我是画布的新手，我正在尝试创建一个看起来很逼真的浮动粒子动画。
目前，我正在创建400个在400x400画布上随机散布的粒子。
然后，在每个requestAnimationFrame中，我正在调整x和y坐标，如下所示：
this.particles[i].x += Math.random() * 0.3 - 0.15;
this.particles[i].y += Math.random() * 0.3 - 0.15;
现在，我正在试图弄清楚如何使粒子看起来更像是现实浮动。
他们看起来更现实的一种方式是，如果他们会旅行更远的距离。现在，他们似乎只是在振动，而不是浮动。什么是实现漂移动画的一种方法，使粒子行进明显的距离，但不会从画布上完全消失？
class ParticleCanvas {
constructor(canvas, width, height) {
this.main = {
element: canvas
};
this.buffer = {
element: document.createElement("canvas")
};
this.main.context = this.main.element.getContext("2d");
this.buffer.context = this.buffer.element.getContext("2d");
this.main.element.width = this.buffer.element.width = this.width = width;
this.main.element.height = this.buffer.element.height = this.height = height;
this.makeParticles(400);
this.animate();
}
makeParticles(n) {
this.particles = [];
for (let i = 0; i < n; i++) {
this.particles.push(
new Particle(
this.width / 2 + Math.random() * this.width - this.width / 2,
this.height / 2 + Math.random() * this.height - this.height / 2,
Math.random() * 3 + 2,
"#919191",
"circle"
)
);
}
}
animate() {
this.main.context.clearRect(0, 0, this.width, this.height);
for (var i = 0; i < this.particles.length; i++) {
this.particles[i].x += Math.random() * 0.3 - 0.15;
this.particles[i].y += Math.random() * 0.3 - 0.15;
this.particles[i].draw(this.main.context);
}
requestAnimationFrame(this.animate.bind(this));
}
}
class Particle {
constructor(x, y, radius, dotColor, particleShape) {
this.x = x;
this.y = y;
this.radius = radius;
this.dotColor = dotColor;
this.particleShape = particleShape;
}
draw(context) {
context.save();
context.translate(this.x, this.y);
context.fillStyle = this.dotColor;
switch (this.particleShape) {
case "circle":
context.beginPath();
context.arc(0, 0, this.radius, 0, 2 * Math.PI);
context.fill();
break;
case "square":
context.fillRect(0, 0, this.radius * 2, this.radius * 2);
break;
}
context.restore();
}
}
new ParticleCanvas(document.querySelector("canvas"), 400, 400);body {
margin: 0;
}<canvas></canvas>
答案 0 :(得分：3)
Sin波创建简单的运动，可用于动画粒子。
使粒子看起来像浮动的一种方法是将它们视为漂浮在介质中。介质的运动是使单个粒子移动的原因。这种趋势使得彼此靠近的粒子以类似的方式移动。
在空气中，运动倾向于略呈圆形，如漩涡。
为了达到这个目的，我们可以创建一组代表空气涡旋中心的不可见涡旋粒子。我们在画布周围移动涡旋。每个涡旋都有一个位置，一个大小和相关的强度。它们移动的面积是画布的两倍。
然后通过每个涡旋移动每个粒子。粒子移动的量取决于粒子的质量（与其大小有关）以及它与涡旋中心的距离。
每个粒子也有动量（保持移动的倾向），以及随着时间的推移使粒子上下移动的抽象浮力值（以阻止它们聚集在一个地方）。为了给运动增加一点点，深度（远离眼睛）会为运动增加一点（非常小的）视差。
动画有4个步骤。
这些类型的模拟在许多魔术数字方面都非常有刀刃。在示例的顶部，我添加了一些常量来控制模拟。
您可以使用这些值，可以实现各种各样的效果，模拟空气中的粒子，水，粘性物质等。
看起来最好的整页。
// request first frame (this starts the whole shebang)
requestAnimationFrame(update);
const doFor =(c,C)=>{var i=0;while(i<c && C(i++)!==true);return i};
const randI = (min, max = min + (min = 0)) => (Math.random() * (max - min) + min) | 0;
const rand = (min = 1, max = min + (min = 0)) => Math.random() * (max - min) + min;
const ctx = canvas.getContext("2d");
//==================================================================
// WARNING next two control CPU load.
