There isn't a true (optical) focal point in Java 3D. I think Renoir is
using it to mean the point at which he expects zbuffer rendering to be
fairly accurate. (i.e. closer to the camera might be clipped, and
further away might exhibit zbuffer artifacts).
- John Wright
Starfire Research
alvaro zabala wrote:
>
> Thank you very much everybody!
>
> When I studied Z-Buffer algorithm at university, I did'nt realize how
> important is.
>
> A note: I have only worked with VRML before work with Java3D, so I don't
> know nothing about OpenGL.
>
> Is OpenGL knowledge import for understanding ZBuffer at Java3D?
>
> Only a last question, How can I get the focal point on the terrain??
> Maybe making a pick? This is a very cost processing.
>
> -----Mensaje original-----
> De: Renoir Sewjee <[EMAIL PROTECTED]>
> Para: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> Fecha: miércoles 23 de mayo de 2001 14:37
> Asunto: Re: [JAVA3D] ZBUFFER PROBLEM
>
> >Hi,
> >
> >I adjust the back clip distance and make the front clip distance a ratio of
> the
> >back clip distance:
> >
> > view.setBackClipDistance(radius*2.0f);
> > view.setFrontClipDistance(radius*2.0f/5000.0f);
> >
> >radius is the distance from the camera position to the focal point (the
> point
> >the camera is looking at).
> >
> >--Renoir
> >
> >John Wright wrote:
> >
> >> Alvaro,
> >>
> >> None of us have "solved" the z-buffer problems. The best we can do is
> >> make intelligent choices for front and back clipping distances to best
> >> fit our scene. Dynamically adjusting the front and back clipping values
> >> is an intriguing idea, but it would be pointless to adjust just one of
> >> them.
> >>
> >> - John Wright
> >> Starfire Research
> >>
> >> alvaro zabala wrote:
> >> >
> >> > Hi all!,
> >> > I have a question about changing clipping planes dinamically for solve
> the
> >> > z-buffer tearing problem.
> >> >
> >> > Desiree and Chris suggest me to changing front clip distance, but I
> don't
> >> > understand very well.
> >> >
> >> > Don't I may change the back clipping plane instead?
> >> >
> >> > My idea is to calculate the distance from the Viewing Platform to the
> >> > furtest object , and change the back clipping plane to that distance.
> >> >
> >> > May I have in a blunder??
> >> >
> >> > Please, see the atachment with the z-Buffer problem.
> >> >
> >> > (People who has solved it, like David Yazel would be appreciated)
> >> >
> >> > -----Mensaje original-----
> >> > De: ChrisThorne <[EMAIL PROTECTED]>
> >> > Para: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> >> > Fecha: miércoles 23 de mayo de 2001 1:18
> >> > Asunto: Re: [JAVA3D] Test program (fwd) for Grafic card question
> >> >
> >> > >
> >> > >
> >> > >Desiree Hilbring wrote:
> >> > >
> >> > >> > Sounds like you need to set the back clipping distance further.
> >> > >>
> >> > >> I detected that dist sometimes calculates a negative distance,
> setting
> >> > the
> >> > >> front clipping plane at a minimum of 1 solves the clipping problem,
> but
> >> > >> the original zbuffer issues still exists.
> >> > >
> >> > >Ok, there was a mistake - I should have used absolute values. You
> could
> >> > using the sqrt distance
> >> > >formula - as in the attached version of your test program.
> >> > >
> >> > >It works on my tests using your test program and dist will always be
> +ve.
> >> > >
> >> > >If that doesn't work in your main application then we can try keeping
> the
> >> > forward/back clip ratio
> >> > >to a constant. I see from your later mail you have used this
> solution.
> >> > Are you keeping the
> >> > >ratio to 3000 or a smaller number?
> >> > >
> >> > >cheers,
> >> > >
> >> > >Chris
> >> > >
> >> > >
> >> > >--
> >> > > ,--_|\
> >> > > / Oz \
> >> > >Chris Thorne :)_.--._/
> >> > >[EMAIL PROTECTED] v
> >> > >
> >> > >
> >> >
> >>
> ------------------------------------------------------------------------
> >> > Name: Prueba1.gif
> >> > Prueba1.gif Type: GIF Image (image/gif)
> >> > Encoding: base64
> >>
> >>
> ===========================================================================
> >> To unsubscribe, send email to [EMAIL PROTECTED] and include in the
> body
> >> of the message "signoff JAVA3D-INTEREST". For general help, send email
> to
> >> [EMAIL PROTECTED] and include in the body of the message "help".
> >
> >--
> >Renoir Sewjee
> >Software Engineer
> >ISS International (Welkom)
> >Tel: +27 (0)57 912 2702
> >Fax: +27 (0)57 912 2652
> >--
> >
> >===========================================================================
> >To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> >of the message "signoff JAVA3D-INTEREST". For general help, send email to
> >[EMAIL PROTECTED] and include in the body of the message "help".
>
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