Develop Reference

Ball Collision - Collide with paddle

I'm trying to make a ball switch it's Y-Direction when it collides with the restrictions of the paddle. It is most likely a simple answer. Help would be appreciated. Thank you.
I labeled a couple of things to help.
public class GamePanel extends JPanel implements MouseMotionListener {
int Playerx;
int width;
int height;
// Ball Size
float radius = 20;
float diameter = radius * 2;
// Center of Call
float X = radius + 25;
float Y = radius + 10;
// Direction
float dx = 12;
float dy = 12;
GamePanel(){
setPreferredSize(new Dimension(1440, 900));
setFocusable(true);
setBackground(Color.BLACK);
addMouseMotionListener(this);
Thread thread = new Thread() {
public void run() {
while (true) {
width = getWidth();
height = getHeight();
X = X + dx ;
Y = Y + dy;
if (X - radius < 0) {
dx = -dx;
X = radius;
} else if (X + radius > width) {
dx = -dx;
X = width - radius;
}
if (Y - radius < 0) {
dy = -dy;
Y = radius;
}else if (Y + radius > height) {
dy = -dy;
Y = height - radius;
}
if(X-radius>=Playerx && X-radius <- Playerx + 100 && Y+radius>=800 && Y+radius<=810){
dy = -dy;
Y = height - radius;
}//Statement Above is the issue area
repaint();
try {
Thread.sleep(25);
} catch (InterruptedException ex) {
}
}
}
};
thread.start();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.WHITE);
if(Playerx<=50 && Playerx>= 0){g.fillOval(10,800,100,10);}
if(Playerx>50 && Playerx<1390){g.fillOval(Playerx-50,800,100,10);}
if(Playerx>=1390 && Playerx<1440){g.fillOval(1340,800,100,10);}
g.setColor(Color.BLUE);
g.fillOval((int)(X-radius), (int)(Y-radius), (int)diameter, (int)diameter);
}
#Override
public void mouseDragged(MouseEvent e) {
}
#Override
public void mouseMoved(MouseEvent e) {
Playerx = e.getX();
repaint();
}
}
I've tried setting different restrictions and different Y-Directions but it doesn't seem to work. The Ball goes straight through the paddle as if it's not there.

I managed to fix it.
I realized that my Playerx was in the middle of the paddle making everything offset 50.
float X = radius;
float Y = radius;
and
public void run() {
while (true) {
counter++;
width = getWidth();
height = getHeight();
X = X + dx ;
Y = Y + dy;
if (X - radius < 0) {
dx = -dx;
X = radius;
} else if (X + radius > width) {
dx = -dx;
X = width - radius;
}
if (Y - radius < 0) {
dy = -dy;
Y = radius;
}else if (Y + radius > height) {
dy = -dy;
Y = height - radius;
}if(X > Playerx-50 && X < Playerx+50 && Y+radius > paddleHeight && Y < 715){
dy = -dy;
Y = paddleHeight - radius;
}

Bouncing balls - balls passing through boundaries

I've created a bouncing balls animation, that's drawn on a surface (library from my university) that has 2 frames in it, and 2 arrays of balls that half goes to the first frame and the second to the second frame.
For some reason - the balls pass through to y and x axis of their frame.
I've already tried doing some of the solutions that were suggested (like here) and it didn't help..
my code:
public static void updateBalVelocity(Ball ball, int width, int height,
int minWidth, int minHeight) {
// get default value of the dx and dy
double dx = ball.getVelocity().getDx();
double dy = ball.getVelocity().getDy();
// check if the ball is touching the border (x/y axis) and if so -
// change it's directions
if ((ball.getX() + ball.getSize() + dx) >= width) {
dx = (dx > 0) ? -dx : dx;
} else if ((ball.getX() - ball.getSize()) <= minWidth) {
dx = Math.abs(dx);
}
if ((ball.getY() + ball.getSize() + dy) >= height) {
dy = (dy > 0) ? -dy : dy;
} else if ((ball.getY() - ball.getSize()) <= minHeight) {
dy = Math.abs(dy);
}
// apply the velocity to the ball
ball.setVelocity(dx, dy);
}
public static void moveBalls(Ball[] balls, DrawSurface d, int height,
int width, int minHeight, int minWidth) {
for (Ball ball : balls) {
updateBalVelocity(ball, width, height, minWidth, minHeight);
ball.moveOneStep();
d.setColor(ball.getColor());
d.fillCircle(ball.getX(), ball.getY(), ball.getSize());
ball.drawOn(d);
}
}
and in the run method:
while (true) {
...
// move balls
BouncingBallHelper.moveBalls(ballsD1, d, 500, 500, 50, 50);
BouncingBallHelper.moveBalls(ballsD2, d, 600, 600, 450, 450);
gui.show(d);
// wait for 50 milliseconds.
sleeper.sleepFor(50);
}

