I have been reading/searching for an answer to detect collisions of sprites in two arrays. I am not understanding how to pass two arrays into the detection function and have it check all contents of each array against each other. Any input would be greatly appreciated.
<script type="text/javascript">
var FIRE = 0;
var NORTH = 38;
var SOUTH = 40;
var EAST = 39;
var WEST = 37;
var destX = 350;
var destY = 500;
var canvas = null;
var context = null;
var sprites = null;
var player = null;
var island = null;
var enemies = [];
var fires = [];
var gameLoopInterval = null;
var offScreenFire = null;
var isShooting = false;
var intersect = null;
var Fire = function() {
this.spriteX = 278;
this.spriteY = 110;
this.spriteWidth = 13;
this.spriteHeight = 16;
this.destX = player.destX + 25;
this.destY = player.destY;
this.speed = 5;
}
var Player = function(name) {
this.name = name;
this.spriteX = 5;
this.spriteY = 400;
this.spriteWidth = 64;
this.spriteHeight = 64;
this.destX = 350;
this.destY = 500;
this.speed = 5;
this.level = 1;
}
var Enemy = function() {
this.spriteX = 4;
this.spriteY = 4;
this.spriteWidth = 32;
this.spriteHeight = 32;
this.destX = Math.ceil(Math.random() * (800 - this.spriteWidth));
this.destY = this.spriteWidth;
this.speed = Math.ceil(Math.random() * 5);
}
var Island = function() {
this.spriteX = 168;
this.spriteY = 500;
this.spriteWidth = 64;
this.spriteHeight = 64;
this.destX = Math.ceil(Math.random() * (800 - this.spriteWidth));
this.destY = this.spriteWidth - 64;
this.speed = 2;
}
Fire.prototype.takeTurn = function() {
var intersect;
var projdestX = this.destX;
var projdestY = this.destY;
var projspriteWidth = this.spriteWidth;
var projspriteHeight = this.spriteHeight;
for (enemy in enemies) {
intersect = intersect || intersects(enemy.destX, enemy.destY, enemy.spriteWidth, enemy.spriteHeight, projdestX, projdestY, projspriteWidth, projspriteHeight);
}
if(intersect == true) { alert("colliding"); }
else{drawImage(this);}
// if (intersect != true){
// drawImage(this);
// }
// else {
// alert("boom");
// }
if(this.destY <= 0){
offScreenFire = fires.indexOf(this);
fires.splice(offScreenFire, 1);
}
else
this.destY -= this.speed;
}
Player.prototype.takeTurn = function() {
drawImage(this);
}
Enemy.prototype.takeTurn = function() {
drawImage(this);
if (this.destY < canvas.height)
this.destY += this.speed;
else
this.destY = -32;
}
Island.prototype.takeTurn = function() {
drawImage(this);
this.destY += this.speed;
}
function fireAction() {
var fire = new Fire();
drawImage(fire);
fires.push(fire);
}
function drawImage(sprite) {
context.drawImage(sprites, sprite.spriteX, sprite.spriteY, sprite.spriteWidth, sprite.spriteHeight, sprite.destX, sprite.destY, sprite.spriteWidth, sprite.spriteHeight );
}
function gameLoop () {
context.clearRect(0, 0, canvas.width, canvas.height);
island.takeTurn();
player.takeTurn();
//console.log(fires); //debug
for (fire in fires) {
fires[fire].takeTurn();
}
for (enemy in enemies) {
enemies[enemy].takeTurn();
}
}
function intersects(x1, y1, w1, h1, x2, y2, w2, h2) {
if (w2 !== Infinity && w1 !== Infinity) {
w2 += x2;
w1 += x1;
if (isNaN(w1) || isNaN(w2) || x2 > w1 || x1 > w2)
return false;
}
if (y2 !== Infinity && h1 !== Infinity) {
h2 += y2;
h1 += y1;
if (isNaN(h1) || isNaN(y2) || y2 > h1 || y1 > h2)
return false;
}
return true;
}
window.onload = function() {
//alert('here');
canvas = document.getElementById('gameWorld');
context = canvas.getContext("2d");
sprites = new Image();
player = new Player('Brad');
island = new Island();
sprites.onload = function() {
drawImage(player);
for (i = 0; i < 3; i++) {
var enemy = new Enemy();
drawImage(enemy);
enemies.push(enemy);
}
}
sprites.src = "Sprites/1945.png";
gameLoopInterval = setInterval('gameLoop()', 100)
}
window.onkeypress = function(e){
var evt = window.event ? event : e;
//alert(evt.keyCode);
switch(evt.keyCode) {
case NORTH:
if (player.destY > 0)
player.destY -= player.speed;
else
player.destY == player.destY;
break;
case SOUTH:
if (player.destY < canvas.height - player.spriteWidth)
player.destY += player.speed;
else
player.destY == player.destY;
break;
case EAST:
if (player.destX < canvas.width - player.spriteWidth)
player.destX += player.speed;
else
player.destX == player.destY;
break;
case WEST:
if (player.destX > 0)
player.destX -= player.speed;
else
player.destX == player.destX;
break;
case FIRE:
fireAction();
break;
}
}
</script>
Your problems seems to be in:
for (enemy in enemies) {
intersect = intersects(enemy.destX, enemy.destY, enemy.spriteWidth, enemy.spriteHeight, projdestX, projdestY, projspriteWidth, projspriteHeight);
}
intersect will always have the last value saved. (Meaning you are really only checking if it intersects with the last enemy.)
A quick solution would be to change the inner line to:
intersect = intersect || intersects(enemy.destX, enemy.destY, enemy.spriteWidth, enemy.spriteHeight, projdestX, projdestY, projspriteWidth, projspriteHeight);
This will make intersect stay as true if the fire doesn't intersect with the next enemy.
Edit:
Your second problem is in the same for(). In javascript, when you do a for in, the first variable does not have a reference to the instance, but rather is only the key.
Your final for should look like:
for (enemy in enemies) {
intersect = intersect || intersects(enemies[enemy].destX, enemies[enemy].destY, enemies[enemy].spriteWidth, enemies[enemy].spriteHeight, projdestX, projdestY, projspriteWidth, projspriteHeight);
}
You also seem to not be spawning any enemies. In my fiddle of your code (http://jsfiddle.net/path411/umjnQ/) I added the following snippet into your gameLoop():
if(enemies.length < 1) {
enemies.push(new Enemy());
}
This simply creates a new enemy if you don't already have one. (You will probably want to change later).