I have a small game where the player is moving a circle within a canvas. I am having issues with detecting the edges of the canvas, disallowing a player to move past those edges, and allowing the user to navigate away from any given edge.
Currently, the player can hit canvas edges and move away successfully, most of the time. However, with a combination of certain movements and collision along an edge, the player will become "stuck".
How can I go about creating simple canvas edge collision detection and allow the user to move freely after the event?
My code:
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height - 30;
var dx = 2;
var dy = -2;
var ballRadius = 10;
var rightPressed = false;
var leftPressed = false;
var upPressed = false;
var downPressed = false;
document.addEventListener("keydown", keyDownHandler, false);
document.addEventListener("keyup", keyUpHandler, false);
function keyDownHandler(e) {
if (e.keyCode == 65) {
rightPressed = true;
}
if (e.keyCode == 68) {
leftPressed = true;
}
if (e.keyCode == 87) {
upPressed = true;
}
if (e.keyCode == 83) {
downPressed = true;
}
}
function keyUpHandler(e) {
if (e.keyCode == 65) {
rightPressed = false;
}
if (e.keyCode == 68) {
leftPressed = false;
}
if (e.keyCode == 87) {
upPressed = false;
}
if (e.keyCode == 83) {
downPressed = false;
}
}
function drawBall() {
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI * 2);
ctx.strokeStyle = "black";
ctx.stroke();
ctx.closePath();
}
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawBall();
if (x + dx > canvas.width - ballRadius || x + dx < ballRadius - 3) {
dx = -dx;
}
if (y + dy > canvas.height - ballRadius || y + dy < ballRadius - 3) {
dy = -dy;
}
if (rightPressed) {
x -= dx;
}
if (leftPressed) {
x += dx;
}
if (upPressed) {
y += dy;
}
if (downPressed) {
y -= dy;
}
}
setInterval(draw, 10);
<canvas id="myCanvas"></canvas>
Well i have to admit that have been long time since i don't touch older libraries stored in the bault. Luckley i got the sources at hand, so after taking a look i will tell a method that works for me regarding how to detect the colision of a ball object against a wall.
I guess it will fit to you needs, don't know if the better or worse solution, but works!. Let start by defining how we represent the data for each ball, recall our friends of unix that says that part of the complexity is in the data structure as it is part of the algorithm as a whole... but enought chat, going to the matters.. by using this kind of data structure for representing a Ball
class Ball
{
radio : number
x : number
y : number
}
So you can draw the ball this way:
function draw (Graphics g)
{
int r = ball.getRadio ();
int diam = rad * 2;
int px = (int) ball.getPx () - r;
int py = (int) ball.getPy () - r;
g.setColor (niceColor);
g.fillArc (px,py,diameter,diameter,0,360); // Fills a circular or elliptical arc covering the specified rectangle
}
// Disclaimer, i don't know well the primitives for graphical routines in canvas, but i would assume that you will have somethign to draw a circle with all of that. You got px, py, x, y, radio, diameter.
Anyway the answer for the question comes here where you can use this code:
function isAHorizontalCollision (ball c,int width)
{
return (c.x > width - c.radio || c.x < radio);
}
function isAVerticalCollision (ball c,int height)
{
return (c.y > height - c.radio || c.y < radio);
}
// Assume that enclosing rectangle where the ball can move is between (0,width) for horizontal, and (top,0) vertical.
Is important to advise that this work only if the x values goes incrementally from left to right and the y goes decrementally from top to bottom.
Hope my typescript alike code fits well for explaining. I have a lot of source files in java for this. If need more. (For example collision between two circles).
If you have time i would recommend to check this out, very very powerfull stuff in there.
You complicated things a bit with all the Boolean variables...
The same can be done with just a the dx and dy those are your speed set them to 0 to stop.
Also it look like you where inverting the direction of the keys that was the lines:
if (x + dx > canvas.width - ballRadius || x + dx < ballRadius - 3) {
dx = -dx;
}
if (y + dy > canvas.height - ballRadius || y + dy < ballRadius - 3) {
dy = -dy;
}
When those condition are true the up is now down and the right is left, not sure if that was your intended behavior, when it worked it looked like the ball was bouncing from the edge but from that point on the key was inverted... I remove that from my fix.
Here is my approach, I added a bit of math fun to animate your player:
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var dx = 0;
var dy = 0;
var ballRadius = 10;
document.addEventListener("keydown", keyDownHandler, false);
document.addEventListener("keyup", keyUpHandler, false);
function keyDownHandler(e) {
if (e.keyCode == 65) dx = -2
if (e.keyCode == 68) dx = 2
if (e.keyCode == 87) dy = -2
if (e.keyCode == 83) dy = 2
}
function keyUpHandler(e) {
if (e.keyCode == 65) dx = 0
if (e.keyCode == 68) dx = 0
if (e.keyCode == 87) dy = 0
if (e.keyCode == 83) dy = 0
}
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawBall();
var fx = x + dx
var fy = y + dy
if (ballRadius < fx && fx < canvas.width - ballRadius) x = fx;
if (ballRadius < fy && fy < canvas.height - ballRadius) y = fy;
}
setInterval(draw, 10);
var hr = ballRadius / 2 - 1
var pi2 = Math.PI * 2
var i = 0
function drawBall() {
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, pi2);
ctx.strokeStyle = "black";
ctx.stroke();
// draw some small moving circles inside
ctx.beginPath();
ctx.fillStyle = "red";
ctx.arc(x + hr * Math.sin(i), y + hr * Math.cos(i), hr, 0, pi2);
ctx.fill();
ctx.beginPath();
ctx.fillStyle = "blue";
ctx.arc(x - hr * Math.sin(i), y - hr * Math.cos(i), hr, 0, pi2);
ctx.fill();
ctx.closePath();
i += 0.1 + Math.abs(dx)/15 + Math.abs(dy)/15
}
<canvas id="myCanvas" style="border:1px solid #000000;"></canvas>
Thanks for the help from the two of you who answered my question. Because of you two, I was able to successfully find a solution.
Originally, I was using this to determine the edges of the canvas, and adjust direction accordingly:
if (x + dx > canvas.width - ballRadius || x + dx < ballRadius - 3) {
dx = -dx;
}
if (y + dy > canvas.height - ballRadius || y + dy < ballRadius - 3) {
dy = -dy;
}
However, as pointed out, that reverses the movement direction, making it basically useless for my intended purpose. Not only that, but all 4 sides of the canvas act in a slightly different manor from each other.
