Re: Picking with asymmetric Viewing Frustum

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Wolfgang Trog (Wolfgang.Trog++at++philosys.de)
Tue, 03 Nov 1998 13:07:48 +0100

Hi Marc and all Performers,

there was a related question in a mail in september (see
http://reality.sgi.com/performer/perf-98-09/0153.html). It seems that picking in an
orthogonal frustum will be implemented in Performer 2.2.3. Will this version allow
to do picking in an asymmetric frustum, too? Perhaps, somebody at SGI can clarify
this ?

Thanks,

Wolfgang

Marc Erich Latoschik wrote:

> Wolfgang Trog wrote:
> >
> > I try to do picking in a channel with an asymmetric viewing frustum. The
> > viewing frustum is set by pfMakePerspChan. E.g. to values 30 deg to
> > left, 32 deg to right and 22.5 top and bottom. Then, I do picking with
> >
> > NrHits = pfChanPick( Channel,
> > PFPK_M_NEAREST |
> > PFTRAV_IS_PRIM |
> > PFTRAV_IS_PATH |
> > PFTRAV_LOD_CUR,
> > ChannelX, ChannelY, 0.0f, PickList );
> >
> > The picking calculation seems to use only the smallest value of
> > right/left and top/bottom. So the picking results are shifted to the
> > left/right and top/bottom. In case of my example, the picking results
> > are shifted to the right (looks like a 2 deg shift).
> > When I supply symmetric values to pfMakePerspChan, this works fine.
> >
> > Can anybodye help me ?
> >
> Yes and no Wolfgang ;),
> sorry the answer comes late, but im currently running into the same
> problem.
> To disaapoint you, read the relnotes of Performer 2.2
> under the section Bugs and Workarounds it is said that picking
> in an asymetric frustum is not currently supported.
> Sorry for that.
> I still try to figure out how to do it. Right now it seems that the only
> possibility is to hold all scene geometrie in a seperate process and to
> apply object and viewpoint transformation on my own. :( That is of
> course
> the worst thing but i have no other ideas...
>
> Does anyone have a good one for that problem?
>
> bye
>
> Marc
>
> ********************************************************************************
> Marc Erich Latoschik, AG-WBS, Technische Fakultaet der Universitaet
> Bielefeld
>
> Universitaetsstrasse 25
> Postfach 100 131
> 33501 Bielefeld
> Raum M4-122
> Fon: (0521) 106 2919
> Fax: (0521) 106 2962
>
> marcl++at++techfak.uni-bielefeld.de
> http://www.TechFak.Uni-Bielefeld.DE/techfak/persons/marcl/
> ********************************************************************************

--
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In every hierarchy the cream rises until it sours.
                -- Dr. Laurence J. Peter
_______________________________________________________________________________


        Wolfgang Trog                    phone : (+49) 89/321407-31
        Philosys Software GmbH           fax   : (+49) 89/321407-12
        Edisonstr. 6                     mailto:trog++at++philosys.de
        85716 Unterschleissheim          http://www.philosys.de
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