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Re: [Rendering order] z-depth and 3D effects

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Wed, 18 Nov 2009 12:54:05 +0200
To: www-svg@w3.org, steve@withallyourequire.com
Message-Id: <200911181154.05463.Dr.O.Hoffmann@gmx.de>
Hello,

I think, the main problem with a 'real' z-axis is, that
for 3D-transformed objects there can be a different
z for any fragment of the object.
Therefore if there is more than one object, the 
objects can intersect in a complex way.
From a simple 2D-viewer one cannot expect
a proper computation of such intersections without
the help of the authors. From a 3D-viewer one can
expect this.

If SVG2.0-viewers are not expected to be such
advanced 3D-viewers, objects can have only one
z-value to rearrange the rendering order without
solving the problem of intersections.
If this z-information is explicitly given or at least 
implicitly known to the viewer for each object, 
such a 3D-effects model can be kept simple
(there can be of course different approaches more
or less useful/convenient for authors).

The first step to clarify the intended 3D approach for SVG 2.0
therefore would be to say, whether a shape/object/path
can have more than one z-value or not.
After this decision or clarification one can go into details
how to get any effect at all.

Olaf
Received on Wednesday, 18 November 2009 10:56:28 GMT

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