Using the feedback from the other answer, here's the solution I am using now, which works wonderfully:
if (x + dx > canvas.width - ballRadius) {
var fx = x - dx;
x = fx;
}
if (x + dx < ballRadius) {
var fx = x + dx;
x = fx;
}
if (y + dy > canvas.height - ballRadius) {
var fy = y + dy;
y = fy;
}
if (y + dy < ballRadius) {
var fy = y - dy;
y = fy;
}
This way, I am detecting all 4 sides successfully, stopping user motion on contact, and allowing the player to move away from the side of the canvas.
Related
I am trying to make a game with collision detection and resolution. For some reason, when I move the player to the right of the 'enemy blocks', the player moves to the left of the 'enemy'. How can I solve this problem? I have been working on this for hours and cannot find any solution. I am not sure if it is a small problem or if I have to change the whole enemy object.
//declare variables
var body = document.getElementById("body");
var canvas = document.getElementById("canvas");
var iwidth = window.innerWidth;
var iheight = window.innerHeight;
//variable for drawing
var draw = canvas.getContext("2d");
//variables for character paramaters
var playerwidth = 20;
var playerheight = 20;
var playerx = iwidth / 2 - playerwidth / 2;
var playery = iheight / 2 - playerheight / 2;
var playerspeed = 20;
//mouse co-ordinates
var mousex;
var mousey;
//enemy's parameters
var enemyxpositions = [43, 94, 200];
var enemyypositions = [41, 120, 83];
var enemywidths = [12, 43, 45];
var enemyheights = [43, 11, 87];
var i = 0;
var collision = false;
///////////////////////////////////////////////////////////////////////////////////
/////// separating variables and rest of the code ///////
///////////////////////////////////////////////////////////////////////////////////
//puts canvas in top right corner
body.style.margin = "0";
//changes the canvas's style namely color, margin, width and height
canvas.style.backgroundColor = "black";
canvas.style.margin = "0";
canvas.width = iwidth;
canvas.height = iheight;
//the function that the player is drawn in
function drawplayer() {
//allows animation
requestAnimationFrame(drawplayer);
//clears the canvas every time the function runs so that the image doesn't leave a mark
draw.clearRect(0, 0, iwidth, iheight);
//drawing the player
draw.fillStyle = "#ffff00";
draw.fillRect(playerx, playery, playerwidth, playerheight);
draw.fill();
//checking where the mouse is and letting the player follow it
if (mousex > playerx + playerwidth / 2) {
playerx += (mousex - playerx + playerwidth) / playerspeed;
}
if (mousex < playerx + playerwidth / 2) {
playerx -= (playerx - mousex + playerwidth) / playerspeed;
}
if (mousey > playery + playerheight / 2) {
playery += (mousey - playery + playerheight) / playerspeed;
}
if (mousey < playery + playerheight / 2) {
playery -= (playery - mousey + playerheight) / playerspeed;
}
//the obstacles' object
function Enemy(enemyx, enemyy, enemywidth, enemyheight) {
this.enemyx = enemyx;
this.enemyy = enemyy;
this.enemywidth = enemywidth;
this.enemyheight = enemyheight;
this.enemies = function() {
draw.fillStyle = "#0000ff";
draw.fillRect(enemyx, enemyy, enemywidth, enemyheight);
draw.fill();
}
//collision detection
if (mousex + playerwidth / 2 > this.enemyx &&
mousex - playerwidth / 2 < this.enemyx + this.enemywidth &&
mousey + playerheight / 2 > this.enemyy &&
mousey - playerheight / 2 < this.enemyy + this.enemyheight) {
collision = true;
}
else {
collision = false;
}
//collision implementation
//left collision
if (collision == true && mousex + playerwidth / 2 > this.enemyx) {
playerx = this.enemyx - playerwidth;
}
//right collision
else if (collision == true && mousex - playerwidth / 2 < this.enemyx + this.enemywidth) {
playerx = this.enemyx + this.enemywidth + 50;
}
}
//draws all the obstacles
for (i = 0; i < enemyxpositions.length; i++) {
new Enemy( enemyxpositions[i],
enemyypositions[i],
enemywidths[i],
enemyheights[i]).enemies();
}
}
drawplayer();
//gets the mouse co-ordinates
window.onmousemove = function mousepos(event) {
mousex = event.clientX;
mousey = event.clientY;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>DUNGE</title>
<style>
::-webkit-scrollbar {
display: none;
}
canvas {
display: block;
}
#obstacles {
opacity: 1;
margin-top: -100vh;
}
</style>
</head>
<body id="body">
<canvas id="canvas"></canvas>
<script src="script.js"></script>
</body>
</html>
Collision resolution is a pretty tricky domain and there are a many approaches you can take. For the purposes of squares with mouse control as in your case, a naive approach might be as follows:
If a collision is detected between a player and an immobile obstacle (enemy, wall, whatever), we can resolve the collision by gradually "undoing" the player's motion until it's no longer colliding with the obstacle.
For example, if on the current frame, the player is moving with a y velocity of 5 and an x velocity of 2 and we detect a collision, then we can avoid the collision by undoing the move. However, this would create an unrealistic air gap between the obstacle and the player that can result in a bouncing effect. Instead, we can slowly move the obstacle's x and y positions by a small value like -0.5 until no collision is detected. However, undoing the move on both axes might be incorrect if only one axis experienced a collision.
Here's an initial attempt at separating the x and y axes into distinct steps:
const canvas = document.createElement("canvas");
canvas.width = 300;
canvas.height = 180;
document.body.appendChild(canvas);
const ctx = canvas.getContext("2d");
const mouse = {x: 0, y: 0};
const enemy = {x: 130, y: 70, width: 40, height: 40};
const player = {
x: 0, y: 0, width: 20, height: 20, vx: 0, vy: 0,
velocityDamp: 0.06, collisionDamp: 0.3
};
const collides = (a, b) =>
a.x + a.width >= b.x && a.x <= b.x + b.width &&
a.y + a.height >= b.y && a.y <= b.y + b.height
;
(function render() {
player.vx = (mouse.x - player.x) * player.velocityDamp;
player.vy = (mouse.y - player.y) * player.velocityDamp;
player.x += player.vx;
player.y += player.vy;
while (collides(player, enemy)) {
player.y -= Math.sign(player.vy) * player.collisionDamp;
}
while (collides(player, enemy)) {
player.x -= Math.sign(player.vx) * player.collisionDamp;
}
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.fillStyle = "blue";
ctx.fillRect(enemy.x, enemy.y, enemy.width, enemy.height);
ctx.fillStyle = "yellow";
ctx.fillRect(player.x, player.y, player.width, player.height);
requestAnimationFrame(render);
})();
onmousemove = e => {
mouse.x = e.clientX;
mouse.y = e.clientY;
};
body {margin: 0;}
canvas {background: #000;}
This works fine when the collision is on the y-axis, but collisions on the x-axis cause the player to "pop" out of the obstacle. Ordering the adjustments so that the least offending velocity adjustment is handled first should fix the problem. We do this by "undoing" the last move on one axis, checking if this single-axis move resolved the collision, and adjusting accordingly.
