I understand the basis of collision detection and have developed my way (as far as I know) for collision detection. However, it does not seem to be working. What I have done is instead of drawing full rectangles around sprites, shapes, and other objects, I simply made methods that draw lines (very thin rectangles) on all sides of the object, left, right, top, and bottom.
The methods that draw the thin rectangles on the left,right,top, and bottom of the specified sprites. This is probably not the best way to do collision, but this is what I have, and am open to all ideas and different solutions!
Note: The(int)(x-Game.getCamera().getX()),(int)(y + height -Game.getCamera().getY()), is simply for the camera, so when the player moves, the trees (in my case the object I want to collide with) do not move with him
public Rectangle getBounds() {
return new Rectangle((int)(x-Game.getCamera().getX()),
(int)(y + height - Game.getCamera().getY()),width,height-height);
}
public Rectangle getBoundsTop() {
return new Rectangle((int)(x-Game.getCamera().getX()),
(int)(y- Game.getCamera().getY()),width,height-height);
}
public Rectangle getBoundsRight() {
return new Rectangle((int)(x + width -Game.getCamera().getX()),
(int)(y - Game.getCamera().getY()),width - width,height);
}
public Rectangle getBoundsLeft() {
return new Rectangle((int)(x -Game.getCamera().getX()),
(int)(y- Game.getCamera().getY()),width - width,height);
}
Actual collision CHECKING (in player class)-
if(getBounds().intersects(treeTile.getBoundsTop())) {
//What happens when they collide
//When the bottom of the player collides with the top of the tree.
}
if(getBoundsTop().intersects(treeTile.getBounds())) {
//What happens when they collide
//When the top of the player collides with the bottom of the tree
}
if(getBoundsRight().intersects(treeTile.getBoundsLeft())) {
//What happens when they collide
//when the right side of the player collides with the left of the
//tree
}
if(getBoundsLeft().intersects(treeTile.getBoundsRight())) {
//What happens when they collide
//When the left of the player collides with the right of the tree
}
I appreciate all the help I can get
Here is collision and movement code-
for (int i = 0; i < handler.object.size(); i++) {
Square handle = handler.object.get(i);
if (getBounds().intersects(treeTile.getBoundsTop())) {
handle.setvelY(-1);
}
if (getBoundsTop().intersects(treeTile.getBounds())) {
handle.setvelY(0);
}
if (getBoundsRight().intersects(treeTile.getBoundsLeft())) {
handle.setvelX(0);
}
if (getBoundsLeft().intersects(treeTile.getBoundsRight())) {
handle.setvelX(0);
}
}
Movement-
public void keyPressed(KeyEvent e) {
int code = e.getKeyCode();
for (int i = 0; i < handler.object.size(); i++) {
Square handle = handler.object.get(i);
if (handle.getId() == ObjectId.Zelda) {
if (code == KeyEvent.VK_D) {
handle.right();
}
if (code == KeyEvent.VK_A) {
handle.left();
}
if (code == KeyEvent.VK_W) {
handle.up();
}
if (code == KeyEvent.VK_S) {
handle.down();
}
}
My new collision idea -
boolean walkRight = true;
boolean walkLeft = true;
boolean walkDown = true;
boolean walkUp = true;
public void tick() {
if(walkRight == true) {
velX = 2;
}if(walkLeft == true) {
velX = -2;
}if(walkDown == true) {
velY = 2;
}if(walkUp == true) {
velY = -2;
}
if (getBounds().intersects(treeTile.getBoundsTop())) {
walkDown = false;
}
if (getBoundsTop().intersects(treeTile.getBounds())) {
walkUp = false;
}
if (getBoundsRight().intersects(treeTile.getBoundsLeft())) {
walkRight = false;
}
if (getBoundsLeft().intersects(treeTile.getBoundsRight())) {
walkLeft = false;
}
Something like this, not exactly, it is just an example.
Have you tried using 1 instead of width - width and height - height ?
I think these evaluating to 0 for the width / height is causing the intersects function to fail.
