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Processing - rendering shapes is too slow

I have been doing a small little project using Processing, and the effect I wanted to achieve was a kind of "mountains" forming and moving, using Perlin Noise with the noise() function, with 2 parameters.
I was originally using a image for the background, but for illustrational purposes, I made the background black, and it's basically the same effect.
My issue is that I want to have a "history" of the mountains because they should fade away after some time, and so I made a history of PShapes, and draw the history and update it each frame.
Updating it is no issue, but drawing the PShapes seems to take a lot of time, reducing the frame rate from 60 to 10 when the length of the history is 100 elements.
Below is the code I used :
float noise_y = 0;
float noise_increment = 0.01;
// increment x in the loop by this amount instead of 1
// makes the drawing faster, since the PShapes have less vertices
// however, mountains look sharper, not as smooth
// bigger inc = better fps
final int xInc = 1;
// maximum length of the array
// bigger = less frames :(
final int arrLen = 100;
int lastIndex = 0;
PShape[] history = new PShape[arrLen];
boolean full = false;
// use this to add shapes in the history
PShape aux;
void setup() {
size(1280, 720);
}
void draw() {
background(0);
// create PShape object
aux = createShape();
aux.beginShape();
aux.noFill();
aux.stroke(255);
aux.strokeWeight(0.5);
for (float x = 0; x < width + xInc; x = x + xInc) {
float noise = noise(x / 150, noise_y) ;
// get the actual y coordinate
float y = map(noise, 0, 1, height / 2, 0);
// create vertex of shape at x, y
aux.vertex(x, y);
}
aux.endShape();
// push the current one in the history
history[lastIndex++] = aux;
// if it reached the maximum length, start it over ( kinda works like a queue )
if (lastIndex == arrLen) {
lastIndex = 0;
full = true;
}
// draw the history
// this part takes the MOST TIME to draw, need to fix it.
// without it is running at 60 FPS, with it goes as low as 10 FPS
if (full) {
for (int i = 0; i < arrLen; i++) {
shape(history[i]);
}
} else {
for (int i = 0; i < lastIndex; i++) {
shape(history[i]);
}
}
noise_y = noise_y - noise_increment;
println(frameRate);
}
I have tried to use different ways of rendering the "mountains" : I tried writing my own class of a curve and draw lines that link the points, but I get the same performance. I tried grouping the PShapes into a PShape group object like
PShape p = new PShape(GROUP);
p.addChild(someShape);
and I got the same performance.
I was thinking of using multiple threads to render each shape individually, but after doing some research, there's only one thread that is responsible with rendering - the Animation Thread, so that won't do me any good, either.
I really want to finish this, it seems really simple but I can't figure it out.

One possible solution would be, not to draw all the generated shapes, but to draw only the new shape.
To "see" the shapes of the previous frames, the scene can't be cleared at the begin of the frame, of course.
Since the scene is never cleared, this would cause, that the entire view is covered, by shapes over time. But if the scene would be slightly faded out at the begin of a new frame, instead of clearing it, then the "older" shapes would get darker and darker by time. This gives a feeling as the "older" frames would drift away into the depth by time.
Clear the background at the initlization:
void setup() {
size(1280, 720);
background(0);
}
Create the scene with the fade effect:
void draw() {
// "fade" the entire view
blendMode(DIFFERENCE);
fill(1, 1, 1, 255);
rect(0, 0, width, height);
blendMode(ADD);
// create PShape object
aux = createShape();
aux.beginShape();
aux.stroke(255);
aux.strokeWeight(0.5);
aux.noFill();
for (float x = 0; x < width + xInc; x = x + xInc) {
float noise = noise(x / 150, noise_y) ;
// get the actual y coordinate
float y = map(noise, 0, 1, height / 2, 0);
// create vertex of shape at x, y
aux.vertex(x, y);
}
aux.endShape();
// push the current one in the history
int currentIndex = lastIndex;
history[lastIndex++] = aux;
if (lastIndex == arrLen)
lastIndex = 0;
// draw the newes shape
shape(history[currentIndex]);
noise_y = noise_y - noise_increment;
println(frameRate, full ? arrLen : lastIndex);
}
See the preview:

