Nieve que se acumula al final de la página

En una entrada anterior habíamos visto como conseguir un efecto de nieve en el blog mediante el uso de la etiqueta "marquee" y poco después veíamos como incluir el efecto nieve usando un script.

En esta ocasión vamos a ver de nuevo como incluir nieve en el blog mediante el uso de un script. El script irá incluido directamente en la plantilla y lo he "marcado" para que, una vez pasadas las fiestas, sea fácil su localización para retirarlo.

Este script consigue un efecto muy lindo, ya que los copos que van cayendo quedan acumulados al final de la página y mientras unos caen, los del pie de la página se van deshaciendo poco a poco...
Además si movemos el ratón por la pagina, los copos cambian de dirección como movidos por un ligero viento.

Antes de decidir si vais a usarlo o no, podéis ver una demostración online en un blog donde también e incluido el script para copiar.

Lo único que hemos de hacer para conseguir el efecto nieve, es copiar el script y colocarlo en el código de nuestra plantilla antes de </head>

<!-- Comienzo del script para nieve -->

<script type="text/javascript">
//<![CDATA[

/*
DHTML Snowstorm! OO-style Jascript-based Snow effect
----------------------------------------------------
Version 1.4.20091115 (Previous rev: v1.3.20081215)
Code by Scott Schiller - http://schillmania.com
----------------------------------------------------

Initializes after body onload() by default (via addEventHandler() call at bottom.)
To customize properties, edit below or override configuration after this script
has run (but before body.onload), eg. snowStorm.snowStick = false;

*/

var snowStorm = null;

function SnowStorm() {

// --- PROPERTIES ---

this.flakesMax = 150; // Limit total amount of snow made (falling + sticking)
this.flakesMaxActive = 64; // Limit amount of snow falling at once (less = lower CPU use)
this.animationInterval = 33; // Theoretical "miliseconds per frame" measurement. 20 = fast + smooth, but high CPU use. 50 = more conservative, but slower
this.flakeBottom = null; // Integer for Y axis snow limit, 0 or null for "full-screen" snow effect
this.targetElement = null; // element which snow will be appended to (document body if null/undefined) - can be an element ID string, or a DOM node reference
this.followMouse = true; // Snow will change movement with the user's mouse
this.snowColor = '#fff'; // Don't eat (or use?) yellow snow.
this.snowCharacter = '&bull;'; // &bull; = bullet, &middot; is square on some systems etc.
this.snowStick = true; // Whether or not snow should "stick" at the bottom. When off, will never collect.
this.useMeltEffect = true; // When recycling fallen snow (or rarely, when falling), have it "melt" and fade out if browser supports it
this.useTwinkleEffect = false; // Allow snow to randomly "flicker" in and out of view while falling
this.usePositionFixed = false; // true = snow not affected by window scroll. may increase CPU load, disabled by default - if enabled, used only where supported

// --- less-used bits ---

this.flakeLeftOffset = 0; // amount to subtract from edges of container
this.flakeRightOffset = 0; // amount to subtract from edges of container
this.flakeWidth = 8; // max pixel width for snow element
this.flakeHeight = 8; // max pixel height for snow element
this.vMaxX = 5; // Maximum X velocity range for snow
this.vMaxY = 4; // Maximum Y velocity range
this.zIndex = 0; // CSS stacking order applied to each snowflake

// --- End of user section ---

// jslint global declarations
/*global window, document, navigator, clearInterval, setInterval */

var addEvent = (typeof(window.attachEvent)=='undefined'?function(o,evtName,evtHandler) {
return o.addEventListener(evtName,evtHandler,false);
}:function(o,evtName,evtHandler) {
return o.attachEvent('on'+evtName,evtHandler);
});

var removeEvent = (typeof(window.attachEvent)=='undefined'?function(o,evtName,evtHandler) {
return o.removeEventListener(evtName,evtHandler,false);
}:function(o,evtName,evtHandler) {
return o.detachEvent('on'+evtName,evtHandler);
});

function rnd(n,min) {
if (isNaN(min)) {
min = 0;
}
return (Math.random()*n)+min;
}

function plusMinus(n) {
return (parseInt(rnd(2),10)==1?n*-1:n);
}

var s = this;
var storm = this;
this.timers = [];
this.flakes = [];
this.disabled = false;
this.active = false;

