Develop Reference

How to create a smooth transition p5.js with key function?

I'm trying to achieve that, everytime you type a different letter key, the lines of the letters 'merge' into eachother instead of just 'jumping' to the next letter like it's doing now. I'm looking into the lerp() function but i'm not sure how to apply this to my code. Can someone help me into the right direction? This is what i have untill now:
var redtown;
var fontSize = 500;
var myArray;
var r = 3;
function preload(){
redtown = loadFont('redtown.otf');
}
function setup(){
createCanvas(windowWidth,windowHeight);
textFont(redtown);
textSize(fontSize);
}
function draw(){
background(0);
myArray = redtown.textToPoints(key, width/2, 500, fontSize, {
sampleFactor:0.5
});
// text(key, width/2, height/2 );
for (var i = 0; i < myArray.length; i++) {
// ellipse(myArray[i].x, myArray[i].y, 10, 10)
push();
translate(myArray[i].x, myArray[i].y);
rotate(r);
r++;
stroke(255);
strokeWeight(1);
line(-10,-10,10,10,10);
frameRate(17);
pop();
}
}

Here is a snippet that transitions from one character to another by using textToPoints to get the points from the last two keys that have been pressed and then slides each point in the old character to its position in the new character.
It uses this formula to get the x and y positions of points along a line from the point in the old character to the point in the new character.
x = (1-t)*x+t*nextX;
y = (1-t)*y+t*nextY;
It also uses the spinning lines idea from the question to give the points some motion although it pins the line size to a constant.
rotate(r+=0.1);
line(-1,-1,1,1);
You can see it in action here Fonts Transition
var myFont;
var fontSize = 160;
var fontPoints =[];
var previousFontPoints = [];
var r = 0;
var oldKey = ' ';
function preload(){
myFont = loadFont('inconsolata.otf');
}
function setup(){
createCanvas(500, 500);
textFont(myFont);
textSize(fontSize);
frameRate(30);
stroke(255);
strokeWeight(1);
background(0);
}
function draw(){
if (oldKey != key){
previousFontPoints =
myFont.textToPoints(oldKey, width/10, height/2, fontSize, {
sampleFactor:1
});
oldKey = key;
fontPoints = myFont.textToPoints(key, width/10, height/2, fontSize, {
sampleFactor:1
});
t = 0.025;
}
t += .01;
if (fontPoints.length > 0 && t< 1.0){
background(0);
for (i = 0; i < fontPoints.length; i++){
let x = 0;
let y = 0;
// if we don't have enought points we will just float in from 0,0
let nextX = 0;
let nextY = 0;
push();
if (previousFontPoints.length > i){
x = previousFontPoints[i].x;
y = previousFontPoints[i].y;
// in case the new array does not have enough points
nextX = x;
nextY = y;
}
if (fontPoints.length > i){
nextX = fontPoints[i].x;
nextY = fontPoints[i].y;
}
x = (1-t)*x+t*nextX;
y = (1-t)*y+t*nextY;
translate(x, y);
rotate(r+=0.1);
line(-1,-1,1,1);
pop();
}
}
}

Dynamic Wavy Path/Border

There is something I need to build, but my math ability is not up to par. What I am looking to build is something like this demo, but I need it to be a hybrid of a circle and polygon instead of a line, so to speak. The black line should be dynamic and randomly generated that basically acts as a border on the page.
Currently, I am dissecting this answer with the aim of hopefully being able to transpose it into this, but I am having massive doubts that I will be able to figure this out.
Any idea how to do this or can anybody explain the mathematics?
Below are my notes about the code from the answer I linked above.
var
cw = cvs.width = window.innerWidth,
ch = cvs.height = window.innerHeight,
cx = cw / 2,
cy = ch / 2,
xs = Array(),
ys = Array(),
npts = 20,
amplitude = 87, // can be val from 1 to 100
frequency = -2, // can be val from -10 to 1 in steps of 0.1
ctx.lineWidth = 4
// creates array of coordinates that
// divides page into regular portions
// creates array of weights
for (var i = 0; i < npts; i++) {
xs[i] = (cw/npts)*i
ys[i] = 2.0*(Math.random()-0.5)*amplitude
}
function Draw() {
ctx.clearRect(0, 0, cw, ch);
ctx.beginPath();
for (let x = 0; x < cw; x++) {
y = 0.0
wsum = 0.0
for (let i = -5; i <= 5; i++) {
xx = x; // 0 / 1 / 2 / to value of screen width
// creates sequential sets from [-5 to 5] to [15 to 25]
ii = Math.round(x/xs[1]) + i
// `xx` is a sliding range with the total value equal to client width
// keeps `ii` within range of 0 to 20
if (ii < 0) {
xx += cw
ii += npts
}
if (ii >= npts){
xx -= cw
ii -= npts
}
// selects eleven sequential array items
// which are portions of the screen width and height
// to create staggered inclines in increments of those portions
w = Math.abs(xs[ii] - xx)
// creates irregular arcs
// based on the inclining values
w = Math.pow(w, frequency)
// also creates irregular arcs therefrom
y += w*ys[ii];
// creates sets of inclining values
wsum += w;
}
// provides a relative position or weight
// for each y-coordinate in the total path
y /= wsum;
//y = Math.sin(x * frequency) * amplitude;
ctx.lineTo(x, y+cy);
}
ctx.stroke();
}
Draw();