Java Convolution

Hi I am in need of some help. I need to write a convolution method from scratch that takes in the following inputs: int[][] and BufferedImage inputImage. I can assume that the kernel has size 3x3.
My approach is to do the follow:
convolve inner pixels
convolve corner pixels
convolve outer pixels
In the program that I will post below I believe I convolve the inner pixels but I am a bit lost at how to convolve the corner and outer pixels. I am aware that corner pixels are at (0,0), (width-1,0), (0, height-1) and (width-1,height-1). I think I know to how approach the problem but not sure how to execute that in writing though. Please to aware that I am very new to programming :/ Any assistance will be very helpful to me.
import java.awt.*;
import java.awt.image.BufferedImage;
import com.programwithjava.basic.DrawingKit;
import java.util.Scanner;
public class Problem28 {
// maximum value of a sample
private static final int MAX_VALUE = 255;
//minimum value of a sample
private static final int MIN_VALUE = 0;
public BufferedImage convolve(int[][] kernel, BufferedImage inputImage) {
}
public BufferedImage convolveInner(double center, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage1 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//inner pixels
for (int x = 1; x < width - 1; x++) {
for (int y = 1; y < height - 1; y ++) {
//get pixels at x, y
int colorValue = inputImage.getRGB(x, y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed() ;
int green = pixelColor.getGreen() ;
int blue = pixelColor.getBlue();
int innerred = (int) center*red;
int innergreen = (int) center*green;
int innerblue = (int) center*blue;
Color newPixelColor = new Color(innerred, innergreen, innerblue);
int newRgbvalue = newPixelColor.getRGB();
inputImage1.setRGB(x, y, newRgbvalue);
}
}
return inputImage1;
}
public BufferedImage convolveEdge(double edge, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage2 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//inner pixels
for (int x = 0; x < width - 1; x++) {
for (int y = 0; y < height - 1; y ++) {
//get pixels at x, y
int colorValue = inputImage.getRGB(x, y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed() ;
int green = pixelColor.getGreen() ;
int blue = pixelColor.getBlue();
int innerred = (int) edge*red;
int innergreen = (int) edge*green;
int innerblue = (int) edge*blue;
Color newPixelColor = new Color(innerred, innergreen, innerblue);
int newRgbvalue = newPixelColor.getRGB();
inputImage2.setRGB(x, y, newRgbvalue);
}
}
return inputImage2;
}
public BufferedImage convolveCorner(double corner, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage3 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//inner pixels
for (int x = 0; x < width - 1; x++) {
for (int y = 0; y < height - 1; y ++) {
//get pixels at x, y
int colorValue = inputImage.getRGB(x, y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed() ;
int green = pixelColor.getGreen() ;
int blue = pixelColor.getBlue();
int innerred = (int) corner*red;
int innergreen = (int) corner*green;
int innerblue = (int) corner*blue;
Color newPixelColor = new Color(innerred, innergreen, innerblue);
int newRgbvalue = newPixelColor.getRGB();
inputImage3.setRGB(x, y, newRgbvalue);
}
}
return inputImage3;
}
public static void main(String[] args) {
DrawingKit dk = new DrawingKit("Compositor", 1000, 1000);
BufferedImage p1 = dk.loadPicture("image/pattern1.jpg");
Problem28 c = new Problem28();
BufferedImage p5 = c.convolve();
dk.drawPicture(p5, 0, 100);
}
}
I changed the code a bit but the output comes out as black. What did I do wrong:
import java.awt.*;
import java.awt.image.BufferedImage;
import com.programwithjava.basic.DrawingKit;
import java.util.Scanner;
public class Problem28 {
// maximum value of a sample
private static final int MAX_VALUE = 255;
//minimum value of a sample
private static final int MIN_VALUE = 0;
public BufferedImage convolve(int[][] kernel, BufferedImage inputImage) {
int width = inputImage.getWidth();
int height = inputImage.getHeight();
BufferedImage inputImage1 = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
//for every pixel
for (int x = 0; x < width; x ++) {
for (int y = 0; y < height; y ++) {
int colorValue = inputImage.getRGB(x,y);
Color pixelColor = new Color(colorValue);
int red = pixelColor.getRed();
int green = pixelColor.getGreen();
int blue = pixelColor.getBlue();
double gray = 0;
//multiply every value of kernel with corresponding image pixel
for (int i = 0; i < 3; i ++) {
for (int j = 0; j < 3; j ++) {
int imageX = (x - 3/2 + i + width) % width;
int imageY = (x -3/2 + j + height) % height;
int RGB = inputImage.getRGB(imageX, imageY);
int GRAY = (RGB) & 0xff;
gray += (GRAY*kernel[i][j]);
}
}
int out;
out = (int) Math.min(Math.max(gray * 1, 0), 255);
inputImage1.setRGB(x, y, new Color(out,out,out).getRGB());
}
}
return inputImage1;
}
public static void main(String[] args) {
int[][] newArray = {{1/9, 1/9, 1/9}, {1/9, 1/9, 1/9}, {1/9, 1/9, 1/9}};
DrawingKit dk = new DrawingKit("Problem28", 1000, 1000);
BufferedImage p1 = dk.loadPicture("image/pattern1.jpg");
Problem28 c = new Problem28();
BufferedImage p2 = c.convolve(newArray, p1);
dk.drawPicture(p2, 0, 100);
}
}

