We Keep Coding

How to animate several dots moving here and there in html canvas

I have a requirement to move many dots here and there inside a canvas.
Hence I created several arcs with different radius and placed them at random places.
var context = document.getElementById('stage').getContext('2d');
var radian = Math.PI / 180;
var x = 40;
var y = 40;
var r = 20;
var colorPoints = [];
var frames = 50;
var currentFrame = 0;
var toggle = false;
var iconsLoaded = false;
context.beginPath();
context.arc(x,y, r, 0 * radian, 360 * radian, false)
context.fill();
var drawMultipleCurves = function(ctx){
if(!iconsLoaded){
for (let i = 0; i < 600; i++) {
ctx.beginPath();
ctx.filter = 'blur(5px)';
ctx.fillStyle = '#B835FF';
colorPoints.push({x: Math.floor((Math.random() * 700) + 0), xMove: Math.floor((Math.random() * 2) + 0) , yMove: Math.floor((Math.random() * 2) + 0) , y: Math.floor((Math.random() * 700) + 0), radius: Math.floor((Math.random() * 20) + 5)});
ctx.arc(colorPoints[colorPoints.length - 1].x, colorPoints[colorPoints.length - 1].y, colorPoints[colorPoints.length - 1].radius, 0 * radian, 360 * radian, false);
ctx.fill();
ctx.closePath();
iconsLoaded = true;
}
}
else{
for(let i =0;i< colorPoints.length; i++){
if(frames === currentFrame ){
toggle = !toggle;
currentFrame = 0;
}
if(!toggle){
colorPoints[i].xMove === 1 ? colorPoints[i].x = colorPoints[i].x + 5 : colorPoints[i].x = colorPoints[i].x - 5;
colorPoints[i].yMove === 1 ? colorPoints[i].y = colorPoints[i].y + 5 : colorPoints[i].y = colorPoints[i].y - 5;
}
else{
colorPoints[i].xMove === 1 ? colorPoints[i].x = colorPoints[i].x - 5 : colorPoints[i].x = colorPoints[i].x + 5;
colorPoints[i].yMove === 1 ? colorPoints[i].y = colorPoints[i].y - 5 : colorPoints[i].y = colorPoints[i].y + 5;
}
ctx.beginPath();
ctx.arc(colorPoints[i].x, colorPoints[i].y, colorPoints[i].radius, 0 * radian, 360 * radian, false);
context.closePath( );
ctx.fill();
currentFrame = currentFrame + 1;
}
}
}
var animate = function(){
setTimeout(()=>{
context.clearRect(0,0,400,400);
context.beginPath();
drawMultipleCurves(context);
context.fill();
requestAnimationFrame(animate)
}, 1000/30)
}
requestAnimationFrame(animate)
<canvas id="stage" width="400" height="400">
<p>Your browser doesn't support canvas.</p>
</canvas>
Above is the code that I have tried.
I have first created and placed several dots at random places with random radius.
When I created them I saved all these random places in an array 'colorPoints'
Now I'm looping into this array and moving all the dots everytime 'requestAnimation' is called.
I'm able to achieve my animation of moving the dots randomly but as I have used 800 dots and then saving them into an array and then again looping them to move their position, the animation is not looking smooth.
It looks like it is moving and strucking. How can I achieve this animation smoothly?
Thanks in advance :)

Render "fill" once per style
Your code is slowing down due to where you placed fill (same if you use stroke)
When you have many objects with the same style call fill only once per frame for each object.
You had something like
for (const c of circles) {
ctx.beginPath();
ctx.arc(c.x, c.y, c.r, 0, TAU)
ctx.fill();
}
With a filter active the fill command forces the filter to be reset, which for blur is complex.
Rather add all the arcs then fill.
ctx.beginPath();
for (const c of circles) {
ctx.moveTo(c.x + c.r, c.y);
ctx.arc(c.x, c.y, c.r, 0, TAU)
}
ctx.fill();
The move ctx.moveTo(c.x + c.r, c.y); is used to close the previous arc.
You can also close the arc with ctx.closePath but this can be a lot slower when you have many arcs in the path buffer.
// slower than using moveTo
ctx.beginPath();
for (const c of circles) {
ctx.arc(c.x, c.y, c.r, 0, TAU)
ctx.closePath();
}
ctx.fill();
Example
Example draws 600 arcs using the blur filter as it only calls fill once per frame. This should run smooth on all but the most low end devices.
See function drawCircles
requestAnimationFrame(animate);
const ctx = canvas.getContext('2d');
const W = canvas.width;
const BLUR = 5;
const CIRCLE_COUNT = 600;
const MIN_RADIUS = BLUR;
const MAX_RADIUS = 30;
const MAX_DELTA = 1;
const MAX_CIR_R = MAX_RADIUS + BLUR;
const MOVE_SIZE = MAX_CIR_R * 2 + W;
const TAU = 2 * Math.PI;
const setOf = (c, cb, i = 0, a = []) => { while(i < c) { a.push(cb(i++)) } return a };
const rnd = (m, M) => Math.random() * (M - m) + m;
const style = {
filter: "blur(" + BLUR + "px)",
fillStyle: '#B835FF',
};
var currentStyle;
function setStyle(ctx, style) {
if (currentStyle !== style) {
Object.assign(ctx, style);
currentStyle = style;
}
}
const circle = {
get x() { return rnd(-MAX_CIR_R, W + MAX_CIR_R) },
get y() { return rnd(-MAX_CIR_R, W + MAX_CIR_R) },
get dx() { return rnd(-MAX_DELTA, MAX_DELTA) },
get dy() { return rnd(-MAX_DELTA, MAX_DELTA) },
get r() { return rnd(MIN_RADIUS, MAX_RADIUS) },
move() {
var x = this.x + this.dx + MOVE_SIZE + MAX_CIR_R;
var y = this.y + this.dy + MOVE_SIZE + MAX_CIR_R;
this.x = x % MOVE_SIZE - MAX_CIR_R;
this.y = y % MOVE_SIZE - MAX_CIR_R;
}
};
const circles = setOf(CIRCLE_COUNT, () => Object.assign({}, circle));
function drawCircles(circles, ctx, style) {
setStyle(ctx, style);
ctx.beginPath();
for (const c of circles) {
ctx.moveTo(c.x + c.r, c.y);
ctx.arc(c.x, c.y, c.r, 0, TAU);
}
ctx.fill();
}
function updateCircles(circles) {
for (const c of circles) { c.move(); }
}
function animate() {
ctx.clearRect(0,0,W, W);
updateCircles(circles);
drawCircles(circles, ctx, style);
requestAnimationFrame(animate);
}
<canvas id="canvas" width="600" height="600"> </canvas>
If you have several colors, group all the same colors so you can keep the number of fill calls as low as possible.
There are many ways to get the same effect with many colors (each circle a different color) but will need more setup code.

