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Re: SVG Compositing + 3D Transform

From: Alex Danilo <alex@abbra.com>
Date: Mon, 16 May 2011 21:06:06 +1000
Message-Id: <66CALL.B5MFDI26OLEN@abbra.com>
To: robert@ocallahan.org
Cc: Dirk Schulze <vbs85@gmx.de>, www-svg List <www-svg@w3.org>
Hi Dirk & Rob,

Rob is correct, 
there should be no problems with comp-op as the render of the
object containing the comp-op is atomic and done over the existing background.

Similarly, there would be no issue for z-index if applied to SVG.

Rob, I'm not sure what you mean by preserve-3d?

The comp-op is applied when the object is rendered to the canvas. So if a depth
buffer is used then it will perform the composite in z-order for the Z position
of the object. I'll have to look at preserve-3D more since I haven't looked
at it yet.


--Original Message--:
>On Mon, May 16, 2011 at 7:19 PM, Dirk Schulze <vbs85@gmx.de> wrote:
>I have a short question about combining the new specifications 3D Transform and Compositing (and maybe z-index as well). Isn't it possible that the source graphic could be placed behind the destination graphic with 3D Transforms? How would that influence the compositing of both graphics?
>First of all, let me note that 'comp-op' applied to non-SVG content needs to induce a CSS psuedo-stacking-context as 'opacity', 'filter' and other group compositing operations do, to ensure that the element can be rendered as an atomic unit (without having its parents interleaved with the parts of other elements in z-order).
>Then, your issue isn't a problem for z-index or 3D transforms without preserve-3d. In those cases, elements and their parts can be rendered one by one onto the destination canvas, in the order defined by CSS z-index. When you need to render an element with 'comp-op', the contents of the background are clearly defined and so is the result of the comp-op.
>With preserve-3d though, there might be an issue, depending on whether depth buffering is supposed to be used. I believe the spec there is still unclear. If depth buffering is used then it's not clear what comp-op should do.
>"Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true." [Acts 17:11]
Received on Monday, 16 May 2011 11:06:44 UTC

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