RE: [cgmo-webcgm] ISSUE: In what components is 'transform' defined?

["Weidenbrueck, Dieter" <dweidenbrueck@ptc.com>]

Stuart,

again, inline... 

-----Original Message-----
From: Galt, Stuart A [mailto:stuart.a.galt@boeing.com] 
Sent: Freitag, 18. Januar 2008 19:30
To: Weidenbrueck, Dieter; Cruikshank, David W; Lofton Henderson;
cgmo-webcgm@lists.oasis-open.org
Subject: RE: [cgmo-webcgm] ISSUE: In what components is 'transform'
defined?

My responses are below.

--
Stuart Galt
SGML Resource Group
stuart.a.galt@boeing.com
(206) 544-3656

 

> -----Original Message-----
> From: Weidenbrueck, Dieter [mailto:dweidenbrueck@ptc.com]
> Sent: Friday, January 18, 2008 9:43 AM
> To: Galt, Stuart A; Cruikshank, David W; Lofton Henderson; 
> cgmo-webcgm@lists.oasis-open.org
> Subject: RE: [cgmo-webcgm] ISSUE: In what components is 'transform' 
> defined?
> 
> Stuart,
> 
> interesting idea about segments, however, that would require to turn 
> every addressable object into a segment. So there is a significant 
> overhead just for the purpose of somebody eventually applying a 
> transform.

Would it be possible to only create a segement at the application
structure level if it is actually used in the metafile or called out in
the xcf?  I was just trying to see if we could use or extend existing
constructs.  I agree turning every APS into a virtual segment would
cause too much overhead.
DW: So you are talking about a CGM containing regular grobjects only
that should be considered as segments at runtime?

> 
> It would also mean that transforms could not be applied to WebCGM 1.0 
> or 2.0 (and hence ATA and S1000D) files, which is not really 
> acceptable.

I am not sure how we could do something in 2.1 that would suddenly make
transforms possible with 1.0/2.0 data.  Or were you suggesting that I
could take a 2.1 XCF file and a older CGM file and have it work with a
2.1 viewer?
DW: sure, this is straightforward. Since the style properties/transform
attributes are applied using DOM or XCF they will work as well as
setting a different lineweight or adding a namespaced attribute to a
WebCGM 1.0 file.
 
> The math is clear, and we already know that we need 3x3 matrices (to 
> be able to include shearing). That should make our discussion an easy 
> one, I guess. This is what SVG does, this is what PostScript does.

Yes the 3x3 matrix is what is needed and is used by most things that do
a 2D to 2D coordinate transfomation.  Only six terms in the matrix need
to be specified because the bottom row is not really needed to produce
the new 2D coordinate.