Welcome ewuzz! I wrote a convolution using CUDA about a week ago, and the majority of my experience is with Java, so I feel qualified to provide advice for this problem.
Rather than writing all of the code for you, the best way to solve this large program is to discuss individual elements. You mentioned you are very new to programming. As the programs you write become more complex, it's essential to write small working snippets before combining them into a large successful program (or iteratively add snippets). With this being said, it's already apparent you're trying to debug a ~100 line program, and this approach will cost you time in most cases.
The first point to discuss is the general approach you mentioned. If you think about the program, what is the simplest and most repeated step? Obviously this is the kernel/mask step, so we can start from here. When you convolute each pixel, you are performing a similar option, regardless of the position (corner, edge, inside). While there are special steps necessary for these edge cases, they share similar underlying steps. If you try to write code for each of these cases separately, you will have to update the code in multiple (three) places with each adjustment and it will make the whole program more difficult to grasp.
To support my point above, here's what happened when I pasted your code into IntelliJ. This illustrates the (yellow) red flag of using the same code in multiple places:
The concrete way to fix this problem is to combine the three convolve methods into a single one and use if statements for edge-cases as necessary.
Our pseudocode with this change:
convolve(kernel, inputImage)
for each pixel in the image
convolve the single pixel and check edge cases
endfor
end
That seems pretty basic right? If we are able to successfully check edge cases, then this extremely simple logic will work. The reason I left it so general above to show how convolve the single pixel and check edge cases is logically grouped. This means it's a good candidate for extracting a method, which could look like:
private void convolvePixel(int x, int y, int[][] kernel, BufferedImage input, BufferedImage output)
Now to implement our method above, we will need to break it into a few steps, which we may then break into more steps if necessary. We'll need to look at the input image, if possible for each pixel accumulate the values using the kernel, and then set this in the output image. For brevity I will only write pseudocode from here.
convolvePixel(x, y, kernel, input, output)
accumulation = 0
for each row of kernel applicable pixels
for each column of kernel applicable pixels
if this neighboring pixel location is within the image boundaries then
input color = get the color at this neighboring pixel
adjusted value = input color * relative kernel mask value
accumulation += adjusted value
else
//handle this somehow, mentioned below
endif
endfor
endfor
set output pixel as accumulation, assuming this convolution method does not require normalization
end
The pseudocode above is already relatively long. When implementing you could write methods for the if and the else cases, but it you should be fine with this structure.
There are a few ways to handle the edge case of the else above. Your assignment probably specifies a requirement, but the fancy way is to tile around, and pretend like there's another instance of the same image next to this input image. Wikipedia explains three possibilities:
Extend - The nearest border pixels are conceptually extended as far as necessary to provide values for the convolution. Corner pixels are extended in 90° wedges. Other edge pixels are extended in lines.
Wrap - (The method I mentioned) The image is conceptually wrapped (or tiled) and values are taken from the opposite edge or corner.
Crop - Any pixel in the output image which would require values from beyond the edge is skipped. This method can result in the output image being slightly smaller, with the edges having been cropped.
A huge part of becoming a successful programmer is researching on your own. If you read about these methods, work through them on paper, run your convolvePixel method on single pixels, and compare the output to your results by hand, you will find success.
Summary:
Start by cleaning-up your code before anything.
Group the same code into one place.
Hammer out a small chunk (convolving a single pixel). Print out the result and the input values and verify they are correct.
Draw out edge/corner cases.
Read about ways to solve edge cases and decide what fits your needs.
Try implementing the else case through the same form of testing.
Call your convolveImage method with the loop, using the convolvePixel method you know works. Done!
You can look up pseudocode and even specific code to solve the exact problem, so I focused on providing general insight and strategies I have developed through my degree and personal experience. Good luck and please let me know if you want to discuss anything else in the comments below.
Java code for multiple blurs via convolution.

