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Re: [css3-3d-transforms] Formal definition of 'backface-visibility'

From: Dean Jackson <dino@apple.com>
Date: Sat, 30 Jul 2011 00:44:29 -0700
Cc: www-style@w3.org
Message-id: <428269CF-1292-404D-B940-784BDCFF7567@apple.com>
To: "L. David Baron" <dbaron@dbaron.org>

On 26/07/2011, at 5:18 PM, L. David Baron wrote:

> http://dev.w3.org/csswg/css3-3d-transforms/#backface-visibility-property
> doesn't have any formal definition of when the "back" of something
> is visible.
> 
> For example, some obvious possible definitions would be:
> * if the element's transform involves projecting the vector [0 0 1]
>   to a result with a negative Z component
> * if the element's cross product of the transform of [1 0 0] and
>   the transform of [0 1 0] gives a result with a negative Z
>   component
> These two give different results in some cases (I think when the
> transform matrix has a negative determinant).

Yes, we need to define this. I think it's even a little more complex than this, because it involves the parent transform as well.

I'll try to come up with something and send it here and to the Mozilla bug.

Dean

> 
> Matt Woodrow implemented the latter in Gecko in
> https://bugzilla.mozilla.org/show_bug.cgi?id=505115 ; I'm not sure
> if that was for compatibility with WebKit.
> 
> -David
> 
> -- 
> 𝄞   L. David Baron                         http://dbaron.org/   𝄂
> 𝄢   Mozilla Corporation               http://www.mozilla.com/   𝄂
> 
Received on Saturday, 30 July 2011 07:44:59 GMT

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