How can I correct a slightly off vector movement in java (2D game)

I am making a 2D top-down shooter in Java (uni project) but hit a problem with bullet aiming - I am unsure why the angle is incorrect, and how to correct it.
The player shoots bullets at the cursor location on mousedown. I am using dx/y = (x/ytarget - x/yorigin), normalising and incrementing the bullets x/y pos with dx each tick.
When the cursor is moved, the firing angle tracks the cursor - but the angle is off by 45 degrees or so The white circle is player, red is cursor and bullets the yellow dots.
I dont have rep to post images (first post), here is a link that shows the error of the angle.
http://i.imgur.com/xbUh2fX
Here is the bullet class:
note - update() is called by the main game loop
import java.awt.*;
import java.awt.MouseInfo;
public class Bullet {
private double x;
private double y;
private int r;
private double dx;
private double dy;
private double speed;
private double angle;
private Point c;
private Color color1;
public Bullet(int x, int y) {
this.x = x;
this.y = y;
r = 3;
speed = 30;
color1 = Color.YELLOW;
c = MouseInfo.getPointerInfo().getLocation();
// getting direction
dx = c.x - x;
dy = c.y - y;
double distance = Math.sqrt(dx*dx + dy*dy);
dx /= distance;
dy /= distance;
}
public boolean update() {
x += dx*speed;
y += dy*speed;
if(x < -r || x > GamePanel.WIDTH + r ||
y < -r || y > GamePanel.HEIGHT + r) {
return true;
}
return false;
}
public void draw(Graphics2D g) {
g.setColor(color1);
g.fillOval((int) (x - r), (int) (y - r), 2 * r, 2 * r);
}
}

I got a similar game and this is the code I used
import java.awt.Graphics2D;
import araccoongames.pongadventure.game.Entity;
import araccoongames.pongadventure.game.Game;
import araccoongames.pongadventure.game.MapLoader;
public class Ball extends Entity {
private float speed = 8;
private float speedx;
private float speedy;
private float degree;
public Ball(float posx, float posy, Game game) {
super(0, 0, game);
this.posx = posx;
this.posy = posy;
// posx = ball x position
// posy = ball y position
// game.input.MOUSEY = mouse y position
// game.input.MOUSEX = mouse x position
degree = (float) (270 + Math.toDegrees(Math.atan2(posy - game.input.MOUSEY, posx - game.input.MOUSEX))) % 360;
speedx = (float) (speed * Math.sin(Math.toRadians(degree)));
speedy = (float) (speed * Math.cos(Math.toRadians(degree)));
}
#Override
public void render(Graphics2D g) {
drawImage(game.texture.SPRITE[0][1], g);
}
#Override
public void update() {
posx += speedx;
posy -= speedy;
}
}

