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Subject: Re: [cgmo-webcgm] Error in nurbs01 test

Rob (& Dave),

Thanks for this analysis...

At 02:03 PM 3/8/2006 -0700, Robert Orosz wrote:
>There is an error in the nurbs01 test in the test suite.  It appears that
>the interpreter/viewer used to generate the reference PNG image ignored the
>weights in the NURBS element.

The file came from Boeing.  It came with an original reference PNG.  When 
the file arrived, the NURBS object was oddly positioned, and so I used 
'cgmconv' to fiddle with the VDC Extent to position and scale the object 
("circle") better in the picture frame.  I then had to regenerate the PNG, 
but didn't look closely enough at it apparently.

Attached is the original CGM that Dave sent.  Unfortunately, I was careless 
and didn't preserve his original PNG.

Dave, could you please:

1.) regenerate a new PNG for the current (FTP) posted version of 
NURBS01.cgm?  (Also for your old original CGM, just for completeness of my 

2.) fly this past the originator of that NURBS test for his/her input?


p.s.  Rob, I'll give your suggested test (below) a try.

>To illustrate my point, I've generated an
>equivalent file (without the boilerplate text labels) containing a NUBS
>element which is unweighted by definition.  The knot vector is identical to
>the nurbs01 test, and I've placed the control points at metrically
>equivalent positions in VDC space.  This file views identically to the NURBS
>element in the NURBS01.cgm file as depicted in the PNG image.  Applying
>weights to the spline should significantly alter the shape of the curve.
>You could do an equivalent test by using your convert program to remove the
>weights in the NURBS element (i.e. set them all to 1.0) in the NURBS01.cgm
>file.  You will see similar results.
>  <<NUBS01_rob.cgm>>


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