From: Benedikt Kessler (bjk++at++munich.sgi.com)
Date: 11/21/2000 01:05:31
Hi!
If I remember well, there must be at least ine segment in the cylinder.
The volume does not replace the segment intersection tests but does
improve them (as it is mentionned in the manpage):
"When a bounding volume is supplied, the intersection traversal may use
the cylinder to improve performance. The largest improvement is for
groups of at least several segments which are closely grouped segments.
Placing a bounding cylinder around small groups or widely dispersed
segments can decrease performance."
In detail:
// if the cylinder doesn't intesect the bounding geometry, then prune.
// else check all segments and do intersection tests.
The cylinder alone will not generate any hit. It will only prevent the
library to do many unnecessary segment intersection tests if the
cylinder does not intersect any bounding volume.
BTW, What is the stange PFTRAV_IS_IS_BCYL constant that you are using;
If I look at the manpage and the include file I can only find the
PFTRAV_IS_BCYL constant that should be or-ed in the mode field;
Bye! Benedikt
'Bwana' Bob Buckley wrote:
>
> Dude!
>
> Angus Dorbie wrote:
> >
> > Did you set the right querry information on the way in and then querry
> > hit for the right stuff afterwards?
> >
>
> I place a unit cube at 5m from the origin on the y axis. I then rotate
> it around the origin in the xy plane at that 5m radius. Using a single
> seg pointing down the y axis I do get a proper intersect. However, when
> zeroing out the active mask and enabling the cylinder volume I get no
> intersects. The cylinder sits exactly on the cubes path at 5m. I place a
> callback on the scene and it does get called as expected, but apparently
> the intersect fails and the traversal is truncated at that point. It
> properly traverses when using that single seg and I test using
> breakpoints in the callbacks of child nodes.
>
> Here's the setup:
>
> pfClyinder cylinder;
> cylinder.center.set(0.0f, 5.0f, 0.0f);
> cylinder.axis.set (0.0f, 1.0f, 0.0f);
> cylinder.radius = 1.0f;
> cylinder.halfLength = 1.0f;
>
> pfSegSet segSet;
> //segSet.activeMask = 0x01;
> segSet.activeMask = 0x0;
> segSet.isectMask = 0xffffffff;
> segSet.userData = NULL;
> segSet.discFunc = NULL;
> //segSet.bound = NULL;
> segSet.bound = (void *) &cylinder;
> //segSet.mode = PFTRAV_IS_PRIM | PFTRAV_IS_NORM |
> PFTRAV_IS_CULL_BACK | PFTRAV_IS_IS_BCYL;
> segSet.mode = PFTRAV_IS_GEODE | PFTRAV_IS_GSET |
> PFTRAV_IS_IS_BCYL;
> segSet.segs[0].dir.set(0.0f, 1.0f, 0.0f);
> segSet.segs[0].pos.set(0.0f, 0.0f, 0.0f);
> segSet.segs[0].length = 1000.0f;
>
> Within the main sim loop I have:
>
> pfHit **hits[32];
> int numHits = scene->isect(&segSet, hits);
>
> >
> > What happens then if you querry down to the tri information? Do you get
> > the bounds hit info?
> >
>
> It never traverses beyond the scene using strictly the volume test.
>
> >
> > You aren't expecting *coordinate* information for the bounds hit querry
> > are you?
> >
>
> Right now I'm just trying to get a non-zero hit count on the isect using
> volumes. Actually, just trying to get it to traverse beyond the scene
> node.
>
> >
> > P.S. if I told you the Performer handshake it wouldn't be a secret.
> >
>
> :)
>
> >
> > Cheers,Angus.
> >
> > 'Bwana' Bob Buckley wrote:
> > >
> > > I've been trying to implement a pfNode isect call using strictly
> > > bounding volume to bounding volume tests. There have been two threads in
> > > the past two years on this with no answers. I have a test case put
> > > together that puts a cube out there and runs an isect using strictly a
> > > cylinder test as mentioned in the man pages and in the insight book. No
> > > intersects are successful. Is anyone aware that this feature is either
> > > implemented or not? Is there some secret handshake to get it to work
> > > properly?
> > >
> > > Thanks.
> >
> > --
> > For Performer+OpenGL tutorials http://www.dorbie.com/
> >
> > "In the middle of difficulty lies opportunity."
> > --Albert Einstein
-- +---------------------------------+----------------------------------+ |Benedikt J. Kessler | Silicon Graphics GmbH | |Professional Services | Am Hochacker 3 - Technopark | |SGI | 85630 Grasbrunn-Neukeferloh, FRG | | --- __o ,__o | | | ------_ \<,_ _-\_<, | Phone: (+49) 89 46108-366 or -0 | |----- (*)/ (*) (*)/'(*) | Fax: (+49) 89 46107-366 | +---------------------------------+----------------------------------+ |E-Mail: bjk++at++sgi.com Web (private): http://reality.sgi.com/bjk | | Web: http://www.sgi.de/dienstleistungen/ | +--------------------------------------------------------------------+
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