Pure CSS parallax without fixed background height?

Question

I'm trying to get a pure CSS parallax effect working without having a fixed background height. This has been described in a few places, but they have the common constraint that the background layer must have a fixed, known height.

I would like to get the effect working without having a fixed, known height for the background due to some dynamic content.

My minimal example is here: https://jsfiddle.net/yf8oyben/

#container {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  perspective: 1px;
  overflow-x: hidden;
  overflow-y: scroll;
}
.background {
  transform: translateZ(-1px) scale(2);
  width: 100%;
  background: lightgreen;
  height: 250px;  /* Assumes bg height */
  position: absolute;  /* Assumes bg height */
  top: calc(125px - 50vh);  /* Assumes bg height */
}
.foreground {
  background: rgba(0, 0, 255, 0.5);
  width: 100%;
  position: absolute;  /* Assumes bg height */
  top: 250px;  /* Assumes bg height */
}

<body>
  <div id='container'>
    <div id="group1">
      <div class="background">
        <div style="height: 10rem"></div>
        <center>Banner</center>
        <div style="height: 10rem"></div>
      </div>
      <div class="foreground">
        <div style="height: 10rem"></div>
        <center>Content</center>
        <div style="height: 100rem"></div>
      </div>
    </div>
  </div>
</body>

It works now but assumes that the background is 250px, as annotated in the CSS. Is it possible to remove this and still retain the effect as it currently is?

I struggled with this problem a lot and haven't found any possible solution, basically the main issue is that a parent div can't set its height to an absolute child div, so you have to insert a one line js to set its height. — Emi-C, Aug 01 '16 at 09:37

web-tiki · Accepted Answer · 2016-08-01T11:32:03.990

You can achieve this parallax effect without knowing the height of the banner. you just need to drop the absolute positioning and adapt the perspective-origin and transform-orign properties They need to be positioned one on top of the other.

Here is a demo: CSS only parallax effect

*{margin:0;padding:0;}
#wrap{
  position:fixed;
  width:100%; height:100%;
  overflow-x:hidden;
  overflow-y:scroll;
  perspective: 1px;
  perspective-origin:0 0;
}
.bg{
  background:teal;
  transform-origin:0 0;
  transform: translateZ(-1px) scale(2);
}
.bg img{
  display:block;
  width:100%; height:auto;
}
.cont{
  position:relative;
  background:rgba(0,0,0,0.8);
  color:#fff;
  padding:5%;
}
.cont *{
  max-width:900px;
  margin:5% auto;
}

<div id="wrap">
  <div class="bg">
    <img src="http://i.imgur.com/hPLqUtN.jpg" alt="" />
  </div>
  <div class="cont">
    <h1>Lorem Ipsum</h1>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris et purus porta, porta dolor vel, pulvinar turpis. Suspendisse aliquam placerat turpis, sed ullamcorper nisl vestibulum eu. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec euismod tempor elit a pulvinar. Integer vehicula purus ipsum, id ultricies risus placerat sit amet. Cras vel ante egestas diam egestas sagittis. Mauris facilisis, dolor pulvinar tempus vestibulum, elit lectus gravida sem, sed volutpat dui dolor vel purus. Praesent nec ligula ac mi faucibus hendrerit vitae sed felis. Nullam vehicula magna vitae ultrices dapibus. Pellentesque facilisis dui a diam scelerisque pharetra. Vestibulum dapibus imperdiet molestie. Fusce fringilla facilisis metus, in iaculis lectus fermentum eget. Ut tortor quam, imperdiet sit amet nisi in, fringilla porta sapien. Aenean a enim vestibulum, bibendum dolor sed, consequat mi.</p>
    <p>Fusce faucibus nulla id iaculis sagittis. Duis ac arcu a ex elementum feugiat. Proin ut quam quis tortor vulputate semper a id nunc. Morbi rhoncus ultricies ultricies. Praesent semper id massa sed euismod. Fusce sagittis felis nec libero malesuada, in luctus enim aliquam. Aliquam sagittis, orci eget blandit vestibulum, mi dui blandit mauris, et tincidunt tellus nisi sagittis lacus. Sed dignissim, sapien vitae cursus imperdiet, augue massa tempor ex, non finibus risus metus ac enim. Mauris blandit eros nisi.</p>
    <p>Sed bibendum ante ac metus hendrerit, nec commodo tortor venenatis. Pellentesque porta eros non eros cursus, vitae commodo sapien facilisis. Praesent sit amet volutpat lacus. Nullam sed quam ac dolor blandit lacinia. Ut euismod turpis sit amet libero pulvinar, non aliquet lacus bibendum. Nullam libero massa, facilisis sed neque id, porta fringilla eros. Curabitur vestibulum nisi nec tempor tempor. Sed fermentum mauris diam, eu volutpat magna tempus et. Ut semper dapibus purus eget ullamcorper. Aenean varius rutrum purus id congue. Mauris sit amet turpis ornare, pharetra ex et, porta lorem. In hac habitasse platea dictumst.</p>
    <p>Nulla sed pellentesque nibh, eu consectetur neque. Curabitur eu risus at felis sagittis blandit. Nunc non massa non massa mattis semper. Curabitur dapibus tortor velit, id tincidunt ligula rutrum sed. Quisque feugiat consequat molestie. Curabitur lobortis neque ac porta imperdiet. Sed malesuada nibh sit amet magna commodo, sed bibendum turpis vestibulum. Suspendisse vel rutrum dolor, sed bibendum turpis. Morbi condimentum fermentum urna id venenatis.</p>
  </div>
</div>

Pure CSS parallax without fixed background height?

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