SVG animation delay on each repetition

Question

I'd like to add a delay to each iteration of an SVG animation loop. Here's a simple example.

<svg xmlns="http://www.w3.org/2000/svg" width="100px" height="100px">
  <circle cx="50" cy="50" r="15" fill="blue">
    <animate id="op" attributeType="CSS" attributeName="opacity"
             from="1" to="0" dur="3s" repeatCount="indefinite" />
  </circle>
</svg>

Using begin only delays the first iteration, so is there a way to delay every iteration?

Answer 1

You can add the end event of a SMIL animated element to the begin attribute.
Also, you can add multiple values, separated by ; to this begin attribute :

<svg xmlns="http://www.w3.org/2000/svg" width="300px" height="100px">
  <circle cx="50" cy="50" r="15" fill="blue">
    <animate id="op" attributeType="CSS" attributeName="opacity"
             from="1" to="0" dur="3s" begin="3s;op.end+3s" />
  </circle>
</svg>

Answer 2

Define dummy loop and set relative start time. See How to make SVG Loop Animation?

<svg xmlns="http://www.w3.org/2000/svg" width="300px" height="200px">
  <rect>
    <animate id="o1" begin="0;o1.end" dur="10s"
    attributeName="visibility" from="hide" to="hide"/>
  </rect>
  <circle fill="orange" cx="-50" cy="100" r="20">
    <animate begin="o1.begin" 
    attributeName="cx" from="250" to="50" dur="5.05s"/>
  </circle>
  <circle fill="blue" cx="150" cy="100" r="50" />
  <circle fill="orange" cx="-50" cy="100" r="20">
    <animate begin="o1.begin+5s" 
    attributeName="cx" from="50" to="250" dur="5.05s"/>
  </circle>
</svg>

Answer 3

I think what you're looking for is the additive/accumulative attributes of the svg. This is an example that i got from css tricks

svg {
  border: 3px solid #eee;
  display: block;
  margin: 1em auto;
}

<svg width="500" height="100">
  <circle id="orange-circle" r="30" cx="50" cy="50" fill="orange" />

  <animate xlink:href="#orange-circle" attributeName="cx" from="0" to="100" additive="sum" repeatCount="3" calcMode="spline" keyTimes="0;1" keySplines=".42 0 1 1" dur="1s" begin="click" fill="freeze" />
</svg>

In fact here is a better exaample (same source)

svg {
  border: 3px solid #eee;
  display: block;
  margin: 1em auto;
}

<svg width="500" height="150">
  <style>
    rect {
      -moz-transform-origin: 75px 75px;
      transform-origin: 50% 50%;
    }
  </style>
  <rect id="deepPink-rectangle" width="50" height="50" x="50" y="50" fill="deepPink" />
  
  <animateTransform 
           xlink:href="#deepPink-rectangle"
           attributeName="transform" 
           attributeType="XML"
           type="rotate"
           from="0 75 75"
           to="360 75 75" 
           dur="2s"
           begin="0s; 5s; 9s; 17s;"
           end="2s; 8s; 15s; 25s;"
           fill="freeze" 
           restart="whenNotActive"
           />
  
</svg>