Javascript 使用 HTML 5 和 JS 创建落雪
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原文地址: http://stackoverflow.com/questions/13983764/
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Creating Falling Snow using HTML 5 and JS
提问by L84
I visited the Stack Exchange Winter Bash websiteand I love the falling snow! My question is, how can I recreate a similar effect that looks as nice. I attempted to reverse engineer the code to see if I could figure it out but alas no luck there. The JS is over my head. I did a bit of googling and came across some examplesbut they were not as elegant as the SE site or did not look very good.
我访问了Stack Exchange Winter Bash 网站，我喜欢下雪！我的问题是，我怎样才能重新创建一个看起来不错的类似效果。我试图对代码进行逆向工程，看看我是否能弄清楚，但可惜没有运气。JS 在我头上。我用谷歌搜索了一下，发现了一些例子，但它们没有 SE 网站那么优雅，或者看起来不太好。
Can anyone provide some instructions on how to replicate what the SE Winter Bash site creates or a place where I might learn how to do this?
任何人都可以提供一些有关如何复制 SE Winter Bash 站点创建的内容或我可以学习如何执行此操作的地方的说明吗？
Edit:I would like to replicate the effect as close as possible, IE: falling snow with snowflakes, and being able to move the mouse and cause the snow to move or swirl with the mouse moments.
编辑：我想尽可能地复制效果，即：雪花飘落，并且能够移动鼠标并使雪随着鼠标时刻移动或旋转。
回答by Loktar
Great question, I actually wrote a snow plugin a while ago that I continually update see it in action. Also a link to the pure js source
好问题，实际上我不久前写了一个雪插件，我会不断更新查看它的实际效果。还有一个指向纯js源的链接
I noticed you tagged the question html5 and canvas, however you can do it without using either, and just standard elements with images or different background colors.
我注意到你标记了问题 html5 和 canvas，但是你可以不使用任何一个，只使用带有图像或不同背景颜色的标准元素。
Here's two really simple ones I put together just now for you to mess with. The key in my opinion is using sin to get the nice wavy effect as the flakes fall. The first one uses the canvas element, the 2nd one uses regular dom elements.
这是我刚刚整理的两个非常简单的内容，供您使用。在我看来，关键是使用 sin 来在薄片落下时获得漂亮的波浪效果。第一个使用 canvas 元素，第二个使用常规 dom 元素。
Since I'm absolutely addicted to canvas here's a canvas version that performs quite nicely in my opinion.
由于我完全沉迷于画布，这里有一个画布版本，在我看来表现相当不错。
(function() {
var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000 / 60);
};
window.requestAnimationFrame = requestAnimationFrame;
})();
var flakes = [],
canvas = document.getElementById("canvas"),
ctx = canvas.getContext("2d"),
flakeCount = 200,
mX = -100,
mY = -100
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
function snow() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (var i = 0; i < flakeCount; i++) {
var flake = flakes[i],
x = mX,
y = mY,
minDist = 150,
x2 = flake.x,
y2 = flake.y;
var dist = Math.sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y)),
dx = x2 - x,
dy = y2 - y;
if (dist < minDist) {
var force = minDist / (dist * dist),
xcomp = (x - x2) / dist,
ycomp = (y - y2) / dist,
deltaV = force / 2;
flake.velX -= deltaV * xcomp;
flake.velY -= deltaV * ycomp;
} else {
flake.velX *= .98;
if (flake.velY <= flake.speed) {
flake.velY = flake.speed
}
flake.velX += Math.cos(flake.step += .05) * flake.stepSize;
}
ctx.fillStyle = "rgba(255,255,255," + flake.opacity + ")";
flake.y += flake.velY;
flake.x += flake.velX;
if (flake.y >= canvas.height || flake.y <= 0) {
reset(flake);
}
if (flake.x >= canvas.width || flake.x <= 0) {
reset(flake);
}
ctx.beginPath();
ctx.arc(flake.x, flake.y, flake.size, 0, Math.PI * 2);
ctx.fill();
}
requestAnimationFrame(snow);
};
function reset(flake) {
flake.x = Math.floor(Math.random() * canvas.width);
flake.y = 0;
flake.size = (Math.random() * 3) + 2;
flake.speed = (Math.random() * 1) + 0.5;
flake.velY = flake.speed;
flake.velX = 0;
flake.opacity = (Math.random() * 0.5) + 0.3;
}
function init() {
for (var i = 0; i < flakeCount; i++) {
var x = Math.floor(Math.random() * canvas.width),
y = Math.floor(Math.random() * canvas.height),
size = (Math.random() * 3) + 2,
speed = (Math.random() * 1) + 0.5,
opacity = (Math.random() * 0.5) + 0.3;
flakes.push({
speed: speed,
velY: speed,
velX: 0,
x: x,
y: y,
size: size,
stepSize: (Math.random()) / 30,
step: 0,
angle: 180,
opacity: opacity
});
}
snow();
};
canvas.addEventListener("mousemove", function(e) {
mX = e.clientX,
mY = e.clientY
});
init();?