// Number of particles is width * height / density
const density = 1000; // particles per pixel squared WARNING Small numbers bad
const airVortexCount = 8; // number of vortex Warning big number bad
//==================================================================
const airVortexSpeed = 10; // speed of vortex movement in pixels
const vortexTurn = 0.02; // bigger values and vortex movement more circular
var airList;
const airForceCof = 1; // amount of force airVortex applys to circle
const circleDrag = 0.99; // drag is 1-circleDrag Must be less than 1
// the smaller the number the less movement in circles
const buoyancySpeed = 0.01; // Particle buoyancy speed
var circleList;
const circleMinSize = 2; // size is radius in pixels
const circleMaxSize = 4;
const floatPhaseCycleMax = 0.02; // Particle buoyancy phase shift. Bigger numbers
// create faster updown movement
var airWidth,airHeight;
var cirWidth,cirHeight;
function createParticles(){
airList = {...list};
circleList = {...list};
airList.init();
circleList.init();
doFor(airVortexCount, () => airList.add({...particle, ...air}).init());
var circleCount = (canvas.width * canvas.height) / density;
doFor(circleCount, () => circleList.add({...particle, ...circle}).init());
airWidth = canvas.width * 2;
airHeight = canvas.height * 2;
cirWidth = canvas.width + circleMaxSize * 2;
cirHeight = canvas.height + circleMaxSize * 2;
}
function updateAll(){
airList.update();
airList.each(circleList.update.bind(circleList));
circleList.update();
ctx.beginPath();
circleList.draw();
ctx.fill();
}
var w,h,cw,ch;
function update(timer){
ctx.setTransform(1,0,0,1,0,0); // reset transform
if(w !== innerWidth || h !== innerHeight){ // resize canvas if needed
cw = (w = canvas.width = innerWidth) / 2;
ch = (h = canvas.height = innerHeight) / 2;
createParticles();
}
ctx.fillStyle = "black";
ctx.fillRect(0,0,w,h);
ctx.fillStyle = "rgba(255,200,100,0.5)";
updateAll();
requestAnimationFrame(update);
}
// air is a Vortex (bad naming when I started)
const air = {
update(){
this.x += Math.cos(this.phase) * airVortexSpeed;
this.y += Math.sin(this.phase) * airVortexSpeed;
this.phase += this.phaseShift;
this.x = ((this.x % airWidth) + airWidth) % airWidth;
this.y = ((this.y % airHeight) + airHeight) % airHeight;
},
init(){
this.x = randI(canvas.width);
this.y = randI(canvas.height);
this.size2 = randI(canvas.height * canvas.width);
this.size = Math.sqrt(this.size2);
this.phase = rand(Math.PI * 2);
this.phaseShift = rand(-vortexTurn,vortexTurn);
return this;
},
}
// the things that float in air
const circle = {
init(){
this.x = randI(canvas.width);
this.y = randI(canvas.height);
this.dx = 0;
this.dy = 0;
this.size = rand(circleMinSize,circleMaxSize);
this.mass = this.size ** 3;
this.depth = rand(0.5,1);
this.floatPhase = rand(Math.PI * 2);
this.floatPhaseCycle = rand(floatPhaseCycleMax );
return this;
},
update(air){ // if air is undefined then do momentum and bouyancy
if(air === undefined){
this.dy += Math.sin(this.floatPhase)*buoyancySpeed;
this.floatPhase += this.floatPhaseCycle;
this.x += this.dx * this.depth;
this.y += this.dy * this.depth;
