CODEWITHSUNDEEP
csssvghoversvg-animateradial-gradients
John
John

Reputation: 115

Radial SVG gradient is not animating on hover

The radial gradient is supposed to grow from 10% to 100% on hover, but it's just not doing anything. Can't understand what I'm doing wrong.

<svg id="svgDoc" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 500 500" shape-rendering="geometricPrecision" text-rendering="geometricPrecision">

<style><![CDATA[
#svgDoc {
    pointer-events: all
}

#svgDoc:hover #svgGrad {
    animation: svgGrad_f_p 3000ms linear 1 normal forwards
}

@keyframes svgGrad_f_p {
    0% {
        offset: 10%
    } 
    100% {
        offset: 100%
    }
}
]]>
</style>

<defs>
<radialGradient id="svgGrad-fill" cx="0" cy="0" r="0.5" spreadMethod="pad" gradientUnits="objectBoundingBox" gradientTransform="translate(0.5 0.5)">
<stop id="svgGrad-fill-0" offset="0%" stop-color="#ff0000"/>
<stop id="svgGrad-fill-1" offset="10%" stop-color="#000"/>
</radialGradient>
</defs>

<rect id="svgGrad" width="500" height="500" rx="0" ry="0" fill="url(#svgGrad-fill)"/>
</svg>

Upvotes: 0

Views: 161

Answers (2)

herrstrietzel
herrstrietzel

Reputation: 17316

You can't manipulate the stop attribute via CSS as it "collides" with the CSS offset-path related property of the same name.

Workaround 1: SMIL animations triggered by begin attribute

A workaround might be to animate the gradient via SMIL animation like so:

<h3>Hover me</h3>
<svg id="svgDoc" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 500 500">
  <defs>
    <radialGradient id="svgGrad-fill" cx="0" cy="0" r="0.5" spreadMethod="pad" gradientUnits="objectBoundingBox" gradientTransform="translate(0.5 0.5)">
      <stop id="svgGrad-fill-0" offset="0%" stop-color="#ff0000" />
      <stop id="svgGrad-fill-1" offset="10%" stop-color="#000" >
           <animate attributeName="offset" fill="freeze" values="0.1;1" dur="1s" repeatCount="1" begin="svgGrad.mouseover"  /> 
           <animate attributeName="offset" fill="freeze" values="1;0.1" dur="1s" repeatCount="1" begin="svgGrad.mouseout"  /> 
      </stop>
    </radialGradient>
  </defs>

  <rect id="svgGrad" width="500" height="500" rx="0" ry="0" fill="url(#svgGrad-fill)" />
</svg>

Fortunately, SVG's <animate> element allows you to add events to start (or stop) playback. See "mdn docs: begin"

<animate attributeName="offset" fill="freeze" values="1;0.1" dur="1s" repeatCount="1" begin="svgGrad.mouseout"  />

Adding transition easing

We need to calcMode="spline" and keySplines attributes to define a custom easing – similar to CSS easing:

  • Ease-in: keySplines="0.42 0 1 1"
  • Ease-in-out: keySplines="0.42 0 0.58 1"
  • Ease: keySplines="0.25 0.1 0.25 1"

Like the keyTimes attribute we can specify multiple values as an array separated by semicolons.
In your case we only have 2 animation states (begin:0.1/10% end: 1/100%) as descibed by the keyTimes attribute. Therefore we only need a single bézier value. Otherwise we need to repeat the keySplines according to the keyTimes where keySplines=keyTimes .length-1.

Here's an example comparing the easing results

body{
font-size:3vmin;
display:grid;
grid-template-columns: 1fr 1fr 1fr 1fr;
gap:1em;
}
<div class="col">
<h3>linear</h3>
<svg viewBox="0 0 500 500">
  <defs>
    <radialGradient id="svgGrad-fill" cx="50%" cy="50%" r="0.5" spreadMethod="pad" gradientUnits="objectBoundingBox">
      <stop offset="0%" stop-color="#ff0000" />
      <stop offset="10%" stop-color="#000">
        
       <animate attributeName="offset" fill="freeze" values="0.1;1;0.1" keyTimes="0;0.5;1"  dur="1s" repeatCount="indefinite" begin="0" />

        <!--
        <animate attributeName="offset" fill="freeze" values="0.1;1" keyTimes="0;1" dur="1s" repeatCount="1" begin="svgGrad.mouseover" />
        <animate attributeName="offset" fill="freeze" values="1;0.1" keyTimes="0;1" dur="1s" repeatCount="1" begin="svgGrad.mouseout" />
-->
      </stop>
    </radialGradient>
  </defs>

  <rect id="svgGrad" width="500" height="500" rx="0" ry="0" fill="url(#svgGrad-fill)" />
</svg>
</div>


<div class="col">
<h3>Ease-in-out</h3>
<svg viewBox="0 0 500 500">
  <defs>
    <radialGradient id="svgGradFillEaseInOut" cx="50%" cy="50%" r="0.5" spreadMethod="pad" gradientUnits="objectBoundingBox">
      <stop offset="0%" stop-color="#ff0000" />
      <stop offset="10%" stop-color="#000">
        
