From: Yair Kurzion (yair++at++polygon.engr.sgi.com)
Date: 08/28/2002 11:46:14
Hi Peter !
Answering your second question:
Please take a look at the following:
- man pages
pfDoubleDCS
pfDoubleSCS
pfDoubleFCS
- sample programs:
/usr/share/Performer/src/pguide/libpf/C/doubleDCS.c
/usr/share/Performer/src/pguide/libpf/C/doubleDCS2.c
- info-performer archives (search for pfDoubleDCS):
http://oss.sgi.com/projects/performer/mail/info-performer/
Good luck,
-yair
> we would like to make a Vissim-Performer application for a flight
> simulator. It should cover a considerable large gaming area (10x10 deg
> lat/lon). Our questions are:
>
> 1. How are the coordinates of the database vertices represented best? What
> is common for such large scale applications:
> - geocentric (lat,lon,alt) (only one referece point)
> - cartesian (x,y,z) (earth-centred reference point)
> - cartesian (x,y,z) (one local reference point, might be far away)
> - cartesian (x,y,z) (various reference points, maybe for each tile to be
> paged)
>
> 2. What is the best practise for positioning in the selected database, in
> order to avoid numerical problems and angular/positioning errors?
>
>
> We are aware, that different representation might cause distortions during
> rendering (e.g. when the reference point is far away from the viewing
> point).
>
> We tried UTM representation with one local reference point resulting in
> considerable angular distortions, when the viewing position was far away
> (> 60 nm) from the refrence point.
>
> We would like to use a geocentric database, but we do not know the proper
> transformation for setting the viewpoint in performer without losing
> numerical accuracy.
>
>
> Thanks for your help.
>
> Peter
>
>
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>
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