Re: pfTexGen problems

New Message Reply Date view Thread view Subject view Author view

Scott McMillan (scott++at++ht.com)
Fri, 26 Sep 1997 14:51:23 -0400 (EDT)

>
> Hi.
>
> I'm using pfTexGen with SPHEREMAP mode to generate cute shiney reflections.
>
> As a test, I modelled a white sphere, and picked a suitably distorted
> environment map with sky in the top half of the circle and ground in the
> bottom half.
>
> I model the sphere under a pfDCS node - and everything looks great - I
> spin the DCS and the ground stays reflected in the bottom half of the
> sphere and the sky in the top half.
>
> However, if I roll the eyepoint inverted (using pfChanView for example)
> the reflection rolls with me. So, the sky is now reflected in the wrong part
> of the sphere. The pfESky shows blue on the bottom half of the screen - but
> that bottom half of the sphere is still green.
>
> Is this an inherent problem with pfTexGen or am I doing something wrong ?
>
> Could it be something to do with when the pfTexGen is pfApply'ed ? Right
> now, I attach the pfTexGen to the pfGeoState - so I don't have control of
> when this happens.
>
> Thanks in advance...
>
> Steve Baker

I am pretty sure the behaviour you describe is exactly what to expect. I
have taken a look at the SPHERE_MAP math in the OGL Programmer's guide, and
the tex coords are computed using vectors defined with respect to the eye
coordinates....so it will appear that the reflection map is constant with
respect to the eye position/orientation and not the world/Performer CS.

scott

-- 
  Scott McMillan  |     HT Medical, Inc.    | Disclaimers
   scott++at++ht.com   |    http://www.ht.com    | available
 Ph: 301-984-3706 | 6001 Montrose Rd., #902 | upon re-
Fax: 301-984-2104 |   Rockville, MD 20852   | quest.
=======================================================================
List Archives, FAQ, FTP:  http://www.sgi.com/Technology/Performer/
            Submissions:  info-performer++at++sgi.com
        Admin. requests:  info-performer-request++at++sgi.com

New Message Reply Date view Thread view Subject view Author view

This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:56:00 PDT

This message has been cleansed for anti-spam protection. Replace '++at++' in any mail addresses with the '@' symbol.