EDIT
I think you're over complicating this. If you just have one big collision box, instead of four small ones, then where ever you're moving your player, you can
// Square previousPosition = currentPosition
// do move player code, which presumably updates the currentPosition
// loop through all the trees you have
// if the player is colliding with a tree
// currentPosition = previousPosition
This should handle the player colliding with any side of the tree, since we just move them back to where they were previously.
Related
I have a moving image as a background
PImage background;
int x=0; //global variable background location
rocket Rocket;
void setup(){
size(800,400);
background = loadImage("spaceBackground.jpg");
background.resize(width,height);
Rocket = new rocket();
}
void draw ()
{
image(background, x, 0); //draw background twice adjacent
image(background, x+background.width, 0);
x -=4;
if(x == -background.width)
x=0; //wrap background
Rocket.defender();
Rocket.move();
}
In a different class i'm trying to make a rocket move up and down
class rocket {
float x;
float y;
float speedy;
boolean up;
boolean down;
rocket(){
x = 50;
y = 200;
speedy = 3;
}
void move() {
if(up)
{
y = y - speedy;
}
if(down)
{
y = y + speedy;
}
}
void defender(){
fill(255,0,0);
rect(x,y,50,20);
triangle(x+50,y,x+50,y+20,x+60,y+10);
fill(0,0,100);
rect(x,y-10,20,10);
}
void keyPressed(){
if(keyCode == UP)
{
up = true;
}
if(keyCode == DOWN)
{
down = true;
}
}
void keyReleased(){
if(keyCode == UP)
{
up = false;
}
if(keyCode == DOWN)
{
down = false;
}
}
}
The rocket will display but won't move. I tried everything I know but nothing works. I also tried the rocket class just as a project by itself and the rocket moves, so it has to be something with the class. i'm quite new to coding so please keep that in mind, thank you in advance.
The keyPressed() and keyReleased() functions (and any other event function) need to be at the sketch level, not inside another class. If they're inside another class, Processing doesn't know how to find them.
So, what you need to do is move the keyPressed() and keyReleased() functions to the sketch, and then call functions on your Rocket class (class names should start with an upper-case letter, btw), similar to how you're calling rocket.defender() and rocket.move() (variable names should start with a lower-case letter) from the sketch-level draw() function.
I am creating a racing game using java and have got a checkpoint counter and a lap counter. I have drawn lines on the track to increment the checkpoint counter. When the checkpoint counter reaches 9 and they pass over the blue line the lap counter then increments. The problem is that when the car goes over a line the checkpoint counter or the lap counter will either keep incrementing or it will not move at all.
Player player;
float scaleFactor, translateX, translateY;
color c;
int counterlap=0;
int countercheck=0;
void setup() {
size(displayWidth, displayHeight);
frame.setResizable(true); //make the screen adjustable
background=loadImage("track.png");
player = new Player(100, 100); //initialize the player object
scaleFactor = 2;
}
PImage background; //define an image for the background
void draw() {
background(0);
imageMode(CORNER);
pushMatrix();
translate(width/2, height/2);
scale(scaleFactor);
translate(-width/2, -height/2);
pushMatrix();
translate(-player.position.x+width/2, -player.position.y+height/2);
image(background, 0, 0, background.width, background.height); //draw background
popMatrix();
popMatrix();
c = get(width/2, height/2);
println(hue(c));
player.draw(); //draws the player
text("Laps "+counterlap, width-50, 20);//lapcounter
if (countercheck>=9) {
if ((hue(c)>135)&&(hue(c)<141)) {
counterlap++;
if ((counterlap>=1)&&(countercheck>=9)) {
countercheck=0;
}
}
}
text("Checkpoint "+countercheck+"/9", width-200, 20);//checkpoint counter
if ((hue(c)>249)&&(hue(c)<254)) {
countercheck++;
}
}
class Player { //creates the player class for the player object
PVector position, velocity; //defines position & velocity vectors
float vel, accel, heading; //scalar magnitudes
PImage car;
Player(float xposition, float yposition) {
position = new PVector(xposition, yposition); //initialize everything and pass the spawn point
velocity = new PVector(0, 0);
accel=0;
car = loadImage("car.png"); //loads the image for the player
}
void draw() {
