Develop Reference

How should I calculate every possible endpoint if my player can end on x movements in a turn-based game?

I'm currently recreating a Civilization game in Processing. I'm planning to implement the feature in a which a given unit can see every possible move it can make with a given number of hexes it is allowed to move. All possible endpoints are marked with red circles. However, units cannot move through mountains or bodies of water. I'm trying to approach this by finding out every possible combination of moves I can make without the unit going into a mountain or body of water but I can't figure out how I can determine every combination.
There are 6 directions that any unit can go in, north-east, north, north-west, south-east, south, south-west. The max number of movements I'm assigning to any unit would probably go up to 6. Any higher and I'm afraid processing may become to slow every time I move a unit.
I'm trying to recreate this:
What I'm hoping the result will look like with two possible movements (without the black arrows):
Raw version of that image:
Here is the code I use to draw the hex grid. Immediately after drawing each individual hex, its center's x coords and y coords are stored in xHexes and yHexes respectively. Also, immediately after generating the type of tile (e.g. grass, beach), the type of tile is also stored in an array named hexTypes. Therefore, I can get the x and y coords and type of hex of any hex I want on the map just by referencing its index.
Code used to draw a single hexagon:
beginShape();
for (float a = PI/6; a < TWO_PI; a += TWO_PI/6) {
float vx = x + cos(a) * gs*2;
float vy = y + sin(a) * gs*2;
vertex(vx, vy);
}
x is the x coord for centre of hexagon
y is the y coord for centre of hexagon
gs = radius of hexagon
Code used to tesselate hex over the window creating a hex grid:
void redrawMap() {
float xChange = 1.7;
float yChange = 6;
for (int y = 0; y < ySize/hexSize; y++) {
for (int x = 0; x < xSize/hexSize; x++) {
if (x % 2 == 1) {
// if any part of this hexagon being formed will be visible on the window and not off the window.
if (x*hexSize*xChange <= width+2*hexSize && int(y*hexSize*yChange) <= height+3*hexSize) {
drawHex(x*hexSize*xChange, y*hexSize*yChange, hexSize);
}
// only record and allow player to react with it if the entire tile is visible on the window
if (x*hexSize*xChange < width && int(y*hexSize*yChange) < height) {
xHexes.add(int(x*hexSize*xChange));
yHexes.add(int(y*hexSize*yChange));
}
} else {
if (x*hexSize*xChange <= width+2*hexSize && int(y*hexSize*yChange) <= height+3*hexSize) {
drawHex(x*hexSize*xChange, y*hexSize*yChange+(hexSize*3), hexSize);
}
if (x*hexSize*xChange < width && int(y*hexSize*yChange+(hexSize*3)) < height) {
xHexes.add(int(x*hexSize*xChange));
yHexes.add(int(y*hexSize*yChange+(hexSize*3)));
}
}
}
}
}
hexSize is a user-specified size for each hexagon, determining the number of hexagons that will be on the screen.

