BattleCity game using Phaser.IO, part 4 – simple collision.

November 2, 2017 User Battlecity game, GameDev, JavaScript, Phaser.IO, Programming 0

In the last part we created moving player tank in our city, but it can move anywhere through the walls without any collision. So in this part we will investigate hwo to enable collision detection between our player tank and city walls. Also we will enable and outputt some debugging information to better understand what exactly happens on our map.

To enable collision between our tank and walls/city  we have to enable collision for tiles ( now we will just enable collision for all tiles of our tile set ). In  create function, after add tileset, add:

[code lang=”js” htmlscript=”true”]map.setCollisionBetween(1, 10000);[/code]
Also we have to enable player tank physics, in create function, after game add sprite, we add:

[code lang=”js” htmlscript=”true”]
game.physics.enable(player_tank);
player_tank.body.collideWorldBounds = true;
[/code]

In update function we add collision check of player vs layer:

[code lang=”js” htmlscript=”true”]
game.physics.arcade.collide(player_tank, layer);
[/code]

One note: after doing all this, collision still was not working. I found that it was realated to scaling. You should change layer.scale.set(2); to layer.setScale(); and it is fixed.

Debugging collision. To see collision rectangles you could add
[code lang=”js” htmlscript=”true”]
layer.debug = true;
[/code] after layer creation and also add a render callback function (in new Phaser.Game you should add

[code lang=”js” htmlscript=”true”]
function render() {

// Useful debug things you can turn on to see what’s happening

// game.debug.spriteBounds(sprite);
// game.debug.cameraInfo(game.camera, 32, 32);
// game.debug.body(sprite);
game.debug.bodyInfo(player_tank, 10, 10);

game.debug.body(player_tank);

}
[/code]

Also, after enabling debugging, you can see that tank image is smaller than sprite itself but collision happens on sprite size. To deal with it we could change player tank body size on each key press like that:

[code lang=”js” htmlscript=”true”]
if (cursors.left.isDown)
{
//if left cursor is down – play left animation, add velocity
player_tank.animations.play(‘left’);
player_tank.body.velocity.x = -100;
player_tank.body.setSize(13,13,2,1);

}
[/code]

So after all, your index.html should look something like this:

[code lang=”js” htmlscript=”true”]
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Battlecity</title>
<script type="text/javascript" src="js/phaser.js"></script>
<style type="text/css">
body {
margin: 0;
}
</style>
</head>
<body>

<script type="text/javascript">

var game = new Phaser.Game(512, 480, Phaser.AUTO, ”, { preload: preload, create: create, update: update, render: render });

function preload() {
game.load.tilemap(’tilemap’, ‘assets/tilemaps/maps/battlecity_map1.json’, null, Phaser.Tilemap.TILED_JSON);
game.load.image(’tiles16x16′, ‘assets/tilemaps/tiles/battlecity_general.png’);
// load spritesheet for our player and enemies, all of them use same spritesheet
game.load.spritesheet(‘tanks’, ‘assets/tilemaps/tiles/battlecity_general.png’, 16, 16);
}

var map;
var layer;
var player_tank;
var cursors;

function create() {
game.stage.backgroundColor = ‘#787878′;

map = game.add.tilemap(’tilemap’);
map.addTilesetImage(‘battlecity’,’tiles16x16′);
map.setCollisionBetween(1, 10000);

layer = map.createLayer(‘Ground’);
layer.setScale(2);
layer.debug = true;
layer.resizeWorld();

//create cursor key handler
cursors = game.input.keyboard.createCursorKeys();

//create our player tank, position it at x,y and use sprite sheet ‘tanks’
player_tank = this.game.add.sprite(135, 448, ‘tanks’);
game.physics.enable(player_tank);
player_tank.body.collideWorldBounds = true;
player_tank.frame = 0;
player_tank.scale.set(2);
player_tank.animations.add(‘left’, [2,3], 10, true);
player_tank.animations.add(‘right’, [6,7], 10, true);
player_tank.animations.add(‘up’, [0,1], 10, true);
player_tank.animations.add(‘down’, [4,5], 10, true);

}

function update() {
game.physics.arcade.collide(player_tank, layer);

if (cursors.left.isDown)
{
//if left cursor is down – play left animation, add velocity
player_tank.animations.play(‘left’);
player_tank.body.velocity.x = -100;
player_tank.body.setSize(13,13,2,1);

}
else if (cursors.right.isDown)
{
player_tank.animations.play(‘right’);
player_tank.body.velocity.x = 100;
player_tank.body.setSize(13,13,1,1);
}
else if (cursors.up.isDown)
{
player_tank.animations.play(‘up’);
player_tank.body.velocity.y = -100;
player_tank.body.setSize(13,13,1,2);
}
else if (cursors.down.isDown)
{
player_tank.animations.play(‘down’);
player_tank.body.velocity.y = 100;
player_tank.body.setSize(13,13,1,1);
}
else
{
player_tank.animations.stop();
player_tank.body.velocity.set(0);
}
}

function render() {

// Useful debug things you can turn on to see what’s happening

// game.debug.spriteBounds(sprite);
// game.debug.cameraInfo(game.camera, 32, 32);
// game.debug.body(sprite);
game.debug.bodyInfo(player_tank, 10, 10);

game.debug.body(player_tank);

}

</script>

</body>
</html>
[/code]

So, with enabled collision and moving player tank, that is what we have at this moment:

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