The CanvasRenderingContext2D blur filter is quite heavy - especially if you use it on a canvas consisting of 600 circles. That means on every screen update it has to re-draw 600 circles and apply a blur filter afterwards.
The usual approach is a little different. Initially you create a master texture with a blurred circle. This texture can then be re-used and drawn onto the canvas using the drawImage() method. To vary the size of the circles there is no radius anymore though. We can get the same effect by using a scale instead.
Here's an example:
var context = document.getElementById('stage').getContext('2d');
var radian = Math.PI / 180;
var x = 40;
var y = 40;
var r = 20;
var colorPoints = [];
var frames = 50;
var currentFrame = 0;
var toggle = false;
var iconsLoaded = false;
var texture = document.createElement("canvas");
var textureContext = texture.getContext("2d");
texture.width = 80;
texture.height = 80;
textureContext.filter = 'blur(5px)';
textureContext.fillStyle = '#B835FF';
textureContext.arc(texture.width / 2, texture.height / 2, 25, 0 * radian, 360 * radian, false);
textureContext.fill();
textureContext.closePath();
var drawMultipleCurves = function(ctx) {
if (!iconsLoaded) {
for (let i = 0; i < 600; i++) {
colorPoints.push({
x: Math.floor((Math.random() * 700) + 0),
xMove: Math.floor((Math.random() * 2) + 0),
yMove: Math.floor((Math.random() * 2) + 0),
y: Math.floor((Math.random() * 700) + 0),
scale: 0.2 + Math.random() * 0.8
});
iconsLoaded = true;
}
} else {
for (let i = 0; i < colorPoints.length; i++) {
if (frames === currentFrame) {
toggle = !toggle;
currentFrame = 0;
}
if (!toggle) {
colorPoints[i].xMove === 1 ? colorPoints[i].x = colorPoints[i].x + 5 : colorPoints[i].x = colorPoints[i].x - 5;
colorPoints[i].yMove === 1 ? colorPoints[i].y = colorPoints[i].y + 5 : colorPoints[i].y = colorPoints[i].y - 5;
} else {
colorPoints[i].xMove === 1 ? colorPoints[i].x = colorPoints[i].x - 5 : colorPoints[i].x = colorPoints[i].x + 5;
colorPoints[i].yMove === 1 ? colorPoints[i].y = colorPoints[i].y - 5 : colorPoints[i].y = colorPoints[i].y + 5;
}
ctx.drawImage(texture, colorPoints[i].x, colorPoints[i].y, texture.width * colorPoints[i].scale, texture.height * colorPoints[i].scale);
currentFrame = currentFrame + 1;
}
}
}
var animate = function() {
setTimeout(() => {
context.clearRect(0, 0, 400, 400);
context.beginPath();
drawMultipleCurves(context);
context.fill();
requestAnimationFrame(animate)
})
}
requestAnimationFrame(animate)
<canvas id="stage" width="400" height="400">
<p>Your browser doesn't support canvas.</p>
</canvas>

Build a pyramid of balls using the canvas

I'm having difficulties replicating the pyramid below on the canvas.
I'm struggling with the math portion on how to draw a new ball on each new line. Here is my code so far.
<canvas id="testCanvas" width="300" height="300" style="border:1px solid #d3d3d3;"></canvas>
<script>
// Access canvas element and its context
const canvas = document.getElementById('testCanvas');
const context = canvas.getContext("2d");
const x = canvas.width;
const y = canvas.height;
const radius = 10;
const diamater = radius * 2;
const numOfRows = canvas.width / diamater;
function ball(x, y) {
context.arc(x, y, radius, 0, 2 * Math.PI, true);
context.fillStyle = "#FF0000"; // red
context.fill();
}
function draw() {
for (let i = 0; i < numOfRows; i++) {
for (let j = 0; j < i + 1; j++) {
ball(
//Pos X
(x / 2),
//Pos Y
diamater * (i + 1)
);
}
}
ball(x / 2, y);
context.restore();
}
draw();
</script>
I've been stuck on this problem for a while. I appreciate any assistance you can provide.
Thank you.

I noticed that the circle do not touch. I am not sure if you need or want them to but as this presented an interesting problem I create this answer.
Distance between stacked circles.
The distance between rows can be calculated using the right triangle as shown in the following image
Where R is the radius of the circle and D is the distance between rows.
D = ((R + R) ** 2 - R ** 2) ** 0.5;
With that we can get the number of rows we can fit given a radius as
S = (H - R * 2) / D;
Where H is the height of the canvas and S is the number of rows.
Example
Given a radius fits as many rows as possible into the give canvas height.
const ctx = canvas.getContext("2d");
const W = canvas.width, H = canvas.height, CENTER = W / 2;
const cols = ["#E80", "#0B0"];
draw();
function fillPath(path, x, y, color) {
ctx.fillStyle = color;
ctx.setTransform(1, 0, 0, 1, x, y);
ctx.fill(path);
}
function draw() {
const R = 10;
const D = ((R * 2) ** 2 - R ** 2) ** 0.5;
const S = (H - R * 2) / D | 0;
const TOP = R + (H - (R * 2 + D * S)) / 2; // center horizontal
const circle = new Path2D();
circle.arc(0, 0, R, 0, Math.PI * 2);
var y = 0, x;
while (y <= S) {
x = 0;
const LEFT = CENTER - (y * R);
while (x <= y) {
fillPath(circle, LEFT + (x++) * R * 2, TOP + y * D, cols[y % 2]);
}
y ++;
}
}
canvas {
border:1px solid #ddd;
}
<canvas id="canvas" width="300" height="180"></canvas>
Radius to fit n rows of stacked circles
Or if you have the height H and the number of rows S you want to fit. As shown in next image.
We want to find R given H and S we rearrange for H and solve the resulting quadratic with
ss = S * S - 2 * S + 1;
a = 4 / ss;
b = -4 * H / ss;
c = H * H / ss;
R = (-b-(b*b - 4 * a * c) ** 0.5) / (2 * a); // the radius
Example
Given the number of rows (number input) calculates the radius that will fit that number of rows
const ctx = canvas.getContext("2d");
const W = canvas.width, H = canvas.height, CENTER = W / 2;
rowsIn.addEventListener("input", draw)
const cols = ["#DD0", "#0A0"];
draw();
function fillPath(path, x, y, color) {
ctx.fillStyle = color;
ctx.setTransform(1, 0, 0, 1, x, y);
ctx.fill(path);
}
function draw() {
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.clearRect(0,0,W,H);
const S = Number(rowsIn.value);
const ss = S * S - 2 * S + 1;
const a = 4 / ss - 3, b = -4 * H / ss, c = H * H / ss;
const R = (- b - ((b * b - 4 * a * c) ** 0.5)) / (2 * a); // the radius
const TOP = R;
const D = ((R * 2) ** 2 - R ** 2) ** 0.5;
//const S = (H - R * 2) / D;
const circle = new Path2D();
circle.arc(0, 0, R, 0, Math.PI * 2);
var y = 0, x;
while (y < S) {
x = 0;
const LEFT = CENTER - (y * R);
while (x <= y) {
fillPath(circle, LEFT + (x++) * R * 2, TOP + y * D, cols[y % 2]);
}
y ++;
}
}
canvas {
border:1px solid #ddd;
}
<canvas id="canvas" width="300" height="180"></canvas>
<input type="number" id="rowsIn" min="3" max="12" value="3">Rows