This is my answer. Please read the comments in the code. I hope this is what you need.
// initiate the canvas
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
let cw = (canvas.width = 600),
cx = cw / 2;
let ch = (canvas.height = 400),
cy = ch / 2;
ctx.fillStyle = "white"
// define the corners of an rectangle
let corners = [[100, 100], [500, 100], [500, 300], [100, 300]];
let amplitud = 20;// oscilation amplitude
let speed = 0.01;// the speed of the oscilation
let points = []; // an array of points to draw the curve
class Point {
constructor(x, y, hv) {
// the point is oscilating around this point (cx,cy)
this.cx = x;
this.cy = y;
// the current angle of oscilation
this.a = Math.random() * 2 * Math.PI;
this.hv = hv;// a variable to know if the oscilation is horizontal or vertical
this.update();
}
// a function to update the value of the angle
update() {
this.a += speed;
if (this.hv == 0) {
this.x = this.cx;
this.y = this.cy + amplitud * Math.cos(this.a);
} else {
this.x = this.cx + amplitud * Math.cos(this.a);
this.y = this.cy;
}
}
}
// a function to divide a line that goes from a to b in n segments
// I'm using the resulting points to create a new point object and push this new point into the points array
function divide(n, a, b) {
for (var i = 0; i <= n; i++) {
let p = {
x: (b[0] - a[0]) * i / n + a[0],
y: (b[1] - a[1]) * i / n + a[1],
hv: b[1] - a[1]
};
points.push(new Point(p.x, p.y, p.hv));
}
}
divide(10, corners[0], corners[1]);points.pop();
divide(5, corners[1], corners[2]);points.pop();
divide(10, corners[2], corners[3]);points.pop();
divide(5, corners[3], corners[0]);points.pop();
// this is a function that takes an array of points and draw a curved line through those points
function drawCurves() {
//find the first midpoint and move to it
let p = {};
p.x = (points[points.length - 1].x + points[0].x) / 2;
p.y = (points[points.length - 1].y + points[0].y) / 2;
ctx.beginPath();
ctx.moveTo(p.x, p.y);
//curve through the rest, stopping at each midpoint
for (var i = 0; i < points.length - 1; i++) {
let mp = {};
mp.x = (points[i].x + points[i + 1].x) / 2;
mp.y = (points[i].y + points[i + 1].y) / 2;
ctx.quadraticCurveTo(points[i].x, points[i].y, mp.x, mp.y);
}
//curve through the last point, back to the first midpoint
ctx.quadraticCurveTo(
points[points.length - 1].x,
points[points.length - 1].y,
p.x,
p.y
);
ctx.stroke();
ctx.fill();
}
function Draw() {
window.requestAnimationFrame(Draw);
ctx.clearRect(0, 0, cw, ch);
points.map(p => {
p.update();
});
drawCurves();
}
Draw();
canvas{border:1px solid; background:#6ab150}
<canvas></canvas>

How do I draw a box around multiple shapes in html5 canvas

I am trying to draw a box around multiple shapes in canvas to say that those shapes are related like a group.
Tried as below :
var ctx = c.getContext("2d"),
radius = 10,
rect = c.getBoundingClientRect(),
ctx.fillText("Draw something here..", 10, 10);
ctx.fillStyle = "red";
ctx.beginPath();
ctx.arc(250, 300, radius, 0, 6.28);
ctx.fill();
ctx.fillStyle = "yellow";
ctx.beginPath();
ctx.arc(200, 100, radius, 0, 10.28);
ctx.fill();
ctx.fillStyle = "brown";
ctx.beginPath();
ctx.arc(350, 210, radius, 0, 10.28);
ctx.fill();
var x = (250+200+350)/3;
var y = (300+100+210)/3;
var radius = Math.sqrt((x1*x1)+(y1*y1));
var _minX = x - radius;
var _minY = y - radius;
var _maxX = x + radius;
var _maxY = y + radius;
ctx.rect(_minX,_minY,(_maxX-_minX+2),(_maxY-_minY+2));
ctx.stroke();
But it is not drawing properly.
How to get bounding box coordinates for canvas content? this link explains only for the path not for the existing shapes.
Below is the image how I want to draw:

Fabric <-- See if this library helps had used this for one of my project it is simple and quick.

