Капля случайной формы на JS

Для более наглядного примера использования этого фона, я добавил поверх несколько блоков, кликая на которые, капля примет новую форму.

Пример:

Блок 1

Блок 2

Блок 3

HTML:

<div class="blob-container">
	<div id="blob">
		<div class="blocks">
			<div class="block">
				Блок 1
			</div>
			<div class="block">
				Блок 2
			</div>
			<div class="block">
				Блок 3
			</div>
		</div>
	</div>
</div>

Блок 1

</div>

Блок 2

</div>

Блок 3

</div>

CSS:

.blob-container {
	position: relative;
	margin: 20px 0;
	box-shadow: 0 4px 12px rgba(0,0,0,0.2), 0 16px 20px rgba(0,0,0,0.2);
}
.blocks {
	display: flex;
	flex-wrap: wrap;
	justify-content: space-around;
	position: relative;
	z-index: 1;
	padding: 100px 0;
}
.block {
	margin: 20px;
	padding: 100px 50px;
	border: 6px solid #BFE2FF;
	border-radius: 10px;
	background-color: #fff;
	text-align: center;
	text-transform: uppercase; 
	font-size: 20px;
	font-weight: bold;
	color: #337AB7;
	cursor: pointer;
	box-shadow: 0 4px 12px rgba(0,0,0,0.2), 0 16px 20px rgba(0,0,0,0.1);
}

.blob-container {

position: relative;

margin: 20px 0;

box-shadow: 0 4px 12px rgba(0,0,0,0.2), 0 16px 20px rgba(0,0,0,0.2);

}

.blocks {

display: flex;

flex-wrap: wrap;

justify-content: space-around;

position: relative;

z-index: 1;

padding: 100px 0;

}

.block {

margin: 20px;

padding: 100px 50px;

border: 6px solid #BFE2FF;

border-radius: 10px;

background-color: #fff;

text-align: center;

text-transform: uppercase;

font-size: 20px;

font-weight: bold;

color: #337AB7;

cursor: pointer;

box-shadow: 0 4px 12px rgba(0,0,0,0.2), 0 16px 20px rgba(0,0,0,0.1);

}

JS:

Раскомментировав строчку block[i].addEventListener('mouseenter', mouseClick); и удалив или закомментировав предыдущую (block[i].addEventListener('click', mouseClick);), капля будет меняться при заходе курсора на блок, а не по клику.