var isIE = navigator.userAgent.match(/msie/i);
var isIE6 = navigator.userAgent.match(/msie 6/i);
var isOldIE = (isIE && (isIE6 || navigator.userAgent.match(/msie 5/i)));
var isWin9X = navigator.appVersion.match(/windows 98/i);
var isiPhone = navigator.userAgent.match(/iphone/i);
var isBackCompatIE = (isIE && document.compatMode == 'BackCompat');
var noFixed = ((isBackCompatIE || isIE6 || isiPhone)?true:false);
var screenX = null;
var screenX2 = null;
var screenY = null;
var scrollY = null;
var vRndX = null;
var vRndY = null;
var windOffset = 1;
var windMultiplier = 2;
var flakeTypes = 6;
var fixedForEverything = false;
var opacitySupported = (function(){
try {
document.createElement('div').style.opacity = '0.5';
} catch (e) {
return false;
}
return true;
})();
var docFrag = document.createDocumentFragment();
if (s.flakeLeftOffset === null) {
s.flakeLeftOffset = 0;
}
if (s.flakeRightOffset === null) {
s.flakeRightOffset = 0;
}

this.meltFrameCount = 20;
this.meltFrames = [];
for (var i=0; i<this.meltFrameCount; i++) {
this.meltFrames.push(1-(i/this.meltFrameCount));
}

this.randomizeWind = function() {
vRndX = plusMinus(rnd(s.vMaxX,0.2));
vRndY = rnd(s.vMaxY,0.2);
if (this.flakes) {
for (var i=0; i<this.flakes.length; i++) {
if (this.flakes[i].active) {
this.flakes[i].setVelocities();
}
}
}
};

this.scrollHandler = function() {
// "attach" snowflakes to bottom of window if no absolute bottom value was given
scrollY = (s.flakeBottom?0:parseInt(window.scrollY||document.documentElement.scrollTop||document.body.scrollTop,10));
if (isNaN(scrollY)) {
scrollY = 0; // Netscape 6 scroll fix
}
if (!fixedForEverything && !s.flakeBottom && s.flakes) {
for (var i=s.flakes.length; i--;) {
if (s.flakes[i].active === 0) {
s.flakes[i].stick();
}
}
}
};

this.resizeHandler = function() {
if (window.innerWidth || window.innerHeight) {
screenX = window.innerWidth-(!isIE?16:2)-s.flakeRightOffset;
screenY = (s.flakeBottom?s.flakeBottom:window.innerHeight);
} else {
screenX = (document.documentElement.clientWidth||document.body.clientWidth||document.body.scrollWidth)-(!isIE?8:0)-s.flakeRightOffset;
screenY = s.flakeBottom?s.flakeBottom:(document.documentElement.clientHeight||document.body.clientHeight||document.body.scrollHeight);
}
screenX2 = parseInt(screenX/2,10);
};

this.resizeHandlerAlt = function() {
screenX = s.targetElement.offsetLeft+s.targetElement.offsetWidth-s.flakeRightOffset;
screenY = s.flakeBottom?s.flakeBottom:s.targetElement.offsetTop+s.targetElement.offsetHeight;
screenX2 = parseInt(screenX/2,10);
};

this.freeze = function() {
// pause animation
if (!s.disabled) {
s.disabled = 1;
} else {
return false;
}
for (var i=s.timers.length; i--;) {
clearInterval(s.timers[i]);
}
};

this.resume = function() {
if (s.disabled) {
s.disabled = 0;
} else {
return false;
}
s.timerInit();
};

this.toggleSnow = function() {
if (!s.flakes.length) {
// first run
s.start();
} else {
s.active = !s.active;
if (s.active) {
s.show();
s.resume();
} else {
s.stop();
s.freeze();
}
}
};

this.stop = function() {
this.freeze();
for (var i=this.flakes.length; i--;) {
this.flakes[i].o.style.display = 'none';
}
removeEvent(window,'scroll',s.scrollHandler);
removeEvent(window,'resize',s.resizeHandler);
if (!isOldIE) {
removeEvent(window,'blur',s.freeze);
removeEvent(window,'focus',s.resume);
}
};

this.show = function() {
for (var i=this.flakes.length; i--;) {
this.flakes[i].o.style.display = 'block';
}
};

