How to create a continuously animated glowing effect on curvy SVG lines using a clipping mask?

Could someone provide insights or guidance on how to accurately clip the SVG to the lines and ensure the animation loops continuously?

I’m working with an SVG that features curvy lines, and my goal is to create a visual effect where these lines appear to glow. To achieve this, I intend to use a clipping mask on a blurred white rectangle. The plan is to animate this rectangle so that as it moves across the lines, it gives the illusion of the lines glowing. While I have made some progress, I’m encountering two main issues.

First, I’m struggling to get the SVG to clip precisely along the curvy lines. Second, the animation of the moving rectangle doesn’t repeat infinitely as intended.

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@artem Yes, it is possible to create an SVG animation that precisely clips along curved lines and guarantees continuous looping by carefully evaluating your SVG structure and animation settings. Let’s dissect the actions to deal with your two primary concerns:

1. Accurate Trimming Along Spiral Lines:

  • SVG Path Element: Make sure the path element is used to define your SVG’s curved lines. With path commands like M, C, and L, you can define intricate shapes with the path element. The exact control over the lines’ form is offered by these commands.

  • Clipping Path: The clipPath element can be used to clip the glowing effect along the curved lines. Use a path element to define the clip-path that resembles the contours of your curved lines. This will limit the glowing effect to the area that has been defined.

  • Using the Clip Path: To clip any additional element or only the glowing rectangle, apply the clipping path. To access the id of the clip-path element, use the CSS property or the clip-path attribute.

2. Animation that Loops Constantly:

  • SVG Animation: You can use SVG animations like animate or animateTransform to make sure the moving rectangle’s animation continues indefinitely. To achieve the necessary motion, these animations can be applied to the rectangle’s x or y attributes.

  • Looping with begin and dur: Set the begin attribute to “0s” and the dur attribute to the length of the desired animation to make the animation loop constantly. If you have an infinite loop, set dur to a high value, such as “indefinite”.

  • Restarting on End: JavaScript allows you to restart an animation after it ends, resulting in a smooth loop. To accomplish this, reset the begin attribute to “0s” and add an event listener to the animation’s finish event.

For example:

Here’s an example of SVG code with a curvy line and a glowing rectangle animation:

<svg xmlns="" width="200" height="200">
  <!-- Define the path for the curvy line -->
  <path d="M10 80 C 40 10, 65 10, 95 80 S 150 150, 180 80" id="curvyLine"/>

  <!-- Define the clip path using the same path as the curvy line -->
  <clipPath id="clipPath">
    <use xlink:href="#curvyLine"/>

  <!-- Create a glowing rectangle with the clip path -->
  <rect x="10" y="10" width="180" height="180" fill="white" filter="url(#glow)" clip-path="url(#clipPath)">
    <!-- Add animation to move the rectangle -->
    <animate attributeName="x" from="10" to="190" dur="5s" begin="0s" repeatCount="indefinite" />

In this example, the rectangle moves along the curvy line, and the animation repeats infinitely. Make sure to adjust the values and attributes according to your specific SVG structure and animation requirements.