pushMatrix();
translate(width/2, height/2); //translates car origin to the position vector
scale(scaleFactor);
rotate(heading+PI); //rotates to the current heading
imageMode(CENTER); //centers the car image for better rotation
tint(color(255, 0, 255)); //colour of the car
image(car, 0, 0, 64, 40); //draws the image and resizes to 64x40
noTint(); //disable tint for remainder of frame
popMatrix();
if (up) { //acclerate when up is pressed
accel=0.15;
} else { //otherwise no accleration
accel=0;
}
if (down) { //brake/reverse
accel=-0.15;
}
if (left) {
heading-=0.04*sqrt(abs(vel)); //
}
if (right) {
heading+=0.04*sqrt(abs(vel));
}
if (!(up||down||left||right)) {
}
vel+=accel;
velocity=PVector.fromAngle(heading);
velocity.setMag(vel);
if (hue(c)==97.48252) {
vel*=0.9;
} else {
vel*=0.99;
}
velocity.limit(50);
position.add(velocity);
if (position.x>background.width) {
position.x=background.width;
velocity.x*=-0.1;
}
if (position.x<0) {
position.x=0;
velocity.x*=-0.1;
}
if (position.y>background.height) {
position.y=background.height;
velocity.y*=-0.1;
}
if (position.y<0) {
position.y=0;
velocity.y*=-0.1;
}
}
}
boolean up, down, left, right;
void mouseWheel(MouseEvent e)
{
scaleFactor *= pow(2, e.getAmount() /10F);
translateX -= e.getAmount() * mouseX / 100;
translateY -= e.getAmount() * mouseY / 100;
}
void keyPressed() {
if (keyCode == UP) {
up = true;
text("D", width-500, 20);
}
if (keyCode == DOWN) {
down = true;
text("R", width-500, 20);
}
if (keyCode == LEFT) {
left = true;
}
if (keyCode == RIGHT) {
right = true;
}
if (key == 'r')
{
scaleFactor = 2;
translateX = 0;
translateY = 0;
}
}
void keyReleased() {
if (keyCode == UP) {
up = false;
}
if (keyCode == DOWN) {
down = false;
}
if (keyCode == LEFT) {
left = false;
}
if (keyCode == RIGHT) {
right = false;
}
}
There are two problems in the current approach:
If your player stays on the line, for each frame he stays there, you will count a lap.
If your player passes quickly from a point on one side the lap line to another point on the other side... he has crossed the line, but if there was no intermediate frame when he stood right on top, you will not count a lap.
To fix this, instead of looking at "where is the player in this frame", you should check "has the player moved, in this last frame, from being on one side of the line to being on top or on the other side of the line; -- and has he done the same for all N checkpoint lines before doing so". Since this can happen only once, and exactly once for each lap, you will now count the number of laps correctly.
This means that you cannot rely on hue alone; unless you make sure that, no matter the speed of the car, it is impossible to trigger "from one side to the other without ever being right on top" in a single frame.
I'm working on a Mario game and am in need of assistance and suggestions on how to go about creating hit detection for a tilemap.
Currently, the player has the ability to walk/jump through the blocks.
I added in a fixed detection to the ground for now which I am hoping to replace with regular hit detection.
I understand that there are four sides to each block and the player. Only some blocks need hit detection and some things you might need to know is that the player stays at 300px(middle of screen) 98% of the time.
The only thing that moves is the map
The map is rendered from a .txt file and is rendered like so:
for(int y=0;y<map.length;y++) {
for(int x=0;x<map[y].length;x++) {
int index = map[y][x];
int yOffset = 0;
if(index>(tileSheet.getWidth() / Engine.TILE_WIDTH) -1) {
yOffset++;
index = index - (tileSheet.getWidth() / Engine.TILE_WIDTH);
}
g.drawImage(tileSheet,
((x * Engine.TILE_WIDTH)*scale)+position,
((y * Engine.TILE_HEIGHT)*scale),
(((x * Engine.TILE_WIDTH) + Engine.TILE_WIDTH )*scale)+position,
(((y * Engine.TILE_HEIGHT) + Engine.TILE_HEIGHT)*scale),
index * Engine.TILE_WIDTH,
yOffset * Engine.TILE_HEIGHT,
(index * Engine.TILE_WIDTH) + Engine.TILE_WIDTH,
(yOffset * Engine.TILE_HEIGHT) + Engine.TILE_HEIGHT,
null
);
}
}
//This code is actually longer(included file later on)
Colour hit detection is too slow and inconsistent for multi coloured tiles
Since the map is moving I suppose I need to move the hit detection boxes with it. As for selecting the boxes that it should detect might be difficult. Maybe it would be a better idea to make the code NOT hit detect certain tiles.