Midpoint Ellipse Algorithm in Java

I am trying to write a program to allow a user to draw an ellipse by using clicks. The user left-clicks at first to select the radius, then right-clicks to select the horizontal radius, then right-clicks again to select the vertical radius. Nothing is drawn after clicking. I don't understand where the error is.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Ellipse extends JPanel implements MouseListener{
Graphics P;
public Ellipse()
{
addMouseListener(this);
}
static int Radius = 0;
int CenterX, CenterY, RadiusX, RadiusY;
public void paintComponent(Graphics g)
{
P=g;
EllipseMidpoint(CenterX, CenterY, RadiusX, RadiusY);
}
public void EllipseMidpoint(int Cx, int Cy, int Rx, int Ry)
{
int Rx2 = Rx * Rx;
int Ry2 = Ry * Ry;
int twoRx2 = 2 * Rx2;
int twoRy2 = 2 * Ry2;
int x = 0;
int y = Ry;
int p;
int px= 0;
int py = twoRx2 * y;
PlotEllipsePoint(Cx, Cy, x, y);
//Region 1
p = (int)(Ry2 - (Rx2 * Ry) + (0.25 + Rx2));
while (px < py)
{
x = x + 1;
px = twoRy2 + px;
if (p < 0)
{
p = Ry2 + px + p;
}
else
{
y = y - 1;
py = twoRx2 - py;
p = Ry2 + px - py + p;
}
PlotEllipsePoint(Cx, Cy, x, y);
}
//Region2
p = (int)(Ry2 * (x + 0.5) * (x + 0.5) + Rx2 * (y - 1) * (y - 1) - Rx2 * Ry2);
while (y > 0)
{
y = y - 1;
py = twoRx2 - py;
if (p > 0)
{
p = Rx2 - py + p;
}
else
{
x = x + 1;
px = twoRy2 + px;
p = Rx2 + px - py + p;
}
PlotEllipsePoint(Cx, Cy, x, y);
}
}
public void PlotEllipsePoint(int CX, int CY, int X, int Y)
{
drawPixel(CX + X, CY + Y);
drawPixel(CX - X, CY + Y);
drawPixel(CX + X, CY - Y);
drawPixel(CX - X, CY - Y);
}
public void drawPixel(int x, int y)
{
P.fillOval(x, y, 5, 5);
}
public void mousePressed(MouseEvent e)
{
if (e.getButton() == MouseEvent.BUTTON1)
{
CenterX = e.getX();
CenterY = e.getY();
}
else if (e.getButton() == MouseEvent.BUTTON3)
{
Radius = Radius + 1;
if (Radius == 1)
{
RadiusX = (int) Math.pow((Math.pow((e.getX() - CenterX), 2) + Math.pow((e.getY() - CenterY), 2)), 0.5);
}
else if (Radius == 2)
{
RadiusY = (int) Math.pow((Math.pow((e.getX() - CenterX), 2) + Math.pow((e.getY() - CenterY), 2)), 0.5);
}
PlotEllipsePoint(CenterX, CenterY, RadiusX, RadiusY);
}
}
public static void main(String[] args)
{
JFrame JF = new JFrame("Ellipse");
JF.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JF.setSize(500,500);
Ellipse E = new Ellipse();
JF.getContentPane().add(E);
JF.setVisible(true);
}
public void mouseClicked(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
}

Three things immediately jump out...
You should be calling super.paintComponent before doing any custom painting (and there is no need for paintComponent to be public), see Performing Custom Painting and Painting in AWT and Swing for more details
NEVER, EVER maintain a reference to the graphics context, you want something painted, you make a request to the repaint manager and you wait until one of your paint methods is called. Painting is controlled by the repaint manager an repaints may occur at any time, most of the time without yout knowledge or interaction.
You never call repaint to ask the repaint manager to repaint your component...At the end of your mousePressed method, call repaint()...

Having trouble displaying balls in the right position using Java and vector objects