This answer will help you get to this (green is plains, red is hills and blue is water, also please don't flame my terrible grid):
Note that there is no pathfinding in this solution, only some very simple "can I get there" math. I'll include the full code of the sketch at the end so you can reproduce what I did and test it yourself. One last thing: this answer doesn't use any advanced design pattern, but it assume that you're confortable with the basics and Object Oriented Programming. If I did something which you're not sure you understand, you can (and should) ask about it.
Also: this is a proof of concept, not a "copy and paste me" solution. I don't have your code, so it cannot be that second thing anyway, but as your question can be solved in a bazillion manners, this is only one which I deliberately made as simple and visual as possible so you can get the idea and run with it.
First, I strongly suggest that you make your tiles into objects. First because they need to carry a lot of information (what's on each tile, how hard they are to cross, maybe things like resources or yield... I don't know, but there will be a lot of stuff).
The Basics
I organized my global variables like this:
// Debug
int unitTravelPoints = 30; // this is the number if "travel points" currently being tested, you can change it
// Golbals
float _tileSize = 60;
int _gridWidth = 10;
int _gridHeight = 20;
ArrayList<Tile> _tiles = new ArrayList<Tile>(); // all the tiles
ArrayList<Tile> _canTravel = new ArrayList<Tile>(); // tiles you can currently travel to
The basics being that I like to be able to change my grid size on the fly, but that's just a detail. What's next is to choose a coordinate system for the grid. I choose the simplest one as I didn't want to bust my brain on something complicated, but you may want to adapt this to another coordinate system. I choose the offset coordinate type of grid: my "every second row" is half a tile offset. So, instead of having this:
I have this:
The rest is just adjusting the spatial coordinates of the tiles so it doesn't look too bad, but their coordinates stays the same:
Notice how I consider that the spatial coordinates and the grid coordinates are two different things. I'll mostly use the spatial coordinates for the proximity checks, but that's because I'm lazy, because you could make a nice algorithm which do the same thing without the spatial coordinates and it would probably be less costly.
What about the travel points? Here's how I decided to work: your unit has a finite amount of "travel points". Here there's no unit, but instead a global variable unitTravelPoints which will do the same thing. I decided to work with this scale: one normal tile is worth 10 travel points. So:
Plains: 10 points
Hills: 15 points
Water: 1000 points (this is impassable terrain but without going into the details)
I'm not going to go into the details of drawing a grid, but that's mostly because your algorithm looks way better than mine on this front. On the other hand, I'll spend some time on explaining how I designed the Tiles.
The Tiles
We're entering OOP: they are Drawable. Drawable is a base class which contains some basic info which every visible thing should have: a position, and an isVisible setting which can be turned off. And a method to draw it, which I call Render() since draw() is already taken by Processing:
class Drawable {
PVector position;
boolean isVisible;
public Drawable() {
position = new PVector(0, 0);
isVisible = true;
}
public void Render() {
// If you forget to overshadow the Render() method you'll see this error message in your console
println("Error: A Drawable just defaulted to the catch-all Render(): '" + this.getClass() + "'.");
}
}
The Tile will be more sophisticated. It'll have more basic informations: row, column, is it currently selected (why not), a type like plains or hills or water, a bunch of neighboring tiles, a method to draw itself and a method to know if the unit can travel through it:
class Tile extends Drawable {
int row, column;
boolean selected = false;
TileType type;
ArrayList<Tile> neighbors = new ArrayList<Tile>();
Tile(int row, int column, TileType type) {
super(); // this calls the parent class' constructor
this.row = row;
this.column = column;
this.type = type;
// the hardcoded numbers are all cosmetics I included to make my grid looks less awful, nothing to see here
position.x = (_tileSize * 1.5) * (column + 1);
position.y = (_tileSize * 0.5) * (row + 1);
// this part checks if this is an offset row to adjust the spatial coordinates
if (row % 2 != 0) {
position.x += _tileSize * 0.75;
}
}
// this method looks recursive, but isn't. It doesn't call itself, but it calls it's twin from neighbors tiles
void FillCanTravelArrayList(int travelPoints, boolean originalTile) {
if (travelPoints >= type.travelCost) {
// if the unit has enough travel points, we add the tile to the "the unit can get there" list
if (!_canTravel.contains(this)) {
// well, only if it's not already in the list
_canTravel.add(this);
}
// then we check if the unit can go further
for (Tile t : neighbors) {
if (originalTile) {
t.FillCanTravelArrayList(travelPoints, false);
} else {
t.FillCanTravelArrayList(travelPoints - type.travelCost, false);
}
}
}
}
void Render() {
if (isVisible) {
// the type knows which colors to use, so we're letting the type draw the tile
type.Render(this);
}
}
}
The Tile Types
The TileType is a strange animal: it's a real class, but it's never used anywhere. That's because it's a common root for all tile types, which will inherit it's basics. The "City" tile may need very different variables than, say, the "Desert" tile. But both need to be able to draw themselves, and both need to be owned by the tiles.
class TileType {
// cosmetics
color fill = color(255, 255, 255);
color stroke = color(0);
float strokeWeight = 2;
// every tile has a "travelCost" variable, how much it cost to travel through it
int travelCost = 10;
// while I put this method here, it could have been contained in many other places
// I just though that it made sense here
void Render(Tile tile) {
fill(fill);
if (tile.selected) {
stroke(255);
} else {
stroke(stroke);
}
strokeWeight(strokeWeight);
DrawPolygon(tile.position.x, tile.position.y, _tileSize/2, 6);
textAlign(CENTER, CENTER);
fill(255);
text(tile.column + ", " + tile.row, tile.position.x, tile.position.y);
}
}
Each tile type can be custom, now, yet each tile is... just a tile, whatever it's content. Here are the TileType I used in this demonstration:
// each different tile type will adjust details like it's travel cost or fill color
class Plains extends TileType {
Plains() {
this.fill = color(0, 125, 0);
this.travelCost = 10;
}
}
class Water extends TileType {
// here I'm adding a random variable just to show that you can custom those types with whatever you need
int numberOfFishes = 10;
Water() {
this.fill = color(0, 0, 125);
this.travelCost = 1000;
}
}
class Hill extends TileType {
Hill() {
this.fill = color(125, 50, 50);
this.travelCost = 15;
}
}
Non-class methods
I added a mouseClicked() method so we can select a hex to check how far from it the unit can travel. In your game, you would have to make it so when you select a unit all these things fall into place, but as this is just a proof of concept the unit is imaginary and it's location is wherever you click.
void mouseClicked() {
// clearing the array which contains tiles where the unit can travel as we're changing those
_canTravel.clear();
for (Tile t : _tiles) {
// select the tile we're clicking on (and nothing else)
t.selected = IsPointInRadius(t.position, new PVector(mouseX, mouseY), _tileSize/2);
if (t.selected) {
// if a tile is selected, check how far the imaginary unit can travel