How you can approach this problem is by breaking it down into one step at a time.
On (1)st row draw 1 circle
On (2)nd row draw 2 circles
On (3)rd row draw 3 circles
And so on...
Then you have to figure out where to draw each circle. That also you can break down into steps.
1st-row 1st circle in the center (width)
2nd-row 1st circle in the center minus diameter
2nd-row 2nd circle in the center plus diameter
and so on.
Doing this way you will find a pattern to convert into 2 for loops.
Something like this:
//1st row 1st circle
ball(w/2,radius * 1, red);
//2nd row 1st circle
ball(w/2 - radius,radius * 3, blue);
//2nd row 2nd circle
ball(w/2 + radius,radius * 3, blue);
The code below shows each step how each ball is drawn. I have also done few corrections to take care of the numberOfRows.
const canvas = document.getElementById('testCanvas');
const context = canvas.getContext("2d");
const w = canvas.width;
const h = canvas.height;
const radius = 10;
const diamater = radius * 2;
const numOfRows = Math.min(h / diamater, w / diamater);
const red = "#FF0000";
const blue = "#0000FF";
var k = 1;
function ball(x, y, color) {
setTimeout(function() {
context.beginPath();
context.arc(x, y, radius, 0, 2 * Math.PI, true);
context.fillStyle = color;
context.fill();
}, (k++) * 250);
}
for (var i = 1; i <= numOfRows; i++) {
for (var j = 1; j <= i; j++) {
var y = (i * radius * 2) - radius;
var x = (w / 2) - ((i * radius) + radius) + (j * diamater);
ball(x, y, i % 2 ? red : blue);
}
}
<canvas id="testCanvas"
width="300" height="180"
style="border:1px solid #d3d3d3;"></canvas>

hyperdrive effect in canvas across randomly placed circles

I'm trying to create a hyperdrive effect, like from Star Wars, where the stars have a motion trail. I've gotten as far as creating the motion trail on a single circle, it still looks like the trail is going down in the y direction and not forwards or positive in the z direction.
Also, how could I do this with (many) randomly placed circles as if they were stars?
My code is on jsfiddle (https://jsfiddle.net/5m7x5zxu/) and below:
var canvas = document.querySelector("canvas");
var context = canvas.getContext("2d");
var xPos = 180;
var yPos = 100;
var motionTrailLength = 16;
var positions = [];
function storeLastPosition(xPos, yPos) {
// push an item
positions.push({
x: xPos,
y: yPos
});
//get rid of first item
if (positions.length > motionTrailLength) {
positions.pop();
}
}
function update() {
context.clearRect(0, 0, canvas.width, canvas.height);
for (var i = positions.length-1; i > 0; i--) {
var ratio = (i - 1) / positions.length;
drawCircle(positions[i].x, positions[i].y, ratio);
}
drawCircle(xPos, yPos, "source");
var k=2;
storeLastPosition(xPos, yPos);
// update position
if (yPos > 125) {
positions.pop();
}
else{
yPos += k*1.1;
}
requestAnimationFrame(update);
}
update();
function drawCircle(x, y, r) {
if (r == "source") {
r = 1;
} else {
r*=1.1;
}
context.beginPath();
context.arc(x, y, 3, 0, 2 * Math.PI, true);
context.fillStyle = "rgba(255, 255, 255, " + parseFloat(1-r) + ")";
context.fill();
}