Putting it all together, here's a proof-of-concept:
const canvas = document.createElement("canvas");
canvas.width = 300;
canvas.height = 180;
document.body.appendChild(canvas);
const ctx = canvas.getContext("2d");
const mouse = {x: 0, y: 0};
const enemy = {x: 130, y: 70, width: 40, height: 40};
const player = {
x: 0, y: 0, width: 20, height: 20, vx: 0, vy: 0,
velocityDamp: 0.06, collisionDamp: 0.3
};
const collides = (a, b) =>
a.x + a.width >= b.x && a.x <= b.x + b.width &&
a.y + a.height >= b.y && a.y <= b.y + b.height
;
const resolveOnAxis = (player, enemy, axis) => {
while (collides(player, enemy)) {
player[axis] -= Math.sign(player["v"+axis]) * player.collisionDamp;
}
};
const resolveCollision = (player, enemy) => {
player.x -= player.vx;
if (collides(player, enemy)) {
player.x += player.vx;
resolveOnAxis(player, enemy, "y");
resolveOnAxis(player, enemy, "x");
}
else {
player.x += player.vx;
resolveOnAxis(player, enemy, "x");
resolveOnAxis(player, enemy, "y");
}
};
(function render() {
player.vx = (mouse.x - player.x) * player.velocityDamp;
player.vy = (mouse.y - player.y) * player.velocityDamp;
player.x += player.vx;
player.y += player.vy;
if (collides(player, enemy)) {
resolveCollision(player, enemy);
}
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.fillStyle = "blue";
ctx.fillRect(enemy.x, enemy.y, enemy.width, enemy.height);
ctx.fillStyle = "yellow";
ctx.fillRect(player.x, player.y, player.width, player.height);
requestAnimationFrame(render);
})();
onmousemove = e => {
mouse.x = e.clientX;
mouse.y = e.clientY;
};
body {margin: 0;}
canvas {background: #000;}
This isn't perfect collision resolution by any means, but it introduces a few fundamental concepts and should be sufficient for simple games.
Note that I'm only handling one enemy; it's left to the reader to create an array of enemies and loop over them to detect and resolve collisions. Problems can arise if multiple enemies are close together; resolving one collision could push the player into another collision. It gets worse if the obstacles are also moving. If you're making a platformer, a collision grid might be worth looking into to circumvent some of these issues.
If dealing with collision becomes increasingly complicated and overwhelming, there's no shame in using a library like matter.js.
Be careful when using while to resolve these collisions as an infinite loop can easily occur. Consider adding a tries counter to these loops and bail if they exceed more than 20 or 30 iterations (this is a bit unsatisfactory and reveals that this solution is not industrial-strength; this prevents infinite loops but may result in incorrect behavior).
Capping the player's maximum velocity is another important preventative measure: it can avoid situations where the velocity becomes so high the player clips right through obstacles. Explore other ad-hoc solutions to problems as they arise.
Beyond collision detection, I have a few other suggestions:
Use objects to encapsulate all properties associated with a game entity. This makes the code much easier to manage than loose variables like playerwidth, playerheight, playerspeed, etc.
Avoid pointless and noisy comments that reiterate what the code clearly does.
Instead of adding comments to delimit logical parts of a function, create helper functions with the appropriate names. My POC above is not great in this regard--as the game expands, objects, functions and overall design become increasingly important; inlining everything in the update loop makes for a painful coding experience as soon as you want to add features or run into bugs.
Put Enemy's constructor function outside of the game loop. Create enemies one time in an initialization function and scope constructors appropriately.
Use camelCased variables instead of everythinginlowercase.
I am trying to create a scoreboard for my game by using local storage to carry over the score variable after a game is finished by a user. However, this is not working for some reason. I am relatively new to coding so I did some research on local storage but couldn't get the code to work to no avail. Could someone help me with this code thanks.
Page 1:
<html>
<title>Level Selector</title>
<canvas id="myCanvas" width="750" height="400"></canvas>
<style type="text/css">
canvas { background: #eee; }
</style>
<script>
document.addEventListener('load', draw);
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var x = canvas.width/2;
var y = canvas.height-30;
var dx = 2;//Ball is moving in x direction at a constant rate
var dy = -2;//Ball is moving in y direction at a constant rate
var ballRadius = 10;//To see if ball is colliding with brick/canvas
var paddleHeight = 10;
var paddleWidth = 75;
var paddleX = (canvas.width-paddleWidth)/2;
var rightPressed = false;//This variable is false because the 'right arrow' key is not pressed.
var leftPressed = false;//This variable is false because the 'left arrow' key is not pressed.
var brickRowCount = 5;
var brickColumnCount = 8;
var brickWidth = 75;
var brickHeight = 20;
var brickPadding = 10;
var brickOffsetTop = 30;
var brickOffsetLeft = 30;
var score = 0;
var lives = 3;
var paused = false;
var bricks = [];//this is an array holding all the bricks
for(var c=0; c<brickColumnCount; c++) {
bricks[c] = [];
for(var r=0; r<brickRowCount; r++) {
bricks[c][r] = { x: 0, y: 0, status: 1 };//If status is '1' then draw it. However, is status is '0', fill in with background
}
}
document.addEventListener("keydown", keyDownHandler, false);//Functions only when key is pressed
document.addEventListener("keyup", keyUpHandler, false);//Functions only when key is not pressed
document.addEventListener("mousemove", mouseMoveHandler, false);//Functions only when mouse curcor moves
//keyCode(39) is the code for the 'right arrow' key and keyCode(37) is the code for the 'left arrow' key
function keyDownHandler(e) {
if(e.keyCode == 39) {
rightPressed = true;
}
else if(e.keyCode == 37) {
leftPressed = true;
}
}
function keyUpHandler(e) {
if(e.keyCode == 39) {
rightPressed = false;
}
else if(e.keyCode == 37) {
leftPressed = false;
}
}
function mouseMoveHandler(e) {
var relativeX = e.clientX - canvas.offsetLeft;//This represents the hoizontal mouse movement.