window.addEventListener("load",function() {
	const SPEED_ANIM = 5;
	let canv, ctx; 
	let maxx, maxy;
	let events;
	const mrandom = Math.random;
	const mfloor = Math.floor;
	const mround = Math.round;
	const mceil = Math.ceil;
	const mabs = Math.abs;
	const mmin = Math.min;
	const mmax = Math.max;
	const mPI = Math.PI;
	const mPIS2 = Math.PI / 2;
	const mPIS3 = Math.PI / 3;
	const m2PI = Math.PI * 2;
	const m2PIS3 = Math.PI * 2 / 3;
	const msin = Math.sin;
	const mcos = Math.cos;
	const matan2 = Math.atan2;
	const mhypot = Math.hypot;
	const msqrt = Math.sqrt;
	const rac3   = msqrt(3);
	const rac3s2 = rac3 / 2;
	const bcontainer = document.getElementById( 'blob' );
	function alea (mini, maxi) {
		if (typeof(maxi) == 'undefined') return mini * mrandom();
		return mini + mrandom() * (maxi - mini);
	}
	function intAlea (mini, maxi) {
		if (typeof(maxi) == 'undefined') return mfloor(mini * mrandom()); 
		return mini + mfloor(mrandom() * (maxi - mini)); 
	}
	function Noise1DOneShot (period, min = 0, max = 1, random) {
		random = random || Math.random;
		let currx = random();
		let y0 = min + (max - min) * random();
		let y1 = min + (max - min) * random();
		let dx = 1 / period;
		return function() {
			currx += dx;
			if (currx > 1) {
				currx -= 1;
				y0 = y1;
				y1 = min + (max - min) * random();
			}
			let z = (3 - 2 * currx) * currx * currx;
			return z * y1 + (1 - z) * y0;
		}
	}
	function drawBezierArc (p0, p1, p2, p3) {
		let dx, dy, lngth, ltg, lctrl;
		let x1c, y1c; 
		let x2c, y2c; 
		const coeffDir = 0.3; 
		lngth = mhypot(p2[0] - p1[0], p2[1] - p1[1]);
		lctrl = lngth * coeffDir
		dx = p2[0] - p0[0];
		dy = p2[1] - p0[1];
		ltg = mhypot(dx, dy);
		x1c = p1[0] + lctrl * dx / ltg;
		y1c = p1[1] + lctrl * dy / ltg;
		dx = p1[0] - p3[0];
		dy = p1[1] - p3[1];
		ltg = mhypot(dx, dy);
		x2c = p2[0] + lctrl * dx / ltg;
		y2c = p2[1] + lctrl * dy / ltg;
		ctx.bezierCurveTo(x1c ,y1c,
			x2c, y2c,
		p2[0], p2[1]);
	}
	function Blob (xc, yc, radiusMax, nbSteps, lineWidth, hue) {
		this.xc = xc;
		this.yc = yc;
		this.radiusMax = radiusMax;
		this.nbSteps = nbSteps;
		this.lineWidth = lineWidth;
		let nbPts = this.nbPts = intAlea(4, 10);
		this.th0 = alea(m2PI);
		let deltadir = m2PI / nbPts;
		let periodAngle = nbSteps / alea(1,5); 
		let periodRadius = nbSteps / alea(2,5);
		let periodHue = nbSteps /alea(2, 5);
		this.huef = Noise1DOneShot(periodHue, hue, hue + intAlea(90));
		this.points = []; 
		this.pointFunctions = [];
		for (let k = 0; k < nbPts; ++k) {
			this.pointFunctions[k] = {angle: Noise1DOneShot( periodAngle,
			deltadir * (k - 0.4), deltadir * (k + 0.4)),
			radius: Noise1DOneShot( periodRadius,
			0.4, 1) };
		} 
	} 
	Blob.prototype.actualPoints = function (kStep) {
		let pf, angle, radius;
		for (let k = 0; k < this.nbPts; ++k) {
			pf = this.pointFunctions[k];
			angle = this.th0 + pf.angle();
			radius = this.radiusMax * pf.radius() * kStep / this.nbSteps;
			this.points[k] = [this.xc + radius * mcos(angle),
			this.yc + radius * msin(angle)];
		} 
	} 
	Blob.prototype.draw = function() {
		let k, pt;
		let k1, k2, k3;
		ctx.beginPath();
		ctx.moveTo (this.points[1][0],this.points[1][1]);
		k1 = 1;
		k2 = 2;
		k3 = 3;
		if (k3 >= this.nbPts ) k3 -= this.nbPts;
		for (k = 0 ; k < this.nbPts; ++k ) {
			drawBezierArc(
				this.points[k],        
				this.points[k1],
				this.points[k2],
			this.points[k3]);
			k1++; if (k1 >= this.nbPts) k1 -= this.nbPts;
			k2++; if (k2 >= this.nbPts) k2 -= this.nbPts;
			k3++; if (k3 >= this.nbPts) k3 -= this.nbPts;
		}
		ctx.lineWidth = this.lineWidth;
		ctx.strokeStyle = `hsl(${(this.huef() % 360)}, 100%, 50%)`;
		ctx.stroke();
	}
	let animate;
	{ 
		let animState = 0;
		let blob;
		let kStep;
		animate = function(tStamp) {
			let event;
			let tinit, radMax;
			event = events.pop();
			if (event && event.event == 'reset') animState = 0;
			if (event && event.event == 'click') animState = 0;
			window.requestAnimationFrame(animate)
			tinit = performance.now();
			do {
				switch (animState) {
					case 0 :
					if (startOver()) {
						radMax = mhypot(maxx / 2, maxy / 2)
						kStep = mround(radMax * 5);
						blob = new Blob ( maxx / 2, maxy / 2, radMax, kStep, 0.1, intAlea(360));
						++animState;
					}
					break;
					case 1 :
					blob.actualPoints(kStep);
					blob.draw();
					if (--kStep <= 0) {
						++animState;
					}
					break;
					case 2:
					break;
				}
			} while ((animState == 1) && (performance.now() - tinit < SPEED_ANIM));
		} 
	} 
	function startOver() {
		let offsx, offsy;
		let centrx, centry; 
		maxx = bcontainer.offsetWidth;
		maxy = bcontainer.offsetHeight;
		canv.width = maxx;
		canv.height = maxy;
		ctx.clearRect(0, 0, maxx, maxy);
		return true;
	}
	function mouseClick (event) {
		events.push({event:'click'});;
	}
	{
		canv = document.createElement('canvas');
		canv.style.position="absolute";
		canv.style.top=0;
		bcontainer.appendChild(canv);
		ctx = canv.getContext('2d');
	}
	let block = document.getElementsByClassName('block');
	window.addEventListener('resize', mouseClick);  
	for (var i = 0; i < block.length; i++) {
		block[i].addEventListener('click', mouseClick);
		// block[i].addEventListener('mouseenter', mouseClick);
	}  
	events = [{event:'reset'}];
	requestAnimationFrame(animate);
});