This Code is not production ready, Or the best solution, but it works in "most cases".
I'm using the imageData, to check for non-white pixel. (If NOT 0 - RGBA Pixel ==> Object) and with this it narrows the possible Rectangle down. You would also need to tweak it, if you don't want the text to be in the Rectangle.
This code could / should be optimized.
EDIT: Now I am only checking if an Alpha Value is set. And some Random Object creation to test multiple Outcomes
Info: Objects that are clipped/cut happen, because they are out of the canvas size.
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
var colors = ["red", "blue", "green", "black"];
ctx.fillText("Draw something here..", 0, 10);
/** CREATEING SOME RANDOM OBJECTS (JUST FOR TEST) **/
createRandomObjects();
function createRandomIntMax(max){
return parseInt(Math.random() * 1000 * max) % max + 1;
}
function createRandomObjects(){
var objectsToDraw = createRandomIntMax(20);
for(var idx = 0; idx < objectsToDraw; idx++){
ctx.fillStyle = colors[createRandomIntMax(colors.length)];
ctx.beginPath();
ctx.arc(createRandomIntMax(c.width), createRandomIntMax(c.height), createRandomIntMax(30), 0, 2 * Math.PI);
ctx.fill();
}
}
/** GETTING IMAGE DATA **/
var myImageData = ctx.getImageData(0, 0, c.width, c.height);
/** FINDING BORDERS **/
findBorders(myImageData.data);
function findBorders(imageData) {
var result = {
left: c.width,
top: c.height,
right: -1,
bottom: -1
}
var idx = 0;
var lineLow = -1;
var lineHigh = -1;
var currentLine = 0;
var currentPoint, helper;
while (idx < imageData.length) {
currentPoint = imageData[idx + 3];
/** CHECKING FOR OBJECT **/
if (currentPoint != 0) {
helper = parseInt(idx % (c.width * 4)) / 4;
if (lineLow < 0) {
lineLow = helper;
lineHigh = helper;
} else {
lineHigh = helper;
}
}
if (idx !== 0 && (idx % (c.width * 4)) === 0) {
currentLine = idx / (c.width * 4);
// Updating the Border Points
if (lineLow > -1) {
result.left = Math.min(lineLow, result.left);
result.top = Math.min(currentLine, result.top);
result.right = Math.max(lineHigh, result.right);
result.bottom = Math.max(currentLine, result.bottom);
}
lineLow = -1;
lineHigh = -1;
}
idx += 4;
}
ctx.rect(result.left, result.top, result.right - result.left, result.bottom - result.top);
ctx.stroke()
}
<canvas id="canvas"></canvas>

USE getBoundingClientRect() to get the exact boundaries

How to make blur effect particles in javascript

Hi I want to make a blur effect particle like this:
Can I use shadowBlur and shadowOffsetX/shadowOffsetY to do this? The actual shine will glow and fade a little bit repeatedly, so if I have to write some kind of animation how can I achieve this?
I have tried this code (jsfiddle example) but it doesn't look like the effect. So I wonder how to blur and glow the particle at the same time?
const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
const ra = window.requestAnimationFrame
|| window.webkitRequestAnimationFrame
|| window.mozRequestAnimationFrame
|| window.oRequestAnimationFrame
|| window.msRequestAnimationFrame
|| function(callback) {
window.setTimeout(callback, 1000 / 60);
};
class Particle {
constructor(options) {
this.ctx = options.context;
this.x = options.x;
this.y = options.y;
this.radius = options.radius;
this.lightSize = this.radius;
this.color = options.color;
this.lightDirection = true;
}
glow() {
const lightSpeed = 0.5;
this.lightSize += this.lightDirection ? lightSpeed : -lightSpeed;
if (this.lightSize > this.radius || this.lightSize < this.radius) {
this.lightDirection = !this.lightDirection;
}
}
render() {
this.ctx.clearRect(0, 0, canvas.width, canvas.height);
this.glow();
this.ctx.globalAlpha = 0.5;
this.ctx.fillStyle = this.color;
this.ctx.beginPath();
this.ctx.arc(this.x, this.y, this.lightSize,
0, Math.PI * 2
);
this.ctx.fill();
this.ctx.globalAlpha = 0.62;
this.ctx.beginPath();
this.ctx.arc(this.x, this.y, this.radius * 0.7, 0, Math.PI * 2);
this.ctx.shadowColor = this.color;
this.ctx.shadowBlur = 6;
this.ctx.shadowOffsetX = 0;
this.ctx.shadowOffsetY = 0;
this.ctx.fill();
}
}
var particle = new Particle({
context: ctx,
x: 60,
y: 80,
radius: 12,
color: '#4d88ff'
});
function run() {
particle.render();
ra(run);
}
run();
<canvas id='canvas'></canvas>

