We have fixed a few bugs related to state updates for multiple views in 1.1.1.
Give that a try when it comes out. If it still happens, please submit a bug
to us.
Thanks,
Doug Twilleager
Java 3D Team
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> To: Roger Cottam <[EMAIL PROTECTED]>
> CC: [EMAIL PROTECTED]
> Subject: Re: [java3d] view to world transform jitters
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>
> What you are describing and the difficulties you are having in pinning
> it down sound exactly like what I've encountered. In a previous
> posting I reported also seeing jitters when I tried to interactively
> scale an object using just a simple TransformGroup -- no fancy view
> transforms or eye-to-world mappings. The problem seemed to only occur
> for scale factors less than 1.0 and it seemed to affect the whole
> transform even though I was only setting scale.
>
> All the jitter problems I've observed seem to have the same sort of
> jittery "quality" which makes me suspect that they are related, but
> how? They also manifest themselves in slighty different ways such as
> sign flipping, lagging, and just random trashing of the transform.
>
> Hopefully someone from Sun can shed some light on these mysteries. In
> the meantime it's giving me cause for concern because I need all these
> features; 1.1.1 is due to come out soon; and I haven't seen the
> "jitters" mentioned in the bug list.
>
> --jon
>
> Roger Cottam wrote:
> >
> > Jon,
> >
> > Yes, I've seen this as well with multiple views. My scenario isn't simple
> > so it's hard to nail down exactly what the problem is, but multiple views
> > is the key that starts the jitters. I've seen it in TransformGroup objects
> > which I am modifying or have modified with a mouse drag...
> >
> > I also have some issues with code that uses
> > Canvas3D.getCenterEyeInImagePlate(), but I can't say that I have a problem
> > with that method in particular. It seems that if I use the functions for
> > ray casting (generatePickRay and pickQuad) I get a VERY jittery effect on a
> > TransformGroup 'above' the ViewPlatform. This happens with only one
> > canvas. The idea is that when the mouse is dragged with the right button
> > down I project a ray onto a plane perpendicular to the view at the location
> > of the 'selected' object. Over two frames this gives me a delta to move
> > the viewpoint so I can 'pan' in the view plane relative to an object. I
> > print out the 3D points that I calculate on that plane each frame an
> > smoothly run the mouse across the window. I get values that jump pos and
> > neg and big and small, it may be that the sign is the only thing that gets
> > flipped but I haven't studied the data enough to say for sure. I'm not
> > sure why yet, but this 'jitter bug' may have something to do with it...
> >
> > If I find anything I'll let you know.
> >
> > Roger
> >
> > At 06:53 PM 3/2/99 -0800, Jon Barrilleaux wrote:
> > >I think there is a problem with the J3D computation of the
> > >view-to-world transformation. I've seen the problem so far in
> > >Canvas3D.getCenterEyeInImagePlate(), View.getUserHeadToVworld(), and
> > >and, Node.getLocalToVworld().
> > >
> > >What is happening is that the value returned seems to "lag" what the
> > >ViewPlatform is actually doing, but its not just a simple lag. There
> > >seems to be a pronounced "jitter" to it; and if the ViewPlatform stops
> > >moving often the lag will remain until the view-to-world transform is
> > >read a second time.
> > >
> > >Although this is only a guess, perhaps this is related to the problem
> > >I reported last month (which no one at Sun seemed interested in)
> > >concerning jitter which occurs when multiple views are used. That
> > >seemed to be view related also.
> > >
> > >Has anyone seen similar problems with any of the view-to-world
> > >transforms? (I know other people have complained about jitter in
> > >multiple views.)
> > >
>
> --
> ____________________ Peculiar Technologies ____________________
> Jon Barrilleaux 3800 Lake Shore Ave. Purveyors of
> [EMAIL PROTECTED] Oakland, CA 94610 Alternate Reality
> 510.444.4370 voc Augmented Simulation
> 510.444.0231 fax www.augsim.com and 3D Solutions
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