// JavaScript Document
/****************************************** 
* Titre:	De la neige !!!
* Réécrit par Spacefrog	
* Date: 	12/2009
******************************************/ 
var IsIE6 = !!document.all && !window.XMLHttpRequest
  
var ext=(IsIE6)?'gif':'png';	
 
var IsIE=!!document.all; 
  
	  var snowsrc=new Image();
	  snowsrc.src="images/snowflake."+ext 
	  var snowsrc1= new Image;
	  snowsrc1.src="images/snowflake1." +ext	  
			  
  // Configure below to change number of snow to render 
var densite = 50; 
 
 
 
var dx, xp, yp;    // coordinate and position variables 
var am, vx, vy;  // amplitude and step variables 
var i, doc_width , doc_height ; 
var vitesseH = 1 //coefficient de vitesse de balancement
var changevent=true // pour ajouter la variation du sens et de l'intesité du vent
var vent =new Array(10,0,-10,-20,0,-5,-10,-5,-3,0,2,3,5,10,20,30,50,60,80,70,50,30,10,0,-1,-5,-10,-20);//Vent de travers  positif=> G à D _ négatif => D à G.
var forceH=0;
var drift=10; 
 
var changechute=true
var chute= new Array(1,2,3,2,1,1,2,3,4,5,4,3,5,4,6,4,2,3,2,1,1,1,1,1,1) //Vitesse de chute des flocons de 1 à 10
var forceV=0 
var vitesseV = 1 //coefficient de vitesse de chute
 
var dx = new Array(); 
var xp = new Array(); 
var yp = new Array(); 
var am = new Array(); 
var vx = new Array(); 
var vy = new Array(); 
  
function init(){
	  
	//Densité de flocons:
	doc_width = document.body.offsetWidth; 
    doc_height = document.body.offsetHeight;   
	densite=Math.floor(doc_width/10);
	
 
	var flake= document.createElement('img');
	flake.style.border='0';
	flake.style.width="auto";
	flake.style.height="auto";
			
	var flakediv=document.createElement('div');
	    flakediv.style.position='absolute';
		flakediv.style.top='15px';
		flakediv.style.left='15px';
		flakediv.style.display="none";
		
	//Position des flocons
	for (i = 0; i < densite;  i++) {  
		dx[i] = 0;                        // set coordonnés variables 
		xp[i] = Math.random()*(doc_width-50);  // positions variables 
		yp[i] = Math.random()*doc_height; 
		am[i] = Math.random()*40;         // amplitude de balancement 
		vx[i] = 0.02 + Math.random()/10 * vitesseH; // vitesse horizontale variable 
		vy[i] = 0.9 + Math.random() * vitesseV;     // vitesse verticale variable 
	
	
		var opacite=Math.random()*100;
		var newflake=flakediv.cloneNode(true);
		newflake.id="flocon"+i;
		newflake.zIndex=i+1;
		newpic=flake.cloneNode(true);
		newpic.src=(i % 2==0)?snowsrc.src:snowsrc1.src;
		newflake.appendChild(newpic);
		IsIE?newflake.style.filter="alpha(opacity="+opacite+")":newflake.style.opacity=opacite/100;
		document.body.appendChild(newflake);
	}
	var neige=setInterval(function(){snow()},30);  
	if (changevent==true){ var girouette=setInterval(function(){wind()},4250);
		}
	if (changechute==true){ var intesite=setInterval(function(){fall()},7130);
		}
	}	
  
function wind(){
	drift = vent[forceH]
	forceH++	
	forceH=(forceH>vent.length)?0:forceH;
}
 
function fall()	{
	vitesseV = chute[forceV]
	forceV++	
	forceV=(forceV>chute.length-1)?0:forceV;
}  
  
  function snow() {  
	  
	doc_width = document.body.offsetWidth; 
    doc_height = document.body.offsetHeight;  
		  
    for (i = 0; i < densite; i++) {  
      yp[i] += vy[i]; 
      if (yp[i] > doc_height-20) { 
        xp[i] = (Math.random()*(doc_width-am[i]-30)); 
        yp[i] = 0; 
        vx[i] = (0.02 + Math.random()/10)*vitesseH; 
        vy[i] = (0.7 + Math.random())*vitesseV; 
      } 
	  
      dx[i] += vx[i]; 
	  document.getElementById("flocon"+i).style.display="block"
      document.getElementById("flocon"+i).style.top = yp[i]+"px"; 
	  if (drift>0){
					xp[i]=((xp[i]+drift/10)>doc_width)?0:xp[i]+drift/10;
				}
	  if (drift<0){
					xp[i]=((xp[i]+drift/10)<0)?doc_width:xp[i]+drift/10;
	  }
      document.getElementById("flocon"+i).style.left = xp[i] + am[i]*Math.sin(dx[i])+"px"; 
    } 
  }