Блуждающие гравитационные звёзды на HTML5 Canvas
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<canvas id="c"></canvas> <script> var w = c.width = window.innerWidth, h = c.height = window.innerHeight, ctx = c.getContext('2d'), opts = { particles: 200, particleInitialVel: 2, particleInertia: 1000, particleFriction: .99, particleTemplateColor: 'hsla(hue,60%,45%,.1)', particleSize: 4, //more efficient if it's an even number orbits: 7, orbitTemplateColor: 'hsla(hue,80%,55%,.1)', orbitBaseVel: 1, orbitAddedVel: .5, orbitVelWaveIncrementer: .01, orbitRadIncrementer: .01, orbitAddedRad: .01, orbitAddedRadWaveIncrementer: .001, orbitSize: 20, orbitLines: 10, repaintAlpha: .1, cx: w / 2, cy: h / 2 }, calc = { particleHalfSize: opts.particleSize / 2, repaintColor: 'rgba(0,0,0,alp)'.replace('alp', opts.repaintAlpha) }, particleCaches = {}, particles = [], orbits = [], tick = 0; function setup() { for (var i = 0; i < opts.orbits; ++i) orbits.push(new Orbit); ctx.fillStyle = '#111'; ctx.fillRect(0, 0, w, h); anim(); } function redraw() { ctx.fillStyle = calc.repaintColor; ctx.fillRect(0, 0, w, h); } function anim() { window.requestAnimationFrame(anim); ++tick; if (particles.length < opts.particles) particles.push(new Particle); redraw(); orbits.map(stepOrbit); particles.map(stepParticle); } function stepOrbit(orbit) { orbit.step(); } function stepParticle(particle) { particle.step(); } function Orbit() { this.x = Math.random() * w; this.y = Math.random() * h; this.rad = Math.random() * Math.PI * 2; this.radWave = Math.random() * Math.PI * 2; this.velWave = Math.random() * Math.PI * 2; } Orbit.prototype.step = function() { this.rad += opts.orbitRadIncrementer + opts.orbitAddedRad * Math.sin(this.radWave += (Math.random() * opts.orbitAddedRadWaveIncrementer)); var len = opts.orbitBaseVel + opts.orbitAddedVel * Math.sin(this.velWave += opts.orbitVelWaveIncrementer), vx = len * Math.cos(this.rad), vy = len * Math.sin(this.rad), revertX = true, revertY = true; this.x += vx; this.y += vy; if (this.x < 0) this.x = 0; else if (this.x > w) this.x = w; else revertX = false; if (this.y < 0) this.y = 0; else if (this.y > h) this.y = h; else revertY = false; if (revertX || revertY) { if (revertX) vx *= -1; if (revertY) vy *= -1; this.rad = Math.atan(vy / vx) + (vx < 0 ? Math.PI : 0); } ctx.strokeStyle = opts.orbitTemplateColor.replace('hue', this.x / w * 360 + tick); ctx.beginPath(); for (var i = 0; i < opts.orbitLines; ++i) { var len = (1 - Math.sqrt(Math.random())) * opts.orbitSize, rad = Math.random() * Math.PI * 2; ctx.moveTo(this.x + len * Math.cos(rad), this.y + len * Math.sin(rad)); ctx.lineTo(this.x, this.y); } ctx.stroke(); } function Particle() { this.reset(); } Particle.prototype.reset = function() { this.x = opts.cx; this.y = opts.cy; var rad = Math.random() * Math.PI * 2; this.vx = opts.particleInitialVel * Math.cos(rad); this.vy = opts.particleInitialVel * Math.sin(rad); } Particle.prototype.step = function() { for (var i = 0; i < orbits.length; ++i) { var dx = orbits[i].x - this.x, dy = orbits[i].y - this.y, squareD = dx * dx + dy * dy, force = opts.particleInertia / squareD, rad = Math.atan(dy / dx) + (dx < 0 ? Math.PI : 0); this.vx += force * Math.cos(rad); this.vy += force * Math.sin(rad); } this.vx *= opts.particleFriction; this.vy *= opts.particleFriction; //ctx.strokeStyle = 'hsla(hue,80%,50%,.1)'.replace( 'hue', this.x / w * 360 + tick ); //ctx.beginPath(); //ctx.moveTo( this.x, this.y ); this.x += this.vx; this.y += this.vy; //ctx.lineTo( this.x, this.y ); //ctx.stroke(); var hue = (this.x / w * 360 + tick) | 0, cache = particleCaches[hue]; if (!cache) { var canvas = document.createElement('canvas'), context = canvas.getContext('2d'); canvas.width = canvas.height = opts.particleSize; context.fillStyle = opts.particleTemplateColor.replace('hue', hue); context.beginPath(); context.arc(calc.particleHalfSize, calc.particleHalfSize, calc.particleHalfSize, 0, Math.PI * 2); context.fill(); cache = particleCaches[hue] = canvas; } ctx.drawImage(cache, (this.x | 0) - calc.particleHalfSize, (this.y | 0) - calc.particleHalfSize); if (this.x < 0 || this.x > w || this.y < 0 || this.y > h) this.reset(); } setup(); c.addEventListener('mousemove', function(e) { opts.cx = e.clientX; opts.cy = e.clientY; }); c.addEventListener('mouseleave', function() { opts.cx = w / 2; opts.cy = h / 2; }); window.addEventListener('resize', function() { w = c.width = window.innerWidth; h = c.height = window.innerHeight; opts.cx = w / 2; opts.cy = h / 2; ctx.fillStyle = '#111'; ctx.fillRect(0, 0, w, h); }); </script> |
