CGAL 5.1 released

Changelog

Tetrahedral Remeshing (new package)

• This package implements a tetrahedral isotropic remeshing algorithm, that improves the quality of tetrahedra in terms of dihedral angles, while targeting a given edge length.

  See also the associated blog entry.

Surface Mesh Topology (new package)

• This package enables the computation of some topological invariants of surfaces, such as:
  • test if two (closed) curves on a combinatorial surface are homotopic. Users can choose between free homotopy and homotopy with fixed endpoints;
  • test is a curve is contractible;
  • compute shortest non-contractible cycles on a surface, with or without weights on edges.

  See also the associated blog entry.

Optimal Bounding Box (new package)

• This package implements an optimization algorithm that aims to construct a close approximation of the optimal bounding box of a mesh or a point set, which is defined as the smallest (in terms of volume) bounding box that contains a given mesh or point set.

  See also the associated blog entry.

Installation

• The CGAL_Core library no longer requires Boost.Thread, even if the g++ compiler is used.
• The minimal supported version of Boost is now 1.66.0.

Tutorials

• Two new, detailed tutorials have been added:
  • Surface Reconstruction from Point Clouds, which goes over a typical full processing pipeline in a CGAL environment.
  • Geographic Information Systems (GIS), which demonstrates usage of CGAL data structures and algorithms in the context of a typical GIS application.

  Both tutorials provide complete code.

2D and 3D Linear Geometry Kernel

• Added the functor CompareSignedDistanceToLine_2 to the 2D/3D Kernel concept to compare the signed distance of two points to a line, or the line passing through two given points. Corresponding functors in the model (Compare_signed_distance_to_line_2) are also added.

dD Geometry Kernel

• The kernels Epick_d and Epeck_d gain two new functors: Power_side_of_bounded_power_sphere_d and Compute_squared_radius_smallest_orthogonal_sphere_d. Those are essential for the computation of weighted alpha-complexes.

Surface Mesh

• Breaking change: The function CGAL::Surface_mesh::clear() now removes all non-default properties instead of just emptying them.

CGAL and the Boost Graph Library (BGL)

• Added the function CGAL::alpha_expansion_graphcut(), which regularizes a multi-label partition over a user-defined graph.
• Added the function CGAL::regularize_face_selection_borders(), which uses this alpha expansion graphcut to regularize the borders of a selected faces on a triangle mesh.
• Added the function CGAL::set_triangulation_ids(), which must be used to initialize vertex, edge, and face indices of a triangulation meant to be used with BGL algorithms.

3D Fast Intersection and Distance Computation

• The behavior of the internal search tree used to accelerate distance queries has changed: usage of the internal search tree will now be enabled by default, and its construction will be triggered by the first distance query. Automatic construction and usage can be disabled by calling CGAL::AABB_tree::do_not_accelerate_distance_queries() before the first distance query, and the tree can be built at any moment by calling CGAL::AABB_tree::accelerate_distance_queries().
• Breaking change: CGAL::AABB_tree::accelerate_distance_queries() and CGAL::AABB_tree::do_not_accelerate_distance_queries() are no longer const functions.

2D Arrangements

• Changed intersection return type from legacy CGAL::Object to modern boost::variant in all traits concepts and models. As there exists an implicit conversion from boost::variant to CGAL::Object, the new code is backward compatible. However, it is recommended that all calls to the intersection functions are fixed to use the new return type.

2D Regularized Boolean Set-Operations

• Changed intersection return type from legacy CGAL::Object to modern boost::variant in the concept ArrDirectionalTraits::Intersect_2 and its models.

2D Minkowski Sums

• Changed intersection return type from legacy CGAL::Object to modern boost::variant in the (internally used) model Arr_labeled_traits_2.

dD Spatial Searching

• The kd-tree can now be built in parallel: CGAL::Kd_tree::build() is given an optional template parameter ConcurrencyTag (default value remains CGAL::Sequential_tag for backward compatibility).
• Improved the performance of the kd-tree in some cases:
  • Not storing the points coordinates inside the tree usually generates a lot of cache misses, leading to non-optimal performance. This is the case for example when indices are stored inside the tree, or to a lesser extent when the points coordinates are stored in a dynamically allocated array (e.g., Epick_d with dynamic dimension) — we says “to a lesser extent” because the points are re-created by the kd-tree in a cache-friendly order after its construction, so the coordinates are more likely to be stored in a near-optimal order on the heap. In these cases, the new EnablePointsCache template parameter of the CGAL::Kd_tree class can be set to CGAL::Tag_true. The points coordinates will then be cached in an optimal way. This will increase memory consumption but provides better search performance. See the updated GeneralDistance and FuzzyQueryItem concepts for additional requirements when using such a cache.
  • In most cases (e.g., Euclidean distance), the distance computation algorithm knows before its end that the distance will be greater than or equal to some given value. This is used in the (orthogonal) k-NN search to interrupt some distance computations before its end, saving precious milliseconds, in particular in medium-to-high dimension.

Intersecting Sequences of dD Iso-oriented Boxes

• Added parallel versions of the functions CGAL::box_intersection_d() and CGAL::box_self_intersection_d().

Spatial Sorting

• Added parallel versions of the functions CGAL::hilbert_sort() and CGAL::spatial_sort() in 2D and 3D when the median policy is used. The parallel versions use up to four threads in 2D, and up to eight threads in 3D.

