W3C home > Mailing lists > Public > www-style@w3.org > November 2013

Re: [css3-background][css-shapes] spread rounding

From: Alan Stearns <stearns@adobe.com>
Date: Mon, 18 Nov 2013 13:17:04 -0800
To: fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <CEAFC366.339FE%stearns@adobe.com>
On 11/18/13 10:47 AM, "fantasai" <fantasai.lists@inkedblade.net> wrote:

>On 11/15/2013 10:18 AM, Lea Verou wrote:
>> Sooo, after some discussion at TPAC after the recent F2F, some of us
>>(fantasai, dbaron, plinss, me) decided that even though
>> the edge cases about precision aren't that big of a problem, the
>>currently defined behaviour results in abruptness when
>> border-radius interpolates from 0 to any positive value. Therefore, we
>>think the spread rounding should be changed to be
>> defined as:
>> spread rounding = border-radius + spread * ratio(x)
>> where x = border-radius / spread and ratio() is a continuous strictly
>>increasing function that is 0 when border-radius is 0
>> and becomes 1 after a certain point. Therefore, it would still be 0 at
>>0 and mostly the same for small differences between the
>> border-radius and the spread size, but would progressively increase
>>when the border-radius is considerably smaller than the
>> spread size.
>> We tried many functions for what ratio() could be [1], and I made a
>>demo of the three best ones that you can find here [2]. We
>> think Cubic works best, which is 1 + (x-1)^3 in [0,1] and 1 when x > 1.
>>Not only this makes interpolation smoother, but it
>> also is more aesthetically pleasing, which reduces the need for manual
>> ˛filleting˛ (as demonstrated in [3]).
>Given the results from
>   http://dev.w3.org/csswg/css-backgrounds/spread-radius
>and how much better the outer edge looks with the cubic
>interpolation, I'm thinking we should do the same for
>the margin box curve for Shapes.
>Alan, thoughts?

I think that would be fine.


Received on Monday, 18 November 2013 21:17:35 UTC

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