Asteroids Game - Buggy Collision Detection - processing

Question

I am making an asteroid game using Processing 3.5.3. As you will see the collision detection is very buggy. When it detects collision between ship/asteroid sometimes it is greater than the asteroid size, sometimes it is smaller. Also, when the asteroids get smaller, the collision detect still seems to be calling the larger size asteroid. The collision between bullet and asteroid seems to only be a hit when the bullet is in the center of the asteroid.
Apologies for all the comments - they are required for my internal documentation.
Here is my code, it is broken up into classes.
Ship
class Ship {
PVector shipAcceleration;
PVector shipVelocity;
PVector shipPosition;
PShape shipShape;
float shipDirection;
int shipLastFire; //holds the time in millis that the last bullet was fired
int shipDelayTime;
Ship() {
shipAcceleration = new PVector();
shipVelocity = new PVector();
shipPosition = new PVector(width/2, height/2); // player starts in middle of screen
shipDirection = 0; // set to 0 to so "up" is a sense of direction
shipLastFire = 0;
shipDelayTime = 300;
keys = new boolean[5];
shipShape = createShape();
shipShape.beginShape();
shipShape.fill(255, 0, 0);
shipShape.vertex(0, -4);
shipShape.vertex(2, 0);
shipShape.vertex(2, 2);
shipShape.vertex(0, 1);
shipShape.vertex(-2, 2);
shipShape.vertex(-2, 0);
shipShape.vertex(0, -4);
shipShape.endShape();
}
void moveShip() {
shipShape.resetMatrix();
// reset.Matrix sourced from https://processing.org/reference/resetMatrix_.html
shipShape.rotate(radians(shipDirection)); // rotates ship
shape(shipShape, shipPosition.x, shipPosition.y, 10, 10);
}
void updateShip() {
// motion sourced from Chapter 22 of 'Processing: A programming handbook
// for visual designers and asrtists' by Casey Reas and Ben Fry
shipAcceleration.x = 0;
shipAcceleration.y = 0;
if (keys[0]) {
shipAcceleration.x = 0.5 * cos(radians(shipDirection) - PI/2);
shipAcceleration.y = 0.5 * sin(radians(shipDirection) - PI/2);
}
if (keys[1] && !keys[2])
{
shipDirection -= 5;
}
if (keys[2] && !keys[1])
{
shipDirection += 5;
}
shipVelocity.add(shipAcceleration);
// add sourced from https://processing.org/reference/PVector_add_.html
shipPosition.add(shipVelocity);
shipVelocity.mult(.95);
// mult sourced from https://processing.org/reference/PVector_mult_.html
shipPosition.x %= width;
if (shipPosition.x < -10)
{
shipPosition.x = width;
}
shipPosition.y %= height;
if (shipPosition.y < -10)
{
shipPosition.y = height;
}
if (keys[4]) {
if (millis() - shipLastFire > shipDelayTime) {
shipLastFire = millis();
fireBullet(shipPosition, shipVelocity, shipDirection);
}
}
}
}
Bullet
class Bullet {
PVector bulletPosition;
PVector bulletVelocity;
boolean bulletHidden; // used if lifespan is max and to help recycle
int bulletSize;
int bulletCreationTime;
int bulletLifespan; //the time in milli seconds that bullets last
int bulletSpeed;
Bullet() {
bulletHidden = true;
bulletSize = 5;
bulletPosition = new PVector();
bulletVelocity = new PVector();
bulletCreationTime = 0;
bulletLifespan = 3000;
bulletSpeed = 5;
}
void updateBullet() {
if (!bulletHidden) {
bulletPosition.add(bulletVelocity);
if (millis() - bulletCreationTime > bulletLifespan)
// millis sourced from https://processing.org/reference/millis_.html
{
bulletHidden = true;
}
bulletPosition.x %= width;
if (bulletPosition.x < -1)
{
bulletPosition.x = width;
}
bulletPosition.y %= height;
if (bulletPosition.y < -1)
{
bulletPosition.y = height;
}
}
}
void drawBullet() {
if (!bulletHidden) {
updateBullet();
ellipse(bulletPosition.x, bulletPosition.y, bulletSize, bulletSize);
}
}
void reset(PVector pos, PVector spe, float direct) {
bulletPosition = new PVector(pos.x + (20 * cos(radians(direct) - PI/2)), pos.y + (20 * sin(radians(direct) - PI/2)));
bulletVelocity.x = bulletSpeed * cos(radians(direct) - PI/2) + spe.x;
bulletVelocity.y = bulletSpeed * sin(radians(direct) - PI/2) + spe.y;
bulletCreationTime = millis();
bulletHidden = false;
}
}
Asteroid
class Asteroid {
float asteroidSize = (width/80*12);
float x;
float y;
float velocityX;
float velocityY;
PVector[] vertices = new PVector[8];
boolean active = true; //false after collision
int level = 1; // how many times has it been shot. Level 1 is not yet shot
Asteroid(float xPos, float yPos, int aLevel) {
if (xPos == 0 && yPos == 0) { //if begin level asteroids
x = random(width) ; // set random start positions
y = random (height);
} else { // if collision generating 2 smaller asteroids
x = xPos; // set from asteroid x, y
y = yPos;
}
velocityX = random(-2, 2);
velocityY = random(-2, 2);
level = aLevel; //sets asteroid level (how many times shot)
//create polygon. /aLevel generates smaller polygons with each collision.