if(relativeX > 0 && relativeX < canvas.width) {
paddleX = relativeX - paddleWidth/2;
}
}
window.addEventListener('keydown', pauseGameKeyHandler, false);
function pauseGameKeyHandler(e) {
var keyCode = e.keyCode;
switch(keyCode){
case 80: //p
togglePause();
break;
}
}
function togglePause() {
paused = !paused;
draw();
}
/*************************************************************/
// NEW
const ballPowerupHalfWidth = 30;
const paddlePowerupHalfWidth = 30;
let ballPowerups = [];
let paddlePowerups = [];
// This function adds powerup to random position
function addPowerups() {
// I check only if none exist, you could
// add more than 1 powerup if you want
if (ballPowerups.length < 1) {
// otherwise half the triangle could be outside canvas
const padding = 50;
const xMin = 0 + padding;
const xMax = canvas.width - padding;
const yMin = 0 + padding;
const yMax = canvas.height - padding;
ballPowerups.push({
x: Math.floor(Math.random()*(xMax-xMin+1)+xMin),
y: Math.floor(Math.random()*(yMax-yMin+1)+yMin),
});
}
// I check only if none exist, you could
// add more than 1 powerup if you want
if (paddlePowerups.length < 1) {
// otherwise half the triangle could be outside canvas
const padding = 50;
const xMin = 0 + padding;
const xMax = canvas.width - padding;
const yMin = 0 + padding;
const yMax = canvas.height - padding;
paddlePowerups.push({
x: Math.floor(Math.random()*(xMax-xMin+1)+xMin),
y: Math.floor(Math.random()*(yMax-yMin+1)+yMin),
});
}
}
// NEW: do all collision detections
function doCollisionDetection() {
// ball powerups
ballPowerups.forEach((powerup, i) => {
rectangleCollisionDetection(
{x: powerup.x, y: powerup.y},
{w: ballPowerupHalfWidth, h: ballPowerupHalfWidth},
() => {
console.log('BALL POWERUP COLLISION');
// remove powerup
ballPowerups.splice(i, 1);
dy = dy/2
setTimeout(() => { dy=2 }, 5000)
// to make effect last 10 seconds:
// 1. add effect
// 2. and setTimeout(() => { /* code that removes effect */ }, 10000);
});
});
// paddle powerups
paddlePowerups.forEach((powerup, i) => {
rectangleCollisionDetection(
{x: powerup.x, y: powerup.y},
{w: ballPowerupHalfWidth, h: ballPowerupHalfWidth},
() => {
console.log('PADDLE POWERUP COLLISION');
// remove powerup
paddlePowerups.splice(i, 1);
paddleHeight = paddleHeight*1.5
paddleWidth = paddleWidth*1.5
setTimeout(() => { paddleHeight=10; }, 10000)
});
});
// bricks
for(var c=0; c<brickColumnCount; c++) {
for(var r=0; r<brickRowCount; r++) {
var b = bricks[c][r];
if(b.status == 1) {
rectangleCollisionDetection(b, {w: brickWidth, h: brickHeight}, () => {
console.log('BRICK COLLISION');
dy = -dy;
b.status = 0;
score++;
if(score == brickRowCount*brickColumnCount) {
alert("YOU WIN, CONGRATULATIONS!");
window.location = "Intro Screen.html";
}
});
}
}
}
// NEW: collision detection between ball and rectangle shaped
// collision boundary (only need center(x, y) and half width)
function rectangleCollisionDetection(center, size, callback) {
if(
x > center.x &&
x < center.x+size.w &&
y > center.y &&
y < center.y+size.h
) {
callback && callback();
}
}
function drawBallpowerup() {
ballPowerups.forEach(powerup => {
ctx.beginPath();
ctx.moveTo(powerup.x, powerup.y);
ctx.lineTo(powerup.x+ballPowerupHalfWidth, powerup.y+ballPowerupHalfWidth);
ctx.lineTo(powerup.x+ballPowerupHalfWidth*2, powerup.y);
ctx.fillStyle = "#42f445";
ctx.fill();
ctx.closePath();
});
}
function drawPaddlepowerup() {
paddlePowerups.forEach(powerup => {
ctx.beginPath();
ctx.moveTo(powerup.x, powerup.y);
ctx.lineTo(powerup.x+paddlePowerupHalfWidth, powerup.y+paddlePowerupHalfWidth);
ctx.lineTo(powerup.x+paddlePowerupHalfWidth*2, powerup.y);
ctx.fillStyle = "#ce6210";
ctx.fill();
ctx.closePath();
});
}
// my big changes end here
/*************************************************************/
//this is the score variable of the game
function drawScore() {
ctx.font = "16px Arial";
ctx.fillStyle = "#0095DD";
ctx.fillText("Score: "+score, 8, 20);
}
//this is the lives variable of the game
function drawLives() {
ctx.font = "16px Arial";
ctx.fillStyle = "#0095DD";
ctx.fillText("Lives: "+lives, canvas.width-65, 20);
}
//this creates the ball
function drawBall() {
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI*2);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
//this creates the paddle
function drawPaddle() {
ctx.beginPath();
ctx.rect(paddleX, canvas.height-paddleHeight, paddleWidth, paddleHeight);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
//this creates the bricks
function drawBricks() {
for(var c=0; c<brickColumnCount; c++) {
for(var r=0; r<brickRowCount; r++) {
if(bricks[c][r].status == 1) {
var brickX = (c*(brickWidth+brickPadding))+brickOffsetLeft;
var brickY = (r*(brickHeight+brickPadding))+brickOffsetTop;
bricks[c][r].x = brickX;
bricks[c][r].y = brickY;
ctx.beginPath();
ctx.rect(brickX, brickY, brickWidth, brickHeight);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
}
}
}
function draw() {
// clears canvas content from previous frame
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawBall();//this code draws the ball onto the canvas
drawPaddle();//this code draws the paddle onto the canvas
drawBricks();//this code draws the bricks onto the canvas
addPowerups();
doCollisionDetection();
drawScore();//this code draws the score variable onto the canvas
drawLives();//this code draws the lives variable onto the canvas
drawBallpowerup();
drawPaddlepowerup();
//Reverse Ball movement when the ball collides with wall in 'x' direction (Left/Right wall)
if(x + dx > canvas.width-ballRadius || x + dx < ballRadius) {
dx = -dx;
}
//Reverse Ball movement when the ball collides with wall in 'y' direction (Top/Bottom wall)
if(y + dy < ballRadius) {
dy = -dy;
} else if(y + dy > canvas.height-ballRadius) {
if(x > paddleX && x < paddleX + paddleWidth) {
dy = -dy;//If the ball collides with the paddle, the ball is rebounded in the opposite direction.