Canvas feedback and particles.
This type of FX can be done many ways.
You could just use a particle systems and draw stars (as lines) moving away from a central point, as the speed increase you increase the line length. When at low speed the line becomes a circle if you set ctx.lineWidth > 1 and ctx.lineCap = "round"
To add to the FX you can use render feedback as I think you have done by rendering the canvas over its self. If you render it slightly larger you get a zoom FX. If you use ctx.globalCompositeOperation = "lighter" you can increase the stars intensity as you speed up to make up for the overall loss of brightness as stars move faster.
Example
I got carried away so you will have to sift through the code to find what you need.
The particle system uses the Point object and a special array called bubbleArray to stop GC hits from janking the animation.
You can use just an ordinary array if you want. The particles are independent of the bubble array. When they have moved outside the screen they are move to a pool and used again when a new particle is needed. The update function moves them and the draw Function draws them I guess LOL
The function loop is the main loop and adds and draws particles (I have set the particle count to 400 but should handle many more)
The hyper drive is operated via the mouse button. Press for on, let go for off. (It will distort the text if it's being displayed)
The canvas feedback is set via that hyperSpeed variable, the math is a little complex. The sCurce function just limits the value to 0,1 in this case to stop alpha from going over or under 1,0. The hyperZero is just the sCurve return for 1 which is the hyper drives slowest speed.
I have pushed the feedback very close to the limit. In the first few lines of the loop function you can set the top speed if(mouse.button){ if(hyperSpeed < 1.75){ Over this value 1.75 and you will start to get bad FX, at about 2 the whole screen will just go white (I think that was where)
Just play with it and if you have questions ask in the comments.
const ctx = canvas.getContext("2d");
// very simple mouse
const mouse = {x : 0, y : 0, button : false}
function mouseEvents(e){
mouse.x = e.pageX;
mouse.y = e.pageY;
mouse.button = e.type === "mousedown" ? true : e.type === "mouseup" ? false : mouse.button;
}
["down","up","move"].forEach(name => document.addEventListener("mouse"+name,mouseEvents));
// High performance array pool using buubleArray to separate pool objects and active object.
// This is designed to eliminate GC hits involved with particle systems and
// objects that have short lifetimes but used often.
// Warning this code is not well tested.
const bubbleArray = () => {
const items = [];
var count = 0;
return {
clear(){ // warning this dereferences all locally held references and can incur Big GC hit. Use it wisely.
this.items.length = 0;
count = 0;
},
update() {
var head, tail;
head = tail = 0;
while(head < count){
if(items[head].update() === false) {head += 1 }
else{
if(tail < head){
const temp = items[head];
items[head] = items[tail];
items[tail] = temp;
}
head += 1;
tail += 1;
}
}
return count = tail;
},
createCallFunction(name, earlyExit = false){
name = name.split(" ")[0];
const keys = Object.keys(this);
if(Object.keys(this).indexOf(name) > -1){ throw new Error(`Can not create function name '${name}' as it already exists.`) }
if(!/\W/g.test(name)){
let func;
if(earlyExit){
func = `var items = this.items; var count = this.getCount(); var i = 0;\nwhile(i < count){ if (items[i++].${name}() === true) { break } }`;
}else{
func = `var items = this.items; var count = this.getCount(); var i = 0;\nwhile(i < count){ items[i++].${name}() }`;
}
!this.items && (this.items = items);
this[name] = new Function(func);
}else{ throw new Error(`Function name '${name}' contains illegal characters. Use alpha numeric characters.`) }
},
callEach(name){var i = 0; while(i < count){ if (items[i++][name]() === true) { break } } },
each(cb) { var i = 0; while(i < count){ if (cb(items[i], i++) === true) { break } } },
next() { if (count < items.length) { return items[count ++] } },
add(item) {
if(count === items.length){
items.push(item);
count ++;
}else{
items.push(items[count]);
items[count++] = item;
}
return item;
},
getCount() { return count },
}
}
// Helpers rand float, randI random Int
// doFor iterator
// sCurve curve input -Infinity to Infinity out -1 to 1
// randHSLA creates random colour
// CImage, CImageCtx create image and image with context attached
const randI = (min, max = min + (min = 0)) => (Math.random() * (max - min) + min) | 0;
const rand = (min = 1, max = min + (min = 0)) => Math.random() * (max - min) + min;
const doFor = (count, cb) => { var i = 0; while (i < count && cb(i++) !== true); }; // the ; after while loop is important don't remove
const sCurve = (v,p) => (2 / (1 + Math.pow(p,-v))) -1;
const randHSLA = (h, h1, s = 100, s1 = 100, l = 50, l1 = 50, a = 1, a1 = 1) => { return `hsla(${randI(h,h1) % 360},${randI(s,s1)}%,${randI(l,l1)}%,${rand(a,a1)})` }
const CImage = (w = 128, h = w) => (c = document.createElement("canvas"),c.width = w,c.height = h, c);
const CImageCtx = (w = 128, h = w) => (c = CImage(w,h), c.ctx = c.getContext("2d"), c);
// create image to hold text
var textImage = CImageCtx(1024, 1024);
var c = textImage.ctx;
c.fillStyle = "#FF0";
c.font = "64px arial black";
c.textAlign = "center";
c.textBaseline = "middle";
const text = "HYPER,SPEED FX,VII,,Battle of Jank,,Hold the mouse,button to increase,speed.".split(",");
