SVG line animation not working - css

Question

I am trying to create an effect where smoke comes out of a vessel
Like this example where smoke comes out of a coffee cup but I am not able to do it.
Here's a jsfiddle showing my attempt:
SVG code is:
<?xml version="1.0" encoding="UTF-8"?>
<svg width="150px" height="127px" viewBox="0 0 150 127" version="1.1" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
<!-- Generator: Sketch 40.1 (33804) - http://www.bohemiancoding.com/sketch -->
<g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
<g id="Mobile-Portrait" transform="translate(-98.000000, -419.000000)" fill="#FFFFFF">
<g id="food_loading" transform="translate(98.000000, 419.000000)">
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id="food"></path>
<path d="M73.375,27.77425 C73.8625,28.22925 74.5025,28.4579167 75.1425,28.4579167 C75.7825,28.4579167 76.4225,28.22925 76.91,27.77425 C77.8875,26.8619167 77.8875,25.38725 76.91,24.4749167 C74.3725,22.10425 74.3725,18.2495833 76.91,15.8789167 C79.085,13.8489167 80.285,11.1515833 80.285,8.28158333 C80.285,5.41158333 79.0875,2.71425 76.91,0.68425 C75.9325,-0.228083333 74.3525,-0.228083333 73.375,0.68425 C72.3975,1.59658333 72.3975,3.07125 73.375,3.98358333 C74.605,5.13158333 75.285,6.65758333 75.285,8.28158333 C75.285,9.90558333 74.6075,11.4315833 73.375,12.5795833 C68.8875,16.7679167 68.8875,23.5859167 73.375,27.77425 L73.375,27.77425 L73.375,27.77425 L73.375,27.77425 L73.375,27.77425 L73.375,27.77425 Z"
id="food-path" class="food-path" fill="#FFFFFF" stroke="#000000" stroke-width="4"></path>
<path d="M100.875,41.77425 C101.3625,42.22925 102.0025,42.4579167 102.6425,42.4579167 C103.2825,42.4579167 103.9225,42.22925 104.41,41.77425 C105.3875,40.8619167 105.3875,39.38725 104.41,38.4749167 C101.8725,36.10425 101.8725,32.2495833 104.41,29.8789167 C106.585,27.8489167 107.785,25.1515833 107.785,22.2815833 C107.785,19.4115833 106.5875,16.71425 104.41,14.68425 C103.4325,13.7719167 101.8525,13.7719167 100.875,14.68425 C99.8975,15.5965833 99.8975,17.07125 100.875,17.9835833 C102.105,19.1315833 102.785,20.6575833 102.785,22.2815833 C102.785,23.9055833 102.1075,25.4315833 100.875,26.5795833 C96.3875,30.7679167 96.3875,37.5859167 100.875,41.77425 L100.875,41.77425 L100.875,41.77425 L100.875,41.77425 L100.875,41.77425 L100.875,41.77425 Z"
id="food-path" class="food-path" fill="#FFFFFF" stroke="#000000" stroke-width="4"></path>
<path d="M45.875,41.77425 C46.3625,42.22925 47.0025,42.4579167 47.6425,42.4579167 C48.2825,42.4579167 48.9225,42.22925 49.41,41.77425 C50.3875,40.8619167 50.3875,39.38725 49.41,38.4749167 C46.8725,36.10425 46.8725,32.2495833 49.41,29.8789167 C51.585,27.8489167 52.785,25.1515833 52.785,22.2815833 C52.785,19.4115833 51.5875,16.71425 49.41,14.68425 C48.4325,13.7719167 46.8525,13.7719167 45.875,14.68425 C44.8975,15.5965833 44.8975,17.07125 45.875,17.9835833 C47.105,19.1315833 47.785,20.6575833 47.785,22.2815833 C47.785,23.9055833 47.1075,25.4315833 45.875,26.5795833 C41.3875,30.7679167 41.3875,37.5859167 45.875,41.77425 L45.875,41.77425 L45.875,41.77425 L45.875,41.77425 L45.875,41.77425 L45.875,41.77425 Z"
id="food-path" class="food-path" fill="#FFFFFF" stroke="#000000" stroke-width="4"></path>
</g>
</g>
</g>
</svg>
Css is:
.food-path {
stroke-dasharray: 1000;
stroke-dashoffset: 1000;
animation: dash 1.5s linear alternate infinite;
}
#keyframes dash {
from {
stroke-dashoffset: 1000;
}
to {
stroke-dashoffset: 0;
}
}

