CGAL Namespace Reference

Functions
template<class Polyhedron , class SDFPropertyMap , class GeomTraits = typename Polyhedron::Traits>
std::pair< double, double >	compute_sdf_values (const Polyhedron &polyhedron, SDFPropertyMap sdf_values, double cone_angle=2.0/3.0 *CGAL_PI, int number_of_rays=25, GeomTraits traits=GeomTraits())
	Function computing the Shape Diameter Function over a surface mesh.
template<class Polyhedron , class SDFPropertyMap , class SegmentPropertyMap , class GeomTraits = typename Polyhedron::Traits>
int	segment_from_sdf_values (const Polyhedron &polyhedron, SDFPropertyMap sdf_values, SegmentPropertyMap segment_ids, int number_of_levels=5, double smoothing_lambda=0.26, GeomTraits traits=GeomTraits())
	Function computing the segmentation of a surface mesh given an SDF value per facet.
template<class Polyhedron , class SegmentPropertyMap , class GeomTraits = typename Polyhedron::Traits>
int	compute_sdf_values_and_segment (const Polyhedron &polyhedron, SegmentPropertyMap segment_ids, double cone_angle=2.0/3.0 *CGAL_PI, int number_of_rays=25, int number_of_levels=5, double smoothing_lambda=0.26, GeomTraits traits=GeomTraits())
	Function computing the segmentation of a surface mesh.

Detailed Description

CGAL

Function Documentation

template<class Polyhedron , class SDFPropertyMap , class GeomTraits = typename Polyhedron::Traits>

std::pair<double, double> CGAL::compute_sdf_values	(	const Polyhedron &	polyhedron,
		SDFPropertyMap	sdf_values,
		double	cone_angle = 2.0 / 3.0 * CGAL_PI,
		int	number_of_rays = 25,
		GeomTraits	traits = GeomTraits()
	)

Function computing the Shape Diameter Function over a surface mesh.

This function implements the Shape Diameter Function (SDF) as described in Shapira2008Consistent. After the computation of SDF values for each facet, the following post-processing steps are applied:

• Facets with no SDF values (i.e. zero) are assigned to average SDF value of its neighbors. If still there is any facet which has no SDF value, minimum SDF value greater than zero is assigned to it.
• Smoothed with bilateral filtering.
• Linearly normalized between [0,1].

Precondition

polyhedron.is_pure_triangle()

Template Parameters

Polyhedron	a CGAL polyhedron
SDFPropertyMap	a ReadWritePropertyMap with Polyhedron::Facet_const_handle as key and double as value type
GeomTraits	a model of SegmentationGeomTraits

Parameters

	polyhedron	surface mesh on which SDF values are computed
[out]	sdf_values	the sdf value of each facet
	cone_angle	opening angle for cone, expressed in radians
	number_of_rays	number of rays picked from cone for each facet
	traits	traits object

Returns

minimum and maximum SDF values before linear normalization

template<class Polyhedron , class SDFPropertyMap , class SegmentPropertyMap , class GeomTraits = typename Polyhedron::Traits>

int CGAL::segment_from_sdf_values	(	const Polyhedron &	polyhedron,
		SDFPropertyMap	sdf_values,
		SegmentPropertyMap	segment_ids,
		int	number_of_levels = 5,
		double	smoothing_lambda = 0.26,
		GeomTraits	traits = GeomTraits()
	)

Function computing the segmentation of a surface mesh given an SDF value per facet.

This function fills a property map which associates a segment-id (between [0, number of segments -1]) to each facet. Formally, a segment is a set of connected facets which are placed under same cluster.

Note that there is no direct relation between the parameter number_of_levels and number of segments. However, large number of clusters likely to result in detailed segmentation of the mesh with large number of segments.

Precondition

polyhedron.is_pure_triangle()

Template Parameters

Polyhedron	a CGAL polyhedron
SDFPropertyMap	a ReadablePropertyMap with Polyhedron::Facet_const_handle as key and double as value type
SegmentPropertyMap	a ReadWritePropertyMap with Polyhedron::Facet_const_handle as key and int as value type
GeomTraits	a model of SegmentationGeomTraits

Parameters

	polyhedron	surface mesh on which SDF values are computed
	sdf_values	sdf_values the sdf value of each facet
[out]	segment_ids	the segment id of each facet
	number_of_levels	number of clusters for soft clustering
	smoothing_lambda	factor in the interval [0,1] which indicates the importance of surface features in energy minimization
	traits	traits object

Returns

number of segments

template<class Polyhedron , class SegmentPropertyMap , class GeomTraits = typename Polyhedron::Traits>

int CGAL::compute_sdf_values_and_segment	(	const Polyhedron &	polyhedron,
		SegmentPropertyMap	segment_ids,
		double	cone_angle = 2.0 / 3.0 * CGAL_PI,
		int	number_of_rays = 25,
		int	number_of_levels = 5,
		double	smoothing_lambda = 0.26,
		GeomTraits	traits = GeomTraits()
	)

Function computing the segmentation of a surface mesh.

Basically this function combines CGAL::sdf_values_computation and CGAL::surface_mesh_segmentation_from_sdf_values functions by computing SDF values and segmenting the mesh in one go.

Note that for segmenting the mesh several times with different parameters (i.e. number of levels, and smoothing lambda), it is wise to first compute SDF values using CGAL::sdf_values_computation, and then call CGAL::surface_mesh_segmentation_from_sdf_values with the same SDF values.

Precondition

polyhedron.is_pure_triangle()

Template Parameters

Polyhedron	a CGAL polyhedron
SegmentPropertyMap	a ReadWritePropertyMap with Polyhedron::Facet_const_handle as key and int as value type
GeomTraits	a model of SegmentationGeomTraits

Parameters

	polyhedron	surface mesh on which SDF values are computed
[out]	segment_ids	the segment id of each facet
	cone_angle	opening angle for cone, expressed in radians
	number_of_rays	number of rays picked from cone for each facet
	number_of_levels	number of clusters for soft clustering
	smoothing_lambda	factor in the interval [0,1] which indicates the importance of surface features in energy minimization
	traits	traits object

Returns

number of segments