this.dx *= circleDrag;
this.dy *= circleDrag;
this.x = ((this.x % cirWidth) + cirWidth) % cirWidth;
this.y = ((this.y % cirHeight) + cirHeight) % cirHeight;
return;
}
var x = this.x - (air.x - airWidth / 4);
var y = this.y - (air.y - airHeight / 4);
var dist = x * x + y * y;
if(dist < air.size2){
dist = Math.sqrt(dist);
x /= dist;
y /= dist;
var force = (1 - dist / air.size) * airForceCof;
// using f = ma (force = mass * acceleration)
var a = (force / this.mass) * Math.sign(air.phaseShift);
this.dx += -y * a;
this.dy += x * a;
}
},
draw(){
var x = this.x - circleMaxSize;
var y = this.y - circleMaxSize;
ctx.moveTo(x + this.size,y);
ctx.arc(x,y,this.size,0,Math.PI * 2);
}
}
// basic particle
const particle = { x : 0, y : 0, size : 0}
// basic list handles all particle arrays
const list = {
items : [],
init(){ this.items = [] },
add(item) {
this.items.push(item);
return item;
},
each(callback) { for(const item of this.items) { callback(item) } },
update(data) { for(const item of this.items) { item.update(data) } },
draw() { for(const item of this.items) { item.draw() } },
}canvas { position : absolute; top : 0px; left : 0px; }<canvas id="canvas"></canvas>
答案 1 :(得分：1)
你觉得这样吗？我正在使用Bezier.js。
我检查了一些粒子库。单个粒子的路径以某种方式记住了贝塞尔曲线。这就是我提出这个想法的原因。 为简单起见，我只动画了一个粒子。
正如您所看到的，我正在使用Bezier.js库来生成贝塞尔曲线并将其路径作为点。此查找表可用于设置每个粒子的位置。
这是更新的来源！请使用“展开代码段”来显示代码而不会出现格式错误。我已经将整个库添加到代码段中，导致一些缩进。
我实在迫不及待地想看看它是如何看待多个粒子的。通过这样做，我发现了一些应该为每个粒子随机化的参数：
var Bezier=function(t){function n(i){if(r[i])return r[i].exports;var e=r[i]={exports:{},id:i,loaded:!1};return t[i].call(e.exports,e,e.exports,n),e.loaded=!0,e.exports}var r={};return n.m=t,n.c=r,n.p="",n(0)}([function(t,n,r){"use strict";t.exports=r(1)},function(t,n,r){"use strict";var i="function"==typeof Symbol&&"symbol"==typeof Symbol.iterator?function(t){return typeof t}:function(t){return t&&"function"==typeof Symbol&&t.constructor===Symbol&&t!==Symbol.prototype?"symbol":typeof t};!function(){function n(t,n,r,i,e){"undefined"==typeof e&&(e=.5);var o=y.projectionratio(e,t),s=1-o,u={x:o*n.x+s*i.x,y:o*n.y+s*i.y},a=y.abcratio(e,t),f={x:r.x+(r.x-u.x)/a,y:r.y+(r.y-u.y)/a};return{A:f,B:r,C:u}}var e=Math.abs,o=Math.min,s=Math.max,u=Math.cos,a=Math.sin,f=Math.acos,c=Math.sqrt,h=Math.PI,x={x:0,y:0,z:0},y=r(2),p=r(3),l=function(t){var n=t&&t.forEach?t:[].slice.call(arguments),r=!1;if("object"===i(n[0])){r=n.length;var o=[];n.forEach(function(t){["x","y","z"].forEach(function(n){"undefined"!=typeof t[n]&&o.push(t[n])})}),n=o}var s=!1,u=n.length;if(r){if(r>4){if(1!==arguments.length)throw new Error("Only new Bezier(point[]) is accepted for 4th and higher order curves");s=!0}}else if(6!==u&&8!==u&&9!==u&&12!==u&&1!==arguments.length)throw new Error("Only new Bezier(point[]) is accepted for 4th and higher order curves");var a=!s&&(9===u||12===u)||t&&t[0]&&"undefined"!=typeof t[0].z;this._3d=a;for(var f=[],c=0,h=a?3:2;c<u;c+=h){var x={x:n[c],y:n[c+1]};a&&(x.z=n[c+2]),f.push(x)}this.order=f.length-1,this.points=f;var p=["x","y"];a&&p.push("z"),this.dims=p,this.dimlen=p.length,function(t){for(var n=t.order,r=t.points,i=y.align(r,{p1:r[0],p2:r[n]}),o=0;o<i.length;o++)if(e(i[o].y)>1e-4)return void(t._linear=!1);t._linear=!0}(this),this._t1=0,this._t2=1,this.update()};l.fromSVG=function(t){var n=t.match(/[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?