Re: pfLOD / Intersection Traversal Anomaly

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Angus Dorbie (dorbie++at++sgi.com)
Wed, 03 Nov 1999 14:14:05 -0800

Larry Lachman wrote:
>
> Attention: Performer Team
>
> I am using Performer 2.2.5, and want to report an anomaly with pfLOD
> nodes and the intersection traversal. I discovered that if range 0 of
> a pfLOD is set to anything greater than 0.0f, then the intersection
> traversal stops at the pfLOD and does not visit any of the pfLOD's
> children. According to the man page for pfNodeIsectSegs:
>
> "For pfLODs, the default is to traverse only the child that would
> be active at range 0."

Doesn't this mean that nothing is active at range zero, so the manual
and behaviour is currently correct?

>
> But this is not the case given the scenario described above. This
> anomaly occurs regardless of the hardware the program is run on. This
> is either a Performer bug, or behavior that you will probably want to
> document in the pfNodeIsectSegs and pfLOD man pages.
>
> For your convenience, I have enclosed a succinct Performer program
> that reproduces this anomaly.
>
> --
> _______________________________________________________________
>
> Larry Lachman WWW: http://www.multigen-paradigm.com
> MultiGen-Paradigm, Inc. larry++at++paradigmsim.com
> 14900 Landmark, Suite 400 (972) 960-2301 ext 287 voice
> Dallas, Texas 75240 USA (972) 960-2303 fax
>
> --
>
> #include <stdlib.h>
> #include <Performer/pf.h>
> #include <Performer/pfdu.h>
>
> int main( int argc, char *argv[] )
> {
> void *arena;
> pfScene *scene;
> pfPipe *pipe;
> pfChannel *chan;
> pfGeoState *gstate;
> pfCoord view;
> pfPipeWindow *pwin;
> pfNode *esprit, *egg;
> pfLOD *lod;
> pfSegSet segset;
> float yval = -20.0;
>
> fprintf( stderr,"\n\n\nPerformer %d.%d\n\n\n",
> PF_MAJOR_VERSION, PF_MINOR_VERSION );
>
> pfInit(); /* Initialize Performer */
> arena = pfGetSharedArena(); /* Get shared memory arena */
> pfMultiprocess( PFMP_APPCULLDRAW | PFMP_FORK_DBASE );
> pfConfig();
>
> if ( ! getenv( "PFPATH" ) ) pfFilePath( "." );
>
> scene = pfNewScene();
>
> esprit = pfdLoadFile( "esprit.flt" );
> egg = pfdLoadFile( "egg.flt" );
>
> if ( esprit && egg )
> {
> lod = pfNewLOD();
>
> pfAddChild( lod, esprit );
> pfAddChild( lod, egg );
>
> #ifdef DISABLE_INTERSECTION
> pfLODRange( lod, 0, 1.0f );
> #else
> pfLODRange( lod, 0, 0.0f );
> #endif
>
> pfLODRange( lod, 1, 60.0f );
> pfLODRange( lod, 2, 999000.0f );
>
> pfNodeTravMask( lod, PFTRAV_ISECT, 0xFF,
> PFTRAV_SELF | PFTRAV_DESCEND | PFTRAV_IS_CACHE,
> PF_SET );
>
> pfAddChild( scene, lod );
> }
> else
> {
> printf( "esprit == 0x%x and egg == 0x%x\n", esprit, egg );
> exit( -1 );
> }
>
> /* Create a scene pfGeoState with lighting enabled */
> gstate = pfNewGState( arena );
> pfGStateMode( gstate, PFSTATE_ENLIGHTING, PF_ON );
> pfSceneGState( scene, gstate);
> pfAddChild( scene, pfNewLSource() );
>
> /* Create and configure a pfChannel */
> pipe = pfGetPipe( 0 );
> pwin = pfNewPWin( pipe );
> pfPWinOriginSize( pwin, 0, 0, 400, 400 );
> pfOpenPWin( pwin );
> chan = pfNewChan( pipe );
> pfChanScene( chan, scene );
> pfChanFOV( chan, 45.0f, -1.0f );
>
> /* Set up intersection segment, pointing out for line of sight */
> segset.activeMask = 1;
> segset.isectMask = 0xFF;
> segset.discFunc = NULL;
> segset.bound = NULL;
> segset.mode = PFTRAV_IS_PRIM | PFTRAV_IS_NORM |
> PFTRAV_IS_CULL_BACK | PFTRAV_LOD_RANGE0;
> /* Point the segment straight along Y body axis */
> pfSetVec3 (segset.segs[0].dir, 0.0f, 1.0f, 0.0f);
> segset.segs[0].length = 50000.0f;
>
> while ( 1 )
> {
> pfHit **hits[32];
> int isect;
>
> pfSetVec3( view.xyz, 0.0f, yval, 0.5f );
> pfSetVec3( view.hpr, 0.0f, 0.0f, 0.0f );
> pfChanView( chan, view.xyz, view.hpr );
>
> pfSync();
> pfFrame();
>
> /* decrement view position; if too far, reset */
> yval -= 0.01f;
> if ( yval < -60.0f ) yval = -20.0f;
>
> /* update location of intersection segment */
> pfSetVec3 (segset.segs[0].pos, 0.0f, yval, 0.5f);
>
> /* do an intersection test against the scene graph */
> isect = pfNodeIsectSegs( scene, &segset, hits );
>
> if ( isect )
> {
> pfVec3 pnt, xpnt;
> pfMatrix xmat;
> pfQueryHit( *hits[0], PFQHIT_POINT, &pnt );
> /* transform object point into scene coordinates */
> pfQueryHit( *hits[0], PFQHIT_XFORM, xmat );
> pfXformPt3( xpnt, pnt, xmat );
> printf( "Intersection at %.3f %.3f %.3f\n",
> xpnt[PF_X], xpnt[PF_Y], xpnt[PF_Z] );
> }
> }
>
> pfExit();
> }
> 

-- 
"Success is the ability to go from one failure to another with
 no loss of enthusiasm."    -    Winston Churchill.


Performer + OpenGL examples and tutors: http://www.dorbie.com/

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