How can I add a transition effect when opening my custom modal window?

Question

I'm trying to add a transition when my modal window appears, but I really don't know how to do with my own code. I don't want use a custom plugin. The effect that I want is on this page: http://tympanus.net/Development/ModalWindowEffects/ It's the "Slide in (bottom)".

This is my HTML code:

    <div class="overlay-box">
        <div class="overlay-box-container">
            <span class="overlay-box-closer" title="Close the overlay"></span>
            <h1 class="big-title" style="margin-bottom: 15px;">The paragraph title</h1>
            <p>This is the big paragraph</p>
        </div>
    </div>
    <div id="expose-mask"></div>

My CSS:

.overlay-box
{
    background-color: #FFFFFF;
    position: fixed;
    top: 35%;
    right: 0;
    left: 0;
    z-index: 4;
    width: 70%;
    margin: 0 auto;
    box-shadow: rgba(0, 0, 0, 0.3) 0 1px 7px;
    -webkit-box-shadow: rgba(0, 0, 0, 0.3) 0 1px 7px;
    -moz-box-shadow: rgba(0, 0, 0, 0.3) 0 1px 7px;
}

.overlay-box-container
{
    margin: 20px;
}

.overlay-box-container .big-title
{
    background-color: #F5F5F5;
    margin: -20px -20px 20px;
    padding: 20px;
    border-bottom: 1px solid #CCCCCC;
}

.overlay-box-closer
{
    position: absolute;
    top: -20px;
    right: -15px;
    width: 30px;
    height: 30px;
    color: #FFFFFF;
    cursor: pointer;
    font-size: 19px;
    border-radius: 50%;
    text-align: center;
    background-color: rgba(0, 0, 0, 0.9);
    border: 3px solid #FFFFFF;
    box-shadow: 1px 1px 5px #000000;
    -webkit-box-shadow: 1px 1px 5px #000000;
    -moz-box-shadow: 1px 1px 5px #000000;

}

.overlay-box-closer:hover
{
    background-color: rgba(187, 0, 0, 0.9);
}

.overlay-box-closer:before
{
    content: "\f00d";
}

#expose-mask
{
    background-color: rgba(0, 0, 0, 0.6);
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    z-index: 3;
}

and my JavaScript code:

(function($)
{
    $('#expose-mask').click(function(e)
    {
        $('body').removeClass('side-block');
    })
    $('.overlay-trigger').click(function(e)
    {
        e.preventDefault();
        $('#expose-mask').css({'display': 'inherit'}).fadeIn(function()
        {
            $('.overlay-box').css({'display': 'inherit'});
        });
    });
    $('#expose-mask, .overlay-box').css({'display': 'none'});
    $('.overlay-box-closer, #expose-mask').click(function()
    {
        $('.overlay-box, #expose-mask').css({'display': 'none'});
        $('#expose-mask');
    });
})(jQuery);

Result: http://prntscr.com/7g8eeb

I'm looking for a solution for a long time, but I can't...

Answer 1

The idea is to use css transitions, I've created a fiddle with your code, tweaked a little bit and added the transitions that the example you've provided uses, you should keep tweaking it until you think you really like it :) What i'm going to provide is a rough example but the transitions are working the way you want to.

HTML:

<div class="overlay-trigger">Show Modal</div>

<div class="overlay-box">
        <div class="overlay-box-container">
            <span class="overlay-box-closer" title="Close the overlay"></span>
            <h1 class="big-title" style="margin-bottom: 15px;">The paragraph title</h1>
            <p>This is the big paragraph</p>
        </div>
    </div>
    <div id="expose-mask"></div>

JS:

(function ($) {
    $('#expose-mask').click(function (e) {
        $('body').removeClass('side-block');
    });
    $('.overlay-trigger').click(function (e) {
        e.preventDefault();
        $('.overlay-box').addClass('shown');
    });
    $('#expose-mask').css({'display': 'none'});
    $('.overlay-box-closer, #expose-mask').click(function () {
        $('#expose-mask').css({'display': 'none'});
        $('.overlay-box').removeClass('shown');
    });
})(jQuery);

CSS:

.overlay-box.shown {
    visibility: visible;
}

.overlay-box
{
  position: fixed;
  top: 50%;
  left: 50%;
  width: 50%;
  max-width: 630px;
  min-width: 320px;
  height: auto;
  z-index: 2000;
  visibility: hidden;
  -webkit-backface-visibility: hidden;
  -moz-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-transform: translateX(-50%) translateY(-50%);
  -moz-transform: translateX(-50%) translateY(-50%);
  -ms-transform: translateX(-50%) translateY(-50%);
  transform: translateX(-50%) translateY(-50%);
}

.overlay-box .overlay-box-container {
  -webkit-transform: translateY(20%);
  -moz-transform: translateY(20%);
  -ms-transform: translateY(20%);
  transform: translateY(20%);
  opacity: 0;
  -webkit-transition: all 0.3s;
  -moz-transition: all 0.3s;
  transition: all 0.3s;
    margin: 20px;
}

.overlay-box.shown .overlay-box-container {
  -webkit-transform: translateY(0);
  -moz-transform: translateY(0);
  -ms-transform: translateY(0);
  transform: translateY(0);
  opacity: 1;
}

.overlay-box-container .big-title
{
    background-color: #F5F5F5;
    margin: -20px -20px 20px;
    padding: 20px;
    border-bottom: 1px solid #CCCCCC;
}

.overlay-box-closer
{
    position: absolute;
    top: -20px;
    right: -15px;
    width: 30px;
    height: 30px;
    color: #FFFFFF;
    cursor: pointer;
    font-size: 19px;
    border-radius: 50%;
    text-align: center;
    background-color: rgba(0, 0, 0, 0.9);
    border: 3px solid #FFFFFF;
    box-shadow: 1px 1px 5px #000000;
    -webkit-box-shadow: 1px 1px 5px #000000;
    -moz-box-shadow: 1px 1px 5px #000000;

}

.overlay-box-closer:hover
{
    background-color: rgba(187, 0, 0, 0.9);
}

.overlay-box-closer:before
{
    content: "\f00d";
}

#expose-mask
{
    background-color: rgba(0, 0, 0, 0.6);
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    z-index: 3;
}

http://jsfiddle.net/x76usd8j/1/