There are several ways to do this. For a particle system my option is to pre render the blur using a blur filter. A common filter is the convolution filter. It uses a small array to determine the amount neighboring pixels contribute to each pixel of the image. You are best to look up convolution functions to understand it.
Wiki Convolution and Wiki Gaussian blur for more info.
I am not much of a fan of the standard Gaussian blur or the convolution filter used so in the demo snippet below you can find my version that I think creates a much better blur. The convolution blur filter is procedurally created and is in the imageTools object.
To use create a filter pass an object with properties size the blur amount in pixels and power is the strength. Lower powers is less spread on the blur.
// image must be loaded or created
var blurFilter = imageTools.createBlurConvolutionArray({size:17,power:1}); // size must be greater than 2 and must be odd eg 3,5,7,9...
// apply the convolution filter on the image. The returned image may be a new
//image if the input image does not have a ctx property pointing to a 2d canvas context
image = imageTools.applyConvolutionFilter(image,blurFilter);
In the demo I create a image, draw a circle on it, copy it and pad it so that there is room for the blur. Then create a blur filter and apply it to the image.
When I render the particles I first draw all the unblurred images, then draw the blurred copies with the ctx.globalCompositeOperation = "screen"; so that they have a shine. To vary the amount of shine I use the ctx.globalAlpha to vary the intensity of the rendered blurred image. To improve the FX I have drawn the blur image twice, once with oscillating scale and next at fixed scale and alpha.
The demo is simple, image tools can be found at the top. Then there is some stuff to setup the canvas and handle resize event. Then there is the code that creates the images, and apply the filters. Then starts the render adds some particles and renders everything.
Look in the function drawParticles for how I draw everything.
imageTools has all the image functions you will need. The imageTools.applyConvolutionFilter will apply any filter (sharpen, outline, and many more) you just need to create the appropriate filter. The apply uses the photon count colour model so gives a very high quality result especially for blurs type effects. (though for sharpen you may want to get in and change the squaring of the RGB values, I personally like it other do not)
The blur filter is not fast so if you apply it to larger images It would be best that you break it up in so you do not block the page execution.
A cheap way to get a blur is to copy the image to blur to a smaller version of itself, eg 1/4 then render it scaled back to normal size, the canvas will apply bilinear filtering on the image give a blur effect. Not the best quality but for most situations it is indistinguishable from the more sophisticated blur that I have presented.
UPDATE
Change the code so that the particles have a bit of a 3dFX to show that the blur can work up to larger scales. The blue particles are 32 by 32 image and the blur is 9 pixels with the blur image being 50by 50 pixels.
var imageTools = (function () {
var tools = {
canvas : function (width, height) { // create a blank image (canvas)
var c = document.createElement("canvas");
c.width = width;
c.height = height;
return c;
},
createImage : function (width, height) {
var image = this.canvas(width, height);
image.ctx = image.getContext("2d");
return image;
},
image2Canvas : function (img) {
var image = this.canvas(img.width, img.height);
image.ctx = image.getContext("2d");
image.drawImage(img, 0, 0);
return image;
},
padImage : function(img,amount){
var image = this.canvas(img.width + amount * 2, img.height + amount * 2);
image.ctx = image.getContext("2d");
image.ctx.drawImage(img, amount, amount);
return image;
},
getImageData : function (image) {
return (image.ctx || (this.image2Canvas(image).ctx)).getImageData(0, 0, image.width, image.height);
},
putImageData : function (image, imgData){
(image.ctx || (this.image2Canvas(image).ctx)).putImageData(imgData,0, 0);
return image;
},
createBlurConvolutionArray : function(options){
var i, j, d; // misc vars
var filterArray = []; // the array to create