My attempts have ended in obfuscation of code. Can anyone suggest the easiest way to implement the hit detection? (keep in mind I have jumping).
The important codes are listed below:
Board.java(The panel where everything is drawn)
package EvilMario; //Include this class in the EvilMario game package
import java.awt.*; //Imported to allow use of Image
import java.awt.event.*; //Imported to allow use of ActionListener
import javax.swing.*; //Import swing
public class Board extends JPanel implements ActionListener { //Class Board
private TileLayer l; //Instance of TileLayer class
private Menu m; //Instance of menu class
private Player p; //Instance of player class
Timer time; //A timer
public static enum STATE {MENU,GAME}; //The game states
public static STATE State = STATE.MENU; //Set the first state to menu
//END
//GLOBAL
//DECLARATIONS
public Board() {
l = TileLayer.FromFile("D:/ICS3U1/EvilMario/map.txt"); //Tile map data from .txt file
this.addMouseListener(new MouseInput()); //Listen for mouse input
this.addKeyListener(new AL()); //Listen for key input
p = new Player(); //Start running Player class
m = new Menu(); //Start running Menu class
setFocusable(true); //Allows movement
time = new Timer(20,this); //Timer set to update "this" class every 20 milliseconds(Approximately 50fps)
time.start(); //Actually start the timer
}
public void actionPerformed(ActionEvent e) {
p.move(); //Call the move method from the player class
repaint(); //Repaint
}
public void paintComponent(Graphics g) { //Graphics method
super.paintComponent(g); //Super hero?
Graphics2D g2d = (Graphics2D) g; //Cast 2D graphics
if(State==STATE.GAME) {
if(p.distanceTraveled<300)l.DrawLayer(g,0);else l.DrawLayer(g, -(p.distanceTraveled-300)); //Draw the tile map
g2d.drawImage(p.getImage(), p.getX(), p.getY(), 48, 48, null); //Draw the player
if(p.distanceTraveled==3488) System.out.println("You have won the game!"); //Draw the end game screen
} else {
m.render(g); //Render the menu
}
}
private class AL extends KeyAdapter { //Action Listener extends key adapter
public void keyPressed(KeyEvent e) { //On key press
p.keyPressed(e); //Send whatever key was pressed TO the keyPressed method in the player class
}
public void keyReleased(KeyEvent e) { //On key release
p.keyReleased(e); //Send whatever key was released TO the keyReleased method in the player class
}
}
}
Player.java(player logic)
package EvilMario; //Include this class in the EvilMario game package
import java.awt.Image;
import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
public class Player {
int x, dx, y, distanceTraveled; //x coordinate,change in x coordinate,y coordinate,1st rep bg,2nd rep bg,dist traveled
Image player; //The player variable
ImageIcon walk_L_anim = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/walk_L_anim.gif");
ImageIcon walk_L_idle = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/walk_L_idle.png");
ImageIcon walk_R_anim = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/walk_R_anim.gif");
ImageIcon walk_R_idle = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/walk_R_idle.png");
ImageIcon jump_L_anim = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/jump_L_anim.gif");
ImageIcon jump_L_idle = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/jump_L_idle.png");
ImageIcon jump_R_anim = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/jump_R_anim.gif");
ImageIcon jump_R_idle = new ImageIcon("D:/ICS3U1/EvilMario/images/animatedMario/jump_R_idle.png");
boolean holdingLeft = false;
boolean holdingRight = false;
static boolean jumping = false;
static boolean falling = false;
static int jumpingTime = 350;
public Player() {
player = walk_R_idle.getImage(); //Give the player the image
x = 75; //The original x position of the player
y = 277; //The original y position of the player
distanceTraveled = 75; //Original distance traveled
}
public void move() {
if(x>=0 && x<=300) { //If the player is within the moving area
x = x+dx; //The x position is updated to become itself+the amount you moved
}
