Re: [csswg-drafts] [css-borders-4] Interpolation of `corner-shape` superellipsis (#11608)

The CSS Working Group just discussed ``[css-borders-4] Interpolation of `corner-shape` superellipsis``, and agreed to the following:

* `RESOLVED: interpolate linearly across the corner diagonal and compute the parameter backwards from that`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> noamr: this shoudln't be contentious<br>
&lt;TabAtkins> noamr: let me show how it interpolates<br>
&lt;TabAtkins> noamr: the interpolation takes the "half corner", th emiddle point, put it on the diagonal line and interpolate *that*. work backwards to get the superellipse parameter<br>
&lt;TabAtkins> noamr: otherwise any interpolation in the paramter space itself would spend too much time in the extreme values<br>
&lt;fantasai> TabAtkins: This does sound like the most reasonable interpolation method<br>
&lt;TabAtkins> astearns: any indication from Simon?<br>
&lt;TabAtkins> noamr: he did this visualization.<br>
&lt;TabAtkins> noamr: everything i'm presenting here I worked together with Simon<br>
&lt;TabAtkins> ack<br>
&lt;astearns> ack TabAtkins<br>
&lt;TabAtkins> fantasai: TAb, you mentioned the "effectively square" is 10 or so on both sides<br>
&lt;TabAtkins> fantasai: above 10<br>
&lt;TabAtkins> fantasai: it basically doesn't do much?<br>
&lt;TabAtkins> noamr: it's basically equivlanent unless your screen is enormous<br>
&lt;TabAtkins> fantasai: should we declare that 10 gets rounded to a sharp corner?<br>
&lt;TabAtkins> fantasai: so the CSS range is effectively -10 to 10?<br>
&lt;TabAtkins> astearns: if your shape is very large you might get a jump<br>
&lt;TabAtkins> noamr: shouldn't have it as part of interpolation<br>
&lt;TabAtkins> noamr: the animation would appear to be faster in the middle if we did that<br>
&lt;TabAtkins> noamr: in the current chrome prototype we *do* clamp to 10/-10, it makes the math easier<br>
&lt;TabAtkins> noamr: but not sure it's useful in the specs<br>
&lt;TabAtkins> fantasai: the reason it might be useful is, it's harder for the authro to know that to get an actually sharp corner they need to use a much bigger value<br>
&lt;fantasai> TabAtkins: The interpolation behavior defined here is that we don't interpolate the parameter, we interpolate the diagonal line.<br>
&lt;fantasai> TabAtkins: so you get a linear interpolation through the diagonal space<br>
&lt;fantasai> TabAtkins: so you get a visually smooth value instead of changing speed<br>
&lt;fantasai> fantasai: Would it make sense to make that the parameter?<br>
&lt;fantasai> TabAtkins: No, because then squircles and other common values would be weird numbers.<br>
&lt;TabAtkins> noamr: yeah, round is sqrt(2)/2<br>
&lt;TabAtkins> astearns: any other comments/question?<br>
&lt;TabAtkins> astearns: so proposed is we interpolate linearly across the corner diagonal and compute the parameter backwards from that<br>
&lt;TabAtkins> astearns: objection?<br>
&lt;TabAtkins> RESOLVED: interpolate linearly across the corner diagonal and compute the parameter backwards from that<br>
</details>


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Received on Tuesday, 1 April 2025 15:23:23 UTC