t.FillCanTravelArrayList(unitTravelPoints, true);
}
}
}
At last, I added 2 "helper methods" to make things easier:
// checks if a point is inside a circle's radius
boolean IsPointInRadius(PVector center, PVector point, float radius) {
// simple math, but with a twist: I'm not using the square root because it's costly
// we don't need to know the distance between the center and the point, so there's nothing lost here
return pow(center.x - point.x, 2) + pow(center.y - point.y, 2) <= pow(radius, 2);
}
// draw a polygon (I'm using it to draw hexagons, but any regular shape could be drawn)
void DrawPolygon(float x, float y, float radius, int npoints) {
float angle = TWO_PI / npoints;
beginShape();
for (float a = 0; a < TWO_PI; a += angle) {
float sx = x + cos(a) * radius;
float sy = y + sin(a) * radius;
vertex(sx, sy);
}
endShape(CLOSE);
}
How Travel is calculated
Behind the scenes, that's how the program knows where the unit can travel: in this example, the unit has 30 travel points. Plains cost 10, hills cost 15. If the unit has enough points left, the tile is marked as "can travel there". Every time a tile is in travel distance, we also check if the unit can get further from this tile, too.
Now, if you're still following me, you may ask: how do the tiles know which other tile is their neighbor? That's a great question. I suppose that an algorithm checking their coordinates would be the best way to handle this, but as this operation will happen only once when we create the map I decided to take the easy route and check which tiles were the close enough spatially:
void setup() {
// create the grid
for (int i=0; i<_gridWidth; i++) {
for (int j=0; j<_gridHeight; j++) {
int rand = (int)random(100);
if (rand < 20) {
_tiles.add(new Tile(j, i, new Water()));
} else if (rand < 50) {
_tiles.add(new Tile(j, i, new Hill()));
} else {
_tiles.add(new Tile(j, i, new Plains()));
}
}
}
// detect and save neighbor tiles for every Tile
for (Tile currentTile : _tiles) {
for (Tile t : _tiles) {
if (t != currentTile) {
if (IsPointInRadius(currentTile.position, t.position, _tileSize)) {
currentTile.neighbors.add(t);
}
}
}
}
}
Complete code for copy-pasting
Here's the whole thing in one place so you can easily copy and paste it into a Processing IDE and play around with it (also, it includes how I draw my awful grid):
// Debug
int unitTravelPoints = 30; // this is the number if "travel points" currently being tested, you can change it
// Golbals
float _tileSize = 60;
int _gridWidth = 10;
int _gridHeight = 20;
ArrayList<Tile> _tiles = new ArrayList<Tile>();
ArrayList<Tile> _canTravel = new ArrayList<Tile>();
void settings() {
// this is how to make a window size's dynamic
size((int)(((_gridWidth+1) * 1.5) * _tileSize), (int)(((_gridHeight+1) * 0.5) * _tileSize));
}
void setup() {
// create the grid
for (int i=0; i<_gridWidth; i++) {
for (int j=0; j<_gridHeight; j++) {
int rand = (int)random(100);
if (rand < 20) {
_tiles.add(new Tile(j, i, new Water()));
} else if (rand < 50) {
_tiles.add(new Tile(j, i, new Hill()));
} else {
_tiles.add(new Tile(j, i, new Plains()));
}
}
}
// detect and save neighbor tiles for every Tile
for (Tile currentTile : _tiles) {
for (Tile t : _tiles) {
if (t != currentTile) {
if (IsPointInRadius(currentTile.position, t.position, _tileSize)) {
currentTile.neighbors.add(t);
}
}
}
}
}
void draw() {
background(0);
// show the tiles
for (Tile t : _tiles) {
t.Render();
}
// show how far you can go
for (Tile t : _canTravel) {
fill(0, 0, 0, 0);
if (t.selected) {
stroke(255);
} else {
stroke(0, 255, 0);
}
strokeWeight(5);
DrawPolygon(t.position.x, t.position.y, _tileSize/2, 6);
}
}
class Drawable {
PVector position;
boolean isVisible;
public Drawable() {
position = new PVector(0, 0);
isVisible = true;
}
public void Render() {
// If you forget to overshadow the Render() method you'll see this error message in your console
println("Error: A Drawable just defaulted to the catch-all Render(): '" + this.getClass() + "'.");
}
}
class Tile extends Drawable {
int row, column;
boolean selected = false;
TileType type;
ArrayList<Tile> neighbors = new ArrayList<Tile>();
Tile(int row, int column, TileType type) {
super(); // this calls the parent class' constructor
this.row = row;
this.column = column;
this.type = type;
// the hardcoded numbers are all cosmetics I included to make my grid looks less awful, nothing to see here
position.x = (_tileSize * 1.5) * (column + 1);
position.y = (_tileSize * 0.5) * (row + 1);
// this part checks if this is an offset row to adjust the spatial coordinates
if (row % 2 != 0) {
position.x += _tileSize * 0.75;
}
}
// this method looks recursive, but isn't. It doesn't call itself, but it calls it's twin from neighbors tiles
void FillCanTravelArrayList(int travelPoints, boolean originalTile) {
if (travelPoints >= type.travelCost) {
// if the unit has enough travel points, we add the tile to the "the unit can get there" list
if (!_canTravel.contains(this)) {
// well, only if it's not already in the list
_canTravel.add(this);
}
// then we check if the unit can go further
for (Tile t : neighbors) {
if (originalTile) {
t.FillCanTravelArrayList(travelPoints, false);
} else {
t.FillCanTravelArrayList(travelPoints - type.travelCost, false);
}
}
}
}
void Render() {
if (isVisible) {
// the type knows which colors to use, so we're letting the type draw the tile
type.Render(this);
}
}
}
class TileType {
// cosmetics
color fill = color(255, 255, 255);
color stroke = color(0);
float strokeWeight = 2;
// every tile has a "travelCost" variable, how much it cost to travel through it
int travelCost = 10;
// while I put this method here, it could have been contained in many other places
// I just though that it made sense here
void Render(Tile tile) {
fill(fill);
if (tile.selected) {
stroke(255);
} else {
stroke(stroke);
}
strokeWeight(strokeWeight);
DrawPolygon(tile.position.x, tile.position.y, _tileSize/2, 6);
textAlign(CENTER, CENTER);
fill(255);
text(tile.column + ", " + tile.row, tile.position.x, tile.position.y);
}
}
// each different tile type will adjust details like it's travel cost or fill color
class Plains extends TileType {
Plains() {
this.fill = color(0, 125, 0);
this.travelCost = 10;
}
}
class Water extends TileType {
// here I'm adding a random variable just to show that you can custom those types with whatever you need
int numberOfFishes = 10;
Water() {
this.fill = color(0, 0, 125);
this.travelCost = 1000;
}
}
class Hill extends TileType {
Hill() {
this.fill = color(125, 50, 50);
this.travelCost = 15;
}
}
void mouseClicked() {
// clearing the array which contains tiles where the unit can travel as we're changing those
_canTravel.clear();
for (Tile t : _tiles) {
// select the tile we're clicking on (and nothing else)
t.selected = IsPointInRadius(t.position, new PVector(mouseX, mouseY), _tileSize/2);
if (t.selected) {
// if a tile is selected, check how far the imaginary unit can travel
t.FillCanTravelArrayList(unitTravelPoints, true);
}
}
}
// checks if a point is inside a circle's radius
boolean IsPointInRadius(PVector center, PVector point, float radius) {
// simple math, but with a twist: I'm not using the square root because it's costly
// we don't need to know the distance between the center and the point, so there's nothing lost here
return pow(center.x - point.x, 2) + pow(center.y - point.y, 2) <= pow(radius, 2);
}
// draw a polygon (I'm using it to draw hexagons, but any regular shape could be drawn)
void DrawPolygon(float x, float y, float radius, int npoints) {
float angle = TWO_PI / npoints;
beginShape();
for (float a = 0; a < TWO_PI; a += angle) {
float sx = x + cos(a) * radius;
float sy = y + sin(a) * radius;
vertex(sx, sy);
}
endShape(CLOSE);
}
Hope it'll help. Have fun!