        <animate attributeName="offset" fill="freeze" values="0.1;1;0.1" keyTimes="0;0.5;1" calcMode="spline" keySplines="0.42 0 0.58 1; 0.42 0 0.58 1" dur="1s" repeatCount="indefinite" begin="0" />
        <!--
        <animate attributeName="offset" fill="freeze" values="0.1;1" keyTimes="0;1" calcMode="spline" keySplines="0.42 0 0.58 1" dur="1s" repeatCount="1" begin="svgGradEaseInOut.mouseover" />
        <animate attributeName="offset" fill="freeze" values="1;0.1" keyTimes="0;1" calcMode="spline" keySplines="0.42 0 0.58 1" dur="1s" repeatCount="1" begin="svgGradEaseInOut.mouseout" />
-->
      </stop>
    </radialGradient>
  </defs>
  <rect id="svgGradEaseInOut" width="500" height="500" rx="0" ry="0" fill="url(#svgGradFillEaseInOut)" />
</svg>
</div>


<div class="col">
<h3>Ease-in</h3>
<svg viewBox="0 0 500 500">
  <defs>
    <radialGradient id="svgGradFillEaseIn" cx="50%" cy="50%" r="0.5" spreadMethod="pad" gradientUnits="objectBoundingBox">
      <stop offset="0%" stop-color="#ff0000" />
      <stop offset="10%" stop-color="#000">
        <animate attributeName="offset" fill="freeze" values="0.1;1;0.1" keyTimes="0;0.5;1" calcMode="spline" keySplines="0.42 0 1 1; 0.42 0 1 1" dur="1s" repeatCount="indefinite" begin="0" />

        <!--
        <animate attributeName="offset" fill="freeze" values="0.1;1" keyTimes="0;1" calcMode="spline" keySplines="0.42 0 1 1" dur="1s" repeatCount="1" begin="svgGradEaseIn.mouseover" />
        <animate attributeName="offset" fill="freeze" values="1;0.1" keyTimes="0;1" calcMode="spline" keySplines="0.42 0 1 1" dur="1s" repeatCount="1" begin="svgGradEaseIn.mouseout" />
-->
      </stop>
    </radialGradient>
  </defs>
  <rect id="svgGradEaseIn" width="500" height="500" rx="0" ry="0" fill="url(#svgGradFillEaseIn)" />
</svg>
</div>

<div class="col">
<h3>Ease</h3>
<svg viewBox="0 0 500 500">
  <defs>
    <radialGradient id="svgGradFillEase" cx="50%" cy="50%" r="0.5" spreadMethod="pad" gradientUnits="objectBoundingBox">
      <stop offset="0%" stop-color="#ff0000" />
      <stop offset="10%" stop-color="#000">
        
        <animate attributeName="offset" fill="freeze" values="0.1;1;0.1" keyTimes="0;0.5;1" calcMode="spline" keySplines="0.25 0.1 0.25 1; 0.25 0.1 0.25 1" dur="1s" repeatCount="indefinite" begin="0" />

        
        <!--
        <animate attributeName="offset" fill="freeze" values="0.1;1" keyTimes="0;1" calcMode="spline" keySplines="0.25 0.1 0.25 1" dur="1s" repeatCount="1" begin="svgGradEase.mouseover" />
        <animate attributeName="offset" fill="freeze" values="1;0.1" keyTimes="0;1" calcMode="spline" keySplines="0.25 0.1 0.25 1" dur="1s" repeatCount="1" begin="svgGradEase.mouseout" />
-->
      </stop>
    </radialGradient>
  </defs>
  <rect id="svgGradEase" width="500" height="500" rx="0" ry="0" fill="url(#svgGradFillEase)" />
</svg>
</div>

Workaround 2: CSS custom @property

By defining custom properties for start and end offsets we can also achieve a smooth gradient transition.

@property --offset1 {
  syntax: "<percentage>";
  inherits: false;
  initial-value: 0%;
}


@property --offset2 {
  syntax: "<percentage>";
  inherits: false;
  initial-value: 10%;
}


.gradient{
  background: radial-gradient( #FF0000 var(--offset1), #000 var(--offset2));
  transition:1s --offset1, 1s --offset2;
}

.gradient:hover{
  --offset1: 5%;
  --offset2:100%;
}
<h3>Gradient CSS</h3>
<svg id="svgDoc2" class="gradient" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 500 500">
</svg>

This won't work with CSS variables as we can't transition the background property itself.

In this approach we're applying a CSS gradient to the outermost (parent) SVG element – accepting CSS gradient styles just like a HTML element (unlike inner SVG elements).

However, the SMIL approach probably still offers the best cross-browser compatibility.

See also:

Upvotes: 3

Awais Chaudhry
Awais Chaudhry

Reputation: 3

To animate the radial gradient in your SVG you need to ensure that the properties being animated are compatible with CSS animations. In SVG you cannot directly animate the offset property of gradient stops using CSS. Instead, you need to use SMIL (Synchronized Multimedia Integration Language) for animating $VG properties.

Here's how you can modify your SVG to animate the radial gradient using SMIL:

<svg id="svgDoc" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 500 500" shape-rendering="geometricPrecision" text-rendering="geometricPrecision">

<defs>
  <radialGradient id="svgGrad-fill" cx="50%" cy="50%" r="50%" spreadMethod="pad" gradientUnits="objectBoundingBox">
    <stop id="svgGrad-fill-0" offset="0%" stop-color="#ff0000">
      <animate attributeName="offset" from="0%" to="10%" dur="3s" begin="svgDoc:hover" repeatCount="indefinite" />
    </stop>
    <stop id="svgGrad-fill-1" offset="10%" stop-color="#000">
      <animate attributeName="offset" from="10%" to="100%" dur="3s" begin="svgDoc:hover" repeatCount="indefinite" />
    </stop>
  </radialGradient>
</defs>

<rect id="svgGrad" width="500" height="500" rx="0" ry="0" fill="url(#svgGrad-fill)"/>
</svg>

Upvotes: 0

Related Questions