var flakes = [],
bodyHeight = getDocHeight(),
bodyWidth = document.body.offsetWidth;
function snow() {
for (var i = 0; i < 50; i++) {
var flake = flakes[i];
flake.y += flake.velY;
if (flake.y > bodyHeight - (flake.size + 6)) {
flake.y = 0;
}
flake.el.style.top = flake.y + 'px';
flake.el.style.left = ~~flake.x + 'px';
flake.step += flake.stepSize;
flake.velX = Math.cos(flake.step);
flake.x += flake.velX;
if (flake.x > bodyWidth - 40 || flake.x < 30) {
flake.y = 0;
}
}
setTimeout(snow, 10);
};
function init() {
var docFrag = document.createDocumentFragment();
for (var i = 0; i < 50; i++) {
var flake = document.createElement("div"),
x = Math.floor(Math.random() * bodyWidth),
y = Math.floor(Math.random() * bodyHeight),
size = (Math.random() * 5) + 2,
speed = (Math.random() * 1) + 0.5;
flake.style.width = size + 'px';
flake.style.height = size + 'px';
flake.style.background = "#fff";
flake.style.left = x + 'px';
flake.style.top = y;
flake.classList.add("flake");
flakes.push({
el: flake,
speed: speed,
velY: speed,
velX: 0,
x: x,
y: y,
size: 2,
stepSize: (Math.random() * 5) / 100,
step: 0
});
docFrag.appendChild(flake);
}
document.body.appendChild(docFrag);
snow();
};
document.addEventListener("mousemove", function(e) {
var x = e.clientX,
y = e.clientY,
minDist = 150;
for (var i = 0; i < flakes.length; i++) {
var x2 = flakes[i].x,
y2 = flakes[i].y;
var dist = Math.sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y));
if (dist < minDist) {
rad = Math.atan2(y2, x2), angle = rad / Math.PI * 180;
flakes[i].velX = (x2 / dist) * 0.2;
flakes[i].velY = (y2 / dist) * 0.2;
flakes[i].x += flakes[i].velX;
flakes[i].y += flakes[i].velY;
} else {
flakes[i].velY *= 0.9;
flakes[i].velX
if (flakes[i].velY <= flakes[i].speed) {
flakes[i].velY = flakes[i].speed;
}
}
}
});
init();
function getDocHeight() {
return Math.max(
Math.max(document.body.scrollHeight, document.documentElement.scrollHeight), Math.max(document.body.offsetHeight, document.documentElement.offsetHeight), Math.max(document.body.clientHeight, document.documentElement.clientHeight));
}?
回答by Niet the Dark Absol
The falling snow is simple: Create a canvas, create a bunch of snowflakes, draw them.
下雪很简单：创建一个画布，创建一堆雪花，绘制它们。
You can create a snowflake class like so:
你可以像这样创建一个雪花类：
function Snowflake() {
this.x = Math.random()*canvas.width;
this.y = -16;
this.speed = Math.random()*3+1;
this.direction = Math.random()*360;
this.maxSpeed = 4;
}
Or something like that. Then you have a timer that, each step, adjusts each snowflake's direction by a small amount, and then calculates its new X and Y by factoring in the Speed and Direction.
或类似的东西。然后你有一个计时器，它每一步都会少量调整每个雪花的方向，然后通过考虑速度和方向来计算新的 X 和 Y。
It's hard to explain, but actually quite basic.
这很难解释，但实际上非常基本。