text.forEach((line,i) => { c.fillText(line,512,i * 68 + 68) });
const maxLines = text.length * 68 + 68;
function starWarIntro(image,x1,y1,x2,y2,pos){
var iw = image.width;
var ih = image.height;
var hh = (x2 - x1) / (y2 - y1); // Slope of left edge
var w2 = iw / 2; // half width
var z1 = w2 - x1; // Distance (z) to first line
var z2 = (z1 / (w2 - x2)) * z1 - z1; // distance (z) between first and last line
var sk,t3,t3a,z3a,lines, z3, dd = 0, a = 0, as = 2 / (y2 - y1);
for (var y = y1; y < y2 && dd < maxLines; y++) { // for each line
t3 = ((y - y1) * hh) + x1; // get scan line top left edge
t3a = (((y+1) - y1) * hh) + x1; // get scan line bottom left edge
z3 = (z1 / (w2 - t3)) * z1; // get Z distance to top of this line
z3a = (z1 / (w2 - t3a)) * z1; // get Z distance to bottom of this line
dd = ((z3 - z1) / z2) * ih; // get y bitmap coord
a += as;
ctx.globalAlpha = a < 1 ? a : 1;
dd += pos; // kludge for this answer to make text move
// does not move text correctly
lines = ((z3a - z1) / z2) * ih-dd; // get number of lines to copy
ctx.drawImage(image, 0, dd , iw, lines, t3, y, w - t3 * 2, 1.5);
}
}
// canvas settings
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center
var ch = h / 2;
// diagonal distance used to set point alpha (see point update)
var diag = Math.sqrt(w * w + h * h);
// If window size is changed this is called to resize the canvas
// It is not called via the resize event as that can fire to often and
// debounce makes it feel sluggish so is called from main loop.
function resizeCanvas(){
points.clear();
canvas.width = innerWidth;
canvas.height = innerHeight;
w = canvas.width;
h = canvas.height;
cw = w / 2; // center
ch = h / 2;
diag = Math.sqrt(w * w + h * h);
}
// create array of points
const points = bubbleArray();
// create optimised draw function itterator
points.createCallFunction("draw",false);
// spawns a new star
function spawnPoint(pos){
var p = points.next();
p = points.add(new Point())
if (p === undefined) { p = points.add(new Point()) }
p.reset(pos);
}
// point object represents a single star
function Point(pos){ // this function is duplicated as reset
if(pos){
this.x = pos.x;
this.y = pos.y;
this.dead = false;
}else{
this.x = 0;
this.y = 0;
this.dead = true;
}
this.alpha = 0;
var x = this.x - cw;
var y = this.y - ch;
this.dir = Math.atan2(y,x);
this.distStart = Math.sqrt(x * x + y * y);
this.speed = rand(0.01,1);
this.col = randHSLA(220,280,100,100,50,100);
this.dx = Math.cos(this.dir) * this.speed;
this.dy = Math.sin(this.dir) * this.speed;
}
Point.prototype = {
reset : Point, // resets the point
update(){ // moves point and returns false when outside
this.speed *= hyperSpeed; // increase speed the more it has moved
this.x += Math.cos(this.dir) * this.speed;
this.y += Math.sin(this.dir) * this.speed;
var x = this.x - cw;
var y = this.y - ch;
this.alpha = (Math.sqrt(x * x + y * y) - this.distStart) / (diag * 0.5 - this.distStart);
if(this.alpha > 1 || this.x < 0 || this.y < 0 || this.x > w || this.h > h){
this.dead = true;
}
return !this.dead;
},
draw(){ // draws the point
ctx.strokeStyle = this.col;
ctx.globalAlpha = 0.25 + this.alpha *0.75;
ctx.beginPath();
ctx.lineTo(this.x - this.dx * this.speed, this.y - this.dy * this.speed);
ctx.lineTo(this.x, this.y);
ctx.stroke();
}
}
const maxStarCount = 400;
const p = {x : 0, y : 0};
var hyperSpeed = 1.001;
const alphaZero = sCurve(1,2);
var startTime;
function loop(time){
if(startTime === undefined){
startTime = time;
}
if(w !== innerWidth || h !== innerHeight){
resizeCanvas();
}
// if mouse down then go to hyper speed
if(mouse.button){
if(hyperSpeed < 1.75){
hyperSpeed += 0.01;
}
}else{
if(hyperSpeed > 1.01){
hyperSpeed -= 0.01;
}else if(hyperSpeed > 1.001){
hyperSpeed -= 0.001;
}
}
var hs = sCurve(hyperSpeed,2);
ctx.globalAlpha = 1;
ctx.setTransform(1,0,0,1,0,0); // reset transform
//==============================================================
// UPDATE the line below could be the problem. Remove it and try
// what is under that
//==============================================================
//ctx.fillStyle = `rgba(0,0,0,${1-(hs-alphaZero)*2})`;
// next two lines are the replacement
ctx.fillStyle = "Black";
ctx.globalAlpha = 1-(hs-alphaZero) * 2;
//==============================================================
ctx.fillRect(0,0,w,h);
// the amount to expand canvas feedback
var sx = (hyperSpeed-1) * cw * 0.1;
var sy = (hyperSpeed-1) * ch * 0.1;
// increase alpha as speed increases
ctx.globalAlpha = (hs-alphaZero)*2;
ctx.globalCompositeOperation = "lighter";
// draws feedback twice
ctx.drawImage(canvas,-sx, -sy, w + sx*2 , h + sy*2)
ctx.drawImage(canvas,-sx/2, -sy/2, w + sx , h + sy)
ctx.globalCompositeOperation = "source-over";
// add stars if count < maxStarCount
if(points.getCount() < maxStarCount){
var cent = (hyperSpeed - 1) *0.5; // pulls stars to center as speed increases
doFor(10,()=>{
p.x = rand(cw * cent ,w - cw * cent); // random screen position
p.y = rand(ch * cent,h - ch * cent);
spawnPoint(p)
})
}
// as speed increases make lines thicker
ctx.lineWidth = 2 + hs*2;
ctx.lineCap = "round";
points.update(); // update points
points.draw(); // draw points
ctx.globalAlpha = 1;
// scroll the perspective star wars text FX
var scrollTime = (time - startTime) / 5 - 2312;
if(scrollTime < 1024){
starWarIntro(textImage,cw - h * 0.5, h * 0.2, cw - h * 3, h , scrollTime );
}
requestAnimationFrame(loop);
}
requestAnimationFrame(loop);
canvas { position : absolute; top : 0px; left : 0px; }
<canvas id="canvas"></canvas>

