Responsive Website Design: Background Animation (Falling snow)

index.html

animation.js

var requestAnimationFrame = window.requestAnimationFrame || 
                            window.mozRequestAnimationFrame || 
                            window.webkitRequestAnimationFrame ||
                            window.msRequestAnimationFrame;

var transforms = ["transform", 
                  "msTransform", 
                  "webkitTransform", 
                  "mozTransform", 
                  "oTransform"];
                   
var transformProperty = getSupportedPropertyName(transforms);

// Array to store our Snowflake objects
var snowflakes = [];

// Global variables to store our browser's window size
var browserWidth;
var browserHeight;

// Specify the number of snowflakes you want visible
var numberOfSnowflakes = 50;

// Flag to reset the position of the snowflakes
var resetPosition = false;

//
// It all starts here...
//
function setup() {
 window.addEventListener("DOMContentLoaded", generateSnowflakes, false);
 window.addEventListener("resize", setResetFlag, false);
}
setup();

//
// Vendor prefix management
//
function getSupportedPropertyName(properties) {
    for (var i = 0; i < properties.length; i++) {
        if (typeof document.body.style[properties[i]] != "undefined") {
            return properties[i];
        }
    }
    return null;
}

//
// Constructor for our Snowflake object
//
function Snowflake(element, speed, xPos, yPos) {

// set initial snowflake properties
    this.element = element;
    this.speed = speed;
    this.xPos = xPos;
    this.yPos = yPos;
 
 // declare variables used for snowflake's motion
    this.counter = 0;
    this.sign = Math.random() < 0.5 ? 1 : -1;
 
 // setting an initial opacity and size for our snowflake
    this.element.style.opacity = .1 + Math.random();
    this.element.style.fontSize = 12 + Math.random() * 50 + "px";
}

//
// The function responsible for actually moving our snowflake
//
Snowflake.prototype.update = function () {

// using some trigonometry to determine our x and y position
 this.counter += this.speed / 5000;
 this.xPos += this.sign * this.speed * Math.cos(this.counter) / 40;
 this.yPos += Math.sin(this.counter) / 40 + this.speed / 30;
 
 // setting our snowflake's position
 setTranslate3DTransform(this.element, Math.round(this.xPos), Math.round(this.yPos));
    
    // if snowflake goes below the browser window, move it back to the top
 if (this.yPos > browserHeight) {
  this.yPos = -50;
 }
}

//
// A performant way to set your snowflake's position
//
function setTranslate3DTransform(element, xPosition, yPosition) {
 var val = "translate3d(" + xPosition + "px, " + yPosition + "px" + ", 0)";
    element.style[transformProperty] = val;
}

//
// The function responsible for creating the snowflake
//
function generateSnowflakes() {
 
 // get our snowflake element from the DOM and store it
 var originalSnowflake = document.querySelector(".snowflake");
 
 // access our snowflake element's parent container
 var snowflakeContainer = originalSnowflake.parentNode;
    
    // get our browser's size
 browserWidth = document.documentElement.clientWidth;
 browserHeight = document.documentElement.clientHeight;
         
    // create each individual snowflake
 for (var i = 0; i < numberOfSnowflakes; i++) {
 
  // clone our original snowflake and add it to snowflakeContainer
  var snowflakeClone = originalSnowflake.cloneNode(true);
  snowflakeContainer.appendChild(snowflakeClone);
 
  // set our snowflake's initial position and related properties
     var initialXPos = getPosition(50, browserWidth);
     var initialYPos = getPosition(50, browserHeight);
     var speed = 5+Math.random()*40;
     
     // create our Snowflake object
  var snowflakeObject = new Snowflake(snowflakeClone, 
           speed, 
           initialXPos, 
           initialYPos);
  snowflakes.push(snowflakeObject);
 }
    
    // remove the original snowflake because we no longer need it visible
 snowflakeContainer.removeChild(originalSnowflake);
 
 // call the moveSnowflakes function every 30 milliseconds
    moveSnowflakes();
}

//
// Responsible for moving each snowflake by calling its update function
//
function moveSnowflakes() {
 for (var i = 0; i < snowflakes.length; i++) {
     var snowflake = snowflakes[i];
     snowflake.update();
 }
    
 // Reset the position of all the snowflakes to a new value
 if (resetPosition) {
  browserWidth = document.documentElement.clientWidth;
  browserHeight = document.documentElement.clientHeight; 
  
  for (var i = 0; i < snowflakes.length; i++) {
   var snowflake = snowflakes[i];
   
   snowflake.xPos = getPosition(50, browserWidth);
   snowflake.yPos = getPosition(50, browserHeight);
  }
  
  resetPosition = false;
 }
    
    requestAnimationFrame(moveSnowflakes);
}

//
// This function returns a number between (maximum - offset) and (maximum + offset)
//
function getPosition(offset, size) {
 return Math.round(-1*offset + Math.random() * (size+2*offset));
}

//
// Trigger a reset of all the snowflakes' positions
//
function setResetFlag(e) {
 resetPosition = true;
}

animation.min.js

Wednesday 6 May 2015

Background Animation (Falling snow)

index.html

animation.js

animation.min.js

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