I'm trying to have asteroids moving across the screen for a game. The first few asteroids work and then each asteroid will start blinking and bugging out to the point where they won't move across the screen. The variables acx and acy are the x and y coordinates for the asteroids respectively.
setInterval(throwAsteroid1A, 5000);
function throwAsteroid1A() {
var asteroidCanvas = document.getElementById('asteroidCanvas');
var context = asteroidCanvas.getContext('2d');
var acx = Math.floor(Math.random() * 200);
var acy = Math.floor(Math.random() * 10);
setInterval( () => {
asteroid.onload = function() {
context.drawImage(asteroid, asx, asy, aswidth, asheight, acx, acy, 20, 20);
acx += 1;
acy += 1;
}
asteroid.src = 'https://i.imgur.com/WfQKE6T.png';
}, 10)
setInterval(asteroidPath, 50)
}
function asteroidPath() {
// let computedStyle = getComputedStyle(canvasDisplay)
var asteroidCanvas = document.getElementById('asteroidCanvas');
let ctx = asteroidCanvas.getContext("2d");
ctx.clearRect(acx,acy, canvasDisplay.width, canvasDisplay.height);
}
Well there's obviously something conceptually wrong with your approach. I think the blinking is caused by a timing issue in-between the numerous individual interval timers you set up. The callback function asteroidPath() clears a part of the canvas and this might happen at the same time a new Asteroid has been added to the screen - which will delete it either entirely or partly depending on it's screen position.
To work around it you should:
keep a list of all asteroid objects
clear the screen completely once
update all asteroid's at once - not each one with it's own timer
So an example based on your code might look a little something like this (just click 'Run code snippet'):
Asteroid = function() {
this.acx = Math.floor(Math.random() * 200);
this.acy = Math.floor(Math.random() * 10);
this.image = new Image();
this.image.onload = function(e) {
this.loaded = true;
this.aswidth = e.target.naturalWidth;
this.asheight = e.target.naturalHeight;
}
this.image.src = 'https://i.imgur.com/WfQKE6T.png';
}
var asteroidCanvas = document.getElementById('asteroidCanvas');
var context = asteroidCanvas.getContext('2d');
let asteroids = [];
function spawnAsteroid() {
asteroids.push(new Asteroid());
}
function updateCanvas() {
context.clearRect(0, 0, asteroidCanvas.width, asteroidCanvas.height);
let asteroid;
for (let a = 0; a < asteroids.length; a++) {
asteroid = asteroids[a];
if (asteroid.image.loaded) {
context.drawImage(asteroid.image, 0, 0, asteroid.image.aswidth, asteroid.image.asheight, asteroid.acx, asteroid.acy, 20, 20);
asteroid.acx += 1;
asteroid.acy += 1;
}
}
}
setInterval(spawnAsteroid, 2000);
setInterval(updateCanvas, 50);
spawnAsteroid();
<canvas id="asteroidCanvas"></canvas>
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Help, I've been using this website called "codepen" to do some javascript coding. But I accidently made it send me infinite prompts, everytime I open the project. Now I can't access the code. I searched for some time for an answer but I found none. heres a link to the problem: https://codepen.io/Aibel-Roy/pen/zYPBeEW
//I can't post the code because of the infinite prompts. Sorry.
Here's your code:
//config
var tick = 50;
var fieldOfView = 25;
var Speed = 0.25;
var ZMulti = 4;
var ClearOnDraw = true;
// variables
var keymap = [];
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var meshA = [
"0,0,0",
"1,0,0",
"1,1,0",
"0,1,0",
"0,0,1",
"1,0,1",
"0,1,1",
"1,1,1"
];
var textures = [
"http://www.textures4photoshop.com/tex/thumbs/red-sofa-leather-seamless-texture-53.jpg"
];
var cameraData = [0, 0, 0];
//keymap
window.addEventListener(
"keydown",
(event) => {
var name = event.key;
keymap.push(name);
},
false
);
window.addEventListener(
"keyup",
(event) => {
var name = event.key;
if (keymap.includes(name)) {
keymap.splice(keymap.indexOf(name), 1);
}
},
false
);
//render img
function draw() {
if (ClearOnDraw) {
ctx.clearRect(0, 0, 10000, 1000);
}
var img = new Image(); // texturing
img.src = textures[0];
prompt(img.src);
img.onLoad = function () {
var pattern = context.createPattern(imageObj, "repeat");
ctx.fillStyle = pattern;
var prevVert;
for (let i = 0; i <= meshA.length; i++) {
//convert 3D vector to 2D
var vert = meshA[i];
if (i >= meshA.length) {
vert = meshA[0];
}
var vertPos = vert.split(",");
var zMag = (vertPos[2] - cameraData[2]) * (fieldOfView / ZMulti);
var vertPos2D = [
(vertPos[0] - cameraData[0]) * fieldOfView + zMag,
(vertPos[1] - cameraData[1]) * fieldOfView + zMag
];
ctx.beginPath();
ctx.moveTo(vertPos2D[0], vertPos2D[1]);
