Re: pfTexGen problems

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Angus Dorbie (dorbie++at++multipass.engr.sgi.com)
Fri, 26 Sep 1997 17:47:42 -0700

This is the correct behaviour but you can fix for eye roll using
a texture matrix no callbacks required. Unfortunately you won't
be able to fix for eye heading....unless you regenerate the texture image.

In fact this is the nature of texgen spheremap. It cannot account
eye position or orientation and so doesn't even for roll.

Cheers,Angus.

On Sep 26, 2:32pm, Steve Baker wrote:
> Subject: Re: pfTexGen problems
>
> [ plain text
> Encoded with "quoted-printable" ] :
On Fri, 26 Sep 1997, Rémi Arnaud wrote:
>
> > Steve Baker wrote:
> > >
> > >
> > > 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.
> > >
> >
> > SPHEREMAP works in eye space. It consider the eye space the coordinate
> > system that defines the up/down/left/right directions.
> > I guess that you will have to 'undo' the eye rotations using the texture
matrix.
> >
> > [pfApplyTMat in 2.2]
> > [mmode(MTEXTURE); loadmatrix(m); mmode(MVIEWING); before 2.2]
>
> Ah - I thought it might be something nasty like that. This is ugly since
Performer
> is doing the pfApply of the TexGen. I guess I'll need a pfGeoState callback
or
> something.
>
> Thanks.
>
>
>
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>-- End of excerpt from Steve Baker

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