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<canvas id='canvas'></canvas>
html,
body {
margin: 0;
height: 100%;
overflow: hidden;
}
canvas {
width: 100%;
height: 100%;
/* background: linear-gradient(60deg, turquoise, mediumpurple); */
background: white;
}
var config = {
radius: 350, // The radius from the center of the canvas to the point where our spiral begins Try making this kinda small ( < 100 or so) for some cool "inverse" blooming effects.
increment: 3.7 / 5.5, // Play with the numerator and denominator of this fraction. This is multiplied by Math.PI, hence you should think of it as a ratio of PI. Prime numbers seem to be the most interesting. Maybe someone more mathematically inclined can tell me why.
cycles: 100, // the (max) number of cycles in the spiral
initialAngle: -Math.PI / 2, // the initial point where the spiral begins
dR: 0, // the initial change in the line segment length after each vertex. Mainly just affects the starting point of the animation.
dRR: 0.019, // the rate of change in the dR variable *each frame*. This is responsible for the cool animation. If you set this too high, the animation will be ridiculously fast.
min_dR: -15, // reverse the animation when the line segment length is this low
max_dR: 15, // reverse the animation when the line segment length is this large
color: 'rgba(30, 180, 180, 1)', // line color
// shadowBlur: 5,
// shadowColor: 'green',
requestsPerFrame: 1, // how many requestAnimationFrame()'s are made before we actually draw a frame. Hacky framerate control :)
lineWidth: 2
};
var canvas, cxt, width, height, animationFrame, animationFrameCount = 0, animateForward = false;
var mouseX, mouseY;
function initialize() {
canvas = document.getElementById("canvas");
cxt = canvas.getContext("2d");
window.addEventListener("resize", resize, false);
window.addEventListener('mousemove', mouseMove, false);
animateForward = "true";
setup();
}
function setup() {
width = window.innerWidth;
height = window.innerHeight;
canvas.width = width;
canvas.height = height;
draw();
}
function draw() {
animationFrameCount++;
if (animationFrameCount % config.requestsPerFrame === 0) {
var mouseBasedIncrement = setIncrement();
var increment = isNaN(mouseBasedIncrement) ? config.increment : mouseBasedIncrement;
animationFrameCount = 0;
cxt.clearRect(0, 0, width, height);
var points = [];
radius = config.radius;
if (animateForward) {
config.dR += config.dRR;
} else {
config.dR -= config.dRR;
}
for (
var angle = config.initialAngle;
angle <= config.cycles * 2 * Math.PI && radius > 0;
angle += increment * Math.PI
) {
var x = width / 2 + radius * Math.cos(angle);
var y = height / 2 + radius * Math.sin(angle);
points.push({ x, y });
radius -= config.dR;
}
cxt.beginPath();
cxt.strokeStyle = config.color;
cxt.lineWidth = config.lineWidth;
cxt.lineCap = 'round';
//cxt.shadowBlur = config.shadowBlur;
//cxt.shadowColor = config.shadowColor;
for (var i = 0; i < points.length - 1; i++) {
cxt.moveTo(points[i].x, points[i].y);
cxt.lineTo(points[i + 1].x, points[i + 1].y);
}
cxt.stroke();
cxt.closePath();
if (config.dR <= config.min_dR) {
animateForward = true;
} else if (config.dR >= config.max_dR) {
animateForward = false;
}
// console.log(config.dR);
}
animationFrame = requestAnimationFrame(draw);
}
function resize() {
if (animationFrame !== undefined) {
cancelAnimationFrame(animationFrame);
}
setup();
}
function mouseMove(event) {
mouseX = event.pageX;
mouseY = event.pageY;
}
function setIncrement() {
var x = 100 * mouseX / width;
var y = 100 * mouseY / height;
return x/y;
}
initialize();
Also see: Tab Triggers