[webkit-dev] css: rotateY(90) with perspective()

Shawn Singh shawnsingh at chromium.org
Tue Feb 12 11:49:48 PST 2013

Hi Marcin,

I wonder if you might accidentally have a "perspective-origin" set
differently?  Or maybe there is something in your code where window size
that affects how the transforms appear?  Maybe you can attach a reduced
simple example of the difference you're seeing?   I just whipped up the
following example, which renders almost exactly the same geometry on both
Firefox and tip-of-tree Chromium.

  <div style="-moz-transform: perspective(500px) rotateY(80deg);

              -webkit-transform: perspective(500px) rotateY(80deg);

              background-color: lime;

              width: 300px;

              height: 300px;" >

Changing the rotateY to use 90deg makes the layer disappear for both
Firefox and Chromium, too.


On Tue, Feb 12, 2013 at 9:53 AM, Dana Jansens <danakj at chromium.org> wrote:

> +shawnsingh
> On Tue, Feb 12, 2013 at 9:22 AM, Marcin Szamotulski <mszamot at gmail.com>wrote:
>> Dear WebKit-Dev,
>> I found an interesting difference between implementation of css 3d
>> transforms in Gecko (FireFox) and Chromium (WebKit).  In Gecko, the
>> following css rule:
>> tranform: perspective(500px) rotateY(90)
>> rotates an element (let say an image) so that it is perpendicular to the
>> viewer, i.e. it shows the side of the element - hence nothing is printed
>> to the screen, since html elements have no depth.  While in WebKit based
>> browsers (I have tested this in both Chromium and surf from suckles.org)
>> the elements is shown at an angle: both rotations (Gecko & WebKit) have
>> the same axis (the vertical screen directions).  Testing different
>> angles I have found that I need to use rotateY(107deg), but this might
>> depend on the perspective.   The reason for this is that WebKit and
>> Gecko are computing 3d view in a different way.  The additional minor
>> difference is that rotateY(30deg) in Gecko turns an element 30deg to the
>> right while in WebKit it rotates to the left (with a different 3d view).
>> The reason I found it is because I try to make an animation which turns
>> a picture around 180deg showing a new picture on the other side, and
>> I wanted to change the picture in the middle (90deg).  This works for
>> Gecko but for WebKit I need to know how to compute the angle at which
>> the element (image) is perpendicular to the view source (showing its
>> side to the viewer).  Can somebody point me how the 3d rotationY with
>> a given perspective is calculated so I can make the necessary
>> converstion.
>> Best regards,
>> Marcin Szamotulski
>> _______________________________________________
>> webkit-dev mailing list
>> webkit-dev at lists.webkit.org
>> https://lists.webkit.org/mailman/listinfo/webkit-dev
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