我正在使用 Codepen 演示,但在检查 Chrome 中的 CPU 使用率后,它使用了大约 100% 的 CPU。经过努力,我无法解决问题,因为我不是 javascript 和 canvas 方面的专家。我需要进行哪些修改才能使其使用更少的 CPU。 Codepen Link 根据我的理解,问题出在粒子动画上,或者也许我错了。
// Global Animation Setting
window.requestAnimFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000/60);
};
// Global Canvas Setting
var canvas = document.getElementById('particle');
var ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Particles Around the Parent
function Particle(x, y, distance) {
this.angle = Math.random() * 2 * Math.PI;
this.radius = Math.random() ;
this.opacity = (Math.random()*5 + 2)/10;
this.distance = (1/this.opacity)*distance;
this.speed = this.distance*0.00003;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw = function() {
ctx.fillStyle = "rgba(255,255,255," + this.opacity + ")";
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
ctx.fill();
ctx.closePath();
}
this.update = function() {
this.angle += this.speed;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw();
}
}
function Emitter(x, y) {
this.position = { x: x, y: y};
this.radius = 30;
this.count = 3000;
this.particles = [];
for(var i=0; i< this.count; i ++ ){
this.particles.push(new Particle(this.position.x, this.position.y, this.radius));
}
}
Emitter.prototype = {
draw: function() {
ctx.fillStyle = "rgba(0,0,0,1)";
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
ctx.fill();
ctx.closePath();
},
update: function() {
for(var i=0; i< this.count; i++) {
this.particles[i].update();
}
this.draw();
}
}
var emitter = new Emitter(canvas.width/2, canvas.height/2);
function loop() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
emitter.update();
requestAnimFrame(loop);
}
loop();
body{background:#000;}
<canvas id="particle"></canvas>
最佳答案
尽可能避免半透明。
使用 alpha 进行绘画是 CPU killer ,通过使用纯色尽可能避免混合:
// Global Animation Setting
window.requestAnimFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000/60);
};
// Global Canvas Setting
var canvas = document.getElementById('particle');
var ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Particles Around the Parent
function Particle(x, y, distance) {
this.angle = Math.random() * 2 * Math.PI;
this.radius = Math.random() ;
this.opacity = (Math.random()*5 + 2)/10;
// convert to solid color '#nnnnnn'
this.color = '#' + Math.floor((this.opacity * 255)).toString(16).padStart(2, 0).repeat(3);
this.distance = (1/this.opacity)*distance;
this.speed = this.distance*0.00003;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw = function() {
ctx.fillStyle = this.color;
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
ctx.fill();
ctx.closePath();
}
this.update = function() {
this.angle += this.speed;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw();
}
}
function Emitter(x, y) {
this.position = { x: x, y: y};
this.radius = 30;
this.count = 3000;
this.particles = [];
for(var i=0; i< this.count; i ++ ){
this.particles.push(new Particle(this.position.x, this.position.y, this.radius));
}
}
Emitter.prototype = {
draw: function() {
ctx.fillStyle = "rgba(0,0,0,1)";
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
ctx.fill();
ctx.closePath();
},
update: function() {
for(var i=0; i< this.count; i++) {
this.particles[i].update();
}
this.draw();
}
}
var emitter = new Emitter(canvas.width/2, canvas.height/2);
function loop() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
emitter.update();
requestAnimFrame(loop);
}
loop();
body{background:#000;}
<canvas id="particle"></canvas>
但这还不够,
尽可能避免绘画。
Canvas 上的绘制操作非常慢(与非绘制操作相比),应尽可能避免。为此,您可以按颜色对粒子进行排序,并通过单个 Path 对象的堆栈来绘制它们,但这需要我们对 opacity
值进行舍入(在固化时完成) > 颜色)。
// Global Animation Setting
window.requestAnimFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000/60);
};
// Global Canvas Setting
var canvas = document.getElementById('particle');
var ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Particles Around the Parent
function Particle(x, y, distance) {
this.angle = Math.random() * 2 * Math.PI;
this.radius = Math.random() ;
this.opacity = (Math.random()*5 + 2)/10;
// convert to solid color '#nnnnnn'
this.color = '#' + Math.floor((this.opacity * 255)).toString(16).padStart(2, 0).repeat(3);
this.distance = (1/this.opacity)*distance;
this.speed = this.distance*0.00003;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw = function() {