if(x<0) //If the player has reached he very left side of the screen(0px)
x=0; //Move him up a pixel so he can move again
if(x>300) //If the player has reached the center of the screen(300px)
x=300; //Move him down a pixel so he can move again
distanceTraveled=distanceTraveled+dx; //Calculate distanceTraveled
if(distanceTraveled<0) //Make sure distanceTraveled isn't a negative
distanceTraveled=0; //Make sure distanceTraveled isn't a negative
if(distanceTraveled>=300) //Keep player at center position once past 300 mario meters
x=300; //Keep player at center position once past 300 mario meters
if(holdingLeft && !holdingRight) {
if(distanceTraveled<300)dx=-5; else dx=-4;
if(jumping && !falling) {
player = jump_L_anim.getImage();
y-=8;
} else {
player = walk_L_anim.getImage();
if(y<277)
y+=8;
}
} else if(holdingRight && !holdingLeft) {
if(distanceTraveled<300)dx=5; else dx=4;
if(jumping && !falling) {
player = jump_R_anim.getImage();
y-=8;
} else {
player = walk_R_anim.getImage();
if(y<277)
y+=8;
}
} else if(!holdingRight && !holdingLeft) {
dx = 0;
if(jumping && !falling) {
player = jump_R_anim.getImage();
y-=8;
} else {
if(y<277)
y+=8;
}
}
if(y==277) {
falling = false;
}
System.out.println("LEFT: "+holdingLeft+" JUMP: "+jumping+" RIGHT: "+holdingRight+" FALLING: "+falling+" Y: "+y);
}
public int getX() { return x; } //This method will return the x. Is used by other classes
public int getY() { return y; } //This method will return the y. Is used by other classes
public Image getImage() { return player; } //This method will return the player. Is used by other classes
public void keyPressed(KeyEvent e) { //Called from the board class, the argument is whatever key was pressed
int key = e.getKeyCode(); //The key originally sent from the board class
if(key == KeyEvent.VK_LEFT && !holdingLeft)
holdingLeft = true;
if(key == KeyEvent.VK_RIGHT && !holdingRight)
holdingRight = true;
if(key == KeyEvent.VK_UP && !jumping && !falling)
new Thread(new JumpThread(this)).start();
}
public void keyReleased(KeyEvent e) { //Called from the board class, the argument is whatever key was released
int key = e.getKeyCode(); //The key originally sent from the board class
if(key == KeyEvent.VK_LEFT) { //If the left or right key was released
dx = 0; //Stop moving
holdingLeft = false;
player = walk_L_idle.getImage();
}
if(key == KeyEvent.VK_RIGHT) {
dx = 0;
holdingRight = false;
player = walk_R_idle.getImage();
}
}
}
TileLayer.java (Rendering of the tile layer)(Probably most important part relating to the question)
package EvilMario; //Include this class in the EvilMario game package
import java.awt.Graphics; //
public class TileLayer {
private int[][] map; //2D array
private BufferedImage tileSheet; //The tile sheet
public TileLayer(int[][] existingMap) { //
map = new int[existingMap.length][existingMap[0].length]; //map initialized
for(int y=0;y<map.length;y++) { //Loop through all boxes
for(int x=0;x<map[y].length;y++) { //Loop through all boxes
map[y][x] = existingMap[y][x]; //Update the map
}
}
tileSheet = LoadTileSheet("D:/ICS3U1/EvilMario/images/tilemap.gif"); //Load the tilesheet
}
public TileLayer(int width, int height) {
map = new int[height][width];
}
public static TileLayer FromFile(String fileName) {
TileLayer layer = null;
ArrayList<ArrayList<Integer>> tempLayout = new ArrayList<>();
try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
String currentLine;
while((currentLine = br.readLine()) !=null) {
if(currentLine.isEmpty())
continue;
ArrayList<Integer> row = new ArrayList<>();
String[] values = currentLine.trim().split(" ");
for(String string: values) {
if(!string.isEmpty()) {
int id = Integer.parseInt(string);
row.add(id);
}
}
tempLayout.add(row);
}
} catch(IOException e) {
System.out.println("ERROR");
}
int width = tempLayout.get(0).size();
int height = tempLayout.size();
layer = new TileLayer(width,height);
for(int y=0;y<height;y++) {
for(int x=0;x<width;x++) {
layer.map[y][x] = tempLayout.get(y).get(x);
}
}
layer.tileSheet = layer.LoadTileSheet("D:/ICS3U1/EvilMario/images/tilemap.gif");
return layer;
}
