CGAL 5.6 released

Changelog

General Changes

• Breaking change: Package-specific assertions, preconditions, and postconditions (such as CGAL_triangulation_assertion) have been removed. Corresponding CGAL-wide versions (such as CGAL_assertion) should be used instead.

Shape Detection (major changes)

• Breaking change: The region growing part of the package have been reworked to fix design issues introduced with the handling of FaceGraph models. In particular, the notion of Item has been introduced to reference an element in the input range of elements. Region maps now operates on Item and no longer on the value type of the input range.
• Breaking change: The method update() in the concept RegionType now returns a Boolean instead of void, that is used inside the class Region_growing for detecting if the input conditions for the new region are satisfied. This change affects only user-defined types of regions.
• Breaking change: The constructors of all models used together with the region growing algorithm now enable users to provide parameters through the named parameters mechanism.
• All fitting classes in the region growing framework are now using better versions of the region conditions, more precise and faster, including the correct normal orientations.
• Added new models of the concept RegionType for getting linear regions in a set of 2D and 3D segments and on 2D and 3D polylines.
• Added the class Polyline_graph for extracting a set of polylines from a face graph, which splits this graph into a set of user-defined regions.
• Added new shapes to the Region Growing algorithm on a point set: circles in 2D, spheres in 3D, and cylinders in 3D.

2D Straight Skeleton and Polygon Offsetting (major changes)

• Added weighted straight skeletons: weighted straight skeletons are a generalization of straight skeletons. Contour edges are assigned a positive weight, which can be understood as assigning a speed to the wavefront spawned from the contour edge.
• Added straight skeleton extrusion: this CGAL package now implements the extrusion of weighted straight skeletons of polygons with holes. The output is a closed, combinatorially 2-manifold surface triangle mesh. See also the news entry.

2D and 3D Linear Geometry Kernel

• Added the functor CompareAngle_3 to the concept Kernel to compare an angle defined by three points to the cosinus of another angle.

Combinatorial Maps, Generalized Maps, and Linear Cell Complex

• Added a version that uses indices instead of handles as dart and attribute descriptors. As the indices are integers convertible from and to std::size_t, they can be used as index into vectors which store properties. To use the index version, Use_index must be defined and be equal to CGAL::Tag_true in the item class.

Linear Cell Complex

• Added the class Linear_cell_complex_incremental_builder_3.

2D Arrangements

• Introduced an overload function template, namely draw(arr), that renders arrangements based on the Basic_viewer_qt class template. As of now, only 2D arrangements on the plane induced by (i) segments, (ii) conics, and (iii) circular arcs or (linear) segments are supported.
• Improved the traits class template that handles conics, namely Arr_conic_traits_2. This includes the following: 1. Fixed a couple of bugs and slightly optimized some functions. 2. Introduced functionality that approximates conics with polylines. (This is used to draw conic curves.) 3. Breaking change: Changed the interface to generate conic curves. In the past, curves where generated directly using the constructors of the conic and x-monotone conic constructs. Now, they are constructed via function objects provided by the traits. This eliminates the constructions of temporary kernels. The old functionality is obsolete, but still supported for a limited number of versions. It depends on a static member function of the traits. In a future version this function will no longer be static, implying that the old functionality will no longer be supported.
• Introduced functionality that approximates circular segments with polylines. (This is used to draw conic curves.)

Polygon Mesh Processing

• Added functions CGAL::Polygon_mesh_processing::region_growing_of_planes_on_faces() and CGAL::Polygon_mesh_processing::detect_corners_of_regions(), which enable partitioning a mesh into planar regions using the region growing algorithm from the Shape Detection package.

• Added the functions CGAL::Polygon_mesh_processing::remesh_planar_patches() and CGAL::Polygon_mesh_processing::remesh_almost_planar_patches(), which can be used to remesh patches of coplanar faces in a mesh.

• Added the function CGAL::Polygon_mesh_processing::surface_Delaunay_remeshing(), which can be used to remesh a surface triangle mesh using the Delaunay refinement algorithm from the 3D Mesh Generation package.

• Added the function CGAL::Polygon_mesh_processing::remove_almost_degenerate_faces(), which can be used to remove badly shaped triangles faces in a mesh.

