Mesh Generation Functions

The two main functions to generate a mesh are make_mesh_3() and refine_mesh_3().

The other functions enable to optimize an existing mesh.

Functions
template<typename NamedParameters = CGAL::parameters::Default_named_parameters>
CGAL::Image_3	CGAL::Mesh_3::generate_label_weights (const CGAL::Image_3 &image, const float &sigma)
	Free function that generates a CGAL::Image_3 of weights associated to each voxel of image, to make the output mesh surfaces smoother.
template<typename C3T3 , typename NamedParameters = CGAL::parameters::Default_named_parameters>
Mesh_optimization_return_code	CGAL::exude_mesh_3 (C3T3 &c3t3, const NamedParameters &np=parameters::default_values())
	The function exude_mesh_3() performs a sliver exudation process on a Delaunay mesh.
template<typename C3T3 , typename MeshDomain , typename NamedParameters = CGAL::parameters::Default_named_parameters>
Mesh_optimization_return_code	CGAL::odt_optimize_mesh_3 (C3T3 &c3t3, const MeshDomain &domain, const NamedParameters &np=parameters::default_values())
	The function odt_optimize_mesh_3() is a mesh optimization process based on the minimization of a global energy function.
template<typename C3T3 , typename MeshDomain , typename NamedParameters = CGAL::parameters::Default_named_parameters>
Mesh_optimization_return_code	CGAL::lloyd_optimize_mesh_3 (C3T3 &c3t3, const MeshDomain &domain, const NamedParameters &np=parameters::default_values())
	The function lloyd_optimize_mesh_3() is a mesh optimization process based on the minimization of a global energy function.
template<typename C3T3 , typename MeshDomain , typename NamedParameters = CGAL::parameters::Default_named_parameters>
Mesh_optimization_return_code	CGAL::perturb_mesh_3 (C3T3 &c3t3, const MeshDomain &domain, const NamedParameters &np=parameters::default_values())
	The function perturb_mesh_3() is a mesh optimizer that improves the quality of a Delaunay mesh by changing the positions of some vertices of the mesh.
template<typename C3T3 , typename MeshDomain , typename MeshCriteria , typename NamedParameters = CGAL::parameters::Default_named_parameters>
void	CGAL::refine_mesh_3 (C3T3 &c3t3, const MeshDomain &domain, const MeshCriteria &criteria, const NamedParameters &np=parameters::default_values())
	The function refine_mesh_3() is a 3D mesh generator.
template<typename C3T3 , typename MeshDomain , typename MeshCriteria , typename NamedParameters = CGAL::parameters::Default_named_parameters>
C3T3	CGAL::make_mesh_3 (const MeshDomain &domain, const MeshCriteria &criteria, const NamedParameters &np=parameters::default_values())
	The function make_mesh_3() is a 3D mesh generator.

Function Documentation

exude_mesh_3()

template<typename C3T3 , typename NamedParameters = CGAL::parameters::Default_named_parameters>

Mesh_optimization_return_code CGAL::exude_mesh_3	(	C3T3 &	c3t3,
		const NamedParameters &	np = parameters::default_values()
	)

#include <CGAL/exude_mesh_3.h>

The function exude_mesh_3() performs a sliver exudation process on a Delaunay mesh.

The sliver exudation process consists in optimizing the weights of vertices of the weighted Delaunay triangulation in such a way that slivers disappear and the quality of the mesh improves.

Warning

This optimizer modifies the weight of vertices of the triangulation and, if called, must be the last optimizer to be called. If the mesh is refined after this optimization has been performed, all improvements will be lost.

Template Parameters

C3T3	a model of the concept MeshComplex_3InTriangulation_3.
NamedParameters	a sequence of Named Parameters

Parameters

c3t3	the initial mesh that will be modified by the algorithm to represent the final optimized mesh.
np	an optional sequence of Named Parameters among the ones listed below:

Optional Named Parameters

time_limit is used to set up, in seconds, a CPU time limit after which the optimization process is stopped. This time is measured using the Real_timer class. The default value is 0 and means that there is no time limit. Type: double Precondition: time_limit >= 0 Default: 0

sliver_bound is designed to give, in degrees, a targeted lower bound on dihedral angles of mesh cells. The exudation process considers in turn all the mesh cells that have a smallest dihedral angle less than sliver_bound and tries to make them disappear by weighting their vertices. The optimization process stops when every cell in the mesh achieves this quality. The default value is 0 and means that there is no targeted bound: the exuder then runs as long as it can improve the smallest dihedral angles of the set of cells incident to some vertices. Type: double Precondition: 0<= sliver_bound <= 180 Default: 0