}
else {
lives--;
if(!lives) {
alert("GAME OVER");
localStorage.setItem("score", score);
}
window.location = "Intro Screen.html";
}
else {
x = canvas.width/2;
y = canvas.height-30;
dx = 2;
dy = -2;
paddleX = (canvas.width-paddleWidth)/2;
}
}
}
if(rightPressed && paddleX < canvas.width-paddleWidth) {//limits paddle movement in between the canvas width
paddleX += 7;//Paddle shifts 7 pixels in the positive x direction
}
else if(leftPressed && paddleX > 0) {//limits paddle movement in between the canvas width
paddleX -= 7;//Paddle shifts 7 pixels in the negative x direction
}
x += dx;//Ball is updated by painting it over each position it moves in
y += dy;//Ball is updated by painting it over each position it moves in
if(!paused) {
requestAnimationFrame(draw);
}
}
draw();
</script>
<body onload="draw();>
</body>
</html>
Page 2:
if (typeof(Storage) !== "undefined") {
// Retrieve
document.getElementById("result").innerHTML = localStorage.getItem("score"));
}
When I run it and after playing the game, the score should be added onto the scoreboard in decending order (highest to lowest). I have trouble bringing over the variable.
While there are no standard specifications about it, most browsers will consider different pages served from the file:// protocol as being different-origin.
This means your two pages will be considered as different-origin and will thus have their own Storage Area that they won't be able to share, just like you won't be able to access the Storage Area from www.xxxxx.com from www.yyyyy.com.
To overcome this limitation, the easiest is to run a local web-server on your machine. Many OSes comes with preinstalled such server, and all it requires is to activate it, and for the ones that don't do it, there are many free and easy solutions.
And if you are planning to play with web standards, it's a must have anyway.
I'm attempting to create a simple draw/paint programme using html5 canvas and plain javascript. I've got it working ok, but when drawing and moving the mouse too fast the line disconnects and I just end up with a line of dots - how can I make this a smooth continuous line?
Advice would be much appreciated! I'm quite new to JS so code examples would be really useful, thanks in advance.
Current JS is:
var canvas, ctx
var mouseX, mouseY, mouseDown = 0
function draw(ctx,x,y,size) {
ctx.fillStyle = "#000000"
ctx.beginPath()
ctx.arc(x, y, size, 0, Math.PI*2, true)
ctx.closePath()
ctx.fill()
}
function clearCanvas(canvas,ctx) {
ctx.clearRect(0, 0, canvas.width, canvas.height)
}
function onMouseDown() {
mouseDown = 1
draw(ctx, mouseX, mouseY, 2)
}
function onMouseUp() {
mouseDown = 0
}
function onMouseMove(e) {
getMousePos(e)
if (mouseDown == 1) {
draw(ctx, mouseX, mouseY, 2)
}
}
function getMousePos(e) {
if (!e)
var e = event
if (e.offsetX) {
mouseX = e.offsetX
mouseY = e.offsetY
}
else if (e.layerX) {
mouseX = e.layerX
mouseY = e.layerY
}
}
function init() {
canvas = document.getElementById('sketchpad')
ctx = canvas.getContext('2d')
canvas.addEventListener('mousedown', onMouseDown, false)
canvas.addEventListener('mousemove', onMouseMove, false)
window.addEventListener('mouseup', onMouseUp, false)
}
init();
<canvas id="sketchpad" width="500" height="500"></canvas>
Drawing a smooth curve with the mouse.
Sadly it is not that easy if you wish to stay true to the artists intended line.
It involves recording the whole mouse stroke. When the stroke is complete, reduce the number of points to the detail limit (set by artist) then apply a bezier smoothing function on the remaining points.
It can be done as the stroke is drawn but for some devices this can become too much if the line becomes very long. As the line detail reduction looks at all points when showing the smoothed line live some people dont like the way it slightly changes as the line gets longer.
Demo
The code below demonstrates a solution I have found useful.
Use the left button to draw with smoothing done one button release.
Use the right button to draw with live smoothing (blue line).
Middle mouse button click to clear.
Use the two sliders at the top to set the amount of smoothing, and the amount of detail. Left click to drag out a stroke, the raw line is shown. When the mouse is released the line is then simplified, smoothed, and added to the background image.
var canvas = document.getElementById("canV");
var ctx = canvas.getContext("2d");
// mouse stuff
var mouse = {
x:0,
y:0,
buttonLastRaw:0, // user modified value
buttonRaw:0,
buttons:[1,2,4,6,5,3], // masks for setting and clearing button raw bits;
};
function mouseMove(event){
mouse.x = event.offsetX; mouse.y = event.offsetY;
if(mouse.x === undefined){ mouse.x = event.clientX; mouse.y = event.clientY;}
if(event.type === "mousedown"){ mouse.buttonRaw |= mouse.buttons[event.which-1];
}else if(event.type === "mouseup"){mouse.buttonRaw &= mouse.buttons[event.which+2];
}else if(event.type === "mouseout"){ mouse.buttonRaw = 0; mouse.over = false;
}else if(event.type === "mouseover"){ mouse.over = true; }
event.preventDefault();
}
canvas.addEventListener('mousemove',mouseMove);
canvas.addEventListener('mousedown',mouseMove);
canvas.addEventListener('mouseup' ,mouseMove);
canvas.addEventListener('mouseout' ,mouseMove);
canvas.addEventListener('mouseover' ,mouseMove);
canvas.addEventListener("contextmenu", function(e){ e.preventDefault();}, false);
// Line simplification based on
// the Ramer–Douglas–Peucker algorithm
// referance https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm
// points are and array of arrays consisting of [[x,y],[x,y],...,[x,y]]
// length is in pixels and is the square of the actual distance.
// returns array of points of the same form as the input argument points.
var simplifyLineRDP = function(points, length) {
var simplify = function(start, end) { // recursize simplifies points from start to end
var maxDist, index, i, xx , yy, dx, dy, ddx, ddy, p1, p2, p, t, dist, dist1;
p1 = points[start];
p2 = points[end];
xx = p1[0];
yy = p1[1];
ddx = p2[0] - xx;
ddy = p2[1] - yy;
dist1 = (ddx * ddx + ddy * ddy);
maxDist = length;
for (var i = start + 1; i < end; i++) {
p = points[i];
if (ddx !== 0 || ddy !== 0) {
t = ((p[0] - xx) * ddx + (p[1] - yy) * ddy) / dist1;
if (t > 1) {
dx = p[0] - p2[0];
dy = p[1] - p2[1];
} else
if (t > 0) {
dx = p[0] - (xx + ddx * t);
dy = p[1] - (yy + ddy * t);
} else {
dx = p[0] - xx;
dy = p[1] - yy;
}
}else{
dx = p[0] - xx;
dy = p[1] - yy;
}
dist = dx * dx + dy * dy
if (dist > maxDist) {
index = i;
maxDist = dist;
}
}
if (maxDist > length) { // continue simplification while maxDist > length
if (index - start > 1){
simplify(start, index);
}
newLine.push(points[index]);
if (end - index > 1){
simplify(index, end);
}
}
}
var end = points.length - 1;
var newLine = [points[0]];
simplify(0, end);
newLine.push(points[end]);
return newLine;
}
// This is my own smoothing method
// It creates a set of bezier control points either 2nd order or third order
// bezier curves.
