Spirograph
This sketch uses simple transformations to create a
Spirograph-like effect with interlocking circles (called sines).
Press the spacebar to switch between tracing and showing the underlying geometry.
Example created by R. Luke DuBois.
http://en.wikipedia.org/wiki/Spirograph
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let NUMSINES = 20; // how many of these things can we do at once?
let sines = new Array(NUMSINES); // an array to hold all the current angles
let rad; // an initial radius value for the central sine
let i; // a counter variable
// play with these to get a sense of what's going on:
let fund = 0.005; // the speed of the central sine
let ratio = 1; // what multiplier for speed is each additional sine?
let alpha = 50; // how opaque is the tracing system
let trace = false; // are we tracing?
function setup() {
createCanvas(710, 400);
rad = height / 4; // compute radius for central circle
background(204); // clear the screen
for (let i = 0; i<sines.length; i++) {
sines[i] = PI; // start EVERYBODY facing NORTH
}
}
function draw() {
if (!trace) {
background(204); // clear screen if showing geometry
stroke(0, 255); // black pen
noFill(); // don't fill
}
// MAIN ACTION
push(); // start a transformation matrix
translate(width / 2, height / 2); // move to middle of screen
for (let i = 0; i < sines.length; i++) {
let erad = 0; // radius for small "point" within circle... this is the 'pen' when tracing
// setup for tracing
if (trace) {
stroke(0, 0, 255 * (float(i) / sines.length), alpha); // blue
fill(0, 0, 255, alpha / 2); // also, um, blue
erad = 5.0 * (1.0 - float(i) / sines.length); // pen width will be related to which sine
}
let radius = rad / (i + 1); // radius for circle itself
rotate(sines[i]); // rotate circle
if (!trace) ellipse(0, 0, radius * 2, radius * 2); // if we're simulating, draw the sine
push(); // go up one level
translate(0, radius); // move to sine edge
if (!trace) ellipse(0, 0, 5, 5); // draw a little circle
if (trace) ellipse(0, 0, erad, erad); // draw with erad if tracing
pop(); // go down one level
translate(0, radius); // move into position for next sine
sines[i] = (sines[i] + (fund + (fund * i * ratio))) % TWO_PI; // update angle based on fundamental
}
pop(); // pop down final transformation
}
function keyReleased() {
if (key==' ') {
trace = !trace;
background(255);
}
}