vertices[0] = new PVector(random (width/80*3/aLevel), random(height/80*3/aLevel) );
vertices[1] = new PVector(random((width/80*4/aLevel), (width/80*8/aLevel)), random(height/80*3/aLevel) );
vertices[2] = new PVector(random((width/80*9/aLevel), (width/80*12/aLevel)), random(height/80*3/aLevel) );
vertices[3] = new PVector(random((width/80*9/aLevel), (width/80*12/aLevel)), random((height/80*4/aLevel), (height/80*8/aLevel)) );
vertices[4] = new PVector(random((width/80*9/aLevel), (width/80*12/aLevel)), random((height/80*9/aLevel), (height/80*12/aLevel)) );
vertices[5] = new PVector(random((width/80*4/aLevel), (width/80*8/aLevel)), random((height/80*9/aLevel), (height/80*12/aLevel)) );
vertices[6] = new PVector(random(width/80*3/aLevel), random((height/80*9/aLevel), (height/80*12/aLevel)) );
vertices[7] = new PVector(random(width/80*3/aLevel), random((height/80*4/aLevel), (height/80*8/aLevel)) );
}
void moveAsteroid() {
x = x + velocityX; //asteroids to move with a random velocity
y = y + velocityY;
if ( x < -1 * asteroidSize ) {
x = width + asteroidSize;
} //if off screen left, come back in right
if ( x > width + asteroidSize ) {
x = -1 * asteroidSize;
} // if off screen right, come back in left
if ( y < -1 * asteroidSize ) {
y = height + asteroidSize;
} //if off top of screen, come back in bottom
if ( y > height + asteroidSize ) {
y = -1 * asteroidSize ;
} //if off bottom of screen, come back in top
}
void asteroidDraw() {
if (active == false) { // If not active don't draw
return;
}
stroke(150);
fill(255);
// this was how I orginally coded. Have kept commented out for now, so I can see what I did, but will delete before submission.
/*beginShape();
vertex(vertices[0].x, vertices[0].y );
vertex(vertices[1].x, vertices[1].y );
vertex(vertices[2].x, vertices[2].y );
vertex(vertices[3].x, vertices[3].y );
vertex(vertices[4].x, vertices[4].y );
vertex(vertices[5].x, vertices[5].y );
vertex(vertices[6].x, vertices[6].y );
vertex(vertices[7].x, vertices[7].y );
endShape(CLOSE); */
beginShape();
for (PVector v : vertices) {
vertex(x+v.x, y+v.y);
}
endShape(CLOSE);
}
void manDown() {
active = false; //sets to in active so will stop drawing
// add 2 new asteroids to array
asteroids = (Asteroid[]) append( asteroids, new Asteroid( x+20, y+20, level + 1 ) ); // Appends asteroid to array. Changing level makes the asteroid smaller.
asteroids = (Asteroid[]) append( asteroids, new Asteroid( x-20, y-20, level + 1 ) ); // Appends two smaller asteroids to array.