// points: list of points
// cornerThres: when to smooth corners and represents the angle between to lines.
// When the angle is smaller than the cornerThres then smooth.
// match: if true then the control points will be balanced.
// Function will make a copy of the points
var smoothLine = function(points,cornerThres,match){ // adds bezier control points at points if lines have angle less than thres
var p1, p2, p3, dist1, dist2, x, y, endP, len, angle, i, newPoints, aLen, closed, bal, cont1, nx1, nx2, ny1, ny2, np;
function dot(x, y, xx, yy) { // get do product
// dist1,dist2,nx1,nx2,ny1,ny2 are the length and normals and used outside function
// normalise both vectors
dist1 = Math.sqrt(x * x + y * y); // get length
if (dist1 > 0) { // normalise
nx1 = x / dist1 ;
ny1 = y / dist1 ;
}else {
nx1 = 1; // need to have something so this will do as good as anything
ny1 = 0;
}
dist2 = Math.sqrt(xx * xx + yy * yy);
if (dist2 > 0) {
nx2 = xx / dist2;
ny2 = yy / dist2;
}else {
nx2 = 1;
ny2 = 0;
}
return Math.acos(nx1 * nx2 + ny1 * ny2 ); // dot product
}
newPoints = []; // array for new points
aLen = points.length;
if(aLen <= 2){ // nothing to if line too short
for(i = 0; i < aLen; i ++){ // ensure that the points are copied
newPoints.push([points[i][0],points[i][1]]);
}
return newPoints;
}
p1 = points[0];
endP =points[aLen-1];
i = 0; // start from second poitn if line not closed
closed = false;
len = Math.hypot(p1[0]- endP[0], p1[1]-endP[1]);
if(len < Math.SQRT2){ // end points are the same. Join them in coordinate space
endP = p1;
i = 0; // start from first point if line closed
p1 = points[aLen-2];
closed = true;
}
newPoints.push([points[i][0],points[i][1]])
for(; i < aLen-1; i++){
p2 = points[i];
p3 = points[i + 1];
angle = Math.abs(dot(p2[0] - p1[0], p2[1] - p1[1], p3[0] - p2[0], p3[1] - p2[1]));
if(dist1 !== 0){ // dist1 and dist2 come from dot function
if( angle < cornerThres*3.14){ // bend it if angle between lines is small
if(match){
dist1 = Math.min(dist1,dist2);
dist2 = dist1;
}
// use the two normalized vectors along the lines to create the tangent vector
x = (nx1 + nx2) / 2;
y = (ny1 + ny2) / 2;
len = Math.sqrt(x * x + y * y); // normalise the tangent
if(len === 0){
newPoints.push([p2[0],p2[1]]);
}else{
x /= len;
y /= len;
if(newPoints.length > 0){
var np = newPoints[newPoints.length-1];
np.push(p2[0]-x*dist1*0.25);
np.push(p2[1]-y*dist1*0.25);
}
newPoints.push([ // create the new point with the new bezier control points.
p2[0],
p2[1],
p2[0]+x*dist2*0.25,
p2[1]+y*dist2*0.25
]);
}
}else{
newPoints.push([p2[0],p2[1]]);
}
}
p1 = p2;
}
if(closed){ // if closed then copy first point to last.
p1 = [];
for(i = 0; i < newPoints[0].length; i++){
p1.push(newPoints[0][i]);
}
newPoints.push(p1);
}else{
newPoints.push([points[points.length-1][0],points[points.length-1][1]]);
}
return newPoints;
}
// creates a drawable image
var createImage = function(w,h){
var image = document.createElement("canvas");
image.width = w;
image.height =h;
image.ctx = image.getContext("2d");
return image;
}
// draws the smoothed line with bezier control points.
var drawSmoothedLine = function(line){
var i,p;
ctx.beginPath()
ctx.moveTo(line[0][0],line[0][1])
for(i = 0; i < line.length-1; i++){
p = line[i];
p1 = line[i+1]
if(p.length === 2){ // linear
ctx.lineTo(p[0],p[1])
}else
if(p.length === 4){ // bezier 2nd order
ctx.quadraticCurveTo(p[2],p[3],p1[0],p1[1]);
}else{ // bezier 3rd order
ctx.bezierCurveTo(p[2],p[3],p[4],p[5],p1[0],p1[1]);
}
}
if(p.length === 2){
ctx.lineTo(p1[0],p1[1])
}
ctx.stroke();
}
// smoothing settings
var liveSmooth;
var lineSmooth = {};
lineSmooth.lengthMin = 8; // square of the pixel length
lineSmooth.angle = 0.8; // angle threshold
lineSmooth.match = false; // not working.
// back buffer to save the canvas allowing the new line to be erased
var backBuffer = createImage(canvas.width,canvas.height);
var currentLine = [];
mouse.lastButtonRaw = 0; // add mouse last incase not there
ctx.lineWidth = 3;
ctx.lineJoin = "round";
ctx.lineCap = "round";
ctx.strokeStyle = "black";
ctx.clearRect(0,0,canvas.width,canvas.height);
var drawing = false; // if drawing
var input = false; // if menu input
var smoothIt = false; // flag to allow feedback that smoothing is happening as it takes some time.