this.SnowFlake = function(parent,type,x,y) {
var s = this;
var storm = parent;
this.type = type;
this.x = x||parseInt(rnd(screenX-20),10);
this.y = (!isNaN(y)?y:-rnd(screenY)-12);
this.vX = null;
this.vY = null;
this.vAmpTypes = [1,1.2,1.4,1.6,1.8]; // "amplification" for vX/vY (based on flake size/type)
this.vAmp = this.vAmpTypes[this.type];
this.melting = false;
this.meltFrameCount = storm.meltFrameCount;
this.meltFrames = storm.meltFrames;
this.meltFrame = 0;
this.twinkleFrame = 0;
this.active = 1;
this.fontSize = (10+(this.type/5)*10);
this.o = document.createElement('div');
this.o.innerHTML = storm.snowCharacter;
this.o.style.color = storm.snowColor;
this.o.style.position = (fixedForEverything?'fixed':'absolute');
this.o.style.width = storm.flakeWidth+'px';
this.o.style.height = storm.flakeHeight+'px';
this.o.style.fontFamily = 'arial,verdana';
this.o.style.overflow = 'hidden';
this.o.style.fontWeight = 'normal';
this.o.style.zIndex = storm.zIndex;
docFrag.appendChild(this.o);

this.refresh = function() {
if (isNaN(s.x) || isNaN(s.y)) {
// safety check
return false;
}
s.o.style.left = s.x+'px';
s.o.style.top = s.y+'px';
};

this.stick = function() {
if (noFixed || (storm.targetElement != document.documentElement && storm.targetElement != document.body)) {
s.o.style.top = (screenY+scrollY-storm.flakeHeight)+'px';
} else if (storm.flakeBottom) {
s.o.style.top = storm.flakeBottom+'px';
} else {
s.o.style.display = 'none';
s.o.style.top = 'auto';
s.o.style.bottom = '0px';
s.o.style.position = 'fixed';
s.o.style.display = 'block';
}
};

this.vCheck = function() {
if (s.vX>=0 && s.vX<0.2) {
s.vX = 0.2;
} else if (s.vX<0 && s.vX>-0.2) {
s.vX = -0.2;
}
if (s.vY>=0 && s.vY<0.2) {
s.vY = 0.2;
}
};

this.move = function() {
var vX = s.vX*windOffset;
s.x += vX;
s.y += (s.vY*s.vAmp);
if (s.x >= screenX || screenX-s.x < storm.flakeWidth) { // X-axis scroll check
s.x = 0;
} else if (vX < 0 && s.x-storm.flakeLeftOffset<0-storm.flakeWidth) {
s.x = screenX-storm.flakeWidth-1; // flakeWidth;
}
s.refresh();
var yDiff = screenY+scrollY-s.y;
if (yDiff<storm.flakeHeight) {
s.active = 0;
if (storm.snowStick) {
s.stick();
} else {
s.recycle();
}
} else {
if (storm.useMeltEffect && s.active && s.type < 3 && !s.melting && Math.random()>0.998) {
// ~1/1000 chance of melting mid-air, with each frame
s.melting = true;
s.melt();
// only incrementally melt one frame
// s.melting = false;
}
if (storm.useTwinkleEffect) {
if (!s.twinkleFrame) {
if (Math.random()>0.9) {
s.twinkleFrame = parseInt(Math.random()*20,10);
}
} else {
s.twinkleFrame--;
s.o.style.visibility = (s.twinkleFrame && s.twinkleFrame%2===0?'hidden':'visible');
}
}
}
};

this.animate = function() {
// main animation loop
// move, check status, die etc.
s.move();
};

this.setVelocities = function() {
s.vX = vRndX+rnd(storm.vMaxX*0.12,0.1);
s.vY = vRndY+rnd(storm.vMaxY*0.12,0.1);
};

this.setOpacity = function(o,opacity) {
if (!opacitySupported) {
return false;
}
o.style.opacity = opacity;
};

this.melt = function() {
if (!storm.useMeltEffect || !s.melting) {
s.recycle();
} else {
if (s.meltFrame < s.meltFrameCount) {
s.meltFrame++;
s.setOpacity(s.o,s.meltFrames[s.meltFrame]);
s.o.style.fontSize = s.fontSize-(s.fontSize*(s.meltFrame/s.meltFrameCount))+'px';
s.o.style.lineHeight = storm.flakeHeight+2+(storm.flakeHeight*0.75*(s.meltFrame/s.meltFrameCount))+'px';
} else {
s.recycle();
}
}
};

this.recycle = function() {
s.o.style.display = 'none';
s.o.style.position = (fixedForEverything?'fixed':'absolute');
s.o.style.bottom = 'auto';
s.setVelocities();
s.vCheck();
s.meltFrame = 0;
s.melting = false;
s.setOpacity(s.o,1);
s.o.style.padding = '0px';
s.o.style.margin = '0px';
s.o.style.fontSize = s.fontSize+'px';
s.o.style.lineHeight = (storm.flakeHeight+2)+'px';
s.o.style.textAlign = 'center';
s.o.style.verticalAlign = 'baseline';
s.x = parseInt(rnd(screenX-storm.flakeWidth-20),10);
s.y = parseInt(rnd(screenY)*-1,10)-storm.flakeHeight;
s.refresh();
s.o.style.display = 'block';
s.active = 1;
};

this.recycle(); // set up x/y coords etc.
this.refresh();

