Marc,
Your observation on PickCylinderSegment is correct. PickCylinder and
PickCone are written for the purpose picking, especially for point and line.
In our present implemenation, no analytical volume testing is done.
A note on picking : For more accurate picking and better picking performance,
use PickRay instead of PickCone/PickCylnder unless you need to pick line/point.
PickCanvas with a tolerance of 0 will use PickRay for picking.
- Chien Yang
Java 3D Team.
> X-Accept-Language: de
> MIME-Version: 1.0
> Date: Fri, 14 Jul 2000 12:39:14 +0200
> From: Marc Nienhaus <[EMAIL PROTECTED]>
> Subject: [JAVA3D] Confused about PickShapes
> Comments: To: Doug Gehringer <[EMAIL PROTECTED]>, Kelvin Chung
<[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
>
> Hi,
>
> I am a bit confused about the methodology of PickShapes!
> To perform a volume pick test, I am using a PickCylinderSegment to
> recognize geometry for collision detection.
> Volume picking seems to be more safe against numerical divergences.
> The algorithm for collision detection works fine as long as the
> CylinderSegment intersects edges or non parallel geometry.
> But for some reasons the PickTool does not produce any intersections, if
> no edge of the geometry is hit and if the *vector* between the 'start'
> and 'end' of the CylinderSegment does not intersect the geometry (e.g.
> quad or plane - take look at the test program).
> If the vector lies in the geometry (quad or plane), then there is no
> intersection available, too. But the CylinderSegment should (in my
> opinion) produce intersection, at least at its boundary.
> There seems to be no analytical volume test using a (existing)
> PickShape.
>
> Is this intended and if so, why should one use a PickShape at all?
>
> There is a test program attached, which varies the attributes of the
> PickCylinder.
> Pick tests are applied to a quad (plane), which stands perpendicular to
> the xz-plane.
> The series of intersection tests correspond to the above!
>
> Regards,
>
> Marc
>
>
>
>
> --
> Marc Nienhaus
> Software Engineer (Computer Graphics)
>
> echtzeit AG. Reality Business.
> Gottfried-von-Cramm Weg 35-37
> 14193 Berlin
> fon 49 30 884 586 162
> fax 49 30 884 586 22
> www.echtzeit.de
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