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

["Galt, Stuart A" <stuart.a.galt@boeing.com>]

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.

> 
> 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?
 
> 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.