var size = options.size === undefined ? 3: options.size; // array size
var center = Math.floor(size / 2); // center of array
// the power ? needs descriptive UI options
var power = options.power === undefined ? 1: options.power;
// dist to corner
var maxDist = Math.sqrt(center * center + center * center);
var dist = 0; // distance sum
var sum = 0; // weight sum
var centerWeight; // center calculated weight
var totalDistance; // calculated total distance from center
// first pass get the total distance
for(i = 0; i < size; i++){
for(j = 0; j < size; j++){
d = (maxDist-Math.sqrt((center-i)*(center-i)+(center-j)*(center-j)));
d = Math.pow(d,power)
dist += d;
}
}
totalDistance = dist; // total distance to all points;
// second pass get the total weight of all but center
for(i = 0; i < size; i++){
for(j = 0; j < size; j++){
d = (maxDist-Math.sqrt((center-i)*(center-i)+(center-j)*(center-j)));
d = Math.pow(d,power)
d = d/totalDistance;
sum += d;
}
}
var scale = 1/sum;
sum = 0; // used to check
for(i = 0; i < size; i++){
for(j = 0; j < size; j++){
d = (maxDist-Math.sqrt((center-i)*(center-i)+(center-j)*(center-j)));
d = Math.pow(d,power)
d = d/totalDistance;
filterArray.push(d*scale);
}
}
return filterArray;
},
applyConvolutionFilter : function(image,filter){
imageData = this.getImageData(image);
imageDataResult = this.getImageData(image);
var w = imageData.width;
var h = imageData.height;
var data = imageData.data;
var data1 = imageDataResult.data;
var side = Math.round(Math.sqrt(filter.length));
var halfSide = Math.floor(side/2);
var r,g,b,a,c;
for(var y = 0; y < h; y++){
for(var x = 0; x < w; x++){
var ind = y*4*w+x*4;
r = 0;
g = 0;
b = 0;
a = 0;
for (var cy=0; cy<side; cy++) {
for (var cx=0; cx<side; cx++) {
var scy = y + cy - halfSide;
var scx = x + cx - halfSide;
if (scy >= 0 && scy < h && scx >= 0 && scx < w) {
var srcOff = (scy*w+scx)*4;
var wt = filter[cy*side+cx];
r += data[srcOff+0] * data[srcOff+0] * wt;
g += data[srcOff+1] * data[srcOff+1] * wt;
b += data[srcOff+2] * data[srcOff+2] * wt;
a += data[srcOff+3] * data[srcOff+3] * wt;
}
}
}
data1[ind+0] = Math.sqrt(Math.max(0,r));
data1[ind+1] = Math.sqrt(Math.max(0,g));
data1[ind+2] = Math.sqrt(Math.max(0,b));
data1[ind+3] = Math.sqrt(Math.max(0,a));
}
}
return this.putImageData(image,imageDataResult);
}
};
return tools;
})();
/** SimpleFullCanvasMouse.js begin **/
const CANVAS_ELEMENT_ID = "canv";
const U = undefined;
var w, h, cw, ch; // short cut vars
var canvas, ctx;
var globalTime = 0;
var createCanvas, resizeCanvas, setGlobals;
var L = typeof log === "function" ? log : function(d){ console.log(d); }
createCanvas = function () {
var c,cs;
cs = (c = document.createElement("canvas")).style;
c.id = CANVAS_ELEMENT_ID;
cs.position = "absolute";
cs.top = cs.left = "0px";
cs.zIndex = 1000;
document.body.appendChild(c);
return c;
}
resizeCanvas = function () {
if (canvas === U) { canvas = createCanvas(); }
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
ctx = canvas.getContext("2d");
if (typeof setGlobals === "function") { setGlobals(); }
}
setGlobals = function(){
cw = (w = canvas.width) / 2; ch = (h = canvas.height) / 2;
if(particles && particles.length > 0){
particles.length = 0;
}
}
resizeCanvas(); // create and size canvas
window.addEventListener("resize",resizeCanvas); // add resize event
const IMAGE_SIZE = 32;
const IMAGE_SIZE_HALF = 16;
const GRAV = 2001;
const NUM_PARTICLES = 90;
var background = imageTools.createImage(8,8);
var grad = ctx.createLinearGradient(0,0,0,8);
grad.addColorStop(0,"#000");
grad.addColorStop(1,"#048");
background.ctx.fillStyle = grad;
background.ctx.fillRect(0,0,8,8);
var circle = imageTools.createImage(IMAGE_SIZE,IMAGE_SIZE);
circle.ctx.fillStyle = "#5BF";
circle.ctx.arc(IMAGE_SIZE_HALF, IMAGE_SIZE_HALF, IMAGE_SIZE_HALF -2,0, Math.PI * 2);
circle.ctx.fill();
var blurFilter = imageTools.createBlurConvolutionArray({size:9,power:1}); // size must be greater than 2 and must be odd eg 3,5,7,9...
var blurCircle = imageTools.padImage(circle,9);
blurCircle = imageTools.applyConvolutionFilter(blurCircle,blurFilter)
var sun = imageTools.createImage(64,64);
grad = ctx.createRadialGradient(32,32,0,32,32,32);
grad.addColorStop(0,"#FF0");
grad.addColorStop(1,"#A40");
sun.ctx.fillStyle = grad;
sun.ctx.arc(32,32,32 -2,0, Math.PI * 2);
sun.ctx.fill();
var sunBlur = imageTools.padImage(sun,17);
