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corrections and comments for get_visible_facet(e,ray)

This commit is contained in:
Peter Hachenberger 2003-08-18 15:58:41 +00:00
parent a9b0204137
commit 3ea3839fb4
1 changed files with 42 additions and 23 deletions
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65
Packages/Nef_3/include/CGAL/Nef_3/SNC_decorator.h
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@ -488,7 +488,8 @@ public:
}
else if ( assign( sl, fc)) {
SM_decorator SD;
TRACEN( "adjacent facet found (SHalfloop cycle)." << SD.circle(sl) << " with facet " << plane(facet(sl)));
TRACEN( "adjacent facet found (SHalfloop cycle)." << SD.circle(sl)
<< " with facet " << plane(facet(sl)));
f_visible = facet(twin(sl));
TRACEN("f_visible" << plane(f_visible));
}
@ -499,51 +500,69 @@ public:
return f_visible;
}
Halffacet_handle get_visible_facet( const Halfedge_handle e,
Halffacet_handle get_visible_facet( const Halfedge_handle ee,
const Ray_3& ray) const {
//{\Mop when one shoot a ray |ray| in order to find the facet below to
// an object, and an edge |e| is hit, we need to choose one of the two
// facets in the adjacency list of |e| that could be 'seen' from the
// piercing point of the |ray| on the local (virtual) view of |e|
// \precondition |ray| target belongs to |e|. }
//{\Mop when one shoot a ray |ray| in order to find the facet below to
// an object, and an edge |e| is hit, we need to choose one of the two
// facets in the adjacency list of |e| that could be 'seen' from the
// piercing point of the |ray| on the local (virtual) view of |e|
// \precondition |ray| target belongs to |e|. }
SM_decorator SD;
Halfedge_handle e(ee);
SM_decorator SD(source(e));
if( SD.is_isolated(e))
return Halffacet_handle();
// We search for the plane in the adjacency list of e, which is closest
// to the ray. The cross product of the direction of e and the orthogonal
// vector of a plane gives us a vector vec0/vec1 on the plane of the facet
// and orthogonal to e, pointing inside of the facet.
Vector_3 ev(segment(e).direction()), rv(ray.direction());
SHalfedge_around_svertex_circulator sh(SD.first_out_edge(e)), send(sh);
Halffacet_handle res = facet(sh);
SHalfedge_around_svertex_circulator sh(SD.first_out_edge(e));
Halffacet_handle res = facet(sh);
Vector_3 vec0(cross_product(ev,plane(res).orthogonal_vector()));
CGAL_nef3_assertion(Sphere_segment(SD.point(SD.source(sh)),
SD.point(SD.target(sh))).has_on(vec0));
SHalfedge_around_svertex_circulator send(sh);
TRACEN("initial face candidate "<< plane(res) << " with vector " << vec0);
CGAL_For_all(sh,send) {
Vector_3 vec1(cross_product(ev,plane(facet(sh)).orthogonal_vector()));
TRACEN("test face candidate "<< plane(facet(sh)) << " with vector " << vec1);
}
// We compare the vectors vec0/vec1 of the facets. The one that is nearest
// to pointing in the opposite direction of the ray, is chosen. The
// respective facet is the nearest to the ray.
sh++;
CGAL_For_all(sh,send) {
Vector_3 vec1(cross_product(ev,plane(facet(sh)).orthogonal_vector()));
TRACEN("test face candidate "<< plane(facet(sh)) << " with vector " << vec1);
TRACEN("test face candidate "<< plane(facet(sh))<<" with vector "<<vec1);
FT sk0(rv*vec0), sk1(rv*vec1);
if(sk0<FT(0) && sk1>FT(0))
continue;
if(sk0>FT(0) && sk1<FT(0)) {
res = facet(sh);
res = facet(sh);
vec0 = vec1;
continue;
}
// We have to comapare the two skalar products sk0 and sk1. Therefore
// we have to normalize the input vectors vec0 and vec1, which means
// that we have to divide them by their lengths len0 and len1.
// To cicumvent irrational numbers, we sqaure the whole inequality.
FT len0 = vec0.x()*vec0.x()+vec0.y()*vec0.y()+vec0.z()*vec0.z();
FT len1 = vec1.x()*vec1.x()+vec1.y()*vec1.y()+vec1.z()*vec1.z();
FT sq0 = sk0 * sk0;
FT sq1 = sk1 * sk1;
FT diff = len0*sq1 - len1*sq0;
FT diff = len0*sk1*sk1 - len1*sk0*sk0;
if((sk0>FT(0) && diff<FT(0)) || (sk0 < FT(0) && diff>FT(0)))
res= facet(sh);
if((sk0>FT(0) && diff<FT(0)) || (sk0<FT(0) && diff>FT(0))) {
res = facet(sh);
vec0 = vec1;
}
}
// We have to check which of the two halffacet is visible from
// the ray.
if(rv*plane(res).orthogonal_vector() > FT(0))
res = twin(res);