Css animation displaying 3 images at a time

Question

I'm trying to show 3 images (out of currently 12) at a time using css animations. I would like to display image 1-3 first, then 4-6, then 7-9, and then 10-12.

I have this so far, but I can't get my head around how to use the :nth selectors to display the 3 next while hiding the rest.

This is more or less what I have so far:

#crossfade > img {
  max-width: 30%;
  height: auto;
  opacity: 0;
  z-index: 0;
  -webkit-backface-visibility: hidden;
  animation: imageAnimation 30s linear infinite 0s;
}

#crossfade > img:nth-child(n+3) {
  animation-delay: 6s;
}

@keyframes imageAnimation {
  0% {
    opacity: 0;
    animation-timing-function: ease-in;
  }
  8% {
    opacity: 1;
    animation-timing-function: ease-out;
  }
  17% {
    opacity: 1
  }
  25% {
    opacity: 0
  }
  100% {
    opacity: 0
  }
}

Example below [or click here for jsfiddle]

#crossfade {
  height: 185px;
  width: 100%;
  position: relative;
}

#crossfade > img {
  max-width: 30%;
  height: auto;
  opacity: 0;
  z-index: 0;
  -webkit-backface-visibility: hidden;
  -webkit-animation: imageAnimation 30s linear infinite 0s;
  -moz-animation: imageAnimation 30s linear infinite 0s;
  -o-animation: imageAnimation 30s linear infinite 0s;
  -ms-animation: imageAnimation 30s linear infinite 0s;
  animation: imageAnimation 30s linear infinite 0s;
}

#crossfade > img:nth-child(n+3) {
  -webkit-animation-delay: 6s;
  -moz-animation-delay: 6s;
  -o-animation-delay: 6s;
  -ms-animation-delay: 6s;
  animation-delay: 6s;
}

#crossfade > img:nth-child(n+3) {
  -webkit-animation-delay: 12s;
  -moz-animation-delay: 12s;
  -o-animation-delay: 12s;
  -ms-animation-delay: 12s;
  animation-delay: 12s;
}

#crossfade > img:nth-child(4) {
  -webkit-animation-delay: 18s;
  -moz-animation-delay: 18s;
  -o-animation-delay: 18s;
  -ms-animation-delay: 18s;
  animation-delay: 18s;
}

#crossfade > img:nth-child(5) {
  -webkit-animation-delay: 24s;
  -moz-animation-delay: 24s;
  -o-animation-delay: 24s;
  -ms-animation-delay: 24s;
  animation-delay: 24s;
}

@keyframes imageAnimation {
  0% {
    opacity: 0;
    animation-timing-function: ease-in;
  }
  8% {
    opacity: 1;
    animation-timing-function: ease-out;
  }
  17% {
    opacity: 1
  }
  25% {
    opacity: 0
  }
  100% {
    opacity: 0
  }
}

<div id="crossfade">
  <img src="http://dummyimage.com/120x185&text=Img 1" alt="Image 1">
  <img src="http://dummyimage.com/120x185&text=Img 2" alt="Image 2">
  <img src="http://dummyimage.com/120x185&text=Img 3" alt="Image 2">
  <img src="http://dummyimage.com/120x185&text=Img 4" alt="Image 4">
  <img src="http://dummyimage.com/120x185&text=Img 5" alt="Image 5">
  <img src="http://dummyimage.com/120x185&text=Img 6" alt="Image 6">
  <img src="http://dummyimage.com/120x185&text=Img 7" alt="Image 7">
  <img src="http://dummyimage.com/120x185&text=Img 8" alt="Image 8">
  <img src="http://dummyimage.com/120x185&text=Img 9" alt="Image 9">
  <img src="http://dummyimage.com/120x185&text=Img 10" alt="Image 10">
  <img src="http://dummyimage.com/120x185&text=Img 11" alt="Image 11">
  <img src="http://dummyimage.com/120x185&text=Img 12" alt="Image 12">
</div>

Answer 1

I appreciate this has been answered already but here is my jQuery solution if it helps anyone in the future.

I have heavily commented the JavaScript code so should be self explanatory but effectively you provide the function with the number of img/slides to show and how fast to show them and it does the rest. Its a dynamic and will adjust for odd numbers of slides etc.

Hope this helps someone anyway :)

http://jsfiddle.net/BradChelly/qjtcojfc/3/

function slideShow(currentSlide){
  // speed at which the slides change in miliseconds (1000 = 1sec)
  // must not exceed total time for the fade in/out animations
  var duration = 3000; 
  // how many slides to show at a time?
  var slidesPerShow = 3;
  
  // count the number of slides (imgs)
  slideCount = $( "#slideshow_images" ).children().length;

  // Array of next slides to be displayed
  slidesToShow = [];
  
  // add the defined number of slides "slidesPerShow" to the slidesToShow array
  var times = slidesPerShow;
  for(var i=0; i < times; i++){
    slidesToShow.push(currentSlide+i+1);
  }
  // set slides array
  slides = [];
	
  // add each slide to the slides array
  $.each( slidesToShow, function( i, val ) {
  		slide = $( "#slideshow_images img:nth-child(" + val + ")" ).clone();
      slides.push(slide);
  });
  
  // provided the current slideshow is not empty
  // fade out its contents, replace it with new slides and fade back in.
  if ( $("#slideshow").children().length > 0 ) {
    $("#slideshow").children().fadeOut("slow", function(){
      $("#slideshow").empty().append(slides)
      $("#slideshow").children().fadeIn(1000);
    });
  }
  // otherwise, if the current slideshow is empty
  // just load the slides straight away. 
	else {
  	$("#slideshow").append(slides);
    $("#slideshow").children().fadeIn(1000);
  }
  
	// set the current slide to the last slide shown or 0 if max slide count reached
  slidesToShow[(slidesPerShow-1)] >= slideCount ? currentSlide = 0 : currentSlide = slidesToShow[(slidesPerShow-1)];
  
  // repeat after set time (set the duration at the top of function)
  setTimeout( function(){ 
  	slideShow(currentSlide);
  }  , duration );
}

// call the slideshow
slideShow(0);

#slideshow img {display: none;}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>

<div id="crossfade">
  <div id="slideshow_images" style="display:none;">
    <img src="http://dummyimage.com/120x185&text=Img 1" alt="Image 1">
    <img src="http://dummyimage.com/120x185&text=Img 2" alt="Image 2">
    <img src="http://dummyimage.com/120x185&text=Img 3" alt="Image 2">
    <img src="http://dummyimage.com/120x185&text=Img 4" alt="Image 4">
    <img src="http://dummyimage.com/120x185&text=Img 5" alt="Image 5">
    <img src="http://dummyimage.com/120x185&text=Img 6" alt="Image 6">
    <img src="http://dummyimage.com/120x185&text=Img 7" alt="Image 7">
    <img src="http://dummyimage.com/120x185&text=Img 8" alt="Image 8">
    <img src="http://dummyimage.com/120x185&text=Img 9" alt="Image 9">
    <img src="http://dummyimage.com/120x185&text=Img 10" alt="Image 10">
    <img src="http://dummyimage.com/120x185&text=Img 11" alt="Image 11">
    <img src="http://dummyimage.com/120x185&text=Img 12" alt="Image 12">
    <img src="http://dummyimage.com/120x185&text=Img 13" alt="Image 13">
    <img src="http://dummyimage.com/120x185&text=Img 14" alt="Image 14">
  </div>
  <div id="slideshow"></div>
</div>