blurFilter = imageTools.createBlurConvolutionArray({size:17,power:1}); // size must be greater than 2 and must be odd eg 3,5,7,9...
sunBlur = imageTools.applyConvolutionFilter(sunBlur,blurFilter);
var particles = [];
var createParticle = function(x,y,dx,dy){
var dir = Math.atan2(y-ch,x-cw);
var dist = Math.sqrt(Math.pow(y-ch,2)+Math.pow(x-cw,2));
var v = Math.sqrt(GRAV / dist); // get apporox orbital speed
return {
x : x,
y : y,
dx : dx + Math.cos(dir + Math.PI/2) * v, // set orbit speed at tangent
dy : dy + Math.sin(dir + Math.PI/2) * v,
s : (Math.random() + Math.random() + Math.random())/4 + 0.5, // scale
v : (Math.random() + Math.random() + Math.random()) / 3 + 2, // glow vary rate
};
}
var depthSort = function(a,b){
return b.y - a.y;
}
var updateParticles = function(){
var i,p,f,dist,dir;
for(i = 0; i < particles.length; i ++){
p = particles[i];
dist = Math.sqrt(Math.pow(cw-p.x,2)+Math.pow(ch-p.y,2));
dir = Math.atan2(ch-p.y,cw-p.x);
f = GRAV * 1 / (dist * dist);
p.dx += Math.cos(dir) * f;
p.dy += Math.sin(dir) * f;
p.x += p.dx;
p.y += p.dy;
p.rx = ((p.x - cw ) / (p.y + h)) * h + cw;
p.ry = ((p.y - ch ) / (p.y + h)) * h * -0.051+ ch;
//p.ry = ((h-p.y) - ch) * 0.1 + ch;
p.rs = (p.s / (p.y + h)) * h
}
particles.sort(depthSort)
}
var drawParticles = function(){
var i,j,p,f,dist,dir;
// draw behind the sun
for(i = 0; i < particles.length; i ++){
p = particles[i];
if(p.y - ch < 0){
break;
}
ctx.setTransform(p.rs,0,0,p.rs,p.rx,p.ry);
ctx.drawImage(circle,-IMAGE_SIZE_HALF,-IMAGE_SIZE_HALF);
}
// draw glow for behind the sun
ctx.globalCompositeOperation = "screen";
var iw = -blurCircle.width/2;
for(j = 0; j < i; j ++){
p = particles[j];
ctx.globalAlpha = ((Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.4;
var scale = (1-(Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.6;
ctx.setTransform(p.rs * 1.5 * scale,0,0,p.rs * 1.5* scale,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
// second pass to intensify the glow
ctx.globalAlpha = 0.7;
ctx.setTransform(p.rs * 1.1,0,0,p.rs * 1.1,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
}
// draw the sun
ctx.globalCompositeOperation = "source-over";
ctx.globalAlpha = 1;
ctx.setTransform(1,0,0,1,cw,ch);
ctx.drawImage(sun,-sun.width/2,-sun.height/2);
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "screen";
ctx.setTransform(1,0,0,1,cw,ch);
ctx.drawImage(sunBlur,-sunBlur.width/2,-sunBlur.height/2);
var scale = Math.sin(globalTime / 100) *0.5 + 1;
ctx.globalAlpha = (Math.cos(globalTime / 100) + 1) * 0.2 + 0.4;;
ctx.setTransform(1 + scale,0,0,1 + scale,cw,ch);
ctx.drawImage(sunBlur,-sunBlur.width/2,-sunBlur.height/2);
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "source-over";
// draw in front the sun
for(j = i; j < particles.length; j ++){
p = particles[j];
if(p.y > -h){ // don't draw past the near view plane
ctx.setTransform(p.rs,0,0,p.rs,p.rx,p.ry);
ctx.drawImage(circle,-IMAGE_SIZE_HALF,-IMAGE_SIZE_HALF);
}
}
ctx.globalCompositeOperation = "screen";
var iw = -blurCircle.width/2;
for(j = i; j < particles.length; j ++){
p = particles[j];
if(p.y > -h){ // don't draw past the near view plane
ctx.globalAlpha = ((Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.4;
var scale = (1-(Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.6;
ctx.setTransform(p.rs * 1.5 * scale,0,0,p.rs * 1.5* scale,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
// second pass to intensify the glow
ctx.globalAlpha = 0.7;
ctx.setTransform(p.rs * 1.1,0,0,p.rs * 1.1,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
}
}
ctx.globalCompositeOperation = "source-over";
}
var addParticles = function(count){
var ww = (h-10)* 2;
var cx = cw - ww/2;
var cy = ch - ww/2;
for(var i = 0; i < count; i ++){
particles.push(createParticle(cx + Math.random() * ww,cy + Math.random() * ww, Math.random() - 0.5, Math.random() - 0.5));
}
}
function display(){ // put code in here
if(particles.length === 0){
addParticles(NUM_PARTICLES);
}
ctx.setTransform(1,0,0,1,0,0); // reset transform
ctx.globalAlpha = 1; // reset alpha
ctx.drawImage(background,0,0,w,h)
updateParticles();
drawParticles();
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "source-over";
}
function update(timer){ // Main update loop
globalTime = timer;
display(); // call demo code
requestAnimationFrame(update);
}
requestAnimationFrame(update);
/** SimpleFullCanvasMouse.js end **/

