d.drawPoly(x,y);// something like this... probs ton of errors
Author:  gsquare567 [ Tue Nov 07, 2006 11:20 pm ]
Post subject: 
sorry instead of drawPoly i meant drawFill()... or you could just use draw() if you dont want it filled in =) check out the graphics and graphics2d classes in da api
Author:  batman [ Wed Nov 08, 2006 2:36 pm ]
Post subject:  Polygon
Quote:

// should give you a diamond =D
int[] x = {-2, 0, 2, 0};
int[] y = {0, 2, 0, -2};
g2d.setColor(new Color(Color.Blue));
g2d.drawPoly(x,y);// something like this... probs ton of errors


I already know how to draw a polygon thanks for the help though but i was talking about making it in a class then extending using an applet to draw the polyogn. I figured it out but thanks for the help. By the way grd.fillPolygon wont work unless u have x.length,x and y. Not just x,y.
Author:  gsquare567 [ Fri Nov 10, 2006 8:36 pm ]
Post subject: 
no we were both wrong it wud be g2d.drawFill(x[], y[]); Smile

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