for (let i1 = 0; i1 < meshA.length; i1++) {
var prv = meshA[i1].split(",");
var PrevzMag = (prv[2] - cameraData[2]) * (fieldOfView / ZMulti);
var I1VertPos = [
(prv[0] - cameraData[0]) * fieldOfView + PrevzMag,
(prv[1] - cameraData[1]) * fieldOfView + PrevzMag
];
ctx.lineTo(I1VertPos[0], I1VertPos[1]);
ctx.stroke();
}
ctx.closePath();
ctx.fill();
prevVert = vertPos2D;
}
};
}
function Movement() {
if (keymap.includes("w")) {
cameraData[2] -= Speed * 2;
}
if (keymap.includes("s")) {
cameraData[2] += Speed * 2;
}
if (keymap.includes("d")) {
cameraData[0] -= Speed;
}
if (keymap.includes("a")) {
cameraData[0] += Speed;
}
}
draw();
setInterval(function main() {
draw();
Movement();
}, tick);
How to disable the prompt(if the browser doesn't suggest you to suppress it):
On that page, bring up dev tools(Command + Option + I, or F12 on Windows).
Choose the correct page on the dev tool, usually looks like CodePen (Hash ID)
Override the prompt function in the console by typing window.prompt = () => {}.
Change your code, save and refresh the page.
There are probably better ways to do it but disabling JavaScript makes the code section unusable.
In your function draw(), there is a prompt in here:
function draw() {
// Trimmed
prompt(img.src);
// Trimmed
}
You also have setInterval calling draw() at a particular interval defined in tick (where you have assigned 50ms as the value):
setInterval(function main() {
draw();
Movement();
}, tick);
As a result, draw() gets called every 50ms, where prompt(img.src) gets called, leading to infinite prompt.
You need to change whatever you are doing in setInterval().
I'm having a bit of trouble making a progress graph. This is my first time using canvas so I'm a little new to the concept. This page is going to be a little prime number benchmark for an assignment at school. I haven't done the algorithm yet so right now that just counts up. I wanted to have a graph display the progress of the benchmark to the user so it doesn't look like the page has just frozen. I've broken the benchmark down into "sprints", where the device will calculate numbers for a set period of time and then update the graph. Problem is, the graph doesn't seem to update until the end of the "benchmark". Any recommendations?
The javascript is below (execBench is probably the most relevant function):
function startBench() {
// move to benchmark display
//showPage("bench");
jQuery.mobile.changePage("#bench");
setTimeout(
function () {
// run benchmark
var score = execBench(10);
//set score and move page
$(".result").text(score);
setTimeout(function () {
showPage("result");
}, 4000);
}, 2000);
}
function debugmsg(message) {
console.log(message);
}
function execBench(time) {
var graphUpdateRate = 2; // horizontal "resolution" of graph/sprint length in s
var sprintCount = Math.floor(time / graphUpdateRate);
debugmsg("Running " + sprintCount + " " + graphUpdateRate + "-second sprints");
var currentTime = new Date();
var sprintDeadline = currentTime;
var counter = 0; // "score" for the end, # of primes generated
var lastPrime = 0;
var record = []; // datapoints for graph
for (var i = 0; i < sprintCount; i++) {
// perform calculations
sprintDeadline = incrementDate(new Date(), graphUpdateRate);
while (currentTime < sprintDeadline) {
currentTime = Date.now();
lastPrime = generatePrime(lastPrime);
counter++;
}
// report progress
record.push(counter);
drawGraph(document.getElementById('progGraph'), record, sprintCount);
}
return counter;
}
function generatePrime(min) {
//placeholder for algorithm
min++;
return min;
}
function drawGraph(canvas, dataPoints, maxPoints) {
var context = canvas.getContext('2d');
var width = canvas.width;
var height = canvas.height;
var xIncrement = width / maxPoints;
var xBegin = 0;
var prevPoint = 0;
var yScale = -1 * height / Math.max(...dataPoints);
//reset canvas
canvas.width = canvas.width;
context.clearRect(0, 0, canvas.width, canvas.height);
//move context to bottom right and set scale
context.translate(0, height);
context.scale(1, 1);
context.strokeStyle = "#ed1e79";
for (dataPoint in dataPoints) {
currentPoint = (dataPoints[dataPoint] * yScale);
context.beginPath();
context.moveTo(xBegin, prevPoint);
context.lineTo(xBegin + xIncrement, currentPoint);
context.lineWidth = 3;
context.lineCap = 'round';
context.stroke();
prevPoint = currentPoint;
xBegin += xIncrement;
}
debugmsg(Math.max(...dataPoints));
return;
}
function incrementDate(date, seconds) {
return new Date(date.getTime() + (seconds * 1000));
}
As an example of using requestAnimationFrame(), you could try something like this.