Answer 1

For the dash offset line drawing trick to work, you need to have a "line" consisting of just a stroke. Your steam lines are actually closed shapes, where the path runs around the outside of the line. So instead of getting the steam effect you want, you are going to get an animated line that runs around the outside of the steam line.
What you have now is this:
.food-path {
stroke-dasharray: 69;
stroke-dashoffset: 69;
animation: dash 1.5s linear alternate infinite;
}
#keyframes dash {
from {
stroke-dashoffset: 69;
}
to {
stroke-dashoffset: 0;
}
}
<svg width="400px" height="400px" viewBox="20 0 60 60">
<path d="M45.875,41.77425 C46.3625,42.22925 47.0025,42.4579167 47.6425,42.4579167 C48.2825,42.4579167 48.9225,42.22925 49.41,41.77425 C50.3875,40.8619167 50.3875,39.38725 49.41,38.4749167 C46.8725,36.10425 46.8725,32.2495833 49.41,29.8789167 C51.585,27.8489167 52.785,25.1515833 52.785,22.2815833 C52.785,19.4115833 51.5875,16.71425 49.41,14.68425 C48.4325,13.7719167 46.8525,13.7719167 45.875,14.68425 C44.8975,15.5965833 44.8975,17.07125 45.875,17.9835833 C47.105,19.1315833 47.785,20.6575833 47.785,22.2815833 C47.785,23.9055833 47.1075,25.4315833 45.875,26.5795833 C41.3875,30.7679167 41.3875,37.5859167 45.875,41.77425 L45.875,41.77425 L45.875,41.77425 L45.875,41.77425 L45.875,41.77425 L45.875,41.77425 Z" id="food-path" class="food-path" fill="#FFFFFF" stroke="#000000" stroke-width="1"></path>
</svg>
First you will need to load your SVG into an editor and redraw those steam lines as a single thick squiggly line.
What you want in your drawing is more like this:
.food-path {
stroke-dasharray: 31;
stroke-dashoffset: 31;
animation: dash 1s linear alternate infinite;
}
#keyframes dash {
from {
stroke-dashoffset: 31;
}
to {
stroke-dashoffset: 0;
}
}
<svg width="400px" height="400px" viewBox="20 0 60 60">
<path d="M 49.41,41.77425 C50.3875,40.8619167 50.3875,39.38725 49.41,38.4749167 C46.8725,36.10425 46.8725,32.2495833 49.41,29.8789167 C51.585,27.8489167 52.785,25.1515833 52.785,22.2815833 C52.785,19.4115833 51.5875,16.71425 49.41,14.68425" id="food-path" class="food-path" fill="#FFFFFF" stroke="#000000" stroke-width="1"></path>
</svg>
Secondly, to get the drawing effect to work, you need to use values for the dash array and dash offset that correspond to the length of your line. The "1000" you are using is way too long for the lines you are using. See the values I am using in my examples.

Answer 2

The case is to properly adjust values for stroke-dasharray and stroke-dashoffset. You could do that with JS - it's quite easy way to read the actual lengths. stroke-dasharray lets you specify the length of the rendered part of the line, then the length of the gap. stroke-dashoffset lets you change where the dasharray starts.
With some experiment you can also get nice effect without JS. Here is your corrected version:
http://codepen.io/MakiBM/pen/NRaRWO
body {
background-color: lightgray;
}
svg {
position: absolute;
top: 50%;
left: 50%;
transform: translateX(-50%) translateY(-50%);
}
.food-path {
stroke-dasharray: 100;
stroke-dashoffset: 0;
animation: dash 3000ms linear infinite;
}
#keyframes dash {
from {
stroke-dashoffset: 200;
}
to {
stroke-dashoffset: 0;
}
}
For a more reusable solution see the link:
https://jakearchibald.com/2013/animated-line-drawing-svg/