};

this.snow = function() {
var active = 0;
var used = 0;
var waiting = 0;
var flake = null;
for (var i=s.flakes.length; i--;) {
if (s.flakes[i].active == 1) {
s.flakes[i].move();
active++;
} else if (s.flakes[i].active === 0) {
used++;
} else {
waiting++;
}
if (s.flakes[i].melting) {
s.flakes[i].melt();
}
}
if (active<s.flakesMaxActive) {
flake = s.flakes[parseInt(rnd(s.flakes.length),10)];
if (flake.active === 0) {
flake.melting = true;
}
}
};

this.mouseMove = function(e) {
if (!s.followMouse) {
return true;
}
var x = parseInt(e.clientX,10);
if (x<screenX2) {
windOffset = -windMultiplier+(x/screenX2*windMultiplier);
} else {
x -= screenX2;
windOffset = (x/screenX2)*windMultiplier;
}
};

this.createSnow = function(limit,allowInactive) {
for (var i=0; i<limit; i++) {
s.flakes[s.flakes.length] = new s.SnowFlake(s,parseInt(rnd(flakeTypes),10));
if (allowInactive || i>s.flakesMaxActive) {
s.flakes[s.flakes.length-1].active = -1;
}
}
storm.targetElement.appendChild(docFrag);
};

this.timerInit = function() {
s.timers = (!isWin9X?[setInterval(s.snow,s.animationInterval)]:[setInterval(s.snow,s.animationInterval*3),setInterval(s.snow,s.animationInterval)]);
};

this.init = function() {
s.randomizeWind();
s.createSnow(s.flakesMax); // create initial batch
addEvent(window,'resize',s.resizeHandler);
addEvent(window,'scroll',s.scrollHandler);
if (!isOldIE) {
addEvent(window,'blur',s.freeze);
addEvent(window,'focus',s.resume);
}
s.resizeHandler();
s.scrollHandler();
if (s.followMouse) {
addEvent(document,'mousemove',s.mouseMove);
}
s.animationInterval = Math.max(20,s.animationInterval);
s.timerInit();
};

var didInit = false;

this.start = function(bFromOnLoad) {
if (!didInit) {
didInit = true;
} else if (bFromOnLoad) {
// already loaded and running
return true;
}
if (typeof s.targetElement == 'string') {
var targetID = s.targetElement;
s.targetElement = document.getElementById(targetID);
if (!s.targetElement) {
throw new Error('Snowstorm: Unable to get targetElement "'+targetID+'"');
}
}
if (!s.targetElement) {
s.targetElement = (!isIE?(document.documentElement?document.documentElement:document.body):document.body);
}
if (s.targetElement != document.documentElement && s.targetElement != document.body) {
s.resizeHandler = s.resizeHandlerAlt; // re-map handler to get element instead of screen dimensions
}
s.resizeHandler(); // get bounding box elements
s.usePositionFixed = (s.usePositionFixed && !noFixed); // whether or not position:fixed is supported
fixedForEverything = s.usePositionFixed;
if (screenX && screenY && !s.disabled) {
s.init();
s.active = true;
}
};

function doStart() {
s.start(true);
}

if (document.addEventListener) {
// safari 3.0.4 doesn't do DOMContentLoaded, maybe others - use a fallback to be safe.
document.addEventListener('DOMContentLoaded',doStart,false);
window.addEventListener('load',doStart,false);
} else {
addEvent(window,'load',doStart);
}

}

snowStorm = new SnowStorm();
//]]>
</script>

<!-- Fin del script para nieve -->

Notas:

[1] He respetado los créditos al autor original: Schillmania, pienso que no sería pedir demasiado hicieseis lo mismo todos y no borraseis esa parte en el script...

[2] Una cosa a tener en cuenta, es que el efecto nieve también será visible en la parte de Diseño de nuestro blog, esto es normal y además he comprobado que no da ningún problema, aunque si en algún caso eso sucediese bastaría retirar el script.

[3] Para retirar el script una vez no queramos usarlo, nos fijaremos en las anotaciones que he puesto al comienzo y al final y que he destacado en color rojo en el código y borramos todo desde la primera anotación a la última, ambas incluidas.

[4] Hay algunos cambios que podemos hacer, aunque yo personalmente lo dejaría como est... cabe destacar que podemos aumentar la cantidad de copos de nieve en esta línea del script:

this.flakesMax = 150;

Script original de: Schillmania