CGAL 5.5 offers the following improvements and new functionality over CGAL 5.4:
Changelog
3D Alpha Wrapping (new package)

This component takes a 3D triangle mesh, soup, or point set as input, and generates a valid (watertight, intersectionfree, and combinatorially 2manifold) surface triangle mesh that contains the input. The algorithm proceeds by shrinkwrapping and refining a 3D Delaunay triangulation, starting from a loose bounding box of the input. Two userdefined parameters, alpha and offset, offer control over the maximum size of cavities where the shrinkwrapping process can enter, and the tightness of the final surface mesh to the input, respectively. Once combined, these parameters provide a means to trade fidelity to the input for complexity of the output.
See also the announcement page.
2D Straight Skeleton and Polygon Offsetting (breaking change)
 Fix the output of the function CGAL::create_exterior_skeleton_and_offset_polygons_with_holes_2() to not take into account the offset of the outer frame.
 Fix the computation of the exterior offset of a polygon with holes that was not computing the offset of the holes
3D Convex Hulls
 Added an overload of the function
CGAL::convex_hull_3()
, which writes the result in an indexed triangle set.
2D Polygons
 Add vertex, edge, and hole ranges.
 The concept
GeneralPolygonWithHoles_2
now requires the nested typePolygon_2
instead ofGeneral_polygon_2
.
2D Regularized Boolean SetOperations
 The concept
GeneralPolygonSetTraits_2
now requires the nested typeConstruct_polygon_with_holes_2
instead ofConstruct_general_polygon_with_holes_2
.
Combinatorial Maps
 Removed old code deprecated in CGAL 4.9 and 4.10 (global functions, and information associated with darts).
2D Arrangements
 Fixed the
intersect_2
,compare_y_at_x_right
, andcompare_y_at_x_left
function objects of the traits class templateArr_geodesic_arc_on_sphere_traits_2
that handles geodesic arcs on sphere and applied a small syntactical fix to the tracing traits.
Tetrahedral Mesh Generation
 Added the function
remove_isolated_vertices()
as a postprocessing step for the tetrahedral mesh generation.
Polygon Mesh Processing
 Added the function
CGAL::Polygon_mesh_processing::orient_triangle_soup_with_reference_triangle_soup()
, which enables reorienting the faces of a triangle soup based on the orientation of the nearest face in a reference triangle soup.  Added the function
CGAL::Polygon_mesh_processing::compatible_orientations()
, which enables to retrieve the (in)compatibility of orientations of faces from different connected components.  Added the function
CGAL::Polygon_mesh_processing::tangential_relaxation()
, which applies an areabased tangential mesh smoothing to the vertices of a surface triangle mesh.  Added the named parameter
visitor
to the functiontriangulate_hole()
, which enables to track progress with callbacks.  Added more functions in the visitor of the corefinement based methods to track progress.
Surface Mesh Simplification
 Introduced four variations of the GarlandHeckbert simplification algorithm based on the probabilistic approach of Trettner and Kobbelt (Fast and Robust QEF Minimization using Probabilistic Quadrics):
GarlandHeckbert_plane_policies
,GarlandHeckbert_probabilistic_plane_policies
,GarlandHeckbert_triangle_policies
, andGarlandHeckbert_probabilistic_triangle_policies
.  The class
GarlandHeckbert_policies
has been deprecated,GarlandHeckbert_plane_policies
replaces it.
Point Set Processing
 A new optional named parameter,
min_points_per_cell
has been added togrid_simplify_point_set()
. By adding a minimal number of points in a cell such that a point is retained, one can also filter out low density areas and outliers: in the case of densely sampled point clouds, this yields better results than using grid simplification and then outlier removal, while being very vast. The default value is1
to keep the previous behavior as default.
dD Spatial Searching
 Added the member function
write_graphviz()
to the classKd_tree
that writes the tree in a stream in the Graphviz format.
CGAL and the Boost Graph Library (BGL)
 Added the function
invert_selection()
in the classFace_filtered_graph
, which toggles the selected status of a graph: selected faces are deselected, and unselected faces are selected.