Polygons

Frisbee

Basically have a problem here trying to fill a polygon in java.
Restrictions being I have to use the drawVertex Polygon() and fillVertexPolygon() methods.

Also have to convert my polygon from world to local points.
So far:

public void initializePolygon() {
// polygon in world points
points[xpoints] = new Vector2D(Game.WIDTH /3 -10 , Game.HEIGHT /3 +5);
points[ypoints] = new Vector2D(Game.WIDTH /3 -10, Game.HEIGHT /3 -5);
points[zpoints] = new Vector2D(Game.WIDTH /3 -13, Game.HEIGHT /3 +0);

// polygon in local points
pointsLocal[xpoints] = new Vector2D(-10, 5);
pointsLocal[ypoints] = new Vector2D(-10, -5);
pointsLocal[zpoints] = new Vector2D(-13, 0);
}

This is just converting the points from world to screen.

Then:

public void drawVertexPolygon(Graphics2D p, int[] points){
for(int i=0; i<points.length; i++);



}

Ok so I know I have to populate an array of x values and an array of y values representing x and y co-ordinates.
However not entirely sure on:

(1) I'm assuming I should read in the array of x values in the correct order for them to be in tandem with their corresponding y values?

(2) I know there's an npoints method to be used which specifies how many points I have in the array however not exactly sure what this does / how it should be implemented?

Tobias Greeshman

Frisbee wrote: »

(1) I'm assuming I should read in the array of x values in the correct order for them to be in tandem with their corresponding y values??

Why don't you create a structure/class with three ints x, y and z and use this to represent a Point, and have an array of them? Having separate arrays sounds too error prone IMO.

Anima

There already is a Point2D class, you should probably use that.

Frisbee

Been trying this over the weekend and still have gotten basically nowhere with it.

Should I be trying to read in a seperate array of points or jsut taking them from where they've been initialized?

Anima

Why don't you post up more of the code?

Frisbee

It seemed easier to use a seperate polygon class and then call on it where I wanted.

package comp20050.game.object;

import java.awt.Rectangle;
import java.awt.geom.AffineTransform;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;
import comp20050.game.Game;
import comp20050.game.util.Vector2D;
import comp20050.game.object.Ship;


public class Polygon{

public int npoints;
public int xpoints[];
public int ypoints[];

protected Rectangle bounds;

public Polygon() {
xpoints = new int[6];
ypoints = new int[6];
}

public Polygon(int xpoints[], int ypoints[], int npoints) {
if (npoints > xpoints.length || npoints > ypoints.length) { throw new IndexOutOfBoundsException("npoints > xpoints.length || npoints > ypoints.length");
}
this.npoints = npoints;
this.xpoints = new int[npoints];
this.ypoints = new int[npoints];
System.arraycopy(xpoints, 0, this.xpoints, 0, npoints);
System.arraycopy(ypoints, 0, this.ypoints, 0, npoints);
}

public void reset() {
npoints = 0;
bounds = null;
}

public void invalidate() {
bounds = null;
}

public void translate(int deltaX, int deltaY) {
for (int i = 0; i < npoints; i++) {
xpoints += deltaX;
ypoints += deltaY;
}
if (bounds != null) {
bounds.translate(deltaX, deltaY);
}
}



void calculateBounds(int xpoints[], int ypoints[], int npoints) {
int boundsMinX = Integer.MAX_VALUE;
int boundsMinY = Integer.MAX_VALUE;
int boundsMaxX = Integer.MIN_VALUE;
int boundsMaxY = Integer.MIN_VALUE;

for (int i = 0; i < npoints; i++) {
int x = xpoints;
boundsMinX = Math.min(boundsMinX, x);
boundsMaxX = Math.max(boundsMaxX, x);
int y = ypoints;
boundsMinY = Math.min(boundsMinY, y);
boundsMaxY = Math.max(boundsMaxY, y);
}
bounds = new Rectangle(boundsMinX, boundsMinY,
boundsMaxX - boundsMinX,
boundsMaxY - boundsMinY);
}


void updateBounds(int x, int y) {
if (x < bounds.x) {
bounds.width = bounds.width + (bounds.x - x);
bounds.x = x;
}
else {
bounds.width = Math.max(bounds.width, x - bounds.x);
// bounds.x = bounds.x;
}

if (y < bounds.y) {
bounds.height = bounds.height + (bounds.y - y);
bounds.y = y;
}
else {
bounds.height = Math.max(bounds.height, y - bounds.y);
// bounds.y = bounds.y;
}
}


public void addPoint(int x, int y) {
if (npoints == xpoints.length) {
int tmp[];

tmp = new int[npoints * 2];
System.arraycopy(xpoints, 0, tmp, 0, npoints);
xpoints = tmp;

tmp = new int[npoints * 2];
System.arraycopy(ypoints, 0, tmp, 0, npoints);
ypoints = tmp;
}
xpoints[npoints] = x;
ypoints[npoints] = y;
npoints++;

}




}

Not sure though how to get it to read in the exact points I want.
Should I just populate a seperate array?

Anima

I wrote some code that I think might help. The way you're doing it now is making you have to do a lot of bookeeping which in turn means code will be a lot slower and more error prone than it needs to be. I think something like below, which uses the Point2D class I suggested earlier, might make things easier to handle in the long run. I haven't compiled it so there might be some errors but the jist of it is there.

[PHP]public class Polygon
{
ArrayList<Point2D> points = null;

public Polygon() {
points = new ArrayList<Point2D>();
}

public Polygon( Point2D p ) {
points = new ArrayList<Point2D>();
points.add(p);
}

public void translate( Point2D delta ) {
for( Point2D p : points ) {
p.x += delta.x;
p.y += delta.y;
}
}

public void addPoint( Point2D point ) {
points.add(point);
}
}[/PHP]