\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)
CGAL 4.13 - 2D Snap Rounding
CGAL::Snap_rounding_traits_2< Kernel > Class Template Reference

#include <CGAL/Snap_rounding_traits_2.h>


The class Snap_rounding_traits_2<Kernel> is a model of the SnapRoundingTraits_2 concept, and is the only traits class supplied with the package.

This class should be instantiated with an exact geometric kernel that conforms to the CGAL kernel-concept, such as the Exact_predicates_exact_constructions_kernel, or Cartesian<Gmpq>.

This geometric kernel must provide an (arbitrary-precision) rational number type (FT), Point_2, Segment_2 and Iso_rectangle_2. It should be possible to cast numbers of the number type FT to double-precision representation. That is, the function CGAL::to_double(FT) must be supported.

The CGAL::to_double() function is used to implement the operation that rounds the coordinates of a point to a center of a pixel. This operation is one of the traits-concept requirement. The coordinates are converted to double, rounded down to the nearest grid point, and finally adjusted to lie on a center of a pixel. Notice that if CGAL::to_double() returns the closet value, then when it rounds up a given coordinate, the resulting ISR, may be imprecise, and the distance between some vertex and a non-incident edge can be slightly less than the guaranteed half-the width-of-a-pixel.

Is Model Of:
Snap_rounding_2/snap_rounding.cpp, and Snap_rounding_2/snap_rounding_to_integer.cpp.