From: <bugzilla@jessica.w3.org>
Date: Tue, 01 May 2012 23:01:30 +0000

Message-Id: <E1SPM4Y-0005Sx-55@jessica.w3.org>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=16406

--- Comment #4 from Dirk Schulze <dschulze@adobe.com> 2012-05-01 23:01:29 UTC ---
Based on the comments on [1] so far I modified the text to:

""
<h2 id="#two-dimensional-subset">
Two Dimensional Subset
</h2>

<p>
UAs might just support two-dimensional transformations as a
subset of this
specification. In this case <a
href="#three-d-transform-functions">three-dimensional
transforms</a> and the properties 'transform-style',
'perspective', 'perspective-origin' and 'backface-visibility'
must not be supported.
Section <a href="#transform-3d-rendering">3D Transform
Rendering</a> does not apply.
Matrix decomposing uses the technique taken from the "unmatrix"
method in "Graphics
Gems II, edited by Jim Arvo", simplified for the 2D case.
Section
<a href="#mathematical-description">Mathematical Description of
Transform
Functions</a> is still effective but can be reduced by using a
3x3
transformation matrix where <em>a</em> equals <em>m11</em>,
<em>b</em> equals
<em>m12</em>, <em>c</em> equals <em>m21</em>, <em>d</em> equals
<em>m22</em>,
<em>e</em> equals <em>m41</em> and <em>f</em> equals
<em>m42</em> (see <a
href="#MatrixDefined">A 2D 3x2 matrix with six parameter</a>).
</p>

<img src="3x3matrix.png" alt="3x3 matrix" title="\begin{bmatrix}
a & c & e \\ b
& d & f \\ 0 & 0 & 1 \end{bmatrix}" width="82" height="79">

<div class="example">
<p>
Authors can easily provide a fallback for UAs without 3D
support. The following
example has two property definitions for 'transform'. The
first one consists of
two two-dimensional transform functions. The second one has a
two-dimensional and
a three-dimensional transform function.
</p>
<pre>div {
transform: scale(2) rotate(45deg);
transform: scale(2) rotate3d(0, 0, 1, 45deg);
}</pre>

<p>
For a UA with 3D support, the second definition will override
the first one. For
a UA without 3D support, the second definition is invalid and
it falls back to the
first definition.
</p>
</div>
""

[1] http://lists.w3.org/Archives/Public/public-fx/2012AprJun/0089.html

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Received on Tuesday, 1 May 2012 23:01:33 UTC

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