3D Convex Hulls

• A new overload for CGAL::convex_hull_3() that takes a model of VertexListGraph has been added.
• The long-deprecated function CGAL::convex_hull_3_to_polyhedron_3() has been removed. The function CGAL::convex_hull_3_to_face_graph() should be used instead.

Polygon Mesh Processing

• Added the function CGAL::Polygon_mesh_processing::volume_connected_component(), which can be used to get information about the nesting of the connected components of a given triangle mesh and about the volumes defined.
• Added the function CGAL::Polygon_mesh_processing::remove_connected_components_of_negligible_size(), which can be used to remove connected components whose area or volume is under a certain threshold. Area and volume thresholds are either specified by the user or deduced from the bounding box of the mesh.
• Added a new named parameter for CGAL::Polygon_mesh_processing::keep_large_connected_components() and CGAL::Polygon_mesh_processing::remove_connected_components_of_negligible_size, which can be used to perform a dry run of the operation, meaning that the function will return the number of connected components that would be removed with the specified threshold, but without actually removing them.
• Added the function CGAL::Polygon_mesh_processing::split(), which can be used to split meshes along a mesh or a plane.
• Added the function CGAL::Polygon_mesh_processing::split_connected_components() to split a single mesh containing several connected components into several meshes containing one connected component.
• Added the functions CGAL::Polygon_mesh_processing::merge_reversible_connected_components(), CGAL::Polygon_mesh_processing::duplicate_non_manifold_edges_in_polygon_soup(), and CGAL::Polygon_mesh_processing::orient_triangle_soup_with_reference_triangle_mesh(), which can be helpful when repairing a polygon soup.
• Added the function CGAL::Polygon_mesh_processing::sample_triangle_soup(), which generates points on a triangle soup surface.
• Added parallel versions of the functions CGAL::Polygon_mesh_processing::does_self_intersect() and CGAL::Polygon_mesh_processing::self_intersections().
• The function CGAL::Polygon_mesh_processing::stitch_borders() now returns the number of halfedge pairs that were stitched.
• Added the function CGAL::Polygon_mesh_processing::polygon_mesh_to_polygon_soup().
• The function CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh now allows passing a point map (for the point range) and a vertex point map (for the polygon mesh) via named parameters.

Point Set Processing

• Breaking change: CGAL::remove_outliers() has been parallelized and thus has a new template parameter ConcurrencyTag. To update your code simply add as first template parameter CGAL::Sequential_tag or CGAL::Parallel_tag when calling this function.
• Add a function CGAL::cluster_point_set() that segments a point cloud into connected components based on a distance threshold.
• Added wrapper functions for registration:
  • CGAL::OpenGR::compute_registration_transformation(), which computes the registration transformation for two point sets using the Super4PCS algorithm implemented in the third party library OpenGR.
  • CGAL::OpenGR::register_point_sets(), which computes the registration transformation for two point sets using the Super4PCS algorithm implemented in the third party library OpenGR, and registers the points sets by transforming the data point set using the computed transformation.
  • CGAL::pointmatcher::compute_registration_transformation() computes the registration transformation for two point sets using ICP algorithm implemented in the third party library libpointmatcher.
  • CGAL::pointmatcher::register_point_sets(), which computes the registration transformation for two point sets using ICP algorithm implemented in the third party library libpointmatcher, and registers the points sets by transforming the data point set using the computed transformation.

2D Triangulations

• To fix an inconsistency between code and documentation and to clarify which types of intersections are truly allowed in constrained Delaunay triangulations, the tag CGAL::No_intersection_tag has been deprecated in favor of two new tags: CGAL::No_constraint_intersection_tag and CGAL::No_constraint_intersection_requiring_constructions_tag. The latter is equivalent to the now-deprecated CGAL::No_intersection_tag, and allows constraints to intersect as long as no new point has to be created to represent that intersection (for example, the intersection of two constraint segments in a ‘T’-like junction is an existing point and as such does not require any new construction). The former tag, CGAL::No_constraint_intersection_tag, does not allow any intersection, except for the configuration of two constraints having a single common endpoints, for convience.
• Added the function CGAL::split_subconstraint_graph_into_constraints() to Constrained_triangulation_plus_2 to initialize the constraints from a soup of disconnected segments that should first be split into polylines.

3D Triangulations

• The member function CGAL::Triangulation_3::file_input() have been added. It allows to load a CGAL::Triangulation_3 from an input stream, using functors to create vertices and cells.

3D Triangulation Data Structure

• The member function CGAL::TDS_3::file_input() have been added. It allows to load a CGAL::Triangulation_data_structure_3 from an input stream, using functors to create vertices and cells.

Surface Mesh Simplification

• Added a new simplification method based on the quadric error defined by Garland and Heckbert.
• The concept EdgeProfile has been removed. This concept was not actually in use as the CGAL-provided model CGAL::Edge_profile was imposed to the user. Other concepts have been clarified to reflect the fact that the API uses this particular class.

STL Extensions for CGAL

• Added a new concurrency tag: CGAL::Parallel_if_available_tag. This tag is a convenience typedef to CGAL::Parallel_tag if the third party library TBB has been found and linked with, and to CGAL::Sequential_tag otherwise.