You will have to use similar algorithms we use on pathfinding. you create a stack or queue that will hold a class storing the position of the hex and the number of moves left from that point, initially you insert your starting position with the number of moves you have and mark that hex as done ( to not re-use a position you have already been on ), then you pop an element, and you insert every neighbor of that hex with a number of moves -1. when you insert the hexes with zero moves, those are your endpoints. And before inserting any hex check if it's not already done.
I hope I was clear, your question was a bit vague but I tried to give you an idea of how these solutions are usually done, also I think your question fits more into algorithms rather then processing
Best of luck

I cannot figure out a way to move the balls

I am currently working on a 3 cushion billiards game project. I have added two balls on the table so far. I am trying to move one of the balls but I am having a hard time doing that. Should I use a timer? If so then could you tell me an effective way to use the timer on my code so I can move my balls?
Your help would be much appreciated.
Thanks in advance.
Farhan Hasan
I have tried to create a move function for the class balls. But I am not sure what I should put inside the function, I have added the xSpeed and ySpeed. The xLocation and the yLocation changes depending on the xSpeed and ySpeed.
public class Balls
{
private Color ballFillColor;
private Color ballBorderColor;
private int ballX = 0;
private int ballY = 0;
private int xSpeed = 5;
private int ySpeed = 0;
private int ballWidth = 0;
private int ballHeight = 0;
Timer t;
public boolean fillBall = false;
private static Balls ballArray[]; //Required for drawMultipleBalls
Balls(){ //Constructor
ballBorderColor = Color.black;
}
Balls(int ballX, int ballY, int ballWidth, int ballHeight, Color ballBorderColor, JFrame window){ //Constructor
// X , Y , Width, Height, Border Colour, container
this.setBallBorderColor(ballBorderColor);
this.setBallWidth(ballWidth);
this.setBallHeight(ballHeight);
this.setBallX(ballX);
this.setBallY(ballY);
this.drawBall(window);
}
//Here is the move function. I am not really sure what to do here.
public void move()
{
if(this.ballX < 1000 - this.ballWidth)
{
this.ballX += this.xSpeed;
}
try
{
Thread.sleep(1);
}
catch(Exception e)
{
}
}
//GET AND SET FUNCTIONS HERE
//HERE ARE THE FUNCTIONS WHICH ARE RESPONSIBLE FOR DRAWING MY BALLS IN JFRAME
public void drawBall(JFrame frame)
{
frame.getContentPane().add(new MyComponent());
}
public void drawMultipleBalls(JFrame frame, Balls[] balls)
{
ballArray = balls;
frame.getContentPane().add(new MyComponent2());
}
private class MyComponent extends JComponent{
public void paintComponent(Graphics g){
if (fillBall) //Fill first, and then draw outline.
{
g.setColor(ballFillColor);
g.fillOval(getBallX(),getBallY(), getBallHeight(),getBallWidth());
}
g.setColor(getBallBorderColor());
g.drawOval(getBallX(),getBallY(), getBallHeight(),getBallWidth());
}
}
private class MyComponent2 extends JComponent{
public void paintComponent(Graphics g){
for (int i = 0; i < ballArray.length; i++)
{
if (ballArray[i].fillBall) //Fill first, and then draw outline.
{
g.setColor(ballArray[i].ballFillColor);
g.fillOval(ballArray[i].getBallX(),ballArray[i].getBallY(), ballArray[i].getBallHeight(),ballArray[i].getBallWidth());
}
g.setColor(ballArray[i].getBallBorderColor());
g.drawOval(ballArray[i].getBallX(),ballArray[i].getBallY(), ballArray[i].getBallHeight(),ballArray[i].getBallWidth());
}
}
}
Hopefully, I can have two movable balls for the game, the should bounce back as the hit the edge of the screen and they should be able to slow down over time. For that, I am thinking to use a damper (I will multiply the xSpeed and ySpeed with a number less than 1, eventually it will slow down the ball)