/g).map(parseFloat),r=/[cq]/.test(t);return r?(n=n.map(function(t,r){return r<2?t:t+n[r%2]}),new l(n)):new l(n)},l.quadraticFromPoints=function(t,r,i,e){if("undefined"==typeof e&&(e=.5),0===e)return new l(r,r,i);if(1===e)return new l(t,r,r);var o=n(2,t,r,i,e);return new l(t,o.A,i)},l.cubicFromPoints=function(t,r,i,e,o){"undefined"==typeof e&&(e=.5);var s=n(3,t,r,i,e);"undefined"==typeof o&&(o=y.dist(r,s.C));var u=o*(1-e)/e,a=y.dist(t,i),f=(i.x-t.x)/a,c=(i.y-t.y)/a,h=o*f,x=o*c,p=u*f,v=u*c,d={x:r.x-h,y:r.y-x},m={x:r.x+p,y:r.y+v},g=s.A,z={x:g.x+(d.x-g.x)/(1-e),y:g.y+(d.y-g.y)/(1-e)},b={x:g.x+(m.x-g.x)/e,y:g.y+(m.y-g.y)/e},_={x:t.x+(z.x-t.x)/e,y:t.y+(z.y-t.y)/e},w={x:i.x+(b.x-i.x)/(1-e),y:i.y+(b.y-i.y)/(1-e)};return new l(t,_,w,i)};var v=function(){return y};l.getUtils=v,l.prototype={getUtils:v,valueOf:function(){return this.toString()},toString:function(){return y.pointsToString(this.points)},toSVG:function(t){if(this._3d)return!1;for(var n=this.points,r=n[0].x,i=n[0].y,e=["M",r,i,2===this.order?"Q":"C"],o=1,s=n.length;o<s;o++)e.push(n[o].x),e.push(n[o].y);return 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r.forEach(function(r){n=function(t){return t[r]},t=this.dpoints[0].map(n),i[r]=y.droots(t),3===this.order&&(t=this.dpoints[1].map(n),i[r]=i[r].concat(y.droots(t))),i[r]=i[r].filter(function(t){return t>=0&&t<=1}),e=e.concat(i[r].sort(y.numberSort))}.bind(this)),e=e.sort(y.numberSort).filter(function(t,n){return e.indexOf(t)===n}),i.values=e,i},bbox:function(){var t=this.extrema(),n={};return this.dims.forEach(function(r){n[r]=y.getminmax(this,r,t[r])}.bind(this)),n},overlaps:function(t){var n=this.bbox(),r=t.bbox();return y.bboxoverlap(n,r)},offset:function(t,n){if("undefined"!=typeof n){var r=this.get(t),i=this.normal(t),e={c:r,n:i,x:r.x+i.x*n,y:r.y+i.y*n};return this._3d&&(e.z=r.z+i.z*n),e}if(this._linear){var o=this.normal(0),s=this.points.map(function(n){var r={x:n.x+t*o.x,y:n.y+t*o.y};return n.z&&i.z&&(r.z=n.z+t*o.z),r});return[new l(s)]}var u=this.reduce();return u.map(function(n){return n.scale(t)})},simple:function(){if(3===this.order){var 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n,r,i,e,o=this.reduce(),s=o.length-2,u=[];for(n=0;n<s;n++)i=o.slice(n,n+1),e=o.slice(n+2),r=this.curveintersects(i,e,t),u=u.concat(r);return u},curveintersects:function(t,n,r){var i=[];t.forEach(function(t){n.forEach(function(n){t.overlaps(n)&&i.push({left:t,right:n})})});var e=[];return i.forEach(function(t){var n=y.pairiteration(t.left,t.right,r);n.length>0&&(e=e.concat(n))}),e},arcs:function(t){t=t||.5;var n=[];return this._iterate(t,n)},_error:function(t,n,r,i){var o=(i-r)/4,s=this.get(r+o),u=this.get(i-o),a=y.dist(t,n),f=y.dist(t,s),c=y.dist(t,u);return e(f-a)+e(c-a)},_iterate:function(t,n){var r,i=0,e=1;do{r=0,e=1;var o,s,f,c,h,x=this.get(i),p=!1,l=!1,v=e,d=1,m=0;do{l=p,c=f,v=(i+e)/2,m++,o=this.get(v),s=this.get(e),f=y.getccenter(x,o,s),f.interval={start:i,end:e};var