function execBench(time) {
var graphUpdateRate = 2; // horizontal "resolution" of graph/sprint length in s
var sprintCount = Math.floor(time / graphUpdateRate);
debugmsg("Running " + sprintCount + " " + graphUpdateRate + "-second sprints");
var currentTime = new Date();
var sprintDeadline = currentTime;
var counter = 0; // "score" for the end, # of primes generated
var lastPrime = 0;
var record = []; // datapoints for graph
var i = 0;
(function drawSprint() {
// perform calculations
sprintDeadline = incrementDate(new Date(), graphUpdateRate);
while (currentTime < sprintDeadline) {
currentTime = Date.now();
lastPrime = generatePrime(lastPrime);
counter++;
}
// report progress
record.push(counter);
drawGraph(document.getElementById('progGraph'), record, sprintCount);
i++;
if (i < sprintCount) {
requestAnimationFrame(drawSprint);
}
})();
return counter;
}
Your while loop is "blocking". It eats up CPU, not allowing javascript and probably much else on the computer to do anything.
Instead, use setTimeout(fn, t) to schedule the next update.
setTimeout() is non blocking. Its fn will execute in a fresh event thread in t milliseonds time (or shortly thereafter).
Between setTimouts, your computer's processor will have the capacity to instruct the graphich card to render the canvas.
Hello stackoverflow community!
First I must say that I dont have much experience with constructors.
So. What I am trying to do, is to animate a parachutist to fly from top to bottom of the screen.
I thought I could use a constructor to set up a parachutist:
var parachute = function() {
this.height = 35;
this.width = 30;
this.speed = 50;
this.xPos = Math.round(Math.random() * (window.width - this.width));
this.animate = function() {
this.img = new Image();
this.yPos = 0;
this.img.onload = function() {
ctxPara.globalCompositeOperation = 'copy';
ctxPara.translate(0, this.yPos);
ctxPara.drawImage(this.img, this.xPos, 0);
};
this.img.src = 'para.png';
this.yPos++;
};
};
This constructor is used in a function called 'fly':
var fly = function() {
var newParachute = new parachute();
setInterval(newParachute.animate, newParachute.speed);
};
And this 'fly' function is triggered when the window loads:
window.onload = function() {
var canvasBg = document.getElementById('canvasBg');
// I splitt the Background and the parachutists in two canvas elements
// handling the problem (to erase content and draw new content) with
// the canvas animation.
var canvasPara = document.getElementById('canvasPara');
ctxPara = canvasPara.getContext('2d');
canvasPara.width = window.width;
canvasPara.height = window.height;
canvasBg.width = window.width;
canvasBg.height = window.height;
fly();
clouds(); // background is loading here
};
What you should see, is a Parachutist flying down the screen. But unfortunately you don't...
Now, after that Long text. (Iam very sorry that it is so long :-( ) My question is: Do you know what I am doing wrong? Is my constuctor correct? Is, what i am trying to do, supposed to be written like this? Any advices or suggestions for a succesfull opportunity? (I hope my english isn't that terrible I think it is :-) )
Oh i forgot to mention the error. It's a TypeMissMatchError.
That means 'this.img' is not an img element at this line:
ctxPara.drawImage(this.img, this.xPos, 0);
Now, I followed the example of markE.
Instead of showing me a parachutist. It shows me an error in this line: ctxPara.drawImage(this.img, this.xPos, this.yPos);
var fly = function () {
var newParachute = new parachute();
newParachute.img.load.call(newParachute);
setInterval(newParachute.animate.call(newParachute), newParachute.speed);
};
var parachute = function () {
this.height = 35;
this.width = 30;
this.speed = 25;
this.xPos = Math.round(Math.random() * (window.innerWidth - this.width));
this.img = new Image();
this.yPos = 0;
this.img.isLoaded = false;
this.img.load = function () {
this.img.isLoaded = true;
};
this.img.src = 'parachute.png';
this.animate = function () {
if (this.img.isLoaded) {
ctxPara.clearRect(0, 0, canvasPara.width, canvasPara.height);
ctxPara.drawImage(this.img, this.xPos, this.yPos); // ERROR: 'Unknown Error'.
this.yPos++;
console.log('animating');
}
};
};
I am stuck again. But now i don't even know the reason... Please help!?