Here is a simple example I came up with to show a ball moving and bouncing off the edges.
The direction changes based on the boundary. Left and top edges just check for 0. Bottom and right edges need to include the diameter of the ball.
The x and y increments are independent. And these amounts in conjunction with the timer can change the movement. Notice however, that to have objects bounce off of each other (as in a pool game) is more complicated due to angle of trajectories, etc. And the distances bounced will vary and slow with time based on frictional values. Everything else is documented in the Java API.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MovementDemo extends JPanel implements ActionListener {
JFrame frame = new JFrame("Movement Demo");
int size = 500;
int x = 50;
int y = 200;
int diameter = 50;
int yinc = 2;
int xinc = 2;
int xdirection = 1;
int ydirection = 1;
public MovementDemo() {
setPreferredSize(new Dimension(size, size));
frame.add(this);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new MovementDemo().start());
}
public void start() {
Timer timer = new Timer(100, this);
timer.setDelay(5);
timer.start();
}
public void actionPerformed(ActionEvent ae) {
if (x < 0) {
xdirection = 1;
}
else if (x > size - diameter) {
xdirection = -1;
}
if (y < 0) {
ydirection = 1;
}
else if (y > size - diameter) {
ydirection = -1;
}
x = x + xdirection * xinc;
y = y + ydirection * yinc;
repaint();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.BLUE);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.fillOval(x, y, diameter, diameter);
}
}

It seems in general there are a few things you need to figure out:
has the ball collided with another ball
has the ball collided with a wall
otherwise just figure out what is the ball's new position based on its velocity
Below is some sample code that stubs some of this out. You can first compare the current ball's position to all others (not including the current ball of course). If there are any equal positions, process a collision with a ball. If the ball is at the window border i.e it hit a wall, process a collision with a wall. Otherwise just calculate its new position based on its current velocity.
The process collision part is just to apply physics mechanics to whatever degree of complexity you require. One general suggested change would be to update the velocity of the balls then apply it to the position after. The specific calculations for velocity changes you could apply as needed and as you can imagine it can get pretty involved which is why I suggest using a separate method and possibly a sub class for velocity instead of managing each part of the velocity vector in the ball itself. I used the wall as an object because of this. The composition, weights, velocities etc of the object's colliding can affect the resulting collision, but how complex you want that processing to be is up to you.
Sorry I'm no physics expert but I hope this sends you in the right direction in terms of code! Also this might help with the specific calculations you might want to use:
https://www.khanacademy.org/science/physics/one-dimensional-motion/displacement-velocity-time/v/calculating-average-velocity-or-speed
public void move()
{
// check if balls are on same position not including this ball
for(Ball b: ballArray){
if (this.position == b.position && this != b){
processCollision(this, b, null);
} else{
// if the ball hasn't collided with anything process its movement based on speed
// this assumes a 1000 x 1000 window for keeping objects inside it
if(this.ballX < 1000 - this.ballWidth && this.ballY < 1000 - this.ballHeight){
this.ballX += this.xSpeed;
this.ballY += this.ySpeed;
}else {
processCollision(this, null, new Wall());
}
}
}
try
{
Thread.sleep(1);
}
catch(Exception e)
{
}
}
public void processCollision(Ball b1, Ball b2, Wall w){
// if ball hasn't collided with a wall, process a ball - ball collision
if(w == null){
// apply physics mechanics according the complexity desired for ball collisions
b1.xSpeed -= b2.xSpeed;
b1.ySpeed -= b2.ySpeed;
// ball 2 would end up slowing down
b2.xSpeed -= b1.xSpeed;
b2.ySpeed -= b1.ySpeed;
}
// if ball hasn't collided with a ball, process a ball - wall collision
if(b2 == null){
// apply physics mechanics for hitting a wall
// e.g as below: just send ball in opposite direction
b1.xSpeed = b1.xSpeed * -1;
b1.ySpeed = b1.ySpeed * -1;
}
// either way, process ball's new position based on its new speed
b1.ballX += b1.xSpeed;
b1.ballY += b1.ySpeed;
b2.ballX += b2.xSpeed;
b2.ballY += b2.ySpeed;
}

Shape increases in size instead of moving - Java (GUI applet)

I am trying to change the y position of the rectangle, however, whenever I try to, it expands/gets bigger vertically.
public class PlayerPaddle implements Paddle {
double yVelocity;
final double GRAVITY = 0.94;
//move up/down faster (if not accelerating = slow down)
boolean upAccel, downAccel;
//determines if player 1 or player 2 (on left or on right)
int player;
//position of actual paddle
int x;
double y;
Rectangle panel;
public PlayerPaddle(int player) {
upAccel = false;
downAccel = false;
y = 210; //not moving initially
yVelocity = 0;
if (player == 1) {
//left side
x = 20;
} else {
//right side
x = 660;
}
}
#Override
public void draw(Graphics g) {
//draw paddle
g.setColor(Color.WHITE);
g.fillRect(x, (int) y, 20, 80);
}
#Override
public void move() {
if (upAccel) {
yVelocity -= 2;
} else if (downAccel) {
yVelocity += 2;
} else if ((!upAccel) && (!downAccel)) {
yVelocity *= GRAVITY;
}
y += yVelocity; //changes y position of paddle
}
public void setUpAccel(boolean input) {
upAccel = input;
}
public void setDownAccel(boolean input) {
downAccel = input;
}
#Override
public int getY() {
return (int) y;
}
}
I want to know how to make the rectangle move up and down vertically. A similar question had only one answer which said that the previously painted rectangle was not being cleared and as a result is expanding. But even when I say g.clearRect(...) it still expands and does not move.
I am new to Swing and Awt but I am really committed to learning. Thanks for the help.