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window.addEventListener("load",function() {

const SPEED_ANIM = 5;

let canv, ctx;

let maxx, maxy;

let events;

const mrandom = Math.random;

const mfloor = Math.floor;

const mround = Math.round;

const mceil = Math.ceil;

const mabs = Math.abs;

const mmin = Math.min;

const mmax = Math.max;

const mPI = Math.PI;

const mPIS2 = Math.PI / 2;

const mPIS3 = Math.PI / 3;

const m2PI = Math.PI * 2;

const m2PIS3 = Math.PI * 2 / 3;

const msin = Math.sin;

const mcos = Math.cos;

const matan2 = Math.atan2;

const mhypot = Math.hypot;

const msqrt = Math.sqrt;

const rac3 = msqrt(3);

const rac3s2 = rac3 / 2;

const bcontainer = document.getElementById( 'blob' );

function alea (mini, maxi) {

if (typeof(maxi) == 'undefined') return mini * mrandom();

return mini + mrandom() * (maxi - mini);

}

function intAlea (mini, maxi) {

if (typeof(maxi) == 'undefined') return mfloor(mini * mrandom());

return mini + mfloor(mrandom() * (maxi - mini));

}

function Noise1DOneShot (period, min = 0, max = 1, random) {

random = random || Math.random;

let currx = random();

let y0 = min + (max - min) * random();

let y1 = min + (max - min) * random();

let dx = 1 / period;

return function() {

currx += dx;

if (currx > 1) {

currx -= 1;

y0 = y1;

y1 = min + (max - min) * random();

}

let z = (3 - 2 * currx) * currx * currx;

return z * y1 + (1 - z) * y0;

}

function drawBezierArc (p0, p1, p2, p3) {

let dx, dy, lngth, ltg, lctrl;

let x1c, y1c;

let x2c, y2c;

const coeffDir = 0.3;

lngth = mhypot(p2[0] - p1[0], p2[1] - p1[1]);

lctrl = lngth * coeffDir

dx = p2[0] - p0[0];

dy = p2[1] - p0[1];

ltg = mhypot(dx, dy);

x1c = p1[0] + lctrl * dx / ltg;

y1c = p1[1] + lctrl * dy / ltg;

dx = p1[0] - p3[0];

dy = p1[1] - p3[1];

ltg = mhypot(dx, dy);

x2c = p2[0] + lctrl * dx / ltg;

y2c = p2[1] + lctrl * dy / ltg;

ctx.bezierCurveTo(x1c ,y1c,

x2c, y2c,

p2[0], p2[1]);