function draw(){
// if not drawing test for menu interaction and draw the menus
if(!drawing){
if(mouse.x < 203 && mouse.y < 24){
if(mouse.y < 13){
if(mouse.buttonRaw === 1){
ctx.clearRect(3,3,200,10);
lineSmooth.angle = (mouse.x-3)/200;
input = true;
}
}else
if(mouse.buttonRaw === 1){
ctx.clearRect(3,14,200,10);
lineSmooth.lengthMin = (mouse.x-3)/10;
input = true;
}
canvas.style.cursor = "pointer";
}else{
canvas.style.cursor = "crosshair";
}
if(mouse.buttonRaw === 0 && input){
input = false;
mouse.lastButtonRaw = 0;
}
ctx.lineWidth = 0.5;
ctx.fillStyle = "red";
ctx.clearRect(3,3,200,10);
ctx.clearRect(3,14,200,10);
ctx.fillRect(3,3,lineSmooth.angle*200,10);
ctx.fillRect(3,14,lineSmooth.lengthMin*10,10);
ctx.textAlign = "left";
ctx.textBaseline = "top";
ctx.fillStyle = "#000"
ctx.strokeRect(3,3,200,10);
ctx.fillText("Smooth "+(lineSmooth.angle * (180 / Math.PI)).toFixed(0)+"deg",5,2)
ctx.strokeRect(3,14,200,10);
ctx.fillText("Detail "+lineSmooth.lengthMin.toFixed(0) + "pixels",5,13);
}else{
canvas.style.cursor = "crosshair";
}
if(!input){
ctx.lineWidth = 3;
if(mouse.buttonRaw === 4 && mouse.lastButtonRaw === 0){
currentLine = [];
drawing = true;
backBuffer.ctx.clearRect(0,0,canvas.width,canvas.height);
backBuffer.ctx.drawImage(canvas,0,0);
currentLine.push([mouse.x,mouse.y])
}else
if(mouse.buttonRaw === 4){
var lp = currentLine[currentLine.length-1]; // get last point
// dont record point if no movement
if(mouse.x !== lp[0] || mouse.y !== lp[1] ){
currentLine.push([mouse.x,mouse.y]);
ctx.beginPath();
ctx.moveTo(lp[0],lp[1])
ctx.lineTo(mouse.x,mouse.y);
ctx.stroke();
liveSmooth = smoothLine(
simplifyLineRDP(
currentLine,
lineSmooth.lengthMin
),
lineSmooth.angle,
lineSmooth.match
);
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.drawImage(backBuffer,0,0);
ctx.strokeStyle = "Blue";
drawSmoothedLine(liveSmooth );
ctx.strokeStyle = "black";
}
}else
if(mouse.buttonRaw === 0 && mouse.lastButtonRaw === 4){
ctx.textAlign = "center"
ctx.fillStyle = "red"
ctx.fillText("Smoothing...",canvas.width/2,canvas.height/5);
smoothIt = true;
}else
if(smoothIt){
smoothIt = false;
var newLine = smoothLine(
simplifyLineRDP(
currentLine,
lineSmooth.lengthMin
),
lineSmooth.angle,
lineSmooth.match
);
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.drawImage(backBuffer,0,0);
drawSmoothedLine(newLine);
drawing = false;
}
if(mouse.buttonRaw === 1 && mouse.lastButtonRaw === 0){
currentLine = [];
drawing = true;
backBuffer.ctx.clearRect(0,0,canvas.width,canvas.height);
backBuffer.ctx.drawImage(canvas,0,0);
currentLine.push([mouse.x,mouse.y])
}else
if(mouse.buttonRaw === 1){
var lp = currentLine[currentLine.length-1]; // get last point
// dont record point if no movement
if(mouse.x !== lp[0] || mouse.y !== lp[1] ){
currentLine.push([mouse.x,mouse.y]);
ctx.beginPath();
ctx.moveTo(lp[0],lp[1])
ctx.lineTo(mouse.x,mouse.y);
ctx.stroke();
}
}else
if(mouse.buttonRaw === 0 && mouse.lastButtonRaw === 1){
ctx.textAlign = "center"
ctx.fillStyle = "red"
ctx.fillText("Smoothing...",canvas.width/2,canvas.height/5);
smoothIt = true;
}else
if(smoothIt){
smoothIt = false;
var newLine = smoothLine(
simplifyLineRDP(
currentLine,
lineSmooth.lengthMin
),
lineSmooth.angle,
lineSmooth.match
);
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.drawImage(backBuffer,0,0);
drawSmoothedLine(newLine);
drawing = false;
}
}
// middle button clear
if(mouse.buttonRaw === 2){
ctx.clearRect(0,0,canvas.width,canvas.height);
}
mouse.lastButtonRaw = mouse.buttonRaw;
requestAnimationFrame(draw);
}
draw();
.canC { width:1000px; height:500px; border:1px black solid;}
<canvas class="canC" id="canV" width=1000 height=500></canvas>
You could save the last position and draw a line between the last point and the actual point.
if (lastX && lastY && (x !== lastX || y !== lastY)) {
ctx.fillStyle = "#000000";
ctx.lineWidth = 2 * size;
ctx.beginPath();
ctx.moveTo(lastX, lastY);
ctx.lineTo(x, y);
ctx.stroke();
// ...
lastX = x;
lastY = y;
}
On mouseup event set the two variables to zero.
var canvas, ctx
var mouseX, mouseY, mouseDown = 0,
lastX, lastY;
function draw(ctx,x,y,size) {
if (lastX && lastY && (x !== lastX || y !== lastY)) {
ctx.fillStyle = "#000000";
ctx.lineWidth = 2 * size;
ctx.beginPath();
ctx.moveTo(lastX, lastY);
ctx.lineTo(x, y);
ctx.stroke();
}
ctx.fillStyle = "#000000";
ctx.beginPath();
ctx.arc(x, y, size, 0, Math.PI*2, true);
ctx.closePath();
ctx.fill();
lastX = x;
lastY = y;
}
function clearCanvas(canvas,ctx) {
ctx.clearRect(0, 0, canvas.width, canvas.height)
}
function onMouseDown() {
mouseDown = 1
draw(ctx, mouseX, mouseY, 2)
}
function onMouseUp() {
mouseDown = 0;
lastX = 0;
lastY = 0;
}
function onMouseMove(e) {
getMousePos(e)
if (mouseDown == 1) {
draw(ctx, mouseX, mouseY, 2)
}
}
function getMousePos(e) {
if (!e)
var e = event
if (e.offsetX) {
mouseX = e.offsetX
mouseY = e.offsetY
}
else if (e.layerX) {
mouseX = e.layerX
mouseY = e.layerY
}
}
function init() {
canvas = document.getElementById('sketchpad')
ctx = canvas.getContext('2d')
canvas.addEventListener('mousedown', onMouseDown, false)
canvas.addEventListener('mousemove', onMouseMove, false)
window.addEventListener('mouseup', onMouseUp, false)
}
init();
<canvas id="sketchpad" width="600" height="300"></canvas>
Good question! And I recommend you a site https://developer.mozilla.org/zh-CN/docs/Web/API/Canvas_API to learn more canvas API.
I think using lineTo is better than arc.So I hope this code will help you.
var canvas, ctx;
var mouseDown = 0, lastX, lastY;
function draw(ctx,x,y) {
ctx.beginPath();
ctx.moveTo(lastX,lastY);
ctx.lineTo(x,y);
ctx.closePath();
ctx.stroke();
}
function clearCanvas(canvas,ctx) {
ctx.clearRect(0, 0, canvas.width, canvas.height)
}
function onMouseDown(e) {
var xy = getMousePos(e);
lastX = xy.mouseX;
lastY = xy.mouseY;
mouseDown = 1;
}
function onMouseUp() {
mouseDown = 0
}
function onMouseMove(e) {
if (mouseDown == 1) {
var xy = getMousePos(e);
draw(ctx, xy.mouseX, xy.mouseY);
lastX = xy.mouseX, lastY = xy.mouseY;
}
}
function getMousePos(e) {
var o = {};
if (!e)
var e = event
if (e.offsetX) {
o.mouseX = e.offsetX
o.mouseY = e.offsetY
}
else if (e.layerX) {
o.mouseX = e.layerX
o.mouseY = e.layerY
}
return o;
}
function init() {
canvas = document.getElementById('sketchpad')
ctx = canvas.getContext('2d')
canvas.addEventListener('mousedown', onMouseDown, false)
canvas.addEventListener('mousemove', onMouseMove, false)
canvas.addEventListener('mouseup', onMouseUp, false)
}
init();
By default HTML 5 canvas has rectangular shape, though if i do any animation under canvas, it will move into rectangular area.