public BufferedImage LoadTileSheet(String fileName) {
BufferedImage img = null;
try {
img = ImageIO.read(new File(fileName));
} catch(Exception e) {
System.out.println("Could not load image");
}
return img;
}
int scale = 2;
public void DrawLayer(Graphics g, int position) {
for(int y=0;y<map.length;y++) {
for(int x=0;x<map[y].length;x++) {
int index = map[y][x];
int yOffset = 0;
if(index>(tileSheet.getWidth() / Engine.TILE_WIDTH) -1) {
yOffset++;
index = index - (tileSheet.getWidth() / Engine.TILE_WIDTH);
}
g.drawImage(tileSheet,
((x * Engine.TILE_WIDTH)*scale)+position,
((y * Engine.TILE_HEIGHT)*scale),
(((x * Engine.TILE_WIDTH) + Engine.TILE_WIDTH )*scale)+position,
(((y * Engine.TILE_HEIGHT) + Engine.TILE_HEIGHT)*scale),
index * Engine.TILE_WIDTH,
yOffset * Engine.TILE_HEIGHT,
(index * Engine.TILE_WIDTH) + Engine.TILE_WIDTH,
(yOffset * Engine.TILE_HEIGHT) + Engine.TILE_HEIGHT,
null
);
}
}
}
}
Engine.java (Not as important)(Simple variables for tile sizes)
package EvilMario;
public class Engine {
public static final int TILE_WIDTH = 16;
public static final int TILE_HEIGHT = 16;
}
If you need other pieces of code, just ask for them. I am not asking you to give me a specific answer to the question but simply a method that would work with my following code.
A specific answer would be nice though :)
I also believe the answer to this question will be useful to others because this method was explained in a popular java 2d game tutorial video(They never showed hit detection).
Methods I tried:
Creating a new java file called HitDetectionLayer with the exact code in TileLayer.java that stored positions in arrays. It failed :(
Ok, I'm not entirely sure what you are doing, if you throw up some images it would be more clear.
At any rate, 'hit detection' aka collision detection is a very complex topic, but it depends on what you want to do. If you want everything to be boxes or circles, then it is quite easy. If however you want things to rotate or you want collision for complex shapes it becomes extreme difficult.
Most games use circles or spheres for collision. You put the majority of your graphics (it may not fit perfectly either leaving part of your images in or out of the circle but that's life). Now lets say you have your mario sprite and one of those turtles. Well, you have circles around them both and once the circles touch you trigger your event.
The math for this is very easy because circles are by definition a perimeter around a constant length. Look at this:
You probably already know this, and it may seem obvious, but if you think about it this is what a circle really is: a consistent length in every fathomable direction. The directions are measured in degrees and from there you move on to trigonometry but you don't need that. What you need is coordinance aka vectors. So look at this:
All you need to determine circle collision is the distance between the circles. No matter what angle the circles collide from it does not matter because the distances from the circle's centre are consistent all the way around. Even if the circles are different sizes, it doesn't matter, just account for the radii difference.
Too compute all of this, you would write a method like this:
public boolean testDistanceBetween( float radius1, float radius2,
float x1, float x2, float y1, float y2 ){
double distanceBetween = Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
if(distanceBetween < (radius1+radius2) ){
return true;
}
return false;
}
The moral of the story is that circles are just good that way. If you want to do rectangle collision you take the bottom-left and top right point and you test if other rectangles are in between those points. This should be pretty straight forward, each point is a vector, each rectangle has 4 points. If any of the 4 points of one rectangle are between points on the other rectangle, there is collision.
You can use this system to handle ground and walls also. For example, if ground is at Y=300, then if your sprite's y coordinance are == 300, you suspend your gravity.