Returns

a value of type CGAL::Mesh_optimization_return_code which is:

• CGAL::BOUND_REACHED when the targeted bound for the smallest dihedral angle in the mesh is reached.
• CGAL::TIME_LIMIT_REACHED when the time limit is reached.
• CGAL::CANT_IMPROVE_ANYMORE when exudation process stops because it can no longer improve the smallest dihedral angle of the set of cells incident to some vertex in the mesh.

Example

// Exude without sliver_bound, using at most 10s CPU time
exude_mesh_3(c3t3,
             parameters::time_limit(10));

See also

CGAL::Mesh_optimization_return_code

CGAL::make_mesh_3()

CGAL::refine_mesh_3()

CGAL::perturb_mesh_3()

CGAL::lloyd_optimize_mesh_3()

CGAL::odt_optimize_mesh_3()

Examples

Mesh_3/mesh_implicit_domains.cpp, Mesh_3/mesh_implicit_domains_2.cpp, Mesh_3/mesh_implicit_ellipsoid.cpp, and Mesh_3/mesh_optimization_lloyd_example.cpp.

generate_label_weights()

template<typename NamedParameters = CGAL::parameters::Default_named_parameters>

CGAL::Image_3 CGAL::Mesh_3::generate_label_weights	(	const CGAL::Image_3 &	image,
		const float &	sigma
	)

#include <CGAL/Mesh_3/generate_label_weights.h>

Free function that generates a CGAL::Image_3 of weights associated to each voxel of image, to make the output mesh surfaces smoother.

The weights image is generated using the algorithm described by Stalling et al in [17]. The Insight toolkit is needed to compile this function.

Parameters

image

the input labeled image from which the weights image is computed. Both will then be used to construct a Labeled_mesh_domain_3.

sigma

the standard deviation parameter of the internal Gaussian filter, measured in real-world distances. The size of a voxel (e.g. shortest length or longest length) usually is a good value for this parameter. Note that if sigma is too small, the "stair-effect" of meshing from a voxel image can appear. On the other side, if sigma is too large, thin volumes (basically one voxel thick) may be lost in the meshing process because the computed weights are too blurry.

Returns

a CGAL::Image_3 of weights used to build a quality Labeled_mesh_domain_3, with the same dimensions as image

Examples

Mesh_3/mesh_3D_weighted_image.cpp, and Mesh_3/mesh_3D_weighted_image_with_detection_of_features.cpp.

lloyd_optimize_mesh_3()

template<typename C3T3 , typename MeshDomain , typename NamedParameters = CGAL::parameters::Default_named_parameters>

Mesh_optimization_return_code CGAL::lloyd_optimize_mesh_3	(	C3T3 &	c3t3,
		const MeshDomain &	domain,
		const NamedParameters &	np = parameters::default_values()
	)

#include <CGAL/lloyd_optimize_mesh_3.h>

The function lloyd_optimize_mesh_3() is a mesh optimization process based on the minimization of a global energy function.

In lloyd_optimize_mesh_3(), the minimized global energy may be interpreted as the \( L^1\)-norm of the error achieved when the function \( x^2\) is interpolated on the mesh domain using a piecewise linear function which is linear in each cell of the Voronoi diagram of the mesh vertices.

The optimizer lloyd_optimize_mesh_3() works in iterative steps. At each iteration, mesh vertices are moved into positions that bring to zero the energy gradient and the Delaunay triangulation is updated. Vertices on the mesh boundaries are handled in a special way so as to preserve an accurate representation of the domain boundaries.

