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Re: [css3-transforms] interpolation of transform lists

From: L. David Baron <dbaron@dbaron.org>
Date: Mon, 23 Jul 2012 15:21:16 -0700
To: Chris Marrin <cmarrin@apple.com>
Cc: Dirk Schulze <dschulze@adobe.com>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <20120723222116.GA28737@crum.dbaron.org>
On Monday 2012-07-23 09:22 -0700, Chris Marrin wrote:
> 
> On Jul 19, 2012, at 5:51 PM, L. David Baron <dbaron@dbaron.org> wrote:
> 
> > On Thursday 2012-07-19 16:54 -0700, Dirk Schulze wrote:
> >> Do I understand your point correctly, that you just want the
> >> affected transformation functions to get interpolated as matrices?
> > 
> > Yes, rather than forcing the entire list to be interpolated as a
> > single matrix.
> 
> You're complicating the rules by doing this. If I have:
> 
> rotate(...) scale(...) translate(...)
> scale(...) rotate(...) translate(...)
> 
> Do you do two separate matrix animations? Taking that to its
> logical conclusion, you could end up doing a dozen expensive
> matrix animations for a long list of unmatched primitives.

I'm fine with doing that as a single matrix animation.

The "affected transformation functions" in the most deeply quoted
text was referring to perspective(), rotate3d(), matrix(), and
matrix3d().  What I don't like is the idea that interpolating
between:
  transform: perspective(5px) skewY(0deg)
and:
  transform: perspective(5px) skewY(30deg)
should do a matrix interpolation for the entire list because the
perspective function is defined by the current spec as not having a
corresponding primitive.  (This was not a problem in earlier
drafts.)  I'd like to stick to the principle established in the
earlier draft that if the lists match, they're interpolated
item-by-item.  It seems confusing for authors to do that most of the
time but not all of the time.

To be clear, though, to restate my response to the most deeply
quoted text above:  I don't particularly care whether they're
interpolated as matrices or interpolated some other way (esp. for
perspective() and maybe for rotate3d()).

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Monday, 23 July 2012 22:21:42 GMT

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