The main thing I wanted to explain is that if you intend to have rotating rectangles or polygons and you want to detect collision on them... good luck. It can be done yes, but you should understand you are implementing complex physics, especially when/if you implement gravity.
So my answer is cautionary: there is NO easy way to detect collision of rotating rectangles or polygons. Circles and static rectangles are the limits. If you really want to do rotating rectangles/polygons get a physics engine. Box2d is pretty good and has a Java version Jbox2d.
So I understand that I'm not coding this the best way possible at the moment; this is a sort of test run. What I'm trying to do is wall collisions using rectangles and the intersects property (sorry if I'm not using the correct terminology). So far I have 2 rectangles on screen. 1 the player controls and the other which the play is colliding with. When they collide the player stops moving. The problem is that if the player is trying to move into the rectangle while they are already colliding then the player can't move in any direction perpendicular to the movement ie if the player is holding the right arrow key moving into the rectangle, then they cannot move up or down. The game works on the premise that if your x or y coordinates aren't valid, then you will be moved back to the last valid coordinate recorded but I'm having trouble detecting the valid x and y coordinate separately. Here is the code:
public void Collision()
{
if(x < 0)
x = 0;
if(x > 400 - width)
x = 400 - width;
if(y < 0)
y = 0;
if(y > 300 - height)
y = 300 - height;
rect1 = new Rectangle(x, y, 16, 16);
rect2 = new Rectangle(sx, sy, wid, hei);
if(!rect1.intersects(rect2))
{
validX = true;
validY = true;
}
else
{
validX = false;
validY = false;
}
if(validX)
{
lastValidX = x;
}
if(validY)
{
lastValidY = y;
}
if(!validX)
{
x = lastValidX;
}
if(!validY)
{
y = lastValidY;
}
}
The Collision() method in the Guy class is where I'm having the trouble I believe. Yes my code is pretty messy right now but this is only a test.
Thanks, David.
You can implement what you're describing by doing extra logic around here (i.e. detecting cases when one is false and the other is true):
if(!rect1.intersects(rect2))
{
validX = true;
validY = true;
}
else
{
validX = false;
validY = false;
}
However, it seems like maybe you shouldn't be allowing the rectangles to ever be in a "colliding" state in the first place. For example, you can change the Move method to do something like
public void Move()
{
int oldX = x, oldY = y;
x += dx;
y += dy;
if (Collision()) {
x = oldX;
y = oldY;
}
}
I have already got the jumping on the y-axis running fine, but I want to be able to use 'dx' from jumping while pressing the left/right key (ex. if I am pressing right key to go right and jump while still holding it, the character will move in a "diagonal" way)
My main jumping code (timer activated when jump key is pressed):
public void actionPerformed (ActionEvent e) {
dy += 1;
y_pos += dy;
if (y_pos >= 400) {
dy = 0;
y_pos = 400;
timer.stop();
}
repaint();
}
Now my KeyEvent code:
if (command == KeyEvent.VK_RIGHT){
x_pos += 5;
right = true;
}
if (command == KeyEvent.VK_LEFT) {
x_pos -= 5;
right = false;
}
if (command == KeyEvent.VK_UP) {
if (!(timer.isRunning()))
dy = -20;
timer.start();
}
dr.repaint();
Below is how I would implement the input logic. Note that there are several choices when you want to dig further into input handling. Using this implementation, keyboard inputs are separated from the effects they have on the game world, which is handy in several ways. For example, the speed of the character is constant (given the timing of the game loop / movements is handled correctly) regardless of the frequency of key presses / repeats.
Anyway, some pseudo code:
// Global:
array keysdown;
keysdown[left] = false;
keysdown[right] = false;
keysdown[up] = false;
// The all-important game loop:
while (true) {
pollInputs();
doMovement();
draw();
}
function pollInputs () {
foreach (key that you want to handle) {
if (key.state == down) {
keysdown[key] = true;
} else {
keysdown[key] = false;
}
}
}
function doMovement () {
if (keysdown[left]) {
// move character left
} else if (keysdown[right]) {
// move character right
}
if (keysdown[up]) {
// initiate jump
}
}