RE: [Algorithms] EPA : working ?

[Nick N. \(C. S. Ltd\) <Nic...@ci...>]

Not with the witness points exclusively.  Figure 8 (b) in Mirtich's
paper "V-Clip: Fast and robust polyhedral collision detection" shows an
example where this is not the case.  The witness points are intersection
points, however - there may be other points that are penetrating the
volume, but not intersecting the boundary.

You could still traverse the dual graph of the boundary to calculate the
maximum local penetrating depth.  The expense of this depends on the
complexity of your volume.  You'd have to update the closest Voronoi
region on each volume as you traversed them to ensure the set you'd be
looking at was only part of the penetrating primitives, but this still
doesn't feel efficient - it's still too global.

Cheers,
Nick.

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...] On Behalf Of
Pau...@sc...
Sent: 27 April 2004 13:44
To: gda...@li...
Subject: RE: [Algorithms] EPA : working ?

On 27/04/2004 12:47:55 gdalgorithms-list-admin wrote:=20

>V-Clip does correctly identify penetrating objects as intersecting.
> However, it only gives local witnesses to penetration, so this will
not
> give an accurate value for penetration depth.

Marvellous. Actually, can't you easily work out the penetration from
the witness points? Vertex/face, face/vertex, edge/edge and get
a penetration measure from that?

> If you had the linear velocities of the objects you can work this out
> however via the projection onto the relative velocity of the movement
> required to separate the object (along the relative velocity -
> effectively pushing the objects apart to the position of first
contact).

No good if your objects aren't moving, though.

Cheers, Paul.




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