[Webkit-unassigned] [Bug 82956] [chromium] TransformationMatrix::to2dTransform seems unnecessary in LayerRendererChromium
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Mon Apr 2 16:17:29 PDT 2012
https://bugs.webkit.org/show_bug.cgi?id=82956
--- Comment #2 from Adrienne Walker <enne at google.com> 2012-04-02 16:17:29 PST ---
(In reply to comment #1)
> > As it stands, the function seems to be a gigantic no-op then, isn't it? why do we need to do this operation? It doesn't make anything faster; using 2d quads and points will already bypass the 3rd row and 3rd column, and everything else (inversion in particular) still operates on a 4x4 matrix.
>
> The function is not a no-op. For some values of transform,
>
> transform.to2dtransform().inverse().mapQuad(quad) != transform.inverse().mapQuad(quad)
Haha, I realize this is exactly the same as the first thing you quote from me. I think maybe I had some thought that not dropping the 3d transform part of the matrix would result in a different value when you projected back since you'd flattened that point to 2d and inflated in 2d.
Tests would certainly be helpful at this point in the conversation.
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