g=this._error(f,x,i,e);if(p=g<=t,h=l&&!p,h||(d=e),p){if(e>=1){if(f.interval.end=d=1,c=f,e>1){var z={x:f.x+f.r*u(f.e),y:f.y+f.r*a(f.e)};f.e+=y.angle({x:f.x,y:f.y},z,this.get(1))}break}e+=(e-i)/2}else 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")+"]"},addCurve:function(t){this.curves.push(t),this._3d=this._3d||t._3d},length:function(){return this.curves.map(function(t){return t.length()}).reduce(function(t,n){return t+n})},curve:function(t){return this.curves[t]},bbox:function t(){for(var r=this.curves,t=r[0].bbox(),i=1;i<r.length;i++)n.expandbox(t,r[i].bbox());return t},offset:function t(n){var t=[];return this.curves.forEach(function(r){t=t.concat(r.offset(n))}),new i(t)}},t.exports=i}()}]);
class ParticleCanvas {
constructor(canvas, width, height) {
this.main = {
element: canvas
};
this.buffer = {
element: document.createElement("canvas")
};
this.main.context = this.main.element.getContext("2d");
this.buffer.context = this.buffer.element.getContext("2d");
this.main.element.width = this.buffer.element.width = this.width = width;
this.main.element.height = this.buffer.element.height = this.height = height;
this.makeParticles(400);
this.animate();
}
makeParticles(n) {
this.particles = [];
for (let i = 0; i < n; i++) {
this.particles.push(
new Particle(
this.width / 2 + Math.random() * this.width - this.width / 2,
this.height / 2 + Math.random() * this.height - this.height / 2,
Math.random() * 3 + 2,
"#919191",
"circle"
)
);
}
}
animate() {
this.main.context.clearRect(0, 0, this.width, this.height);
for (var i = 0; i < this.particles.length; i++) {
this.particles[i].x = this.particles[i].pathLut[this.particles[i].lutIndex].x;
this.particles[i].y = this.particles[i].pathLut[this.particles[i].lutIndex].y;
this.particles[i].draw(this.main.context);
if(this.particles[i].inverse) {
this.particles[i].lutIndex--;
}
else {
this.particles[i].lutIndex++;
}
if(this.particles[i].lutIndex == 0) {
this.particles[i].inverse = false;
}
if(this.particles[i].lutIndex >= this.particles[i].pathLut.length - 1) {
this.particles[i].inverse = true;
}
}
requestAnimationFrame(this.animate.bind(this));
}
}
class Particle {
constructor(x, y, radius, dotColor, particleShape) {
this.x = x;
this.y = y;
this.radius = radius;
this.dotColor = dotColor;
this.particleShape = particleShape;
this.bezierResolution = Math.floor(Math.random() * (1024 - 256)) + 256;
this.lutIndex = Math.floor(Math.random() * this.bezierResolution);
this.inverse = false;
var randoms = new Array(8);
for(var i = 0; i < 8; i++) {
randoms[i] = Math.floor(Math.random() * 400);
}
this.pathLut = new Bezier(
randoms[0],
randoms[1],
randoms[2],
randoms[3],
randoms[4],
randoms[5],
randoms[6],
randoms[7]
).getLUT(this.bezierResolution);
}
draw(context) {
context.save();
context.translate(this.x, this.y);
context.fillStyle = this.dotColor;
switch (this.particleShape) {
case "circle":
context.beginPath();
context.arc(0, 0, this.radius, 0, 2 * Math.PI);
context.fill();
break;
case "square":
context.fillRect(0, 0, this.radius * 2, this.radius * 2);
break;
}
context.restore();
}
}
new ParticleCanvas(document.querySelector("canvas"), 400, 400);<canvas></canvas>