[Plib-devel] ssgIntersctLOS

[Norman V. <nh...@ca...>]

Hi All,

In the process of rewriting the FlightGear elevation code, 
I have tried to make it generic enough to be of general use 
to the PLib community.  

If anyone is interested in BETA testing a collection of routines
that will gather info about the intersection of a directed line 
segment and a SSG graph,  drop me a line.

Info gathered for each point of intersection:
  pointer to intersected leaf
  index of intersected face in said leaf
  coordinates of intersection point
  normal to face at intersection point

Example Usage:

ssgBranch *scene;
sgVec3 line_orig, line_dir;

// declare it
FGHitList hit_list;

// this is all you have to do :-)
hit_list.Intersect( scene, line_orig, line_dir ) ;

// Things you can do
int closest = -1;
float dist, min_dist = FLT_MAX;
 for ( int i=0; i<hit_list.num_hits(); i++ ) 
{
    ssgEntity *leaf         = hit_list.get_entity(i);
    int tri_index              = hit_list.get_face(i);
    sgVec3 this_point    = hit_list.get_point(i);
    sgVec3 this_normal = hit_list.get_normal(i);

    dist = sgDistanceSquaredVec3( line_orig, this_point);
    if( dist < min_dist ) {
       min_dist = dist;
       closest = i;
    }

    short i1, i2, i3;
    leaf->getTriangle( tri_index, &i1, &i2, &i3 ); 

    float intersected_tri[3][3];
    sgCopyVec3(intersected_tri[0], leaf->getVertex(i1);
    sgCopyVec3(intersected_tri[1], leaf->getVertex(i2);
    sgCopyVec3(intersected_tri[2], leaf->getVertex(i3);
}

Cheers

Norman Vine