How to add a collision function to a game

Question

Ive tried a few things but i cant get a working function if player collides with object set speed to 0( stop moving)

ive tried to use the function under "game over " and change the things to make speedx=0 and speedy=0 but i couldnt format it correctly.

https://www.w3schools.com/graphics/game_obstacles.asp

my code:

<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:4px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>

var myGamePiece;
var endGoalPiece;

function startGame() {
    myGameArea.start();
    myGamePiece = new component(30, 30, "red", 0, 0);
    endGoalPiece = new component(30, 30, "black", 450, 240);
    myObstacle = new component(10, 200, "green", 300, 120);
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.interval = setInterval(updateGameArea, 20);
        window.addEventListener('keydown', function (e) {
            myGameArea.key = e.keyCode;
        })
        window.addEventListener('keyup', function (e) {
            myGameArea.key = false;
        })
    }, 
    clear : function(){
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

function component(width, height, color, x, y) {
    this.gamearea = myGameArea;
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;    
    this.x = x;
    this.y = y;    
    this.update = function() {
        ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.newPos = function() {
        this.x += this.speedX;
        this.y += this.speedY;        
    }
}

function updateGameArea() {
    myGameArea.clear();
    myGamePiece.speedX = 0;
    myGamePiece.speedY = 0;    
    if (myGameArea.key && myGameArea.key == 37) {myGamePiece.speedX = -1; }//left
    if (myGameArea.key && myGameArea.key == 39) {myGamePiece.speedX = 1; }//right
    if (myGameArea.key && myGameArea.key == 38) {myGamePiece.speedY = -1; }//up
    if (myGameArea.key && myGameArea.key == 40) {myGamePiece.speedY = 1; }// down
    myObstacle.update();
    endGoalPiece.update();
    myGamePiece.newPos();    
    myGamePiece.update();
}
</script>
<p>use the arrow keys on you keyboard to move the red square.</p>
</body>
</html>

https://jsfiddle.net/tmanrocks999/e6w9br2s/178/

I expect when the player hits the obstacle for them to stop moving. but at the moment they go through it/ i have 1 && that prevents it from going past the x location of obstacle but that doesn't work right

Ameer · Accepted Answer · 2019-10-22 01:27:26Z

1

So for collision detection and game development in general I suggest you start off with https://developer.mozilla.org/en-US/docs/Games/Techniques or https://www.w3schools.com/graphics/game_intro.asp

The way you would do this is add a collision method in your component class like so:

 this.collison = function(rect2) {
      let rect1 = this;
      if (rect1.x < rect2.x + rect2.width &&
     rect1.x + rect1.width > rect2.x &&
     rect1.y < rect2.y + rect2.height &&
     rect1.y + rect1.height > rect2.y) {
      //credits to https://developer.mozilla.org/en-US/docs/Games/Techniques/2D_collision_detection
      this.color = "yellow";
      //check which side (x) the rect is touching
      if(rect1.x <= rect2.x) {
        rect1.x = rect2.x - 30;
      } 
      if(rect1.x >= rect2.x) {
        rect1.x = rect2.x + rect2.width;
      }

    } else {
      this.color = "red";
    }
 }

Here's the updated JSFiddle: https://jsfiddle.net/mero789y/nvbcu7ja/1/

edited Oct 22, 2019 at 1:27

answered Oct 16, 2019 at 18:02

Ameer

1518 bronze badges

\$\begingroup\$ I should of worded my question a bit diffrently but i want the cube to stop when it hits a wall. but what you gave me does help i Will try setting speed to 0 after they touch thanks . \$\endgroup\$

tmanrocks994
– tmanrocks994

2019-10-16 19:25:32 +00:00
Commented Oct 16, 2019 at 19:25
\$\begingroup\$ jsfiddle.net/tmanrocks999/e6w9br2s heres my updated fiddle with walls working correctly . so if you hit a bounty cube should stop \$\endgroup\$

tmanrocks994
– tmanrocks994

2019-10-16 19:27:56 +00:00
Commented Oct 16, 2019 at 19:27
\$\begingroup\$ I actually cant haha. I will try more when i get home. basically if player after 1 more move will interest with a wall. stop movement. \$\endgroup\$

tmanrocks994
– tmanrocks994

2019-10-16 19:33:46 +00:00
Commented Oct 16, 2019 at 19:33
\$\begingroup\$ Alright, I'll change the code so that when the player hit's the wall it'll stop moving \$\endgroup\$

Ameer
– Ameer

2019-10-17 17:22:17 +00:00
Commented Oct 17, 2019 at 17:22
\$\begingroup\$ can you update it? i still cant get it to work. been working all weekend first time i got on in a while \$\endgroup\$

tmanrocks994
– tmanrocks994

2019-10-20 21:33:57 +00:00
Commented Oct 20, 2019 at 21:33

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