Creating the Butterfly curve with arrays

I have two questions, the first being how do I access the indexes within my array separately, because my console.log of [n][0] results in two values - x and y. Secondly, for the butterfly curve, https://en.wikipedia.org/wiki/Butterfly_curve_%28transcendental%29, how would I determine the values of t? and reiterate through a certain minimum and maximum. In need of logic support.
Here's my progress so far.
/*function drawButterFly(n){
c.beginPath();
console.log(n[2])
for (var i = 0; i < n.length; i++){
if (i === 0) {
c.moveTo();
} else {
c.lineTo();
}
c.stroke();
}
}*/
function butterFly() {
var r = 5;
var N = 3;
var value = [];
for (var a = 0.2; a < 2*Math.PI; a = a + 0.1){
value.push(a);
}
var t = value[Math.floor(Math.random()*value.length)];
var cos = r*Math.cos(t)*( (Math.exp(Math.cos(t))) - (2*Math.cos(4*t)) - (Math.sin(t/12)^5) );
var sin = r*Math.sin(t)*( (Math.exp(Math.cos(t))) - (2*Math.cos(4*t)) - (Math.sin(t/12)^5) );
var n = [];
for (var u = 0; u < N; u++){
var x = sin * -u;
var y = cos * -u;
n.push([x,y]);
}
drawButterFly(n);
}

Since you're pushing an array here: n.push([x,y]) you can access the x component of the first element with n[0][0] and the y component of the same element with n[0][1]
Example:
var n = [];
n.push( ["x", "y"] );
console.log( n[0][0] );
console.log( n[0][1] );
As for the useful values of t - in the image you've shown, you'll notice that the same butterfly is drawn several times at different sizes. To draw a complete butterfly, you need to use the range for t of [0..2pi]. If you want to draw two butterflies, you need to use the range [0..4pi]. That is it's cyclic over the same period that a circle is. Unlike a circle however, each cycle doesn't draw over the previous one.
Here's a quick and nasty example:
function byId(id) {
return document.getElementById(id);
}
window.addEventListener('load', onDocLoaded, false);
function onDocLoaded(evt) {
butterFly();
}
function butterFly() {
var pointArray = [];
var stepSize = 0.05; // ~125 steps for every 360°
var upperLimit = 4 * Math.PI;
var scale = 20;
for (var t = 0.0; t < upperLimit; t += stepSize) {
var xVal = Math.sin(t) * ((Math.exp(Math.cos(t))) - (2 * Math.cos(4 * t)) - (Math.pow(Math.sin(t / 12), 5)));
var yVal = Math.cos(t) * ((Math.exp(Math.cos(t))) - (2 * Math.cos(4 * t)) - (Math.pow(Math.sin(t / 12), 5)));
pointArray.push([scale * xVal, -scale * yVal]); // -1 value since screen-y direction is opposite direction to cartesian coords y
}
drawButterFly(pointArray);
}
function drawButterFly(pointArray) {
var can = byId('myCan');
var ctx = can.getContext('2d');
var originX, originY;
originX = can.width / 2;
originY = can.height / 2;
ctx.beginPath();
for (var i = 0; i < pointArray.length; i++) {
if (i === 0) {
ctx.moveTo(originX + pointArray[i][0], originX + pointArray[i][1]);
} else {
ctx.lineTo(originX + pointArray[i][0], originY + pointArray[i][1]);
}
}
ctx.closePath();
ctx.stroke();
}
canvas {
border: solid 1px red;
}
<canvas id='myCan' width='256' height='256' />