Here's another simple example, based mainly on the same idea as Blindman67, concetric lines moving away from center at different velocities (the farther from center, the faster it moves..) also no recycling pool here.
"use strict"
var c = document.createElement("canvas");
document.body.append(c);
var ctx = c.getContext("2d");
var w = window.innerWidth;
var h = window.innerHeight;
var ox = w / 2;
var oy = h / 2;
c.width = w; c.height = h;
const stars = 120;
const speed = 0.5;
const trailLength = 90;
ctx.fillStyle = "#000";
ctx.fillRect(0, 0, w, h);
ctx.fillStyle = "#fff"
ctx.fillRect(ox, oy, 1, 1);
init();
function init() {
var X = [];
var Y = [];
for(var i = 0; i < stars; i++) {
var x = Math.random() * w;
var y = Math.random() * h;
X.push( translateX(x) );
Y.push( translateY(y) );
}
drawTrails(X, Y)
}
function translateX(x) {
return x - ox;
}
function translateY(y) {
return oy - y;
}
function getDistance(x, y) {
return Math.sqrt(x * x + y * y);
}
function getLineEquation(x, y) {
return function(n) {
return y / x * n;
}
}
function drawTrails(X, Y) {
var count = 1;
ctx.fillStyle = "#000";
ctx.fillRect(0, 0, w, h);
function anim() {
for(var i = 0; i < X.length; i++) {
var x = X[i];
var y = Y[i];
drawNextPoint(x, y, count);
}
count+= speed;
if(count < trailLength) {
window.requestAnimationFrame(anim);
}
else {
init();
}
}
anim();
}
function drawNextPoint(x, y, step) {
ctx.fillStyle = "#fff";
var f = getLineEquation(x, y);
var coef = Math.abs(x) / 100;
var dist = getDistance( x, y);
var sp = speed * dist / 100;
for(var i = 0; i < sp; i++) {
var newX = x + Math.sign(x) * (step + i) * coef;
var newY = translateY( f(newX) );
ctx.fillRect(newX + ox, newY, 1, 1);
}
}
body {
overflow: hidden;
}
canvas {
position: absolute;
left: 0;
top: 0;
}

Javascript - interactive particle logo not working

I'm working through instructions to construct an interactive particle logo design and can't seem to get to the finished product. This is the logo image file -
I'm using a canvas structure / background. Here's the code -
var canvasInteractive = document.getElementById('canvas-interactive');
var canvasReference = document.getElementById('canvas-reference');
var contextInteractive = canvasInteractive.getContext('2d');
var contextReference = canvasReference.getContext('2d');
var image = document.getElementById('img');
var width = canvasInteractive.width = canvasReference.width = window.innerWidth;
var height = canvasInteractive.height = canvasReference.height = window.innerHeight;
var logoDimensions = {
x: 500,
y: 500
};
var center = {
x: width / 2,
y: height / 2
};
var logoLocation = {
x: center.x - logoDimensions.x / 2,
y: center.y - logoDimensions.y / 2
};
var mouse = {
radius: Math.pow(100, 2),
x: 0,
y: 0
};
var particleArr = [];
var particleAttributes = {
friction: 0.95,
ease: 0.19,
spacing: 6,
size: 4,
color: "#ffffff"
};
function Particle(x, y) {
this.x = this.originX = x;
this.y = this.originY = y;
this.rx = 0;
this.ry = 0;
this.vx = 0;
this.vy = 0;
this.force = 0;
this.angle = 0;
this.distance = 0;
}
Particle.prototype.update = function() {
this.rx = mouse.x - this.x;
this.ry = mouse.y - this.y;
this.distance = this.rx * this.rx + this.ry * this.ry;
this.force = -mouse.radius / this.distance;
if (this.distance < mouse.radius) {
this.angle = Math.atan2(this.ry, this.rx);
this.vx += this.force * Math.cos(this.angle);
this.vy += this.force * Math.sin(this.angle);
}
this.x += (this.vx *= particleAttributes.friction) + (this.originX - this.x) * particleAttributes.ease;
this.y += (this.vy *= particleAttributes.friction) + (this.originY - this.y) * particleAttributes.ease;
};
function init() {
contextReference.drawImage(image, logoLocation.x, logoLocation.y);
var pixels = contextReference.getImageData(0, 0, width, height).data;
var index;
for (var y = 0; y < height; y += particleAttributes.spacing) {
for (var x = 0; x < width; x += particleAttributes.spacing) {
index = (y * width + x) * 4;
if (pixels[++index] > 0) {
particleArr.push(new Particle(x, y));
}
}
}
};
init();
function update() {
for (var i = 0; i < particleArr.length; i++) {
var p = particleArr[i];
p.update();
}
};
function render() {
contextInteractive.clearRect(0, 0, width, height);
for (var i = 0; i < particleArr.length; i++) {
var p = particleArr[i];
contextInteractive.fillStyle = particleAttributes.color;
contextInteractive.fillRect(p.x, p.y, particleAttributes.size, particleAttributes.size);
}
};
function animate() {
update();
render();
requestAnimationFrame(animate);
}
animate();
document.body.addEventListener("mousemove", function(event) {
mouse.x = event.clientX;
mouse.y = event.clientY;
});
document.body.addEventListener("touchstart", function(event) {
mouse.x = event.changedTouches[0].clientX;
mouse.y = event.changedTouches[0].clientY;
}, false);
document.body.addEventListener("touchmove", function(event) {
event.preventDefault();
mouse.x = event.targetTouches[0].clientX;
mouse.y = event.targetTouches[0].clientY;
}, false);
document.body.addEventListener("touchend", function(event) {
event.preventDefault();
mouse.x = 0;
mouse.y = 0;
}, false);
html,
body {
margin: 0px;
position: relative;
background-color: #000;
}
canvas {
display: block;
position: absolute;
top: 0;
left: 0;
z-index: 1;
}
img {
display: none;
width: 70%;
height: 400px;
position: absolute;
left: 50%;
transform: translate(-50%, 30%);
}
<html>
<body>
<canvas id="canvas-interactive"></canvas>
<canvas id="canvas-reference"></canvas>
<img src="https://i.stack.imgur.com/duv9h.png" alt="..." id="img">
</body>
</html>
My understanding is the image file has to be set to display: none; and then the image needs to be re-drawn using the javascript commands but I'm not sure if this image is compatible or not. When finished I want the image on a white background.
By way of an example the end design needs to resemble this - Logo particle design

