export function bgStart(){ /* (Book REF) HTML5 Canvas Ch. 5: Math, Physics, and Animation ::: Uniform Circular Motion By Steve Fulton and Jeff Fulton */ window.requestAnimFrame = (function() { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) { window.setTimeout(callback, 1000 / 60); }; })(); var c, $, w, h, msX, msY, midX, midY, num = 650, parts = [], begin = 50, repeat = 20, end = Math.PI * 2, flow, force = null, msdn = false; function start() { c = document.getElementById('canvas'); $ = c.getContext('2d'); w = c.width = window.innerWidth; h = c.height = window.innerHeight; midX = w / 2; midY = h / 2; force = Math.max(w, h) * 0.09; flow = begin; window.requestAnimFrame(create); run(); } function run() { window.requestAnimFrame(run); go(); } function Part() { this.deg = 0; this.rad = 0; this.x = 0; this.y = 0; this.distX = 0; this.distY = 0; this.color = 'rgb(' + Math.floor(Math.random() * 130) + ',' + Math.floor(Math.random() * 50) + ',' + Math.floor(Math.random() * 100) + ')'; this.size; } function create() { var n = num; while (n--) { var p = new Part(); p.deg = Math.floor(Math.random() * 360); p.rad = Math.floor(Math.random() * w * 0.5); p.x = p.distX = Math.floor(Math.random() * w); p.y = p.distY = Math.floor(Math.random() * h); p.size = 1 + Math.floor(Math.random() * (p.rad * 0.055)); parts[n] = p; } c.onmousemove = msmv; c.onmousedown = msdn; c.onmouseup = msup; var int = setInterval(function() { flow--; if (flow === repeat) clearInterval(int); }, 20); } function go() { $.globalCompositeOperation = 'source-over'; $.fillStyle = 'hsla(242, 30%, 5%, .55)'; $.fillRect(0, 0, w, h); $.globalCompositeOperation = 'lighter'; var mx = msX; var my = msY; var bounds = force; if (msdn) { bounds = force * 2; } var n = num; while (n--) { var p = parts[n]; var radi = Math.PI / 180 * p.deg; p.distX = midX + p.rad * Math.cos(radi); p.distY = midY + p.rad * Math.sin(radi) * 0.4; if (mx && my) { var react = Math.floor((bounds * 0.5) + Math.random() * (bounds * 0.9)); if (p.distX - mx > 0 && p.distX - mx < bounds && p.distY - my > 0 && p.distY - my < bounds) { p.distX += react; p.distY += react; } else if (p.distX - mx > 0 && p.distX - mx < bounds && p.distY - my < 0 && p.distY - my > -bounds) { p.distX += react; p.distY -= react; } else if (p.distX - mx < 0 && p.distX - mx > -bounds && p.distY - my > 0 && p.distY - my < bounds) { p.distX -= react; p.distY += react; } else if (p.distX - mx < 0 && p.distX - mx > -bounds && p.distY - my < 0 && p.distY - my > -bounds) { p.distY -= react; p.distY -= react; } } p.x += ((p.distX - p.x) / flow); p.y += ((p.distY - p.y) / flow); var x = p.x; var y = p.y; var s = p.size * (p.y * 1.5 / h); if (s < 0.1) { s = 0; } $.beginPath(); $.fillStyle = p.color; $.arc(x, y, s, 0, end, true); $.fill(); $.closePath(); var vary; if (p.size < 2) { vary = 4; } else if (p.size < 3) { vary = 3; } else if (p.size < 4) { vary = 2; } else { vary = 1; } vary *= (p.y / (h * 0.9)); p.deg += vary; p.deg = p.deg % 360; } } function msmv(e) { var p = getPos(e.target); var sX = window.pageXOffset; var sY = window.pageYOffset; msX = e.clientX - p.x + sX; msY = e.clientY - p.y + sY; } function msdn(e) { msdn = true; } function msup(e) { msdn = false; } function getPos(el) { var cosmo = {}; cosmo.x = el.offsetLeft; cosmo.y = el.offsetTop; while (el.offsetParent) { el = el.offsetParent; cosmo.x += el.offsetLeft; cosmo.y += el.offsetTop; } return cosmo; } start() }