• Added the functions CGAL::Polygon_mesh_processing::does_triangle_soup_self_intersect() and CGAL::Polygon_mesh_processing::triangle_soup_self_intersections() to identify and report self-intersections in a triangle soup, similarly to existing functions on triangle meshes.

• Added the function CGAL::Polygon_mesh_processing::triangulate_polygons(), which allows users to triangulate polygon soups.

• Added a named parameter to CGAL::Polygon_mesh_processing::smooth_shape() to disable the scaling, which otherwise aims to compensate volume loss during smoothing.

• Deprecated the overloads of functions CGAL::Polygon_mesh_processing::triangulate_hole(), CGAL::Polygon_mesh_processing::triangulate_and_refine_hole(), and CGAL::Polygon_mesh_processing::triangulate_refine_and_fair_hole() which have output iterators for vertices and faces as parameter. They are replaced by overloads with two additional named parameters.

2D Convex Hulls

• Breaking change: The concept ConvexHullTraits_2 no longer requires the functor Less_signed_distance_to_line_2, but requires the functor Compare_signed_distance_to_line_2 instead.
• The long-deprecated classes Convex_hull_projective_xy_traits_2, Convex_hull_projective_xz_traits_2, and Convex_hull_projective_yz_traits_2 have been removed. Users should use Projection_traits_xy_3, Projection_traits_xz_3, and Projection_traits_yz_3 instead.

2D Triangulations

• Added the function CGAL::mark_domain_in_triangulation() to mark faces connected with non-constrained edges as inside of the domain based on the nesting level.

2D Conforming Triangulations and Meshes

• Added new overloads to the function write_VTU(), with property maps for specifying the domain.
• Deprecated usage of boost parameters in favor of function named parameters in CGAL::lloyd_optimize_mesh_2().
• Deprecated two overloads of the function refine_Delaunay_mesh(), and replaced them with versions using function named parameters.

2D Hyperbolic Triangulations

• Breaking change: the concept HyperbolicTriangulationFaceBase_2 has been modified to better reflect the triangulation’s requirements and avoid a conflict with the requirements described by the concept TriangulationDataStructure_2::Face. The model CGAL::Hyperbolic_triangulation_face_base_2 has been adapted correspondingly.

3D Simplicial Mesh Data Structure (new package)

• This new package wraps all the existing code that deals with a MeshComplex_3InTriangulation_3 to describe 3D simplicial meshes, and makes the data structure independent from the tetrahedral mesh generation package.

Tetrahedral Remeshing

• Breaking change: The template parameters of CGAL::Tetrahedral_remeshing::Remeshing_vertex_base_3 and CGAL::Tetrahedral_remeshing::Remeshing_cell_base_3 have been modified.

3D Mesh Generation

• Added two new named parameters to the named constructor CGAL::create_labeled_image_mesh_domain() for automatic detection and protection of 1D-curves that lie at the intersection of three or more subdomains extracted from labeled images.
• Added CGAL::Sizing_field_with_aabb_tree, a geometry-aware sizing field for feature edges in polyhedral domains.
• Added new meshing criterion edge_min_size to avoid subdividing sharp edges that are shorter than a prescribed size bound.
• Added new meshing criteria facet_min_size and cell_min_size to prevent Delaunay refinement from creating simplices smaller than a prescribed bound.
• Deprecated usage of boost parameters in favor of function named parameters.

3D Periodic Mesh Generation

• Periodic Mesh Generation now supports non-cubic domains.
• Deprecated usage of boost parameters in favor of function named parameters.

Surface Mesh Simplification

• The stop predicates Count_stop_predicate and Count_ratio_stop_predicate are renamed to Edge_count_stop_predicate and Edge_count_ratio_stop_predicate. Older versions have been deprecated.
• Introduced Face_count_stop_predicate and Face_count_ratio_stop_predicate, which can be used to stop the simplification algorithm based on a desired number of faces in the output, or a ratio between input and output face numbers.

2D Regularized Boolean Set Operations

• Exposed all required member functions of the GeneralPolygonWithHoles_2 concept (e.g., clear_outer_boundary(), clear_holes(), and clear() ).

Known Bug

• MSVC 2015 is still supported by this version of CGAL, but the feature Segment Cell Iterator of the class CGAL::Triangulation_3 does not compile with MSVC 2015.