svg ripple effect to the circle tag/element

Question

I am trying to apply the following animation to an svg circle element:

$color: #65ff78;

html, body {
  width: 100%;
  height: 100%;
}

body {
  background-color: #4e4e4e;
  display: flex;
  align-items: center;
  justify-content: center;
}

.circle-ripple {
  background-color: #35ffc3;
  width: 1em;
  height: 1em;
  border-radius: 50%;
  animation: ripple 0.7s linear infinite;
}

@keyframes ripple {
  0% {
    box-shadow: 0 0 0 0 rgba($color, 0.3),
                0 0 0 1em rgba($color, 0.3),
                0 0 0 3em rgba($color, 0.3),
                0 0 0 5em rgba($color, 0.3);
  }
  100% {
    box-shadow: 0 0 0 1em rgba($color, 0.3),
                0 0 0 3em rgba($color, 0.3),
                0 0 0 5em rgba($color, 0.3),
                0 0 0 8em rgba($color, 0);
  }
}

https://codepen.io/FabienMotte/pen/gPKVxE

Changing the div to a circle did not work, as expected.

In the above codepen a div element has been used, but can I apply the same effect to an svg circle element?

Thanks in advance.

Answer 1

You'll have to use a stack of circles instead of shadows. The radius of a <circle> is not CSS-animatable, so as a workaround you'll have to use a scale transformation. (A SMIL animation could work on the radius, but would not be compatible with Microsoft browsers.)

rect {
  fill: #4e4e4e;
}
circle {
  fill: #65ff78;
  opacity: 0.3;
}
svg > circle:last-child {
  fill: #35ffc3;
  opacity: 1;
}
#rp1 {
  animation: ripple1 0.7s linear infinite;
}
@keyframes ripple1 {
  0% {
    transform: scale(5.5);
    opacity: 0.3;
  }
  100% {
    transform: scale(8.5);
    opacity: 0.0;
  }
}
#rp2 {
  animation: ripple2 0.7s linear infinite;
}
@keyframes ripple2 {
  0% {
    transform: scale(3.5);
  }
  100% {
    transform: scale(5.5);
  }
}
#rp3 {
  animation: ripple3 0.7s linear infinite;
}
@keyframes ripple3 {
  0% {
    transform: scale(1.5);
  }
  100% {
    transform: scale(3.5);
  }
}
#rp4 {
  animation: ripple4 0.7s linear infinite;
}
@keyframes ripple4 {
  0% {
    transform: scale(0.5);
  }
  100% {
    transform: scale(1.5);
  }
}

<svg xmlns="http://www.w3.org/2000/svg" height="100%" width="100%">
<defs>
  <g id="anims">
    <circle id="rp1" r="1em" />
    <circle id="rp2" r="1em" />
    <circle id="rp3" r="1em" />
    <circle id="rp4" r="1em" />
  </g>
</defs>
<rect height="100%" width="100%" />
<use xlink:href="#anims" x="50%" y="50%"/>
<circle r="0.5em" cx="50%" cy="50%" />
</svg>