}

function Blob (xc, yc, radiusMax, nbSteps, lineWidth, hue) {

this.xc = xc;

this.yc = yc;

this.radiusMax = radiusMax;

this.nbSteps = nbSteps;

this.lineWidth = lineWidth;

let nbPts = this.nbPts = intAlea(4, 10);

this.th0 = alea(m2PI);

let deltadir = m2PI / nbPts;

let periodAngle = nbSteps / alea(1,5);

let periodRadius = nbSteps / alea(2,5);

let periodHue = nbSteps /alea(2, 5);

this.huef = Noise1DOneShot(periodHue, hue, hue + intAlea(90));

this.points = [];

this.pointFunctions = [];

for (let k = 0; k < nbPts; ++k) {

this.pointFunctions[k] = {angle: Noise1DOneShot( periodAngle,

deltadir * (k - 0.4), deltadir * (k + 0.4)),

radius: Noise1DOneShot( periodRadius,

0.4, 1) };

}

Blob.prototype.actualPoints = function (kStep) {

let pf, angle, radius;

for (let k = 0; k < this.nbPts; ++k) {

pf = this.pointFunctions[k];

angle = this.th0 + pf.angle();

radius = this.radiusMax * pf.radius() * kStep / this.nbSteps;

this.points[k] = [this.xc + radius * mcos(angle),

this.yc + radius * msin(angle)];

}

Blob.prototype.draw = function() {

let k, pt;

let k1, k2, k3;

ctx.beginPath();

ctx.moveTo (this.points[1][0],this.points[1][1]);

k1 = 1;

k2 = 2;

k3 = 3;

if (k3 >= this.nbPts ) k3 -= this.nbPts;

for (k = 0 ; k < this.nbPts; ++k ) {

drawBezierArc(

this.points[k],

this.points[k1],

this.points[k2],

this.points[k3]);

k1++; if (k1 >= this.nbPts) k1 -= this.nbPts;

k2++; if (k2 >= this.nbPts) k2 -= this.nbPts;

k3++; if (k3 >= this.nbPts) k3 -= this.nbPts;

}

ctx.lineWidth = this.lineWidth;

ctx.strokeStyle = `hsl(${(this.huef() % 360)}, 100%, 50%)`;

ctx.stroke();

}

let animate;

{

let animState = 0;

let blob;

let kStep;

animate = function(tStamp) {

let event;

let tinit, radMax;

event = events.pop();

if (event && event.event == 'reset') animState = 0;

if (event && event.event == 'click') animState = 0;

window.requestAnimationFrame(animate)

tinit = performance.now();

do {

switch (animState) {

case 0 :

if (startOver()) {

radMax = mhypot(maxx / 2, maxy / 2)

kStep = mround(radMax * 5);

blob = new Blob ( maxx / 2, maxy / 2, radMax, kStep, 0.1, intAlea(360));

++animState;

}

break;

case 1 :

blob.actualPoints(kStep);

blob.draw();

if (--kStep <= 0) {

++animState;

}

break;

case 2:

break;

}

} while ((animState == 1) && (performance.now() - tinit < SPEED_ANIM));

}

function startOver() {

let offsx, offsy;

let centrx, centry;

maxx = bcontainer.offsetWidth;

maxy = bcontainer.offsetHeight;

canv.width = maxx;

canv.height = maxy;

ctx.clearRect(0, 0, maxx, maxy);

return true;

}

function mouseClick (event) {

events.push({event:'click'});;

}

{

canv = document.createElement('canvas');

canv.style.position="absolute";

canv.style.top=0;

bcontainer.appendChild(canv);

ctx = canv.getContext('2d');

}

let block = document.getElementsByClassName('block');

window.addEventListener('resize', mouseClick);

for (var i = 0; i < block.length; i++) {

block[i].addEventListener('click', mouseClick);

// block[i].addEventListener('mouseenter', mouseClick);

}

events = [{event:'reset'}];

requestAnimationFrame(animate);

});

Найдено на codepen.io у пользователя Dillon

Пример:

HTML:

CSS:

JS:

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