I'm having issues with the balls that I display in my JFrame window. Here's the main idea of my application:
Point object (with coordinates x and y) --> Vector object (a class I wrote that has the x and y components of a vector, as well as a few methods... gets its location and head/tail points from the Point object) --> Ball object (the position, velocity, and acceleration vectors are collected in an ArrayList, also has radius and color attributes) --> ContainerBox object (contains the balls, defines the min/max x and y for collision detection purposes).
I'm working toward having one ball centered in the window and the other orbiting the first, but right now I'm just trying to get my objects to play nicely. I'm very new to OOP principles and this is the first time I've written a program using classes in this way.
Everything works perfectly, the JFrame comes up and displays the balls... the problem is that the balls won't show up in the right places. No matter what I put in for the x and y coordinates of the balls (either explicitly or using the objects), they always show up in the upper left-hand corner of the screen. Here's a pic of what I get: Picture Here
I don't know whether it's the vectors or the collision detection or what... any ideas? Thanks a lot for reading and replying!
EDIT: Here's some of the code that I'm using (sorry to put so much, I have no idea where the problem is):
EDIT AGAIN: Added the ball class that I forgot.
package chaneyBouncingBall;
import java.util.*;
public class Point
{
float x;
float y;
public Point(float x, float y)
{
this.x = x;
this.y = y;
}
}
package chaneyBouncingBall;
import java.util.ArrayList;
public class Chaney2DVector
{
float x;
float y;
Point fromLocation;
public Chaney2DVector(float x,
float y)
{
this.x = x;
this.y = y;
}
public Chaney2DVector(Point point1,
Point point2)
{
fromLocation = new Point(point1.x, point1.y);
this.x = point2.x - point1.x;
this.y = point2.y - point1.y;
}
}
package chaneyBouncingBall;
import java.awt.*;
import java.util.*;
public class Ball
{
float x, y;
float velX, velY;
float accelX, accelY;
float radius;
private Color color;
public Ball(float x, float y, float velX,
float velY, float accelX,
float accelY, float radius,
Color color)
{
Chaney2DVector position = new Chaney2DVector(x, y);
Chaney2DVector velocity = new Chaney2DVector(velX, velY);
Chaney2DVector acceleration = new Chaney2DVector(accelX, accelY);
ArrayList posVelAcc = new ArrayList();
posVelAcc.add(position);
posVelAcc.add(velocity);
posVelAcc.add(acceleration);
this.radius = radius;
this.color = color;
}
public void draw(Graphics g)
{
g.setColor(color);
g.fillOval((int)(x - radius), (int)(y - radius),
(int)(2 * radius), (int)(2 * radius));
}
public void moveOneStepWithCollisionDetection( ContainerBox box)
{
float ballMinX = box.minX + radius;
float ballMinY = box.minY + radius;
float ballMaxX = box.maxX - radius;
float ballMaxY = box.maxY - radius;
x = x + velX;
y = y + velY;
if (x < ballMinX)
{
velX = -velX;
x = ballMinX;
}
else if (x > ballMaxX)
{
velX = -velX;
x = ballMaxX;
}
if (y < ballMinY)
{
velY = -velY;
y = ballMinY;
}
else if (y > ballMaxY)
{
velY = -velY;
y = ballMaxY;
}
}
}
package chaneyBouncingBall;
import java.awt.*;
/**
* A rectangular container box, containing the bouncing ball.
*/
public class ContainerBox {
int minX, maxX, minY, maxY; // Box's bounds (package access)
private Color colorFilled; // Box's filled color (background)
private Color colorBorder; // Box's border color
private static final Color DEFAULT_COLOR_FILLED = Color.BLACK;
private static final Color DEFAULT_COLOR_BORDER = Color.YELLOW;
/** Constructors */
public ContainerBox(int x, int y, int width, int height, Color colorFilled, Color colorBorder) {
minX = x;
minY = y;
maxX = x + width - 1;
maxY = y + height - 1;
this.colorFilled = colorFilled;
this.colorBorder = colorBorder;
}
/** Constructor with the default color */
public ContainerBox(int x, int y, int width, int height) {
this(x, y, width, height, DEFAULT_COLOR_FILLED, DEFAULT_COLOR_BORDER);
}
/** Set or reset the boundaries of the box. */
public void set(int x, int y, int width, int height) {
minX = x;
minY = y;
maxX = x + width - 1;
maxY = y + height - 1;
}
/** Draw itself using the given graphic context. */
public void draw(Graphics g) {
g.setColor(colorFilled);