A similar question had only one answer which said that the previously painted rectangle was not being cleared and as a result is expanding
And that is still probably the problem here.
Somewhere, not in the code presented here, you need to invoke the draw(...) method of this class.
So in that code you need to make sure the background of the component is cleared before you draw the paddle. Since you should be overriding the paintComponent(...) method of a panel to do custom painting your code should look something like:
#Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
// draw the paddle
}
Read the section from the Swing tutorial on Custom Painting for more information and working examples.
I am new to Swing and Awt but I am really committed to learning.
Then keep a link to the tutorial handy for all Swing basics.

Multiple classes in processing

I'm making a game where you're controlling a square, and objects will spawn in random places, which you have to pick up to get points, while also having to dodge big squares going from side to side. Right now I have 2 classes (one for enemies - big squares -, and one for the hero), I haven't done the point system yet with the spawning objects, but that's not what I'm trying to do now.
So my problem right now is that I don't really know how to make the person lose the game/a life when you touch the "enemies" with your hero. I would know how to do it without classes, but I'd like to know how to do it when they are in separate classes.
If someone could explain with code and comments how this would be done, it would help me out a lot :) (I read something about 'extends' for classes but I'm not sure if this is what I should use or not).
Here's a screenshot of what my game looks like at the moment, just to better illustrate it:
Here's the main code page:
Hero myHero = new Hero(400,480,5);
Enemies myEnemies = new Enemies(50,50,10);
Enemies myEnemies2 = new Enemies(50,350,15);
Enemies myEnemies3 = new Enemies(50,650,12);
void setup() {
size(900,800);
frameRate(30);
smooth();
}
void draw() {
background(0);
myHero.keyPressed();
myEnemies.enemyDisplay();
myEnemies.enemyMove();
myEnemies2.enemyDisplay();
myEnemies2.enemyMove();
myEnemies3.enemyDisplay();
myEnemies3.enemyMove();
}
Class 1:
class Enemies {
float xpos, ypos, speed;
Enemies(float x, float y, float s) {
xpos = x;
ypos = y;
speed = s;
}
void enemyDisplay() {
rect(xpos, ypos, 100, 100);
}
void enemyMove() {
xpos += speed;
if((xpos > width - 100) || (xpos < 0)) {
speed *= -1;
}
}
}
Class 2:
class Hero {
float xpos_, ypos_, speed_;
Hero(float x, float y, float s) {
xpos_ = x;
ypos_ = y;
speed_ = s;
}
void keyPressed() {
if (key == CODED) {
if (keyCode == UP) {
ypos_ -= speed_;
}
if (keyCode == DOWN) {
ypos_ += speed_;
}
if (keyCode == LEFT) {
xpos_ -= speed_;
}
if (keyCode == RIGHT) {
xpos_ += speed_;
}
}
rect(xpos_,ypos_,30,30);
}
}

I believe the question you are asking involves basic collision detection and object interactions.
I would first make the Enemies a List and create it / add elements during the setup() call:
List<Enemies> enemies = new List<Enemies>();
enemies.add(new Enemies(50,50,10));
This allows you to store all of your Enemies under one object. So your draw() method would look something like:
void draw(){
background(0);
myHero.keyPressed();
for(Enemies enemy : enemies)
{
enemy.enemyDisplay();
enemy.enemyMove();
if (hero.isCollidingWith(enemy)) // collision method defined in the hero object, but you could define it in the Enemies class as well, it doesn't really matter
{
hero.removeHealth(); // method defined in hero that removes health
}
}
}
This method would be in one of your classes:
public boolean isColliding(Enemies enemy)
{
// check the x and y coordinates of each object
}
I hope this helps to point you in the right direction.

you need to figure out collision detection and when your objects collide with each other, something basic like:
class Enemy
{
//...
public boolean isColliding(Hero hero)
{
//figure out the distance between two objects, if its less than their size, they are colliding..
//...
}
//...
}
then you need a part of your Game Loop that checks if anything is colliding with your hero, pickups, walls, etc...

It seems the first part you need help with is collision detection. The short answer I would give that will almost undoubtedly lead you to more questions is to look at the Area class (specifically Area.intersect). You might also want to look at the classes I've put together for displaying & managing areas in this project here

