Comment #2 on issue 130339 by tk...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

(No comment was entered for this change.)

Comment #3 on issue 130339 by jam...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

(No comment was entered for this change.)

Comment #4 on issue 130339 by shawnsi...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

Assigning it to myself just so it doesn't get easily lost.   I'll post an  
update when I start working on it.

Comment #5 on issue 130339 by ccame...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

(No comment was entered for this change.)

Comment #6 on issue 130339 by ccame...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

The bug here appears to be with Safari, rather than Chrome.

In particular, if the point <x,y,z> is specified by  
-webkit-transform-origin, and the transformation matrix T is specified by  
-webkit-transform, then the overall transformation should be:
   [1 0 0 x]       [1 0 0 -x]
   [0 1 0 y] * T * [0 1 0 -y]
   [0 0 1 z]       [0 0 0 -z]
   [0 0 0 1]       [0 0 0  1]
It appears that Safari is not performing the final left-multiplication to  
re-center the content at the specified origin after the transform is  
performed.

I've attached a stripped-down version of the originally provided file,  
along with its rendering in Chrome and Safari.  The top image shows that an  
identity transformation with non-zero Z-origin has a non-identity effect on  
Safari.  The middle image shows an ordinary rotateY(180deg).  The bottom  
image verifies that a non-zero Z-origin correctly affects a rotateY(180deg)  
transformation on Chrome.

Marking works-as-intended and will follow up with a bug report to Safari.

Attachments:
        perspective-test-ex.html  1.9 KB
        ex-chrome.png  75.5 KB
        ex-safari.png  97.3 KB

Comment #7 on issue 130339 by shawnsi...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

Did you have a chance to double-check exactly why Safari and Chromium  
behavior differ?  When we left off our offline discussion, we forgot that  
question was still in the back of our heads =)

Its probably worth digging into that, at least for a little while.  
Personally I did not expect that their behavior would differ; I thought the  
transform-origin was handled by WebCore for both Safari and Chromium.

Comment #8 on issue 130339 by ccame...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

Filed bug against WebKit for Safari follow-up
https://bugs.webkit.org/show_bug.cgi?id=88587

Comment #9 on issue 130339 by ccame...@chromium.org: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

Thanks, I just double-checked and WebKit nightly indeed reproduces the  
issue.  From the discussion in the WebKit bug it looks like this is an  
already-known issue.

Comment #11 on issue 130339 by pet...@google.com: Chrome ignores 3rd  
parameter of -webkit-transform-origin
http://code.google.com/p/chromium/issues/detail?id=130339

I spoke to the dev who originally brought this bug to my attention, and we  
both feel it is still a bug in webkit, but working in the 3D space makes it  
a bit harder to figure out.  He's going to create another example and we'll  
get it attached to this this week.