g.fillRect(minX, minY, maxX - minX - 1, maxY - minY - 1);
g.setColor(colorBorder);
g.drawRect(minX, minY, maxX - minX - 1, maxY - minY - 1);
}
}
package chaneyBouncingBall;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
import javax.swing.*;
/**
* The control logic and main display panel for game.
*/
public class BallWorld extends JPanel {
private static final int UPDATE_RATE = 50; // Frames per second (fps)
private Ball ball; // A single bouncing Ball's instance
private Ball ball2;
private ContainerBox box; // The container rectangular box
private DrawCanvas canvas; // Custom canvas for drawing the box/ball
private int canvasWidth;
private int canvasHeight;
/**
* Constructor to create the UI components and init the game objects.
* Set the drawing canvas to fill the screen (given its width and height).
*
* #param width : screen width
* #param height : screen height
*/
public BallWorld(int width, int height) {
canvasWidth = width;
canvasHeight = height;
boolean stationary = true;
Random rand = new Random();
int angleInDegree = rand.nextInt(360);
int radius = 50;
int radius2 = 25;
// double accelAngle;
float x1 = rand.nextInt(canvasWidth - radius * 2 - 20) + radius + 10;
float y1 = rand.nextInt(canvasHeight - radius * 2 - 20) + radius + 10;
float x2 = rand.nextInt(canvasWidth - radius * 2 - 20) + radius + 10;
float y2 = rand.nextInt(canvasHeight - radius * 2 - 20) + radius + 10;
// float x = 100;
// float y = 100;
float velX1 = 0;
float velY1 = 0;
float accelX1 = 0;
float accelY1 = 0;
float velX2 = 0;
float velY2 = 0;
float accelX2 = 0;
float accelY2 = 0;
ball = new Ball(canvasWidth / 2, canvasHeight / 2, velX1, velY1, accelX1, accelY1,
radius, Color.BLUE);
ball2 = new Ball(x2, y2, velX2, velY2, accelX2, accelY2, radius / 5, Color.YELLOW);
// Init the Container Box to fill the screen
box = new ContainerBox(0, 0, canvasWidth, canvasHeight, Color.BLACK, Color.WHITE);
// Init the custom drawing panel for drawing the game
canvas = new DrawCanvas();
this.setLayout(new BorderLayout());
this.add(canvas, BorderLayout.CENTER);
// Handling window resize.
this.addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
Component c = (Component)e.getSource();
Dimension dim = c.getSize();
canvasWidth = dim.width;
canvasHeight = dim.height;
// Adjust the bounds of the container to fill the window
box.set(0, 0, canvasWidth, canvasHeight);
}
});
// Start the ball bouncing
gameStart();
}
/** Start the ball bouncing. */
public void gameStart() {
// Run the game logic in its own thread.
Thread gameThread = new Thread() {
public void run() {
while (true) {
// Execute one time-step for the game
gameUpdate();
// Refresh the display
repaint();
// Delay and give other thread a chance
try {
Thread.sleep(1000 / UPDATE_RATE);
} catch (InterruptedException ex) {}
}
}
};
gameThread.start(); // Invoke GaemThread.run()
}
/**
* One game time-step.
* Update the game objects, with proper collision detection and response.
*/
public void gameUpdate() {
ball.moveOneStepWithCollisionDetection(box);
ball2.moveOneStepWithCollisionDetection(box);
}
/** The custom drawing panel for the bouncing ball (inner class). */
class DrawCanvas extends JPanel {
/** Custom drawing codes */
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g); // Paint background
// Draw the box and the ball
box.draw(g);
ball.draw(g);
ball2.draw(g);
// Display ball's information
g.setColor(Color.WHITE);
g.setFont(new Font("Courier New", Font.PLAIN, 12));
// g.drawString("Ball " + ball.toString(), 20, 30);
}
/** Called back to get the preferred size of the component. */
#Override
public Dimension getPreferredSize() {
return (new Dimension(canvasWidth, canvasHeight));
}
}
}
package chaneyBouncingBall;
import javax.swing.JFrame;
public class Main
{
public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new JFrame("Matt Chaney's Gravity App");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setContentPane(new BallWorld(550, 450));
frame.pack();
frame.setVisible(true);
}
});
}
}

In the constructor of your Ball class, you don't assign all the instance variables to their parameters, these need to be added.
public Ball(float x, float y, float velX, float velY, float accelX, float accelY, float radius, Color color) {
...
this.x = x;
this.y = y;
this.velX = velX;
this.velY = velY;
this.accelX = accelX;
this.accelY = accelY;
}