Demo: http://jsfiddle.net/m1erickson/ym55y/
A couple of issues:
(1) To get the window width you can use:
window.innerWidth
(2) setInterval calls newParachute.animate.
setInterval(newParachute.animate, newParachute.speed);
But this inside animate the window object--not the Parachute object.
To give the correct this to animate you can use the call method like this:
var newParachute = new parachute();
setInterval(function(){newParachute.animate.call(newParachute);}, newParachute.speed);
(3) You need to deal with clearing previously drawn images or they will still show on your canvas.
So I'm a newbie and should obviously spend time in the tuts, but I'm looking for a quick answer. Basically, I've created a grid of movie clips with AS3. When I 'preview' the flash (as a flash or HTML) it shows up fine. Success. Yet, the stage remains empty.
Q1) Will the stage remain empty as I have used AS3 to dynamically 'draw' the grid of mc's? Or is there a slit of code I am missing to make this baby show up on the stage?
Q2) I've managed to use alpha to make the MC's 'fade' on hover - but I want to make them change color (to red) when hovered over. I've searched everywhere and can't seem to find the right script.
Here is my code:
var stage = new createjs.Stage("canvas");
var image = new createjs.Bitmap("images/square.png");
stage.addChild(image);
createjs.Ticker.addEventListener("tick", handleTick);
function handleTick(event) {
image.x += 10;
stage.update();
}
var x0:Number = 0;
var y0:Number = 0;
var nt:Number = 72;
var nc = 10;
var vd:Number = 12;
var hd:Number = 12;
for (var i = 1; i <= nt; i++) {
var mc = this.attachMovie("square", "square" + i, i);
var aprox = Math.floor((i - 1) / nc);
mc._x = x0 + hd * ((i - aprox * nc) - 1);
mc._y = y0 + aprox * vd;
mc.useHandCursor = true;
// fade in
mc.onRollOver = function()
{
this.onEnterFrame = function()
{
if (this._alpha > 0) {
this._alpha -= 10;
} else {
this._alpha = 0;
delete this.onEnterFrame;
}
};
};
// fade out
mc.onRollOut = function()
{
this.onEnterFrame = function()
{
if (this._alpha < 100) {
this._alpha += 10;
} else {
this._alpha = 100;
delete this.onEnterFrame;
}
};
};
}
Thanks in advance - sorry I am a noob.
This will never work. 1/3 of your code is in AS3, 2/3 in AS2. Considering you haven't been thrown any error, I assume you exported it as AS2.
I noticed something weird in my canvas code: Im making a game with little flying ghosts. The class for the ghost is below. When I just draw 1 or 2 of em by manually adding the code and having em fly to the right by updating the x every frame for example everything runs smoothly and fine.
Now I ran another test and added a ghost every 100 frames to an array, update its x by 100 and then draw that ghost to the frame. (code is below the first block, the draw function).
Now the problem is that they are actually added and drawn, but I dont see em on the board until I make the window inactive by clicking on the taskbar for example.
Any1 got a clue what is going wrong here?
/*
* Class for little ghosts
*/
function Ghost (name) {
this.name = name;
this.ghost = new Image();
this.ghost.src = "img/ghost.png";
this.ghostWidth = 150;
this.ghostHeight = 100;
this.ghostSpriteOffsetX = 0;
this.ghostSpriteOffsetY = 0;
this.ghostX = 0;
this.ghostY = 0;
}
Ghost.prototype.drawGhost = function() {
context2D.drawImage(this.ghost, this.ghostSpriteOffsetX, this.ghostSpriteOffsetY, this.ghostWidth, this.ghostHeight, this.ghostX, this.ghostY, this.ghostWidth, this.ghostHeight);
};
Ghost.prototype.goToX = function(x) {
this.ghostX = x;
};
Ghost.prototype.goToY = function(y) {
this.ghostY = y;
};
Ghost.prototype.turnPink = function() {
this.ghostSpriteOffsetX = 0;
};
Ghost.prototype.turnBlue = function() {
this.ghostSpriteOffsetX = 150;
};
Ghost.prototype.turnPurple = function() {
this.ghostSpriteOffsetX = 300;
};
-
function draw()
{
// clear board
context2D.clearRect(0, 0, canvas.width, canvas.height);
if(frame%100==0){
ghosts[ghostId] = new Ghost("g-"+frame);
ghosts[ghostId].goToX(frame-100);
ghostId++;
}
// Draw ghost
for (i=0; i<ghosts.length; i++)
{
ghosts[i].drawGhost();
}
frame++;
}