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Avoid needless orientation checks / distance computations 

If we are right of the edge, the distance is minimum over the edge...
...and that's it. Computing the distance to a segment is about
as expensive as the orientation check, so no point pinpointing
to check if the min is at a vertex.
This commit is contained in:
Mael Rouxel-Labbé 2021-04-27 22:40:22 +02:00
parent 8b77c7139e
commit b95c60fc9f
1 changed files with 22 additions and 10 deletions
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32
Distance_3/include/CGAL/Distance_3/Point_3_Triangle_3.h
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@ -64,26 +64,38 @@ squared_distance_to_triangle(const typename K::Point_3& pt,
const Vector_3 oe3 = vector(t0, t2);
const Vector_3 normal = wcross(e1, oe3, k);
if(normal != NULL_VECTOR &&
on_left_of_triangle_edge(pt, normal, t0, t1, k) &&
on_left_of_triangle_edge(pt, normal, t1, t2, k) &&
on_left_of_triangle_edge(pt, normal, t2, t0, k))
{
// the projection of pt is inside the triangle
inside = true;
return squared_distance_to_plane(normal, vector(t0, pt), k);
}
else
if(normal == NULL_VECTOR)
{
// The case normal == NULL_VECTOR covers the case when the triangle
// is colinear, or even more degenerate. In that case, we can
// simply take also the distance to the three segments.
//
// Note that in the degenerate case, at most 2 edges cover the full triangle,
// and only two distances could be used, but leaving 3 for the case of
// inexact constructions as it might improve the accuracy.
typename K::FT d1 = internal::squared_distance(pt, segment(t2, t0), k);
typename K::FT d2 = internal::squared_distance(pt, segment(t1, t2), k);
typename K::FT d3 = internal::squared_distance(pt, segment(t0, t1), k);
return (std::min)( (std::min)(d1, d2), d3);
}
const bool b01 = on_left_of_triangle_edge(pt, normal, t0, t1, k);
if(!b01)
return internal::squared_distance(pt, segment(t0, t1), k);
const bool b12 = on_left_of_triangle_edge(pt, normal, t1, t2, k);
if(!b12)
return internal::squared_distance(pt, segment(t1, t2), k);
const bool b20 = on_left_of_triangle_edge(pt, normal, t2, t0, k);
if(!b20)
return internal::squared_distance(pt, segment(t2, t0), k);
// The projection of pt is inside the triangle
inside = true;
return squared_distance_to_plane(normal, vector(t0, pt), k);
}
template <class K>