efifogel
commented
1 year ago Hi Barak,
The "Regularized" Boolean operations on polygons in CGAL are based on the arrangement package. If, for example, you want to perform a sequence of operations, for example: (P1 intersect P2) join P3 it is better to use an object of type Polygon_set_2<> (rather than applying free functions on the polygons), simply because the Polygon_set_2 maintains the underlying arrangement, while the free functions (re)construct the underlying arrangements.
With (the underlying) arrangements you can do much more than with the polygons themselves. Construct a Polygon_set_2<> object (say ps) and alter it. Assume it consists of the polygon that you want to intersect with a half-plane. Obtain the underlying arrangement (auto arr = ps.arrangement_2()). Insert the directed line that defines the half-plane into the arrangement and mark all the faces that are not in the intersection.
I can tell you that the arrangement uses a face record that is extended with a Boolean flag that indicates whether the face is in the polygon or not, so you can use it. Come by and I'll show you how.
Efi
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On Mon, 21 Nov 2022 at 11:23, Barak Ugav @.***> wrote:
In each trapezoid we calculate a result of a single measurement, and we intersect itwith the half plane created by the bottom edge of the trapezoid. Currently this is implemented by intersecting the raw result polygon P with a bounding polygon Q, where one of the edges of Q is the bottom edge of the trapezoid. This implementation is the bottleneck of the query performance. CGAL must have a more efficiant way to intersect a polygon with half plane.
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barakugav
In each trapezoid we calculate a result of a single measurement, and we intersect itwith the half plane created by the bottom edge of the trapezoid. Currently this is implemented by intersecting the raw result polygon P with a bounding polygon Q, where one of the edges of Q is the bottom edge of the trapezoid. This implementation is the bottleneck of the query performance. CGAL must have a more efficiant way to intersect a polygon with half plane.