CSS Animation Delay and Keyframe

Question

I have a problem with animation delay on CSS Animation. I have 3 images and I want to make it slideshow. The illustrations is, image 1 to image 2 takes 15 seconds to change and image 2 to image 3 takes 15 seconds to change and image 3 back to image 1 it takes 30 seconds, after the first loop, I want to make the slideshow end in image 3 so image 1 to image 2 still 15 seconds and image 2 to image 3 still 15 seconds and when image 3 load it no need to back to image 1. I tried this code but it gives me 15 seconds delay to all images. This is my code :

ul {
      list-style: none;
      margin: 0;
      padding: 0;
      position: relative;
    }
    
    li {
      position: absolute;
      opacity:0;
    }
    
    li {
      animation: xfade 45s  infinite;
    }
    li:nth-child(2) {
      animation-delay:15s;
    }
    li:nth-child(3) {
      animation-delay:30s;
    }
    
    @keyframes xfade{ 
      3%{opacity:1}
      33% {opacity:1;}
      36%{opacity:0}
    }

    <ul>
      <li><img width="500" height="500" src="http://lorempixel.com/500/500/sports" alt="pic1"></li>
      <li><img width="500" height="500" src="http://lorempixel.com/500/500/people" alt="pic2"></li>
      <li><img width="500" height="500" src="http://lorempixel.com/500/500/transport" alt="pic3"></li>
    </ul>

I want to make delay in my animation according the illustrations above. Anyone could help me solve this problem ? Thank you before.

Answer 1

I am thinking that using GreenSock is better if you want animation with specific scenario like this.

Here is the closest I can get with HTML and CSS, I also need to duplicate the <li> to fit your scenario.

ul {
      list-style: none;
      margin: 0;
      padding: 0;
      position: relative;
    }
    
    li {
      position: absolute;
      opacity: 0;
    }
    
    li:nth-child(6) {
      /*The last item always on the top, direction will goes from last to first*/
      animation: xfade 15s;
    }
    li:nth-child(5) {
      /*Put animation length double the delay (in this case delay is the actual animation length)*/
      animation: xfade 30s 15s;
    }
    li:nth-child(4) {
      animation: xfade 30s 15s;
    }
    li:nth-child(3) {
      animation: xfade 30s 15s;
    }
    li:nth-child(2) {
      animation: xfade 30s 15s;
    }
    li:nth-child(1) {
      opacity: 1;
    }
    
    @keyframes xfade{ 
      0%{opacity:0}
      33% {opacity:1;}
      100%{opacity:0}
    }

<ul>
      <li>1<img width="500" height="500" src="http://lorempixel.com/500/500/sports" alt="pic1"></li>
      <li>2<img width="500" height="500" src="http://lorempixel.com/500/500/people" alt="pic2"></li>
      <li>3<img width="500" height="500" src="http://lorempixel.com/500/500/transport" alt="pic3"></li>

      <!-- Duplicate -->
      <li>4<img width="500" height="500" src="http://lorempixel.com/500/500/sports" alt="pic1"></li>
      <li>5<img width="500" height="500" src="http://lorempixel.com/500/500/people" alt="pic2"></li>
      <li>6<img width="500" height="500" src="http://lorempixel.com/500/500/transport" alt="pic3"></li>
    </ul>

Answer 2

Here's something that gave real food for thought :)

I had to apply 2 animations for opacity change: xfade-25pct and xfade-50pct. Both play only 2 times, fading out briefly after 25% and 50% of the animation. And an additional show animation to make the 3rd image stick after 2 animation loops, with the necessary rule animation-fill-mode: forwards;.

The trick to opacity is this: you have to split the animation in 4 quarters. If you want you can change the total animation duration from 60s to a multiple of 4, and adjust the delays. The 3rd animation delay is the double of the 2nd one.

----#----#----#----#----#----#----#----#----#----#
1st animation      | 1st animation     |
--------------------------------------------------
15s | 2nd animation     | 2nd animation     |
--------------------------------------------------
30s      | 3rd animation     |   3rd animation   |
----#----#----#----#----#----#----#----#----#----#

Feel free to ask. Hope this helps you.

var s = 0,
  c = 1;
/* Code for displaying timer */
window.setInterval(function() {
  s++;
  document.querySelector('DIV').innerHTML = s;
  if (s == 15 && c <= 2 || s == 30) {
    if (s == 30) {
      c = 1;
    } else {
      c++;
    }
    s = 0;
  }
}, 1000);

ul {
  list-style: none;
  margin: 0;
  padding: 0;
  position: relative;
}

li {
  position: absolute;
  opacity: 0;
}

li {
  animation: xfade-25pct 60s 2;
}

li:nth-child(2) {
  animation-delay: 15s;
}

li:nth-child(3) {
  animation-delay: 30s, 120s;
  animation-name: xfade-50pct, show;
  animation-duration: 60s, 1s;
  animation-iteration-count: 2, 1;
  animation-fill-mode: forwards;
}

@keyframes xfade-25pct {
  0% {
    opacity: 0;
  }
  2%,
  25% {
    opacity: 1;
  }
  27% {
    opacity: 0;
  }
}

@keyframes xfade-50pct {
  0% {
    opacity: 0;
  }
  2%,
  50% {
    opacity: 1;
  }
  52% {
    opacity: 0;
  }
}

@keyframes show {
  0%,
  100% {
    opacity: 1;
  }
}

<DIV></DIV>
<ul>
  <li><img width="500" height="500" src="https://www.noao.edu/image_gallery/images/d2/pelican_500.jpg" alt="pic1"></li>
  <li><img width="500" height="500" src="http://whc.unesco.org/uploads/thumbs/news_920-500-500-20151015155516.jpg" alt="pic2"></li>
  <li><img width="500" height="500" src="https://i.pinimg.com/736x/4c/17/65/4c176537aee906de294138c3bac5b8f5--merry-christmas-love-coffee-aroma.jpg" alt="pic3"></li>
</ul>