[gl2ps] PDF not same as rendered image

[David Thompson]

Okay, sorry I haven't gotten back on this sooner--but I was trying to 
meet a deadline. I've now located at least a major issue as to why 
this was happening. What I had, for each ball located in the scene, 
there were actually anywhere from 4 - 20 coinciding balls the exact 
same size. So what was happening was that the triangle from one ball 
may have been at the front whereas in other areas other triangles 
were in front. In our software, our software renderer looks at the 
data structures and determines which one should always be in front 
based on a data value. When this data is passed to OpenGL, then the 
ViewMatrix is assessed and a half-pixel width is added to each object 
moving them toward the viewport keeping one in front of the other. 
However, with so many objects in the same space, this became almost 
unmanageable. OpenGL hardware still rendered it correctly but gl2ps 
didn't get the sorting correct with such small differences. Once I 
removed the coinciding balls, everything worked as expected.

David

At 10:02 PM +0200 9/2/04, Micha Bieber wrote:
>Thursday, September 2, 2004, 21:39:54, Christophe Geuzaine wrote:
>
>To bring it together, David confirmed to me per email, that the error
>shows up in PostScript as well as in native produced PDF. I would guess,
>that it is a problem of the feedback mode or something erroneous in the
>generating code (more likely). It is also interesting, that the most
>distant polyeder owns more or less proper colors and for the object in
>front half of the triangles have also the characteristic of the relevant
>correct blue shades. Considering also the remaining polyeders, the
>errors peculiarities seemingly change with every new object.
>
>Micha 
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>
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.............................................................................
David L. Thompson                   Visualization and Imagery Solutions, Inc.
mailto:dthompsn at vizsolutions.com    5515 Skyway Drive, Missoula, MT 59804
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