}
}
Game Manager
class GameManager {
int scoreCount;
boolean gameState = true;
int lifeCount;
void newGame()
{
gameState = true; //sets game state to in play
scoreCount = 0; //set counter of flies killed to 0
lifeCount = 3;
}
void scoreUpdate()
{
textSize(width*3/100);
textAlign(LEFT);
fill(255);
text("Score " + scoreCount, (width*2/100), (height*4/100));
}
void lifeLost()
{
lifeCount = lifeCount - 1;
if (lifeCount <= 0) {
gameState = false;
gameOver();
}
}
void lifeUpdate()
{
textSize(height*3/100);
textAlign(LEFT);
fill(255);
text("Lives " + lifeCount, (width*2/100), ((height*4/100) + (height*3/100)) );
}
void gameOver()
{
background(0);
textSize(height*5/100);
textAlign(CENTER);
fill(255);
text("Game over", width/2, height/2.6);
//play again button
fill(255);
rect(((width/2)-(width/4)), (((height/2)- (height/12))), width/2, height/8);
fill(0);
text("Play Again", width/2, height/2);
//define area for play again button collision
if (mousePressed)
{
if (
(mouseX > width/4) &&
(mouseX < width/4 +width/2) &&
(mouseY > (height/2-height/10.5)) &&
(mouseY < ((height/2-height/10.5) + height/8))
)
{
setup(); //reset game
}
}
}
}
Main
Asteroid[] asteroids; //K Level 1 starts with 6, add 2 each level, 10 levels
Ship myShip;
GameManager gameManager;
ArrayList<Bullet> bullets;
// Array help sourced from chapter 28 of 'Processing: A programming handbook
// for visual designers and asrtists' by Casey Reas and Ben Fry
int bulletIndex; // used to recycle bullets
// index sourced from https://py.processing.org/reference/list_index.html
int startNum = 6; //K begin game with 6 asteroids in the level
boolean[] keys; // boolean for storing keypressed/released
void setup() {
size(800, 800);
gameManager = new GameManager();
gameManager.newGame();
bulletIndex = 0;
bullets = new ArrayList<Bullet>();
keys = new boolean[5];
myShip = new Ship();
asteroids = new Asteroid [startNum]; //K
for (int a = 0; a < startNum; a++) { //K create asteroids in array
asteroids[a] = new Asteroid(0, 0, 1); //K
}
for (int i = 0; i < 20; i++)
{
bullets.add(new Bullet()); // create bullets
}
}
void draw() {
background(0);
collisionDetect();
gameManager.gameState = true;
myShip.updateShip(); // E
myShip.moveShip(); // E
for (int a = 0; a < asteroids.length; a++) { //K for asteroids in array
asteroids[a].moveAsteroid(); //K
asteroids[a].asteroidDraw(); //K
}
gameManager.scoreUpdate();
gameManager.lifeUpdate();
for (int i = 0; i < bullets.size(); i++)
{
bullets.get(i).drawBullet(); // drawing bullets
}
}
void keyPressed() {
if (key == CODED) {
if (keyCode == UP)
keys[0] = true;
if (keyCode == LEFT)
keys[1] = true;
if (keyCode == RIGHT)
keys[2] = true;
if (keyCode == DOWN)
keys[3] = true;
} else {
if (key == 'w')
keys[0] = true;
if (key == 'a')
keys[1] = true;
if (key == 'd')
keys[2] = true;
if (key == 's')
keys[3] = true;
if (key == ' ')
keys[4] = true;
}
}
void keyReleased() {
if (key == CODED) {
if (keyCode == UP)
keys[0] = false;
if (keyCode == LEFT)
keys[1] = false;
if (keyCode == RIGHT)
keys[2] = false;
if (keyCode == DOWN)
keys[3] = false;
} else {
if (key == 'w')
keys[0] = false;
if (key == 'a')
keys[1] = false;
if (key == 'd')
keys[2] = false;
if (key == 's')
keys[3] = false;
if (key == ' ')
keys[4] = false;
}
}
void fireBullet(PVector pos, PVector spe, float dir) {
bullets.get(bulletIndex).reset(pos, spe, dir);
// set attributes of last used bullet
// get sourced from https://processing.org/reference/get_.html
bulletIndex++; //update index
bulletIndex %= bullets.size(); //keep index in range
}
void collisionDetect(){
Asteroid testHolder;
Bullet bulletHolder;
// asteroid and bullet objects to minimize creating new objects
for(int i = 0; i < asteroids.length; i++){
testHolder = asteroids[i];
if(dist(testHolder.x, testHolder.y, myShip.shipPosition.x,
myShip.shipPosition.y) < testHolder.asteroidSize)
// collision of player and the asteroid
{gameManager.gameOver();}
for(int j = 0; j < bullets.size(); j++){
bulletHolder = bullets.get(j);
// pull and store each bullet from the list
if(bulletHolder.bulletHidden){continue;}
// don't calculate anything if it is hidden
if(dist(testHolder.x, testHolder.y, bulletHolder.bulletPosition.x,
bulletHolder.bulletPosition.y) < testHolder.asteroidSize){
testHolder.manDown();
// used to detect collision and split if collided
bulletHolder.bulletHidden = true;
// hide the bullet so it won't go 'through' the asteroids
j++;
}
}
}
}

Answer 1

For the problem with the smaller asteroids, you need to make the asteroidSize dependent on the level. Currently they are all the same: float asteroidSize = (width/80*12);
As the to collision issue, the first thing is that you also have to take the size to the ship/bullet hitting the asteroid into account:
if(dist(testHolder.x, testHolder.y, myShip.shipPosition.x, myShip.shipPosition.y) < (testHolder.asteroidSize + myShip.size))
For clarity: size is in both cases the radius.
Second, there will always be some area's where this basic type of collision detection does not follow the visual, because your shapes are not circles. The randomness that you use for the asteroids does not help in that respect. A way to get more control over this is to define a couple of shapes per level, and pick one of those at random when creating an asteroid. This way you can tweak the shape/radius to make a good trade off between looks and function so it looks 'believable enough'.