Isect LOD

ns.dept3.buaa.edu.cn (baofyu++at++ns.dept3.buaa.edu.cn)
Mon, 20 Apr 1998 14:11:22 +0800

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    pfSegSet segset;
    const pfSeg **segptr;
    pfHit **hits[32];

    // Create group node to hold SCS's; attach it to scene
    pfGroup * ground =(pfGroup *) pfdLoadFile("yu02.flt");
    pfGroup * root = new pfGroup();
    root->addChild(ground);

    // Set up ground and his children for intersections
    scene->addChild(root);
    ground->setTravMask(PFTRAV_ISECT,0x06,
PFTRAV_SELF|PFTRAV_DESCEND|PFTRAV_LOD_CUR,PF_OR);
    scene->setTravMask(PFTRAV_ISECT, 0x06,
PFTRAV_SELF|PFTRAV_DESCEND|PFTRAV_LOD_CUR,PF_OR);

    // Set up intersection segment, pointing down for "terrain" following
    segset.activeMask = 13;
    segset.isectMask = 0xFFFF;
    segset.discFunc = NULL;
    n = 13;
    segptr = (pfSeg **)pfMalloc(sizeof(pfSeg *)*n,NULL);
    for (int i = 0; i < n; i++)
    {
      segset.segs[i].dir.set(0.0f, 0.0f, -1.0f);
      segset.segs[i].length = 100000.0f;
      segptr[i] = &segset.segs[i];
    }

    // set location of intersection segment of crater
    x = 100.0f;
    y = 100.0f;
    z = 10000.0f;
    segset.segs[0].pos.set(x, y, z);
    r = 16.0f;
    for (i = 1; i < n; i++)
    {
      pfSinCos(360.0f / n * i, &s, &c);
      segset.segs[i+1].pos.set(x + c * r, y + s * r, z);
    }

    cylinder = new pfCylinder();
    cylinder->around(segptr, n);
    segset.bound = &cylinder;
    segset.mode =
PFTRAV_IS_PRIM|PFTRAV_IS_NORM|PFTRAV_IS_CULL_BACK|PFTRAV_IS_BCYL|PFTRAV_LOD_
CUR;

    // do an intersection test against the scene graph
    isect = scene->isect(&segset, hits);

    while (!shared->exitFlag)
    {
           pfFrame();

    // if successful, set crater height to that of the point of contact.

    if (isect)
       {
          .........
        }
    }
  This program works well when terrain node ("ground") is not pfLOD.
pfSegset can inersect with ground and I can query inersetion point and
normal. when I use another terrain flt file which is pfLOD, the pfSegset can
not intersect with terrain. Why? I want know how I should do when I want to
interset with pfLOD terrain using pfSegset. Who can answer me? I need help.
  baofeng Yu

   Advanced Simulation Technology Lab,
   Automatic Control Dept.,
   Beijing University of Aeronautics and Astronautics
   China
   email address: baofyu++at++ns.dept3.buaa.edu.cn

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