CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits > Class Template Reference

#include <CGAL/Classification/Mesh_feature_generator.h>

Definition

template<typename GeomTraits, typename FaceListGraph, typename PointMap, typename ConcurrencyTag, typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>
class CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >

generates a set of generic features for surface mesh classification.

This class takes care of computing and storing all necessary data structures and of generating a set of generic features at multiple scales to increase the reliability of the classification.

A PointMap is required: this map should associate each face of the mesh to a representative point (for example, the center of mass of the face). It is used to generate point set features by considering the mesh as a point set.

Warning

The generated features use data structures that are stored inside the generator. For this reason, the generator should be instantiated within the same scope as the feature set and should not be deleted before the feature set.

Template Parameters

GeomTraits	model of CGAL Kernel.
FaceListGraph	model of FaceListGraph.
PointMap	model of ReadablePropertyMap whose key type is boost::graph_traits<FaceListGraph>::face_descriptor and value type is GeomTraits::Point_3.
ConcurrencyTag	enables sequential versus parallel computation of CGAL::Classification::Local_eigen_analysis objects. Possible values are Parallel_tag (default value if CGAL is linked with TBB) or Sequential_tag (default value otherwise).
DiagonalizeTraits	model of DiagonalizeTraits used for matrix diagonalization. It can be omitted: if Eigen 3 (or greater) is available and CGAL_EIGEN3_ENABLED is defined then an overload using Eigen_diagonalize_traits is provided. Otherwise, the internal implementation Diagonalize_traits is used.

Public Types
using	Iso_cuboid_3 = typename GeomTraits::Iso_cuboid_3
using	Planimetric_grid = Classification::Planimetric_grid< GeomTraits, Face_range, PointMap >
using	Neighborhood = Classification::Mesh_neighborhood< FaceListGraph >
using	Local_eigen_analysis = Classification::Local_eigen_analysis

Constructor
	Mesh_feature_generator (const FaceListGraph &input, PointMap point_map, std::size_t nb_scales, float voxel_size=-1.f)
	initializes a feature generator from an input range. More...

Feature Generation
void	generate_face_based_features (Feature_set &features)
	generates geometric features based on face information. More...
void	generate_point_based_features (Feature_set &features)
	generates geometric features based on point position information. More...

Data Structures Access
const Iso_cuboid_3 &	bbox () const
	returns the bounding box of the input point set.
const Neighborhood &	neighborhood (std::size_t scale=0) const
	returns the neighborhood structure at scale scale.
const Planimetric_grid &	grid (std::size_t scale=0) const
	returns the planimetric grid structure at scale scale.
const Local_eigen_analysis &	eigen (std::size_t scale=0) const
	returns the local eigen analysis structure at scale scale.

Parameters
std::size_t	number_of_scales () const
	returns the number of scales that were computed.
float	grid_resolution (std::size_t scale=0) const
	returns the grid resolution at scale scale. More...
float	radius_neighbors (std::size_t scale=0) const
	returns the radius used for neighborhood queries at scale scale. More...
float	radius_dtm (std::size_t scale=0) const
	returns the radius used for digital terrain modeling at scale scale. More...

Constructor & Destructor Documentation

Mesh_feature_generator()

template<typename GeomTraits , typename FaceListGraph , typename PointMap , typename ConcurrencyTag , typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>

CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >::Mesh_feature_generator	(	const FaceListGraph &	input,
		PointMap	point_map,
		std::size_t	nb_scales,
		float	voxel_size = -1.f
	)

initializes a feature generator from an input range.

If not provided by the user, The size of the smallest scale is automatically estimated using a method equivalent to CGAL::compute_average_spacing() using 6 neighbors. The data structures needed (Neighborhood, Planimetric_grid and Local_eigen_analysis) are computed at nb_scales recursively larger scales.

Parameters

input	input mesh.
point_map	property map to access a representative point of each face.
nb_scales	number of scales to compute.
voxel_size	smallest scale used as a voxel size for the planimetric grid (if the default value -1 is used, its value is automatically estimated).

Member Function Documentation

generate_face_based_features()

template<typename GeomTraits , typename FaceListGraph , typename PointMap , typename ConcurrencyTag , typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>

void CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >::generate_face_based_features

(

Feature_set &

features

)

generates geometric features based on face information.

At each scale, the following features are generated:

• CGAL::Classification::Feature::Eigenvalue with indices 0, 1 and 2
• The version of CGAL::Classification::Feature::Verticality based on eigenvalues

Parameters

features

the feature set where the features are instantiated.

generate_point_based_features()

template<typename GeomTraits , typename FaceListGraph , typename PointMap , typename ConcurrencyTag , typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>

void CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >::generate_point_based_features

(

Feature_set &

features

)

generates geometric features based on point position information.

At each scale, the following features are generated by considering the mesh as a point cloud through PointMap:

• CGAL::Classification::Feature::Distance_to_plane
• CGAL::Classification::Feature::Elevation
• CGAL::Classification::Feature::Height_above
• CGAL::Classification::Feature::Height_below
• CGAL::Classification::Feature::Vertical_dispersion
• CGAL::Classification::Feature::Vertical_range

Parameters

features

the feature set where the features are instantiated.

grid_resolution()

template<typename GeomTraits , typename FaceListGraph , typename PointMap , typename ConcurrencyTag , typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>

float CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >::grid_resolution

(

std::size_t

scale = 0

)

const

returns the grid resolution at scale scale.

This resolution is the length and width of a cell of the Planimetric_grid defined at this scale.

radius_dtm()

template<typename GeomTraits , typename FaceListGraph , typename PointMap , typename ConcurrencyTag , typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>

float CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >::radius_dtm

(

std::size_t

scale = 0

)

const

returns the radius used for digital terrain modeling at scale scale.

This radius represents the minimum size of a building at this scale.

radius_neighbors()

template<typename GeomTraits , typename FaceListGraph , typename PointMap , typename ConcurrencyTag , typename DiagonalizeTraits = CGAL::Default_diagonalize_traits<float,3>>

float CGAL::Classification::Mesh_feature_generator< GeomTraits, FaceListGraph, PointMap, ConcurrencyTag, DiagonalizeTraits >::radius_neighbors

(

std::size_t

scale = 0

)

const

returns the radius used for neighborhood queries at scale scale.

This radius is the smallest radius that is relevant from a geometric point of view at this scale (that is to say that encloses a few cells of Planimetric_grid).