There are several problems here that touch on both application design as well as conventions. These should be addressed first before trying to tackle the collision detection problem.
The Enemies class only represents a single enemy, so the name of the class should reflect that. Additionally, prefixing the method names with "enemy" is redundant and can be removed. Other changes have been commented in the revised class below.
public class Enemy {
// Instead of hard-coding in the width and height of an enemy, allow the
// instantiating code to specify the enemy's size. This will allow you
// to have different size enemies and prevents you from having "magic numbers"
// in your code.
private float xpos, ypos, width, height, speed;
public Enemy(float x, float y, float s, float w, float h) {
xpos = x;
ypos = y;
width = w;
height = h;
speed = s;
}
/* These getters will be used for collision detection later */
public float getX() {
return xpos;
}
public float getY() {
return ypos;
}
public float getWidth() {
return width;
}
public float getHeight() {
return height;
}
// I've changed `display` to `draw` to be consistent with the method name in
// your main `draw` method.
public void draw() {
rect(xpos, ypos, width, height);
}
// This method now accepts a screenWidth parameter so that the enemy can know
// when they've collided with the left or right wall of the screen without
// having to rely on an global variable.
public void move(int screenWidth) {
xpos += speed;
if ((xpos > screenWidth - width) || (xpos < 0)) {
speed *= -1;
}
}
}
I mention the "magic numbers" in one of the comments above. See this wikipedia article for more on that.
The Hero class contains property names that have an underscore postfix. This ranges from unconventional to inconsistent with respect to all of your other property names in your other classes. The original keyPressed() method mixes the logic for both drawing and moving. These two things have been separated and the methods named like those of the Enemy class for consistency.
public class Hero {
private float xpos, ypos, width, height, speed;
public Hero(float x, float y, float s, float w, float h) {
xpos = x;
ypos = y;
width = w;
height = h;
speed = s;
}
// Change this method name to draw for consistency with the Enemy class
public void draw() {
// Key press functionality has been moved to the `move` method for consistency
// with the Enemy class.
rect(xpos, ypos, WIDTH, HEIGHT);
}
// This method uses the variables key, keyCoded, UP, DOWN, LEFT, and RIGHT. You
// did not include any import statements with your code, so they may be coming
// from there; however, if they are globals, you should pass them to this method
// as arguments whenever you call it.
public void move() {
// If this condition isn't satisfied, return immediately. This prevents
// unnecessary nesting and work below.
if (key != CODED) {
return;
}
if (keyCode == UP) {
ypos -= speed;
}
// Use `else if` here and below to prevent multiple unnecessary
// comparisons of keyCode.
else if (keyCode == DOWN) {
ypos += speed;
}
else if (keyCode == LEFT) {
xpos -= speed;
}
else if (keyCode == RIGHT) {
xpos += speed;
}
}
public boolean isColliding(Enemy enemy) {
// Collision detection is easy since all of your game entities (the hero and
// the enemies) are all rectangles and axis-aligned (not rotated). You can
// use a method known as "bounding box intersection."
return (Math.abs(enemy.getX() - xpos) * 2 < (enemy.getWidth() + width))
&& (Math.abs(enemy.getY() - ypos) * 2 < (enemy.getHeight() + height));
}
}
For more on bounding box intersection, see this gamedev stackexchange question.
Now that your classes are in order, its time to address your main code. We'll need to update the method names and, as #James T suggested, you should make a list of enemies instead of creating a new independent object for each enemy. This will make it easier for you to add or remove enemies in the future and to be able to process all enemies with one block of code without repeating yourself.
// Use constants to remove magic numbers.
private static final int SCREEN_WIDTH = 900;
private static final int SCREEN_HEIGHT = 800;
private Hero myHero = new Hero(400, 480, 30, 30, 5);
private List<Enemy> enemies = new ArrayList<Enemy>();
void setup() {
size(SCREEN_WIDTH, SCREEN_HEIGHT);
frameRate(30);
smooth();
enemies.add(new Enemy(50, 50, 100, 100, 10));
enemies.add(new Enemy(50, 350, 100, 100, 15));
enemies.add(new Enemy(50, 650, 100, 100, 12));
}
void draw() {
hasCollision = false;
background(0);
// I've changed the order of draw->move to move->draw. If you draw first, then
// move, then detect collisions, it will appear to your user that your hero has
// not yet collided with an enemy even though you act as they have (e.g.: they
// will not see the collision until the next time you draw the scene).
myHero.move();
myHero.draw();
for (Enemy enemy : enemies) {
enemy.move();
enemy.draw(SCREEN_WIDTH);
if (!hasCollision && myHero.isColliding(enemy)) {
hasCollision = true;
}
}
if (hasCollision) {
// Handle enemy collision here
}
}
You'll notice that I've also added accessibility modifiers to everything. While it is technically valid to exclude them and use the defaults, it makes your code more readable to include them because it is more obvious. When you're first starting out, the more obvious the better.

Alright got it to work thanks to all you helpful wonderful people!
I did this:
public boolean isColliding(Enemies h){
float distance = dist(x,y,h.x,h.y);
if(distance<100){
return true;
}else{
return false;
}
}
and in my draw(){ I have
if(myHero.isColliding(myEnemies)){
println("You lost!");
}
I had a very similar 'fix' earlier, but the reason I got an error was because I had Hero h instead of Enemies h in the 'if' function, so it was just a very dumb error that I overlooked :P

Coding a game of Pool in Java - how can I define the balls and move them (via Graphics g)?