Particle positions from bitmap.
To get the FX you want you need to create a particle system. This is just an array of objects, each with a position, the position where they want to be (Home), a vector defining their current movement, and the colour.
You get each particle's home position and colour by reading pixels from the image. You can access pixel data by rendering an image on a canvas and the using ctx.getImageData to get the pixel data (Note image must be on same domain or have CORS headers to access pixel data). As you read each pixel in turn, if not transparent, create a particle for that pixel and set it colour and home position from the pixels colour and position.
Use requestAnimationFrame to call a render function that every frame iterates all the particles moving them by some set of rules that give you the motion you are after. Once you have move each particle, render them to the canvas using simple shapes eg fillRect
Mouse interaction
To have interaction with the mouse you will need to use mouse move events to keep track of the mouse position relative to the canvas you are rendering to. As you update each particle you also check how far it is from the mouse. You can then push or pull the particle from or to the mouse (depending on the effect you want.
Rendering speed will limit the particle count.
The only issue with these types of FX is that you will be pushing the rendering speed limits as the particle count goes up. What may work well on one machine, will run very slow on another.
To avoid being too slow, and not looking good on some machines you should consider keeping an eye on the frame rate and reducing the particle count if it runs slow. To compensate you can increase the particle size or even reduce the canvas resolution.
The bottleneck is the actual rendering of each particle. When you get to large numbers the path methods really grinds down. If you want really high numbers you will have to render pixels directly to the bitmap, using the same method as reading but in reverse of course.
Example simple particles read from bitmap.
The example below uses text rendered to a canvas to create the particles, and to use an image you would just draw the image rather than the text. The example is a bit overkill as I ripped it from an old answer of mine. It is just as an example of the various ways to get stuff done.
const ctx = canvas.getContext("2d");
const Vec = (x, y) => ({x, y});
const setStyle = (ctx,style) => { Object.keys(style).forEach(key => ctx[key] = style[key]) }
const createImage = (w,h) => {var i=document.createElement("canvas");i.width=w;i.height=h;i.ctx=i.getContext("2d");return i}
const textList = ["Particles"];
var textPos = 0;
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center
var ch = h / 2;
var globalTime;
var started = false;
requestAnimationFrame(update);
const mouse = {x : 0, y : 0, button : false}
function mouseEvents(e){
mouse.x = e.pageX;
mouse.y = e.pageY;
mouse.button = e.type === "mousedown" ? true : e.type === "mouseup" ? false : mouse.button;
}
["down","up","move"].forEach(name => document.addEventListener("mouse"+name,mouseEvents));
function onResize(){
cw = (w = canvas.width = innerWidth) / 2;
ch = (h = canvas.height = innerHeight) / 2;
if (!started) { startIt() }
}
function update(timer){
globalTime = timer;
ctx.setTransform(1,0,0,1,0,0); // reset transform
ctx.globalAlpha = 1; // reset alpha
if (w !== innerWidth || h !== innerHeight){ onResize() }
else { ctx.clearRect(0,0,w,h) }
particles.update();
particles.draw();
requestAnimationFrame(update);
}
function createParticles(text){
createTextMap(
text, 60, "Arial",
{ fillStyle : "#FF0", strokeStyle : "#F00", lineWidth : 2, lineJoin : "round", },
{ top : 0, left : 0, width : canvas.width, height : canvas.height }
)
}
// This function starts the animations
function startIt(){
started = true;
const next = ()=>{
var text = textList[(textPos++ ) % textList.length];
createParticles(text);
setTimeout(moveOut,text.length * 100 + 12000);
}
const moveOut = ()=>{
particles.moveOut();
setTimeout(next,2000);
}
setTimeout(next,0);
}
// the following function create the particles from text using a canvas
// the canvas used is displayed on the main canvas top left fro reference.
var tCan = createImage(100, 100); // canvas used to draw text
function createTextMap(text,size,font,style,fit){
const hex = (v)=> (v < 16 ? "0" : "") + v.toString(16);
tCan.ctx.font = size + "px " + font;
var width = Math.ceil(tCan.ctx.measureText(text).width + size);
tCan.width = width;
tCan.height = Math.ceil(size *1.2);
var c = tCan.ctx;
c.font = size + "px " + font;
c.textAlign = "center";
c.textBaseline = "middle";
setStyle(c,style);
if (style.strokeStyle) { c.strokeText(text, width / 2, tCan.height / 2) }
if (style.fillStyle) { c.fillText(text, width / 2, tCan.height/ 2) }
particles.empty();
var data = c.getImageData(0,0,width,tCan.height).data;
var x,y,ind,rgb,a;
for(y = 0; y < tCan.height; y += 1){
for(x = 0; x < width; x += 1){
ind = (y * width + x) << 2; // << 2 is equiv to * 4
if(data[ind + 3] > 128){ // is alpha above half
rgb = `#${hex(data[ind ++])}${hex(data[ind ++])}${hex(data[ind ++])}`;
particles.add(Vec(x, y), Vec(x, y), rgb);
}
}
}
particles.sortByCol
var scale = Math.min(fit.width / width, fit.height / tCan.height);
particles.each(p=>{
p.home.x = ((fit.left + fit.width) / 2) + (p.home.x - (width / 2)) * scale;
p.home.y = ((fit.top + fit.height) / 2) + (p.home.y - (tCan.height / 2)) * scale;
})
.findCenter() // get center used to move particles on and off of screen
.moveOffscreen() // moves particles off the screen
.moveIn(); // set the particles to move into view.
}
// basic particle
const particle = { pos : null, delta : null, home : null, col : "black", }
// array of particles
const particles = {
items : [], // actual array of particles
mouseFX : { power : 12,dist :110, curve : 2, on : true },
fx : { speed : 0.3, drag : 0.6, size : 4, jiggle : 1 },
// direction 1 move in -1 move out
direction : 1,
moveOut () {this.direction = -1; return this},
moveIn () {this.direction = 1; return this},
length : 0,
each(callback){ // custom iteration
for(var i = 0; i < this.length; i++){ callback(this.items[i],i) }
return this;
},
empty() { this.length = 0; return this },
deRef(){ this.items.length = 0; this.length = 0 },
sortByCol() { this.items.sort((a,b) => a.col === b.col ? 0 : a.col < b.col ? 1 : -1 ) },
add(pos, home, col){ // adds a particle
var p;
if(this.length < this.items.length){
p = this.items[this.length++];
p.home.x = home.x;
p.home.y = home.y;
p.delta.x = 0;
p.delta.y = 0;
p.col = col;
}else{
this.items.push( Object.assign({}, particle,{ pos, home, col, delta : Vec(0,0) } ) );
this.length = this.items.length
}
return this;
},
draw(){ // draws all
var p, size, sizeh;
sizeh = (size = this.fx.size) / 2;
for(var i = 0; i < this.length; i++){
p = this.items[i];
ctx.fillStyle = p.col;
ctx.fillRect(p.pos.x - sizeh, p.pos.y - sizeh, size, size);
}
},
update(){ // update all particles
var p,x,y,d;
const mP = this.mouseFX.power;
const mD = this.mouseFX.dist;
const mC = this.mouseFX.curve;
const fxJ = this.fx.jiggle;
const fxD = this.fx.drag;
const fxS = this.fx.speed;
for(var i = 0; i < this.length; i++){
p = this.items[i];
p.delta.x += (p.home.x - p.pos.x ) * fxS + (Math.random() - 0.5) * fxJ;
p.delta.y += (p.home.y - p.pos.y ) * fxS + (Math.random() - 0.5) * fxJ;
p.delta.x *= fxD;
p.delta.y *= fxD;
p.pos.x += p.delta.x * this.direction;
p.pos.y += p.delta.y * this.direction;
if(this.mouseFX.on){
x = p.pos.x - mouse.x;
y = p.pos.y - mouse.y;
d = Math.sqrt(x * x + y * y);
if(d < mD){
x /= d;
y /= d;
d /= mD;
d = (1-Math.pow(d, mC)) * mP;
p.pos.x += x * d;
p.pos.y += y * d;
}
}
}
return this;
},
findCenter(){ // find the center of particles maybe could do without
var x,y;
y = x = 0;
this.each(p => { x += p.home.x; y += p.home.y });
this.center = Vec(x / this.length, y / this.length);
return this;
},
moveOffscreen(){ // move start pos offscreen
var dist,x,y;
dist = Math.sqrt(this.center.x * this.center.x + this.center.y * this.center.y);
this.each(p => {
var d;
x = p.home.x - this.center.x;
y = p.home.y - this.center.y;
d = Math.max(0.0001,Math.sqrt(x * x + y * y)); // max to make sure no zeros
p.pos.x = p.home.x + (x / d) * dist;
p.pos.y = p.home.y + (y / d) * dist;
});
return this;
},
}
canvas { position : absolute; top : 0px; left : 0px; background : black;}
<canvas id="canvas"></canvas>