Recalculate X and Y Coordinates From New Screensize

I'm trying to display tiles from an array I have so that they always fill the size of the screen when drawn together. I am ignoring aspect ratio for now.
Here's how my code works. I have tile objects that are passed on to a tileset (class for managing an array of tile objects), and then I iterate through the tileset array, returning each tile object id and rendering a subimage of my tileset image based on said ids.
Here's my mapUpdate method, which is called on every JFrame resize event:
public synchronized void mapUpdate(Screen screen) {
factorX = (float)(screen.getWidth() / scW);
factorY = (float)(screen.getHeight() / scH);
for (int i = 0; i < tileset.getRows(); i++) {
for (int j = 0; j < tileset.getCols(); j++) {
int x = tileset.getTile(i, j).getX();
int y = tileset.getTile(i, j).getY();
tileset.getTile(i, j).setX((int)(x * factorX));
tileset.getTile(i, j).setY((int)(y * factorY));
}
}
mapTiles.clear();
for (int i = 0; i * 70 < mapImage.getWidth(); i++) {
mapTiles.add(mapImage.getSubimage(70 * i, 0, 70, 70).getScaledInstance(screen.getWidth() / 10, screen.getHeight() / 10, Image.SCALE_SMOOTH));
}
}
mapTiles is an ArrayList of Images, and on each resize event it resets the arraylist, scales my subimages to 1/10th width and height, and then re-adds the newly sized images for me to pull out for rendering (the tileset image is only 3 tiles with an original size of 70x70).
And here is the componentResized method if you were curious:
public void componentResized(ComponentEvent e) {
canvas.setSize(app.getContentPane().getWidth(), app.getContentPane().getHeight());
if (level1 != null) {
level1.mapUpdate(this);
}
}
As you can see in my mapUpdate method, I attempt to get a float to multiply each current x and y value by to receive the new correct values (it will round the integers), but this doesn't work at all.
Is there any solution to easily re-calculate my X and Y coordinates so that the tiles are drawn correctly?

Your factorX should not be a float. It should be an int. If you use a float you will get rounding, so occasionally you will have a pixel gap between tiles because of rounding. If you just use an int then you don't have to worry about this. Then the location is just the factor * the index value of the for loop.
On the other hand the easiest solution is to just use a JPanel with a GridLayout. Then you can add a JLabel with an Image icon. The GridLayout will resize each component equally.
You can then even use the Stretch Icon and the images will be dynamically resized as the frame is resized.

SOLUTION courtesy of #MadProgrammer - The solution was to simply calculate the new X and Y "origins" for each tile. I still need to implement adjusting the position for tiles that have moved based on the newly calculated origins, but this solution works for tiles that do not move (again, simply recalculate the X and Y origin positions).
public synchronized void mapUpdate(Screen screen) {
int originX = screen.getWidth() / 10;
int originY = screen.getHeight() / 10;
for (int i = 0; i < tileset.getRows(); i++) {
for (int j = 0; j < tileset.getCols(); j++) {
tileset.getTile(i, j).setX((originX * j));
tileset.getTile(i, j).setY((originY * i));
}
}
mapTiles.clear();
for (int i = 0; i * 70 < mapImage.getWidth(); i++) {
mapTiles.add(mapImage.getSubimage(70 * i, 0, 70, 70).getScaledInstance(screen.getWidth() / 10, screen.getHeight() / 10, Image.SCALE_SMOOTH));
}
}

how to scroll my map in java?

