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[Kuan <>]

Thank you for your help.
I forget to mention that the mesh is very large,  so is there any efficient way to do it? Like kd-tree
best wishes
Kuan

2007/10/21, Wesley Smith <>:

I peresonally found this operation in CGAL a bit lacking, so I use the
code from Tomas Moller:
http://www.cs.lth.se/home/Tomas_Akenine_Moller/raytri/raytri.c

You can google their paper describing the method.  It gives values (t,
u, v) where t is the distance along the ray to the intersection point
and u and v are barycentric coordinates of the intersection on the
triangle.

Sample usage:

void ray_mesh_intersction(vector<Facet> &facets, const Ray &r)
{
        Point o = r.source();
        Direction d = r.direction();

        double orig[] = {o.x(), o.y(), o.z()};
        double dir[] = {d.dx(), d.dy(), d.dz()};

        for(int f = 0; f < facets.size(); f++) {
                Triangle tri = V->dual().triangle(facets[f]);

                double vert0[] = {tri.vertex(0).x(), tri.vertex(0).y(), tri.vertex(0).z()};
                double vert1[] = { tri.vertex(1).x(), tri.vertex(1).y(), tri.vertex(1).z()};
                double vert2[] = {tri.vertex(2).x(), tri.vertex(2).y(), tri.vertex(2).z()};
                double t, u, v;

                if(intersect_triangle2(orig, dir, vert0, vert1, vert2, &t, &u, &v)) {
                        if(t > 0) {
                                //printf("intersect: %f %f %f\n", t, u, v);
                                //intersect point is Point(t*dir[0]+orig[0], t*dir[1]+orig[1],
t*dir[2]+orig[2]);
                        }
                }
        }
}
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