Use png saved as PNG-8 and and allow cross-origin
I saw the cool article from Bricks and mortar and thought I'd try it out.
I battled with it for an eternity, thinking that my js was wrong... Turns out that the image has to be saved as a PNG-8 without dither instead of a PNG-24.
Then make sure that you add the crossOrigin="Anonymous" attribute to the image tag:
<img crossOrigin="Anonymous" id="img" src="[link to wherever you host the image]" alt="logo">
I also hid the reference canvas by adding the following styles:
canvas#canvas-reference {
display: none;
}
I also added a debounce and resize function, so it's responsive.
The result:
See Demo with inverted logo

How do I allow a 2D shape to wrap around a canvas using WebGL?

I have created a simple animation in WebGL (html & javascript) where a 2D shape is animated and manipulated on a canvas. The default animation is shape moving to the right at a set speed and then using "WASD" changes its direction. The shape moves in the given direction indefinitely, even after it is off of the canvas and out of the clip-space. I would like to have the shape wrap around the canvas instead of just continuing even after it is unseen. For example, if the shape is moving to the right and moves completely off of the canvas, I would like it to appear on left side still moving to the right and continue cycling. Same goes for if it is moving left or up or down.
Any suggestions on how to implement this?

You have to draw it 2 to 4 times depending on if you want to wrap both left/right and top/bottom
Assume we only want to wrap around horizontally. If the player is near the left edge we need to also draw the player 1 screen width to the right. If the player is near the right edge we need to draw the player again one screen to the left. Same with up and down
Here's an example using canvas 2D but the only difference for WebGL is you'd draw using WebGL. The concept is the same.
Example:
var x = 150;
var y = 100;
var vx = 0;
var vy = 0;
const maxSpeed = 250;
const acceleration = 1000;
const ctx = document.querySelector("canvas").getContext("2d");
const keys = {};
const LEFT = 65;
const RIGHT = 68;
const DOWN = 83;
const UP = 87;
const width = ctx.canvas.width;
const height = ctx.canvas.height;
var then = 0;
function render(now) {
now *= 0.001; // seconds
const deltaTime = now - then;
then = now;
ctx.clearRect(0, 0, width, height);
if (keys[UP]) { vy -= acceleration * deltaTime; }
if (keys[DOWN]) { vy += acceleration * deltaTime; }
if (keys[LEFT]) { vx -= acceleration * deltaTime; }
if (keys[RIGHT]) { vx += acceleration * deltaTime; }
// keep speed under max
vx = absmin(vx, maxSpeed);
vy = absmin(vy, maxSpeed);
// move based on velociy
x += vx * deltaTime;
y += vy * deltaTime;
// wrap
x = euclideanModulo(x, width);
y = euclideanModulo(y, height);
// draw player 4 times
const xoff = x < width / 2 ? width : -width;
const yoff = y < height / 2 ? height : -height;
drawPlayer(x, y);
drawPlayer(x + xoff, y);
drawPlayer(x, y + yoff);
drawPlayer(x + xoff, y + yoff);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
function drawPlayer(x, y) {
ctx.fillStyle = "blue";
ctx.strokeStyle = "red";
ctx.lineWidth = 4;
ctx.beginPath();
ctx.arc(x, y, 20, 0, Math.PI * 2, false);
ctx.fill();
ctx.stroke();
}
function absmin(v, max) {
return Math.min(Math.abs(v), max) * Math.sign(v);
}
function euclideanModulo(n, m) {
return ((n % m) + m) % m;
}
window.addEventListener('keydown', e => {
keys[e.keyCode] = true;
});
window.addEventListener('keyup', e => {
keys[e.keyCode] = false;
});
canvas {
display: block;
border: 1px solid black;
}
<canvas></canvas>
<p><span style="color:red;">click here</span> then use ASWD to move</p>
A WebGL version changes no code related to wrapping.
var x = 150;
var y = 100;
var vx = 0;
var vy = 0;
const maxSpeed = 250;
const acceleration = 1000;
const gl = document.querySelector("canvas").getContext("webgl");
const keys = {};
const LEFT = 65;
const RIGHT = 68;
const DOWN = 83;
const UP = 87;
const width = gl.canvas.width;
const height = gl.canvas.height;
var program = setupWebGL();
var positionLoc = gl.getAttribLocation(program, "position");
var then = 0;
function render(now) {
now *= 0.001; // seconds
const deltaTime = now - then;
then = now;
if (keys[UP]) { vy -= acceleration * deltaTime; }
if (keys[DOWN]) { vy += acceleration * deltaTime; }
if (keys[LEFT]) { vx -= acceleration * deltaTime; }
if (keys[RIGHT]) { vx += acceleration * deltaTime; }
// keep speed under max
vx = absmin(vx, maxSpeed);
vy = absmin(vy, maxSpeed);
// move based on velociy
x += vx * deltaTime;
y += vy * deltaTime;
// wrap
x = euclideanModulo(x, width);
y = euclideanModulo(y, height);
// draw player 4 times
const xoff = x < width / 2 ? width : -width;
const yoff = y < height / 2 ? height : -height;
drawPlayer(x, y);
drawPlayer(x + xoff, y);
drawPlayer(x, y + yoff);
drawPlayer(x + xoff, y + yoff);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
function drawPlayer(x, y) {
gl.useProgram(program);
// only drawing a single point so no need to use a buffer
gl.vertexAttrib2f(
positionLoc,
x / width * 2 - 1,
y / height * -2 + 1);
gl.drawArrays(gl.POINTS, 0, 1);
}
function absmin(v, max) {
return Math.min(Math.abs(v), max) * Math.sign(v);
}
function euclideanModulo(n, m) {
return ((n % m) + m) % m;
}
window.addEventListener('keydown', e => {
keys[e.keyCode] = true;
});
window.addEventListener('keyup', e => {
keys[e.keyCode] = false;
});
function setupWebGL() {
const vs = `
attribute vec4 position;
void main() {
gl_Position = position;
gl_PointSize = 40.;
}
`;
const fs = `
void main() {
gl_FragColor = vec4(1,0,1,1);
}
`;
// compiles and links shaders and assigns position to location 0
return twgl.createProgramFromSources(gl, [vs, fs]);
}
canvas {
display: block;
border: 1px solid black;
}
<canvas></canvas>
<p><span style="color:red;">click here</span> then use ASWD to move</p>
<script src="https://twgljs.org/dist/3.x/twgl-full.min.js"></script>
If you don't want the player appear on both sides then your question has nothing to do with graphics, you just wait until the player's x position is at least screenWidth + haflPlayerWidth which means they're completely off the right side and then you set their x position to -halfPlayerWidth which will put them just off the left and visa versa
var x = 150;
var y = 100;
var vx = 0;
var vy = 0;
const maxSpeed = 250;
const acceleration = 1000;
const ctx = document.querySelector("canvas").getContext("2d");
const keys = {};
const LEFT = 65;
const RIGHT = 68;
const DOWN = 83;
const UP = 87;
const width = ctx.canvas.width;
const height = ctx.canvas.height;
const playerSize = 40;
const halfPlayerSize = playerSize / 2;
var then = 0;
function render(now) {
now *= 0.001; // seconds
const deltaTime = now - then;
then = now;
ctx.clearRect(0, 0, width, height);
if (keys[UP]) { vy -= acceleration * deltaTime; }
if (keys[DOWN]) { vy += acceleration * deltaTime; }
if (keys[LEFT]) { vx -= acceleration * deltaTime; }
if (keys[RIGHT]) { vx += acceleration * deltaTime; }
// keep speed under max
vx = absmin(vx, maxSpeed);
vy = absmin(vy, maxSpeed);
// move based on velociy
x += vx * deltaTime;
y += vy * deltaTime;
// wrap
x = euclideanModulo(x + halfPlayerSize, width + playerSize) - halfPlayerSize;
y = euclideanModulo(y + halfPlayerSize, height + playerSize) - halfPlayerSize;
// draw player
drawPlayer(x, y);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
function drawPlayer(x, y) {
ctx.fillStyle = "blue";
ctx.strokeStyle = "red";
ctx.lineWidth = 4;
ctx.beginPath();
ctx.arc(x, y, halfPlayerSize, 0, Math.PI * 2, false);
ctx.fill();
ctx.stroke();
}
function absmin(v, max) {
return Math.min(Math.abs(v), max) * Math.sign(v);
}
function euclideanModulo(n, m) {
return ((n % m) + m) % m;
}
window.addEventListener('keydown', e => {
keys[e.keyCode] = true;
});
window.addEventListener('keyup', e => {
keys[e.keyCode] = false;
});
canvas {
display: block;
border: 1px solid black;
}
<canvas></canvas>
<p><span style="color:red;">click here</span> then use ASWD to move</p>
this code probably needs an explanation
x = euclideanModulo(x + haflPlayerSize, width + playerSize) - haflPlayerSize;
y = euclideanModulo(y + haflPlayerSize, height + playerSize) - haflPlayerSize;
First off euclideanModulo is just like normal % modulo operator, it returns the remainder after division, except euclidean modulo keeps the same remainder even for negative numbers. In other words
3 % 5 = 3
8 % 5 = 3
13 % 5 = 3
-2 % 5 = -2
-7 % 5 = -2
-12 % 5 = -2
but
3 euclideanMod 5 = 3
8 euclideanMod 5 = 3
13 euclideanMod 5 = 3
-2 euclideanMod 5 = 3
-7 euclideanMod 5 = 3
-12 euclideanMod 5 = 3
So it's a super easy way to wrap things.
x = euclideanModulo(x, screenWidth)
Is similar to
if (x < 0) x += screenWidth;
if (x >= screenWidth) x -= screenWidth;
Except those would fail if x > screenWidth * 2 for example where as the one using euclideanModulo would not.
So, back to
x = euclideanModulo(x + haflPlayerSize, width + playerSize) - haflPlayerSize;
y = euclideanModulo(y + haflPlayerSize, height + playerSize) - haflPlayerSize;
We know the player (in this case a circle) has its position at its center. So, we know when its center is half the playerSize off the left or right of the screen it's completely off the screen and we therefore want to move it to the other side. That means we can imagine the screen is really width + halfPlayerSize + halfPlayerSize wide. The first halfPlayerSize is for the stepping off the left side, the second halfPlayerSize is for stepping off the right side. In other words it's just width + playerSize wide. We then want the player to wrap from left to right when x < -halfPlayerSize. So we add halfPlayerSize to the player's position, then do the euclideanModulo which will wrap the position, then subtract that halfPlayerSize back out.