Firstly, happy new year all.
Ive got a
int[] map = new int[2550];
and in that array I place the id of a block at that pos, so for example if the top left block in the map has a id of one
map[0] = 1
Now I'm trying to think how I would scroll my map now, as I render the map like so -
for(int y = 0 ;y < current.height;y++){
for(int x = 0 ; x < current.width;x++){
Block block = current.getBlock(x, y);
g.drawImage(block.texture, x * 30 , y * 30);
}
}
How would I scroll the map? to make it so for example the block that was at 0,0 is now at 0,1 or whatever. Thanks for the help.
Edit: Im using LWJGL and slick2d to do my rendering and stuff, so I cant use Swing or AWT.

Scrolling is simply drawing all your graphics with a variable offset. Let there be a current scroll position:
int scrollX, scrollY;
Update these variables (and redraw) whenever you want to scroll. In your drawing routine, change the loop like this:
for (int y = 0; y < current.height; y++) {
for (int x = 0; x < current.width; x++) {
Block block = current.getBlock(x, y);
g.drawImage(block.texture, x * 30 - scrollX, y * 30 - scrollY);
}
}
Now, that's basic scrolling, and that will work. However, if you are adding scrolling you probably are planning to have maps much larger than the screen. In that case, it is inefficient to draw the entire map every time. Therefore, instead of iterating over the entire map, you iterate over only the visible portion of the map, which is not too complex:
int startX = Math.max(scrollX / 30, 0);
int startY = Math.max(scrollY / 30, 0);
int limitX = Math.min((scrollX + windowWidth ) / 30 + 1, current.width );
int limitY = Math.min((scrollX + windowHeight) / 30 + 1, current.height);
for (int y = startY; y < limitY; y++) {
for (int x = startX; x < limitX; x++) {
Block block = current.getBlock(x, y);
g.drawImage(block.texture, x * 30 - scrollX, y * 30 - scrollY);
}
}
The min and max are to avoid trying to draw tiles outside the bounds of the map. Note that this is exactly the same loop as before, except that the loop bounds have been changed.
By the way, you should also put the size of your tiles in a variable, so that if you ever decide to resize your tiles, or add zooming, you don't have to change code all over the place:
static final int TILE_SIZE = 30;
...
g.drawImage(block.texture, x * TILE_SIZE - scrollX, y * TILE_SIZE - scrollY);

Creating a Squircle

I'm a first year programmer. I'm trying to create a squircle. (square with round corners).
So far i have managed to get. I have been given the constants of a,b and r. If anyone could help i would be really thankful. I'm a total noob to this. So be nice :)
package squircle;
import java.awt.*;
import javax.swing.*;
import java.lang.Math;
public class Main extends javax.swing.JApplet {
public void paint(Graphics g){
// (x-a)^4 + (y-b)^4 = r^4
// y = quadroot( r^4 - (x-a)^4 + b)
// x values must fall within a-r < x < a+r
int[] xPoints = new int[200];
int[] yPoints = new int[200];
int[] mypoints = new int[200];
for(int c = 0; c <200; c++){
int a = 100;
int r = 100;
int b = 100;
double x = c ;
double temp = (r*r*r*r);
double temp2 = x-a;
double temp3 = ((temp2)*(temp2)*(temp2)*(temp2));
double temp6 = Math.sqrt(temp-temp3);
double y = (Math.sqrt(temp6) + b );
double z = (y*-1)+300;
mypoints[c]=(int)z;
// if (c>100){
// y = y*1;
// }
// else if(c<100){
// y = y*1;
// }
xPoints[c]=(int)x;
yPoints[c]=(int)y;
// change the equation to find x co-ordinates
// change it to find y co-ordinates.
// r is the minor radius
// (a,b) is the location of the centre
// a = 100
// b = 100
// r = 100
// x value must fall within 0 or 200
}
g.drawPolygon(xPoints, yPoints, xPoints.length);
g.drawPolygon(xPoints, (mypoints), xPoints.length);
}
}

Is it homework or is there some other reason why you're not using Graphics#drawRoundRect()?

