How to round out corners when using CSS clip-path

Question

I want to be able to round out the 3 leftmost corners on this shape that I have created, any idea how that can be done?

div {
  position: absolute;
  z-index: 1;
  width: 423px;
  height: 90px;
  background-color: #b0102d;
  color: white;
  right: 0;
  margin-top: 10vw;
  -webkit-clip-path: polygon(100% 0%, 100% 50%, 100% 100%, 25% 100%, 0% 50%, 25% 0%);
  clip-path: polygon(100% 0%, 100% 50%, 100% 100%, 25% 100%, 0% 50%, 25% 0%);
}

<div></div>

Answer 1

use inset with round property :

inset(0% 45% 0% 45% round 10px)

Answer 2

An SVG filter can round any kind of clip-path. You simply need to apply it to a parent element. Adjust the stdDeviation to control the radius:

.box {
  width: 423px;
  height: 90px;
  background-color: #b0102d;
  color: white;
  clip-path: polygon(100% 0%, 100% 50%, 100% 100%, 25% 100%, 0% 50%, 25% 0%);
}

.parent {
  filter: url('#goo');
  overflow:hidden;
  position: fixed;
  right:-50px;
  z-index: 1;
  margin-top: 10vw;
}

<div class="parent">
  <div class="box"></div>
</div>

<svg style="visibility: hidden; position: absolute;" width="0" height="0" xmlns="http://www.w3.org/2000/svg" version="1.1">
  <defs>
        <filter id="goo"><feGaussianBlur in="SourceGraphic" stdDeviation="8" result="blur" />    
            <feColorMatrix in="blur" mode="matrix" values="1 0 0 0 0  0 1 0 0 0  0 0 1 0 0  0 0 0 19 -9" result="goo" />
            <feComposite in="SourceGraphic" in2="goo" operator="atop"/>
        </filter>
    </defs>
</svg>

Related: https://stackoverflow.com/a/65485455/8620333

Answer 3

I've recently found success experimenting with approaches like this...

SVG

<svg width="0" height="0">
  <defs>
    <clipPath id="clipped">
      <circle cx="var(--myRad)" cy="var(--myRad)" r="var(--myRad)"></circle>
      <circle cx="var(--myRad)" cy="calc(var(--myHeight) - var(--myRad))" r="var(--myRad)"></circle>
      <circle cx="calc(var(--myWidth) - var(--myRad))" cy="calc(var(--myHeight) - var(--myRad))" r="var(--myRad)"></circle>
      <circle cx="calc(var(--myWidth) - var(--myRad))" cy="var(--myRad)" r="var(--myRad)"></circle>
      <rect y="var(--myRad)" width="var(--myWidth)" height="calc(var(--myHeight) - (2 * var(--myRad)))"></rect>
      <rect x="var(--myRad)" width="calc(var(--myWidth) - (2 * var(--myRad)))" height="var(--myHeight)"></rect>
    </clipPath>
  </defs>
</svg>

CSS

.clipped {
  --myWidth: 100vw;
  --myHeight: 10rem;
  --myRad: 2rem;
  clip-path: url(#clipped);
}

I found this useful as compared to using border-radius with overflow set to hidden, because this approach doesn't create a BFC or break things like sticky position and css perspective effects. Also, this allows you to "inset" the position of the svg paths to clip inside the element with a "corner-radius" if you want.

Answer 4

You can also mess around with the circle to get some different effects.

-webkit-clip-path: circle(60.0% at 50% 10%);
clip-path: circle(50.0% at 50% 50%);

Codepen

Too bad you can't combine the polygon and circle... or maybe you can and I haven't played around with it enough to figure it out. HTH

Answer 5

clip-path: inset(45% 0% 33% 10% round 10px)

Answer 6

I don't have a comment option yes, so I'm writing it as an answer..

you need to write as many points as possible to round the corner. Nothig else... for, example a few more points to make lower part bit rounder:

-webkit-clip-path: polygon(100% 0%, 100% 100%, 100% 100%, 25% 100%, 5% 70%,1% 60%, 0% 50%, 25% 0%);

oh, yes, or SVG as comment people here.. :)

Answer 7

You could use a child element and do a nested clip-path on that and the child's pseudo element. The parent will do a polygon clip on the shape first, then the pseudo will have an ellipse to round the borders. The clips will have a combined effect.

.parent, .parent div, .parent div:before {
  width: 423px;
  height: 90px;
  position: absolute;
}

.parent {
  right: 0;
  background-image: linear-gradient(to right, transparent 210px, #b0102d 210px);
  margin-top: 15vh;
}

.parent div {
  clip-path: polygon(100% 0%, 100% 100%, 25% 100%, 0 50%, 25% 0);
}

.parent div:before {
  content: "";
  background-color: #b0102d;
  clip-path: ellipse(200px 45px at 210px);
}

<div class="parent">
  <div></div>
</div>

Here is the demo with some adaptations to illustrate what's going on:

.parent, .parent div, .parent div:before {
  width: 423px;
  height: 90px;
  position: absolute;
}

.parent {
  right: 0;
  background-image: linear-gradient(to right, transparent 210px, yellow 210px);
  margin-top: 15vh;
}

.parent div {
  background-color: blue;
  clip-path: polygon(90% 0%, 90% 100%, 25% 100%, 0 50%, 25% 0);
}

.parent div:before {
  content: "";
  background-color: #b0102d;
  clip-path: ellipse(200px 45px at 210px);
}

<div class="parent">
  <div></div>
</div>

The horizontal size and position of the ellipse can be used to get a different effect on the edges. Note that the background starting postion of the parent needs to be adjusted to the same value as the placement of the ellipse (last value in the clip-path) because it fills up whatever gets clipped off on the right side. This can be visualised by removing background-color: blue from .parent div in the second demo.

Here is an additional Codepen to to try it out.