Simon Mills (simon++at++wgs.estec.esa.nl)
Mon, 19 Apr 1999 18:05:18 +0200
- Set up node pre/post draw callbacks to set override of transparency
on/off.
- Use a traverser to set the alpha component of each geoset colour array
under a given node. Blend in any alpha contained in transparent
materials so these fade correctly.
This is slightly different to what Brian wrote below with setting the
pfGeoState transparency on. I tried this also but it makes a permanent
change to the geometry (unless you go to the bother of remembering the
setting for each pfGeoState you use). For me it messed up the order of
rendering so I got artifacts. Also my database shared pfGeoStates with
parts that should not fade.
However my method is not perfect since the ordering by transparency done
by the cull stage doesn't seem to take the above into acccount. So I get
rendering anomalies during fade. Does anyone know a way to fix this?
P.S. I was working on Octane MXE. On Onyx2 iR you can use multisample
transparency to get around this.
Hope it helps, Simon.
Brian Furtaw wrote:
>
> You'll need to enable transparency (blending) for the fading models
> pfGeoState's. To do this call pfGeoState::setMode(PFSTATE_TRANSPARENCY,
> PFTR_ON). Also look at the pfTransparency() call to determine what quality of
> transparency you are interested in.
>
> Brian
>
> On Apr 19, 12:29pm, Gary Quinn wrote:
> > Subject: Howto Fade Models
> > Hi all.
> >
> > I'd like to be able to fade models in and out of
> > view, something along the lines of in/decreasing their
> > transparency or alpha values.
> >
> > There doesn't seem to be anything documented, and
> > I've tried changing geometry set alpha values -
> > but that doesn't seem to do anything.
> >
> > A similar question was posted in Feb 1997,
> > but there wasn't enough detail in the answer
> > for me to implement the solution - which I didn't
> > fully understand anyway :-(
> >
> > Can anybody help please.
> >
> > Cheers,
> > Gary.
> >
> >
> > --
> >
> > Gary Quinn, VR Centre Technical Manager
> > University of Teesside SG Network Admin
> > Borough Road, Middlesbrough Go Player
> > Cleveland, TS1 3BA mailto:Gary++at++tees.ac.uk
> > +44 (0)1642 384303 fax 384310 http://vr.tees.ac.uk
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> >-- End of excerpt from Gary Quinn
>
> --
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________________________________________________________________________
Simon C. Mills
Silicon Worlds S.A.
c/o Modelling & Simulation Section (TOS-EMM) Tel: +31 (0)71 565 3725
European Space Agency (ESA/ESTEC) Fax: +31 (0)71 565 5419
Postbus 299, 2200AG Noordwijk e-mail: simon++at++wgs.estec.esa.nl
The Netherlands http://www.estec.esa.nl/wmwww/EMM
________________________________________________________________________
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