css - Responsive clip-path with inline SVG

Question

On an element with a background (image or solid color don't really matter):

<header id="block-header"></header>

I am trying to apply a clip-path using SVG. To achieve this, I am putting SVG inline into the same element like this:

<header id="block-header">
    …
    <svg width="100%" height="100%" viewBox="0 0 4000 1696" preserveAspectRatio="none">
        <defs>
          <clipPath id="myClip">
            <path d="M0 1568.18V0h4000v1568.18S3206.25 1696 2000 1696C984.37 1696 0 1568.18 0 1568.18z"/>
          </clipPath>
        </defs>
    </svg>
    …
</header>

You can run the code snippet below or check the JSFiddle. You can see original SVG image (in black) put inline, having curviness along the bottom and being responsive. In contrast, the red rectangle shows the same image applied (or, rather, not applied) as a clip-path.

I guess I misunderstand either viewBox or preserveAspectRatio attributes though can not find what is exactly wrong here. Any help would be appreciated.

#block-header {
    background: Red;
    min-height: 100px;
    -webkit-clip-path: url(#myClip);
clip-path: url(#myClip);
}

<h1>SVG image</h1>
<svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100" viewBox="0 0 4000 1696" preserveAspectRatio="none"><path d="M0 1568.18V0h4000v1568.18S3206.25 1696 2000 1696C984.37 1696 0 1568.18 0 1568.18z"/></svg>

<h1><code>clip-path</code> using the same SVG</h1>
<header id="block-header">
    <svg width="100%" height="100" viewBox="0 0 4000 1696" preserveAspectRatio="none">
        <defs>
          <clipPath id="myClip">
            <path d="M0 1568.18V0h4000v1568.18S3206.25 1696 2000 1696C984.37 1696 0 1568.18 0 1568.18z"/>
          </clipPath>
        </defs>
    </svg>
</header>

Answer 1

References to SVG clip paths are to the clip path definitions themselves and the dimensions or other attributes of the <svg> are meaningless in this context.

What is happening in your example is that you are applying a 4000 px wide clip path to your header. Which is probably only of the order of 900 px wide. So the curvature isn't visible.

If you want a responsive clip path, you should define it using clipPathUnits="objectBoundingBox".

#block-header {
    background: Red;
    min-height: 100px;
    -webkit-clip-path: url(#myClip);
clip-path: url(#myClip);
}

<h1>SVG image</h1>
<svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100" viewBox="0 0 1 1" preserveAspectRatio="none"><path d="M0,0 1,0 1,0.9 C 1,0.9, 0.77,1, 0.5,1 0.23,1, 0,0.9,0,0.9z"/></svg>

<h1><code>clip-path</code> using the same SVG</h1>
<header id="block-header">
    <svg width="0" height="0">
        <defs>
          <clipPath id="myClip" clipPathUnits="objectBoundingBox">
            <path d="M0,0 1,0 1,0.9 C 1,0.9, 0.77,1, 0.5,1 0.23,1, 0,0.9,0,0.9z"/>
          </clipPath>
        </defs>
    </svg>
</header>