The mode field of pfSegSet specifies the kind of information recorded when there is a hit at an intersection. The mode value is a bitwise OR of one or more of the values in Table 13-1.

PFTRAV_IS_PRIM, PFTRAV_IS_GSET, and PFTRAV_IS_GEODE define where the geometry is stored and thereby define the depth of the intersection test.

There are several mask fields in the pfSegSet structure to enable you to have conditional intersection traversal. The activeMask field of pfSegSet is a 32-bit mask that allows you to specify which segments are active.

The isectMask is masked with the intersection mask of each node, set on the node by pfNodeTravMask() for PFTRAV_ISECT, in the intersection traversal. The traversal will not intersect with a node or its children if the AND of its isectMask and the pfSegSet isect Mask is zero. This allows you to create intersection classes of objects and intersection types.

pfNodeTravMask() allows you to specify additional things for controlling the intersection traversal of a scene. The function prototype is:

pfNodeTravMask(pfNode *node, int which, uint mask, int setMode, int bitOp);

The setMode enables you to specify intersection caching, and the bitOp enables you to and- or- or set- the specified mask against the previous mask in the node. The following is an example call:

pfNodeTravMask(node, PFTRAV_ISECT, 0xfffffffff,
PFTRAV_SELF|PFTRAV_DESCEND|PFTRAV_IS_CACHE /* turn on caching for entire scene graph below object */, 
PF_OR /* or- with prev bitmask in each node for new bitmask */);

The segment array defines the origin, direction, and length of the segments in the following structure:

typedef struct {
    pfVec3 pos;
    pfVec3 dir;
    float length;
} pfSeg;

The pfSegSet array can have up to 32 segments. The segment array is then set in the pfSegSet structure in the segs[] field.

To further improve intersection performance when you have many segments in a pfSegSet, you can provide a bounding pfCylinder for the segments in the bound field of the pfSegSet. You can create the bounding cylinder can be created with  pfCylAroundSegs(). The array passed to pfCylAroundSegs() needs to be an array of pointers to pfSegs, which is different than the array of pfSegs for the pfSegSet.

The hits array is filled by the intersection traversal, with temporary hit structures for each intersection. The first element corresponds to the segment in the segment array, and the second dimension is a list of pointers to hit structures relating to that segment. The data in the hit structures only remains until another ISECT traversal is called, so you do not want to save pointers to the pfHit structures and you do not want to free them.

To return all of the other information contained in a Hit structure, use the following method:

int pfQueryHit(pfHit *hit, uint which, void *dst);

hit is a pfHit structure that the traversal fills with information regarding an intersection.

which is the information to retrieve from the hit structure.

dst is the pfMemory where the query results are placed.

Table 13-2 shows the PFHIT_ tokens, supplied for which, that specify the hit structure information to return.

PFQHIT_FLAGS is formed by optionally bitwise ORing zero or more of the PFHIT_POINT, PFHIT_NORM, PFHIT_PRIM, PFHIT_TRI, PFHIT_VERTS and PFHIT_XFORM symbols.

uint flags;
pfHit **hits[32];
 
// Assume segset has four active segs, indicies 0 - 3
 
nhits = pfNodeIsectSegs(scene, &segset, hits);
for (i = 0, i < 4 && nhits > 0, i++){
    pfQueryHit(hits[i][0], PRQHIT_FLAGS, &flags);
    if (flags & PFHIT_ISECT) {
        // valid intersection
        nhits--;
    }
}

pfQueryHit(hits[i][0], PFQHIT_POINT, &pt);
pfQueryHit(hit, PFQHIT_FORM, xform)'
if ( (flags & PFHIT_XFORM) == 0) {
    // xform contains garbage. so set it to the identity
    // matrix so there is no transformation.
    pfMakeIdentMat(xform);
}
pfXformPt3(xpt, pt, xform);

if (flags & PFHIT_ISECT) {
    pfVec3 pt, xpt;
    pfMatrix xform;
 
    pfQueryHit(hits[i][0], PFQHIT_POINT, &pt);
    pfQueryHit(hit, PFQHIT_XFORM, xform);
    pfXformPt3(xpt, pt, xform);
 
    shared->zpos = xpt[PF_Z] + 0.7;
}