What if i bound area to radial shape?It shouldn't definitely go out of radial shape.
Can we limit boundary to radial instead of default rectangular shape?
You can look at ball is going out of radial boundary- http://jsfiddle.net/stackmanoz/T4WYH/
I designed boundary in radial shape now i want to limit radial area too.
Limit area for ball-
function bounce() {
if (x + dx > 293 || x + dx < 0) {
dx = -dx;
}
if (y >= 290) {
y = 290;
}
if (y + dy > 290 || y + dy < 0) {
dx *= 0.99;
dy = -dy;
}
if (Math.abs(dx) < 0.01) {
dx = 0;
}
dy++;
}
The cartesian formula for a circle is (x − a)2 + (y − b)2 = r2
So check for this in your bounce condition:
function bounce() {
if( Math.pow(x - 150, 2) + Math.pow(y - 150, 2) > Math.pow(150, 2))
{
dx = -dx * (0.6 + (Math.random() * 0.8));
dy = -dy * (0.6 + (Math.random() * 0.8));
}
}
I am using random bouncing because I could not work out the correct bounce angle using the incident speed and the normal at the bounce point (I'm sure there is somebody ele here who can)
updated fiddle here: http://jsfiddle.net/T4WYH/1/
Few points, use requestAnimationFrame rather than setInterval
I would draw the large circle in the canvas, rather than as a border, then you can use isPointInPath(x, y) to work out if your ball is within the circle (or any other arbitrary path for that matter)
function draw() {
ctx.clearRect(0, 0, 300, 300);
ctx.beginPath()
ctx.lineWidth = 1;
ctx.strokeStyle = '#000';
ctx.arc(150, 150, 150, 0, 2 * Math.PI, true);
ctx.stroke();
ctx.closePath();
console.log(ctx.isPointInPath(x, y)); //Is (center) of ball in big circle
ctx.beginPath();
ctx.arc(x, y, 10, 0, 2 * Math.PI, true);
ctx.closePath();
ctx.fill();
x += dx;
y += dy;
bounce();
}
I don't want to implement this particular task, but you can get ideas how to bounce from circle from this site: bbdizains.com
And coresponding function:
move = function(){
for (i=1; i<=3; i++) {
A.x[i] = A.x[i] - A.v[i]*Math.sin(A.alfa[i]);
A.y[i] = A.y[i] - A.v[i]*Math.cos(A.alfa[i]);
x = A.x[i]-175;
y = A.y[i]-233;
x2 = x*x;
y2 = y*y;
if (x2+y2>=6561) {
if (A.flag[i]==1) {
gamma = Math.atan(y/x);
A.alfa[i] = - 2*gamma - A.alfa[i];
A.flag[i] = 0;
}
} else {
A.flag[i] = 1;
}
$('#r'+i).css('left',A.x[i]+'px');
$('#r'+i).css('top',A.y[i]+'px');
if ((Math.random()>0.95) && (x2+y2<6000)) {
A.alfa[i] = A.alfa[i] + Math.PI*Math.random()*0.1;
}
}
}
I've already created a bouncing ball which bounces off the walls of the HTML5 Canvas that I have specified.
My goal is to make a "Game Over" screen appear when the pointer (mouse) hovers over the ball.
I have already searched and found some tutorials on mouse events in Javascript, but I'm not really sure how to implement them into my code =/.
Any help would be amazing.
<script>
var x = Math.floor((Math.random() * 600) + 1);
var y = Math.floor((Math.random() * 300) + 1);
var dx = 2;
var dy = 4;
function begin()
{
gameCanvas = document.getElementById('gameCanvas');
context = gameCanvas.getContext('2d');
return setInterval (draw, 20);
}
begin();
function draw()
{
context.clearRect(0,0,600,300);
context.fillStyle = "#0000FF";
context.beginPath();
context.arc(x,y,80,0,Math.PI*2,true);
context.closePath();
context.fill();
if (x < 0 || x > 600) dx=-dx
if (y < 0 || y > 300) dy=-dy;
x += dx;
y += dy;
}
gameCanvas.onmousemove = function (e)
{
var gameCanvas = e.target;
var context = gameCanvas.getContext('2d');
var coords = RGraph.getMouseXY(e);
}
You need to check if the mouse is hovering over the ball (hit test) by checking the distance of the ball to the cursor. If the distance is smaller than radius of the ball, it means that the mouse is over the ball.
Note, that you need to adjust the code below to your needs
Example:
var mouse_x = 10, mouse_y = 10, ball_x = 10, ball_y = 10, ball_radius = 70, is_game_over = false
if( Math.sqrt( Math.pow( mouse_x - ball_x, 2 ) + Math.pow( mouse_x - ball_x, 2 )) < ball_radius && !is_game_over ) {
console.log('Cursor is over the mouse, game over')
is_game_over = true
}
Do it for every frame update.
you can add onmousemove=SetValues() to your body element like so:
<body onmousemove=SetValues()>
and change your code to this:
<script>
var x = Math.floor((Math.random() * 600) + 1);
var y = Math.floor((Math.random() * 300) + 1);
var dx = 2;
var dy = 4;
var mouseX;
var mouseY;
function setValues(e)
{
mouseX = e.pageX; //get mouse x
mouseY = e.pageY; //get mouse y
}
function begin()
{
gameCanvas = document.getElementById('gameCanvas');
context = gameCanvas.getContext('2d');
return setInterval (draw, 20);
}
begin();
function draw()
{
context.clearRect(0,0,600,300);
context.fillStyle = "#0000FF";
context.beginPath();
context.arc(x,y,80,0,Math.PI*2,true);
context.closePath();
context.fill();
if (x < 0 || x > 600) dx=-dx
if (y < 0 || y > 300) dy=-dy;
x += dx;
y += dy;
//check if the mouse is on the ball
var centerX = x + 80; //center of ball
var centerY = y; //center of ball
if(Math.pow((mouseX - centerX), 2) + Math.pow((mouseY - centerY), 2) <= 6400){
//do whatever to end game
}
}