If I'm not mistaken, the Butterfly curve is given as a pair of parametric equations, meaning you increment t to get the next (x, y) points on your curve. In other words, your t is what you should be using in place of u in your code, and the range of values for t should be 0 .. 24*pi as that's the range in which sin(t / 12) has its unique values).
Here's a version that demonstrates the drawing of the curve to a canvas:
function getPoint(t, S, O) {
var cos_t = Math.cos(t);
var factor = Math.exp(cos_t) - 2 * Math.cos(4*t) - Math.pow(Math.sin(t/12), 5);
return {
x: S * Math.sin(t) * factor + O.x,
y: S * cos_t * factor + O.y
};
}
var canvas = document.getElementById("c");
canvas.width = 300;
canvas.height = 300;
var ctx = canvas.getContext("2d");
// First path
ctx.beginPath();
ctx.strokeStyle = 'blue';
var offset = {x:150, y:120};
var scale = 40;
var maxT = 24 * Math.PI;
var p = getPoint(0, scale, offset);
ctx.moveTo(p.x, canvas.height - p.y);
for (var t = 0.01; t <= maxT; t += 0.01) {
p = getPoint(t, scale, offset);
ctx.lineTo(p.x, canvas.height - p.y);
}
ctx.stroke();
#c {
border: solid 1px black;
}
<canvas id="c"></canvas>
One thing to note: canvases have y = 0 start at the top, so you need to inverse your y (i.e. canvas.height - y) to have your curve orient correctly.
UPDATE: Added animated version
As requested by royhowie, here's an animated version, using requestAnimationFrame:
function getPoint(t, S, O) {
var cos_t = Math.cos(t);
var factor = Math.exp(cos_t) - 2 * Math.cos(4*t) - Math.pow(Math.sin(t/12), 5);
return {
x: S * Math.sin(t) * factor + O.x,
y: S * cos_t * factor + O.y
};
}
var canvas = document.getElementById("c");
canvas.width = 300;
canvas.height = 300;
var ctx = canvas.getContext("2d");
var offset = {x:150, y:120};
var scale = 40;
var maxT = 24 * Math.PI;
var animationID;
var started = false;
var t = 0;
document.getElementById('start').addEventListener('click', function(e) {
e.preventDefault();
if (!started) {
animationID = requestAnimationFrame(animate);
started = true;
}
});
document.getElementById('pause').addEventListener('click', function(e) {
e.preventDefault();
if (started) {
cancelAnimationFrame(animationID);
started = false;
}
});
function animate() {
animationID = requestAnimationFrame(animate);
var p = getPoint(t, scale, offset);
if (t === 0) {
ctx.beginPath();
ctx.strokeStyle = 'blue';
ctx.moveTo(p.x, canvas.height - p.y);
t += 0.01;
} else if (t < maxT) {
ctx.lineTo(p.x, canvas.height - p.y);
ctx.stroke();
t += 0.01;
} else {
cancelAnimationFrame(animationID);
}
}
#c {
border: solid 1px black;
}
<div>
<button id="start">Start</button>
<button id="pause">Pause</button>
</div>
<canvas id="c"></canvas>

Question 1
For an arbitrary integer i, let n[i] = [xi, yi]. xi can then be accessed via n[i][0] and yi via n[i][1]
Question 2
For values of t, I am sure you're gonna want to use sub-integer values, so I recommend using a constant increment value representing the "resolution" of your graph.
Let's call it dt. Also, I'd advise changing your variable names from single letters to something more descriptive, like min_t and max_t, and instead of n I'm going to call your array points.
function drawButterFly(points){
for (var i = 0, n = points.count; i < n; ++i) {
var x = points[i][0];
var y = points[i][1];
...
}
}
function butterFly(min_t, max_t, dt, r) {
var points = [];
for (var t = min_t; t < max_t; t+=dt){
var x = r*Math.sin(t)*...
var y = r*Math.cos(t)*...
points.push([x,y]);
}
drawButterFly(points, dt);
}
I'm not sure what the other loop inside of that function was for, but if you need it, you can adapt from the pattern above.
Usage example: butterFly(0, 10, 0.01, 3) -> t goes from 0 to 10 with an increment of 0.01, and r=3

Regarding your first question it's a better option to replace the multidimensional array containing the x and y coordinates with an object. Then when iterating over the array you can check for the object values.
So instead of:
n.push([x,y]);
you should do:
m.push({
'xPos' : x,
'yPos' : y
})
Later you can access this by m.xPos or m.yPos
Then you can access the x and y values by object literal names.
Regarding the second question: for a good pseudo code implementation of butterfly curves you might check Paul Burke site: http://paulbourke.net/geometry/butterfly/. So t in your case is:
t = i * 24.0 * PI / N;
As you see t is a parametric value which got incremented on each step when iterating over the array.