If you are submitting this as homework there are some elements of style that may help you. What are the roles of 200, 100 and 300? These are "magic constants" which should be avoided. Are they related or is it just chance that they have these values? Suggest you use symbols such as:
int NPOINTS = 200;
or
double radius = 100.0
That would reveal whether the 300 was actually the value you want. I haven't checked.
Personally I wouldn't write
y*-1
but
-y
as it's too easy to mistype the former.
I would also print out the 200 points as floats and see if you can tell by eye where the error is. It's highly likely that the spurious lines are either drawn at the start or end of the calculation - it's easy to make "end-effect" errors where exactly one point is omitted or calculated twice.
Also it's cheap to experiment. Try iterating c from 0 to 100. or 0 to 10, or 0 to 198 or 1 to 200. Does your spurious line/triangle always occur?
UPDATE Here is what I think is wrong and how to tackle it. You have made a very natural graphics error and a fence-post error (http://en.wikipedia.org/wiki/Off-by-one_error) and it's hard to detect what is wrong because your variable names are poorly chosen.
What is mypoints? I believe it is the bottom half of the squircle - if you had called it bottomHalf then those replying woulod have spotted the problem quicker :-).
Your graphics problem is that you are drawing TWO HALF-squircles. Your are drawing CLOSED curves - when you get to the last point (c==199) the polygon is closed by drawing back to c==0. That makes a D-shape. You have TWO D-shapes, one with the bulge UP and one DOWN. Each has a horizontal line closing the polygon.
Your fence-post error is that you are drawing points from 0 to 199. For the half-squircle you want to draw from 0 to 200. That's 201 points! The loss of one point means that you have a very slightly sloping line. The bottom lines slopes in tghe opposite direction from the top. That gives you a very then wedge shape, which you refer to as a triangle. I'm guessing that your triangle is not actually closed but like a slice from a pie but very then/sharp.
(The code below could be prettier and more compact. However it is often useful to break symmetrical problems into quadrants or octants. It would also be interesting to use an anngle to sweep out the polygon).
You actually want ONE polygon. The code should be something like:
int NQUADRANT = 100;
int NPOINTS = 4*NQUADRANT ; // closed polygon
double[] xpoints = new double[NPOINTS];
double[] ypoints = new double[NPOINTS];
Your squircle is at 100, 100 with radius 100. I have chosen different values here
to emphasize they aren't related. By using symbolic names you can easily vary them.
double xcenter = 500.0;
double ycentre = 200.0;
double radius = 100.;
double deltax = radius/(double) NQUADRANT;
// let's assume squircle is centered on 0,0 and add offsets later
// this code is NOT complete or correct but should show the way
// I might have time later
for (int i = 0; i < NPOINTS; i++) {
if (i < NQUADRANT) {
double x0 = -radius + i* deltax;
double y0 = fourthRoot(radius, x0);
x[i] = x0+xcenter;
y[i] = y0+ycenter;
}else if (i < 2*NQUADRANT) {
double x0 = (i-NQUADRANT)* deltax;
double y0 = fourthRoot(radius, x0);
x[i] = x0+xcenter;
y[i] = y0+ycenter;
}else if (i < 3*NQUADRANT) {
double x0 = (i-2*NQUADRANT)* deltax;
double y0 = -fourthRoot(radius, x0);
x[i] = x0+xcenter;
y[i] = y0+ycenter;
}else {
double x0 = -radius + (i-3*NQUADRANT)* deltax;
double y0 = -fourthRoot(radius, x0);
x[i] = x0+xcenter;
y[i] = y0+ycenter;
}
}
// draw single polygon
private double fourthRoot(double radius, double x) {
return Math.sqrt(Math.sqrt(radius*radius*radius*radius - x*x*x*x));
}

There is a javascript version here. You can view the source and "compare notes" to potentially see what you are doing wrong.

Ok, upon further investigation here is why you are getting the "triangle intersecting it". When you drawPolygon the points are drawn and the last point connects the first point, closing the points and making the polygon. Since you draw one half it is drawn (then connected to itself) and then the same happens for the other side.
As a test of this change your last couple lines to this:
for( int i = 0; i < yPoints.length; i++ ) {
g.drawString( "*", xPoints[ i ], yPoints[ i ] );
}
for( int i = 0; i < mypoints.length; i++ ) {
g.drawString( "*", xPoints[ i ], mypoints[ i ] );
}
// g.drawPolygon( xPoints, yPoints, xPoints.length );
// g.drawPolygon( xPoints, ( mypoints ), xPoints.length );
It is a little crude, but I think you'll get the point. There are lots of solutions out there, personally I would try using an array of the Point class and then sort it when done, but I don't know the specifics of what you can and can not do.

Wow, are you guys overthinking this, or what! Why not just use drawLine() four times to draw the straight parts of the rectangle and then use drawArc() to draw the rounded corners?