// here we remove everything but the 'arc' operation and a moveTo
// no paint
ctx.moveTo(this.position.x + this.radius, this.position.y);
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
}
this.update = function() {
this.angle += this.speed;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
// 'update' should not 'draw'
// this.draw();
}
}
function Emitter(x, y) {
this.position = { x: x, y: y};
this.radius = 30;
this.count = 3000;
this.particles = [];
for(var i=0; i< this.count; i ++ ){
this.particles.push(new Particle(this.position.x, this.position.y, this.radius));
}
// sort our particles by color (opacity = color)
this.particles.sort(function(a, b) {
return a.opacity - b.opacity;
});
}
Emitter.prototype = {
draw: function() {
ctx.fillStyle = "rgba(0,0,0,1)";
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
ctx.fill();
// draw our particles in batches
var particle, color;
ctx.beginPath();
for(var i=0; i<this.count; i++) {
particle = this.particles[i];
if(color !== particle.color) {
ctx.fill();
ctx.beginPath();
ctx.fillStyle = color = particle.color;
}
particle.draw();
}
ctx.fill(); // fill the last batch
},
update: function() {
for(var i=0; i< this.count; i++) {
this.particles[i].update();
}
this.draw();
}
}
var emitter = new Emitter(canvas.width/2, canvas.height/2);
function loop() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
emitter.update();
requestAnimFrame(loop);
}
loop();
body{background:#000;}
<canvas id="particle"></canvas>
这更好,但还不够完美......
最后,要巧妙地设计你的动画。
在动画中,不透明度定义距离。也就是说,离中心越远的粒子是最透明的。这准确地定义了径向渐变是什么。
因此,我们可以将绘制操作减少到两次。是的,3000 个粒子只需两次绘制,使用径向渐变和一些合成,我们可以首先在一次拍摄中绘制所有粒子,然后将渐变应用为将应用的蒙版它的颜色只在已经画过东西的地方。我们甚至可以保持透明度。
// Global Animation Setting
window.requestAnimFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000/60);
};
// Global Canvas Setting
var canvas = document.getElementById('particle');
var ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Particles Around the Parent
function Particle(x, y, distance) {
this.angle = Math.random() * 2 * Math.PI;
this.radius = Math.random() ;
this.opacity = (Math.random()*5 + 2)/10;
this.distance = (1/this.opacity)*distance;
this.speed = this.distance*0.00003;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw = function() {
// still no paint here
ctx.moveTo(this.position.x + this.radius, this.position.y);
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
}
this.update = function() {
this.angle += this.speed;
this.position = {
x: x + this.distance * Math.cos(this.angle),
y: y + this.distance * Math.sin(this.angle)
};
this.draw();
}
}
function Emitter(x, y) {
this.position = { x: x, y: y};
this.radius = 30;
this.count = 3000;
this.particles = [];
for(var i=0; i< this.count; i ++ ){
this.particles.push(new Particle(this.position.x, this.position.y, this.radius));
}
// a radial gradient that we will use as mask
// in particle.constructor
// opacities go from 0.2 to 0.7
// with a distance range of [radius, 1 / 0.2 * this.radius]
this.grad = ctx.createRadialGradient(x, y, this.radius, x, y, 1 / 0.2 * this.radius);
this.grad.addColorStop(0, 'rgba(255,255,255,0.7)');
this.grad.addColorStop(1, 'rgba(255,255,255,0.2)');
}
Emitter.prototype = {
draw: function() {
ctx.fillStyle = "rgba(0,0,0,1)";
ctx.beginPath();
ctx.arc(this.position.x, this.position.y, this.radius, 0, Math.PI*2, false);
ctx.fill();
ctx.closePath();
},
update: function() {
ctx.beginPath(); // one Path
ctx.fillStyle = 'black'; // a solid color
for(var i=0; i< this.count; i++) {
this.particles[i].update();
}
ctx.fill(); // one paint
// prepare the composite operation
ctx.globalCompositeOperation = 'source-in';
ctx.fillStyle = this.grad; // our gradient
ctx.fillRect(0,0,canvas.width, canvas.height); // cover the whole canvas
// reset for next paints (center arc and next frame's clearRect)
ctx.globalCompositeOperation = 'source-over';
this.draw();
}
}
var emitter = new Emitter(canvas.width/2, canvas.height/2);
function loop() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
emitter.update();
requestAnimFrame(loop);
}
loop();
body{background:#000;}
<canvas id="particle"></canvas>
关于javascript - 在 Chrome 中使用高 CPU 的 Canvas ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54579859/