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RE: More on getObjectExtent()

From: Bezaire, Benoit <bbezaire@ptc.com>
Date: Mon, 1 Dec 2008 09:49:11 -0500
Message-ID: <B0D4682CF6F84041AC7C42AA6E9E81330C68D447@HQ-MAIL3.ptcnet.ptc.com>
To: "WebCGM WG" <public-webcgm-wg@w3.org>
Hi Dieter,
I think most of them (except rasters) have been addressed. However, I do
not think the group agreed to treat text as path.


From: public-webcgm-wg-request@w3.org
[mailto:public-webcgm-wg-request@w3.org] On Behalf Of Weidenbrueck,
Sent: Sunday, November 30, 2008 12:50 PM
To: Lofton Henderson; WebCGM WG
Subject: RE: More on getObjectExtent()

good start. Do we need to add something about
- raster images
- text (should be treated as paths)
- visibility/transparency (do they have an impact or not)
- transformations (they do have an impact)


From: public-webcgm-wg-request@w3.org
[mailto:public-webcgm-wg-request@w3.org] On Behalf Of Lofton Henderson
Sent: Sonntag, 30. November 2008 17:26
Subject: Re: More on getObjectExtent()

Since not everyone is satisfied with the simple fix of "s/abstract
locus/locus/" in 5.7.6, I'll make a proposal to close the "locus" issue:
delete the word "abstract" and link "locus" to a glossary entry.  

Here is a first draft proposal:  

locus -- 
The Oxford dictionary defines locus as:  "Curve formed by all points
satisfying particular equation of relation between coordinates, or by
point, line, or surface, moving according to mathematically defined
conditions."  In the WebCGM specification, locus refers to the set of
points that comprise the path or shape of a Graphical Primitive element,
or in the appropriate context, the combined shapes or paths collectively
of all of the Graphical Primitive elements in an Application Structure
(APS).  I.e., the locus of an APS comprises the combined loci of all of
the graphical primitives in the APS.  Locus does not include defining
data that are not part of the shape or path of the graphical primitive,
such as control points of Bezier primitives, or the center point of a
Circular Arc Center primitive.

Question 1:  Are people okay with the solution of adding a definition to
the Glossary?

Question 2:  Suggestions for improvement of the definition?


At 09:45 AM 11/19/2008 -0700, Lofton Henderson wrote:

	At 08:32 AM 11/19/2008 -0800, David Cruikshank wrote:

		I would agree with dropping "abstract".  Locus is a
perfectly valid term to define the path of the primitive.
		Probably ought to capture it somewhere to document the

	Just to clarify that last sentence -- you mean that you support
the issue processing proposal to roll it into Issue3 in the DoC (see URI

		On Wed, Nov 19, 2008 at 8:04 AM, Lofton Henderson
<lofton@rockynet.com> wrote:

			At 09:26 AM 11/19/2008 -0500, Bezaire, Benoit

				I think the wording should be revised. 

			Fair enough.

				Even Google doesn't come up with
anything meaning full for "Abstract locus".

			However, it does give lots of hits for a search
like "definition of mathematical locus".  And we use "locus" repeatedly,
in the proper sense, in the profile (Ch.6) -- i.e., "locus" is a pretty
common term in  and has been used in WebCGM, for example, since 1999.
So it is my hastily-invented modifier "abstract" that is problematic.
			Actually, I think a good solution would be to
drop the word "abstract".  The next sentence after its occurrence fully
explains what "abstract" was meant to convey.  (And we have agreed to
clarify that sentence.)
			(See the getObjectExtent definition in 5.7.6:
http://docs.oasis-open.org/webcgm/v2.1/cs01/WebCGM21-DOM.html#L5095 .)
			(Shall I just add this to fix to the
clarification in DoC #3:
e3  ?)


				From: Lofton Henderson
				Sent: Tuesday, November 18, 2008 6:52 PM
				To: Bezaire, Benoit; WebCGM WG
				Subject: Re: More on getObjectExtent()
				At 01:52 PM 11/18/2008 -0500, Bezaire,
Benoit wrote:

				The wording says "[...] The bounding box
calculation is based on the abstract locus of the primitives within the
				What does 'abstract locus' mean?

				The locus is the set of points
comprising the drawn primitive (it's a term I dredged up from my memory
of some old math courses -- I hope I got it right).  "Abstract locus"
means that things like line width are not included, but rather only the
point positions as if the item were drawn with an abstract, infinitely
fine pen.

				I'd like to know if getObjectExtent()
returns a tight bounding box on a given APS. i.e., given a polybezier,
are control points part of the bounding box calculations or not?

				No.  The control points are part of the
defining data, but not part of the drawn primitive.
Received on Monday, 1 December 2008 14:49:52 UTC

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