CGAL 6.0 - Triangulated Surface Mesh Approximation
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Triangulated Surface Mesh Approximation Reference

Pierre Alliez, David Cohen-Steiner, and Lingjie Zhu
This package implements the Variational Shape Approximation method to approximate an input surface triangle mesh by a simpler surface triangle mesh. The algorithm proceeds by iterative clustering of triangles, the clustering process being seeded randomly, incrementally or hierarchically. While the default function runs an automated version of the algorithm, interactive control is possible via a class interface. The API is flexible and can be extended to user-defined proxies and error metrics.
Introduced in: CGAL 4.14
BibTeX: cgal:az-tsma-24a
Depends on: Eigen
License: GPL
Windows Demo: CGAL Lab

Classified Reference Pages

Parameters

Optional parameters of the functions of this package are implemented as BGL named parameters. The page Named Parameters describes their usage.

Concepts

Main Functions

Classes

Modules

 Concepts
 

Classes

class  CGAL::Surface_mesh_approximation::L21_metric_plane_proxy< TriangleMesh, VertexPointMap, GeomTraits >
 Approximation L21 metric of vector proxy. More...
 
class  CGAL::Surface_mesh_approximation::L2_metric_plane_proxy< TriangleMesh, VertexPointMap, GeomTraits >
 Approximation L2 metric of plane proxy. More...
 
class  CGAL::Variational_shape_approximation< TriangleMesh, VertexPointMap, ErrorMetricProxy, GeomTraits, Concurrency_tag >
 Main class for Variational Shape Approximation algorithm. More...
 

Enumerations

enum  CGAL::Surface_mesh_approximation::Verbose_level { CGAL::Surface_mesh_approximation::SILENT , CGAL::Surface_mesh_approximation::MAIN_STEPS , CGAL::Surface_mesh_approximation::VERBOSE }
 Verbose level enumeration. More...
 
enum  CGAL::Surface_mesh_approximation::Seeding_method { CGAL::Surface_mesh_approximation::RANDOM , CGAL::Surface_mesh_approximation::INCREMENTAL , CGAL::Surface_mesh_approximation::HIERARCHICAL }
 Seeding method enumeration for Variational Shape Approximation algorithm. More...
 

Functions

template<typename TriangleMesh , typename NamedParameters >
bool CGAL::Surface_mesh_approximation::approximate_triangle_mesh (const TriangleMesh &tm, const NamedParameters &np)
 approximates the input mesh with plane proxies.
 

Enumeration Type Documentation

◆ Seeding_method

#include <CGAL/Variational_shape_approximation.h>

Seeding method enumeration for Variational Shape Approximation algorithm.

Enumerator
RANDOM 

Random seeding.

INCREMENTAL 

Incremental seeding.

HIERARCHICAL 

Hierarchical seeding.

◆ Verbose_level

#include <CGAL/Surface_mesh_approximation/approximate_triangle_mesh.h>

Verbose level enumeration.

Enumerator
SILENT 

Silent.

MAIN_STEPS 

Main steps.

VERBOSE 

Verbose.

Function Documentation

◆ approximate_triangle_mesh()

template<typename TriangleMesh , typename NamedParameters >
bool CGAL::Surface_mesh_approximation::approximate_triangle_mesh ( const TriangleMesh &  tm,
const NamedParameters &  np 
)

#include <CGAL/Surface_mesh_approximation/approximate_triangle_mesh.h>

approximates the input mesh with plane proxies.

This function uses the Variational Shape Approximation algorithm described in [1] to approximate a triangle surface mesh, with indexed triangles as output.

Template Parameters
TriangleMeshmodel of FaceListGraph
NamedParametersa sequence of Named Parameters
Parameters
tmtriangle surface mesh to be approximated
npan optional sequence of Named Parameters among the ones listed below
Returns
true if the indexed triangles represent a 2-manifold, oriented surface mesh, and false otherwise.
Approximation Named Parameters
  • an instance of a geometric traits class
  • Type: a model of Kernel
  • Default: a CGAL Kernel deduced from the point type, using CGAL::Kernel_traits
  • Extra: Exact constructions kernels are not supported by this function.

  • a property map associating points to the vertices of tm
  • Type: a class model of ReadablePropertyMap with boost::graph_traits<TriangleMesh>::vertex_descriptor as key type and Point_3 as value type
  • Default: boost::get(CGAL::vertex_point, tm)
  • Extra: If this parameter is omitted, an internal property map for CGAL::vertex_point_t must be available in TriangleMesh.

  • the maximum number of proxies used to approximate the input mesh
  • Type: std::size_t
  • Default: num_faces(tm) / 3, used when min_error_drop is also not provided

  • the minimum error drop of the approximation, expressed as the ratio between two iterations of proxy addition
  • Type: geom_traits::FT
  • Default: 0.1, used when max_number_of_proxies is also not provided

  • the number of relaxation iterations interleaved within seeding
  • Type: std::size_t
  • Default: 5

  • the number of partitioning and fitting iterations after seeding
  • Type: std::size_t
  • Default: std::min(std::max(number_of_faces / max_number_of_proxies, 20), 60)
Meshing Named Parameters
  • the chord subdivision ratio threshold to the chord length or average edge length
  • Type: geom_traits::FT
  • Default: 5.0

  • If true, the subdivision_ratio is the ratio of the furthest vertex distance to the chord length, otherwise is the average edge length
  • Type: Boolean
  • Default: false

  • If true, the subdivision_ratio is weighted by dihedral angle
  • Type: Boolean
  • Default: false

  • If true, optimize the anchor locations
  • Type: Boolean
  • Default: true

  • If true, use PCA plane fitting, otherwise use the default area averaged plane parameters
  • Type: Boolean
  • Default: false
Output Named Parameters
  • a property map to output the proxy index of each face of the input polygon mesh
  • Type: a model of WritablePropertyMap with boost::graph_traits<TriangleMesh>::face_descriptor as key and std::size_t as value type
  • Default: no output operation is performed
  • Extra: A proxy is a set of connected faces which are placed under the same proxy patch (see Figure 79.3)
  • Extra: The proxy-ids are contiguous in range [0, number_of_proxies - 1]

  • an OutputIterator to put proxies in
  • Type: a class model of OutputIterator with CGAL::Surface_mesh_approximation::L21_metric_vector_proxy_no_area_weighting::Proxy value type
  • Default: no output operation is performed

  • an OutputIterator to put anchor points in
  • Type: a class model of OutputIterator with geom_traits::Point_3 value type
  • Default: no output operation is performed

  • an OutputIterator to put indexed triangles in
  • Type: a class model of OutputIterator with std::array<std::size_t, 3> value type
  • Default: no output operation is performed