Hi,
I just set the front clipping plane very far. That helped, but to examine
the viewer needs to zoom into the scene, I am using the MouseZoom
Behavior for that. During zooming the objects is clipped very to
early. Can I adjust the front and back clipping planes during zooming?
Tanks for your help in advance
Desiree
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Desiree Hilbring
Institut fuer Photogrammetrie und Fernerkundung
Universitaet Karlsruhe, Germany
email: [EMAIL PROTECTED]
# 0721 6083676
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On Wed, 9 May 2001, Chris Thorne wrote:
>
> Desiree,
>
> As some may have said, if the range of coordinate values is very large then the z
> buffer tearing
> can be noticeable because of insufficient floating point precision (as identified
> by Justin).
> I.E. if two surfaces are overlapping and only 0.1 apart but your terrain models
> have coordinates
> larger than, say, 1,000,000 then you could well see tearing.
>
> There are two things you can try reduce the floating point precision problem (as
> identified by Justin)
> if it results in z buffer tearing:
>
> 1) modify your clipping distances (as from the Sutras):
> "
> 2.Problems with z-buffer resolution are usually not really due to lack of
> resolution. Instead, the problem is usually that the front clip plane is being
> put too close to the eye, resulting in a loss of z-buffer resolution for objects
> near the back clip plane.
> Try this:
> // Make sure that front and back clip planes are specified as a
> // virtual distance from the eye
> view.setFrontClipPolicy(View.VIRTUAL_EYE);
> view.setBackClipPolicy(View.VIRTUAL_EYE);
> double backClipDistance = <distance to furthest object in scene>
> view.setBackClipDistance( backClipDistance );
> // (back / front) must be < 3000 to avoid loosing z-buffer resolution.
> // The larger the number, the more the z-buffer space will be used
> // for objects in the front of the scene. If you loose z-buffer
> // resolution for objects at the back of your scene, decrease this
> // number. If your objects are getting front clipped, adjust both
> // the front and back clip distances to keep this ratio.
> view.setFrontClipDistance( backClipDistance / 600.0 );
> [Doug Gehringer, Sun Microsystems]
> "
> Note that Doug's statement that the problems are not normally due to lack of
> 'resolution' may be incorrect in this case - i.e. if it is a floating point
> precision problem this is tatamount to 'a lack of resolution'.
>
> 2) This *may* work: Minimize the geometry range (from 0 to largest (or 0 to
> largest/smallest when smallest is <1)). NOTE: scaling down will not generally
> help if it means some values become <1). For example, it could be that all your
> coordinate values are greater than 5000. If you subtract 5000 from all values
> the range that has to be handled is less.
> This sort of solution helps in VRML but may not directly translate to help with
> your Java3D/Gladiac platform.
>
> I have a Gladiac GForce II, 32MB as well. I will *try* to find time to test all
> this out
> an give you a more precise answer but no guarantees - last I asked Chronos for
> more
> time he just laughed and walked off!
>
> Chris
>
>
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