My plan is to design a simple game of Pool in Java.
OOP makes the most sense here for the balls. All the balls have the same functionality, so because of that it would be a good idea to make a Ball class that would handle the relative position of the ball and other variables such as when it goes in a hole it removes itself and increments your score. So when it hits a hole Ball.dispose (); would fit nicely.
My issue is that I do not know how to manipulate the ball and dispose of it. Also inorder to move it I rely on Thread.sleep instead of java.swing.timer because there is no available Action Performed method I can rely on.
How can I move the ball more easily and get rid of it when needed?
The green thing covering the ball is my way of erasing the last position of the ball by drawing a green oval over it.
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
public class Main extends JFrame{
Ball redball = new Ball (285, 600, 20, 20, Color.RED);
//variables to control redball
private int rX = redball.getX();
private int rY = redball.getY();
private final int rWidth = redball.getWidth();
private final int rHeight = redball.getHeight();
int Force = 30;
int Bearing = 20; // True Bearing
public Main (){
setSize(600, 800);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Pool");
}
public void paint(Graphics g){
super.paint(g);
// draw the table
g.setColor (Color.GREEN);
g.fillRect(100, 100, 400, 600);
g.setColor (Color.BLACK);
g.drawRect(99, 99, 401, 601);
//draw start ball
g.setColor(redball.getColor());
g.fillOval(rX, rY, rWidth, rHeight);
if (Force == 30){
for (int i = Force; i > 0;i--){
try {
Thread.sleep(100);
} catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}
Force--;
if (rY > 98 + rWidth) {
rY = rY - i;
rX = rX + (Bearing/5);
}
g.fillOval(rX, rY, rWidth, rHeight);
g.setColor(Color.GREEN);
repaint ();
g.fillOval(rX - (Bearing/5), rY + i, rWidth, rHeight); // repaint last ball
g.setColor(Color.RED);
repaint ();
}
}
// Ball.dispose (redball);
}
public static void main(String[] args) {
new Main();
}
Here is the class for the ball
public class Ball {
private int x;
private int y;
private int width;
private int height;
private Color color;
public Ball (int x, int y, int width, int height, Color color)
{
this.x = x;
this.y = y;
this.width = width;
this.height = height;
this.color = color;
}
public void setX (int x){
this.x = x;
}
public int getX (){
return this.x;
}
public void setY (int x){
this.y = y;
}
public int getY (){
return this.y;
}
public void setWidth (int width){
this.width = width;
}
public int getWidth (){
return this.width;
}
public void setHeight (int height){
this.height = height;
}
public int getHeight (){
return this.height;
}
public void setColor (Color color){
this.color = color;
}
public Color getColor (){
return this.color;
}
public static void dispose(Ball ball) {
ball = null; // if I call this method nothing happens
}
}

What I would do is maintain a List<Ball> field of all active balls. Then each iteration, iterate through that list and update and paint the Balls. When a Ball goes away, it's simply a matter of removing it from the list.
A consideration is: Who determines when its time to dispose of a ball? If something outside the Ball does, you have a few options, among others:
As I mentioned above, you could simply remove the Ball from the list.
You could set a "dead" flag in the Ball elsewhere, then on each iteration remove all Balls from the list whose "dead" flag has been set.
If the Ball itself determines when it is time to go away, you have a few options, among others, there as well:
Perhaps a method boolean Ball.think(), that updates the state of the ball and returns true if the Ball is still good, or false if its dead. Then when you iterate through your list of balls, you call think() on all of them to update, and remove ones from the List that returned false.
Related to option 2 above, if a Ball has a think method or something similar, the ball can set its own "dead" flag (or something outside the Ball can set it), then the main loop can remove dead balls from the list.
If you want to keep the Ball instance around and just not draw it, you have a few options there too:
Simply skip processing of Balls marked as "dead" instead of removing them.
Move "dead" balls to a different dead Ball list.
Personally, I like the boolean think() method, because it easy allows you to specify a base interface for objects in the scene. You can also have objects paint themselves in that case. E.g.:
interface Entity {
public boolean think ();
public void paint (Graphics g);
}
class Ball implements Entity {
#Override public boolean think () {
// return true if alive, false if dead
}
#Override public void paint (Graphics g) {
// draw this ball
}
}
// then in your main update loop:
List<Entity> entities = ...;
Iterator<Entity> eit = entities.iterator();
while (eit.hasNext())
if (!eit.next().think())
eit.remove();
// and in paint:
for (Entity e:entities)
e.paint(graphics);
If you want to take the option I mentioned above of just skipping "dead" balls instead of removing them, something like this would be more appropriate (leaving out Ball for brevity), where isActive() returns true if the ball is active or false if it is temporarily "dead":
interface Entity {
public boolean isActive ();
public void think (); // think returns nothing
public void paint (Graphics g);
}
// then in your main update loop:
List<Entity> entities = ...;
for (Entity e:entities)
if (e.isActive())
e.think();
// it is the responsibility of something outside the ball to restore it to an
// active state, since think() isn't called if !isActive(). alternatively, you
// could always call think(), and just don't paint inactive balls.
// and in paint:
for (Entity e:entities)
if (e.isActive())
e.paint(graphics);
Still, you don't have to do it that way, there are plenty of arguments for all of the options listed above, and more. In your application, for example, there's not much need for an Entity interface if you know you are only dealing with Balls; and think() might not be the most convenient way to go if all of your physics logic is happening somewhere else (although of course the code could be written to place the logic in Ball).
As you can see there are many ways to skin a cat, but I hope something here helps.

Here are some suggestions.
Create a Rack class that contains all of the balls for your game.
Move the draw code for a ball into your Ball class. I realize that this suggestion is not pure MVC, but games are a lot easier to code when objects draw themselves.
Don't try to repaint part of the screen. It's a lot easier, and pretty fast, to just redraw the entire screen.
Don't dispose any Ball instances. Move it to some negative position that your draw code recognizes and doesn't draw.
When you're coding an action game, your main loop should look something like this (psudeocode).
while (running) {
calculateRackPosition();
drawRack();
Thread.sleep(100L);
}
You incrementally move the balls, then redraw the screen. This is how you code any animation. This code would run while the balls are moving.
You would write other code for when the person is aiming his shot.