Template Parameters

C3T3	a model of the concept MeshComplex_3InTriangulation_3.
MD	a model of the concept MeshDomain_3.
NamedParameters	a sequence of Named Parameters

Parameters

c3t3	the initial mesh that will be modified by the algorithm to represent the final optimized mesh.
domain	the domain used to create the c3t3 parameter
np	an optional sequence of Named Parameters among the ones listed below:

Optional Named Parameters

time_limit to set up, in seconds, a CPU time limit after which the optimization process is stopped. This time is measured using CGAL::Real_timer. 0 means that there is no time limit. Type: double Precondition: time_limit >= 0 Default: 0
max_iteration_number limit on the number of performed iterations. 0 means that there is no limit on the number of performed iterations. Precondition: max_iteration_number >=0 Type: int Default: 0
freeze_bound designed to reduce running time of each optimization iteration. Any vertex that has a displacement less than a given fraction of the length of its shortest incident edge, is frozen (i.e. is not relocated). The parameter freeze_bound gives the threshold ratio. If it is set to 0, freezing of vertices is disabled. Precondition: 0<= freeze_bound <=1 Type: double Default: 0.01
convergence threshold ratio of stopping criterion based on convergence: the optimization process is stopped when at the last iteration the displacement of any vertex is less than a given fraction of the length of the shortest edge incident to that vertex. Precondition: 0 <=convergence <= 1 Type: double Default: 0.02
do_freeze completes the freeze_bound parameter. If it is set to true (default value), frozen vertices will not move anymore in next iterations. Otherwise, at each iteration, any vertex that moves, unfreezes all its incident vertices. Type: bool Default: true

Returns

a value of type CGAL::Mesh_optimization_return_code which is:

• CGAL::TIME_LIMIT_REACHED when the time limit is reached.
• CGAL::MAX_ITERATION_NUMBER_REACHED when lloyd_optimize_mesh_3() stops because it has performed max_iteration_number iterations.
• CGAL::CONVERGENCE_REACHED when lloyd_optimize_mesh_3() stops because the convergence criterion is achieved.
• CGAL::ALL_VERTICES_FROZEN when all vertices have been frozen, when the do_freeze parameter is set to true.
• CGAL::CANT_IMPROVE_ANYMORE when lloyd_optimize_mesh_3() stops because most vertices have been frozen, and no better convergence can be reached.

Example

// Lloyd-smoothing until convergence reaches 0.01, freezing vertices which
// move less than 0.001*shortest_incident_edge_length
lloyd_optimize_mesh_3(c3t3,
                      domain,
                      parameters::convergence(0.01).
                      parameters::freeze_bound(0.001).
                      parameters::do_freeze(true));

See also

CGAL::Mesh_optimization_return_code

CGAL::make_mesh_3()

CGAL::refine_mesh_3()

CGAL::exude_mesh_3()

CGAL::perturb_mesh_3()

CGAL::odt_optimize_mesh_3()

Note

This function requires the Eigen library.

Examples

Mesh_3/mesh_optimization_lloyd_example.cpp.

make_mesh_3()

template<typename C3T3 , typename MeshDomain , typename MeshCriteria , typename NamedParameters = CGAL::parameters::Default_named_parameters>

C3T3 CGAL::make_mesh_3	(	const MeshDomain &	domain,
		const MeshCriteria &	criteria,
		const NamedParameters &	np = parameters::default_values()
	)

#include <CGAL/make_mesh_3.h>

The function make_mesh_3() is a 3D mesh generator.

It produces simplicial meshes which discretize 3D domains.

The mesh generation algorithm is a Delaunay refinement process followed by an optimization phase. The criteria driving the Delaunay refinement process may be tuned to achieve the user needs with respect to the size of mesh elements, the accuracy of boundaries approximation, etc.

The optimization phase is a sequence of optimization processes, amongst the following available optimizers: an ODT-smoothing, a Lloyd-smoothing, a sliver perturber, and a sliver exuder. Each optimization process can be activated or not, according to the user requirements and available time. By default, only the perturber and the exuder are activated. Note that the benefits of the exuder will be lost if the mesh is further refined afterward, and that ODT-smoothing, Lloyd-smoothing, and sliver perturber should never be called after the sliver exuder. In the case of further refinement, only the sliver exuder can be used.

The function outputs the mesh to an object which provides iterators to traverse the resulting mesh data structure or can be written to a file (see Examples ).

Template Parameters

C3T3	either a model of the concept MeshComplex_3InTriangulation_3 or of MeshComplexWithFeatures_3InTriangulation_3 if MD is a model of MeshDomainWithFeatures_3. The type C3T3 is in particular required to provide a nested type C3T3::Triangulation for the 3D triangulation embedding the mesh. The vertex and cell base classes of the triangulation C3T3::Triangulation are required to be models of the concepts MeshVertexBase_3 and MeshCellBase_3 respectively.
MD	either a model of the concept MeshDomain_3 or of MeshDomainWithFeatures_3 if 0 and 1-dimensional features of the input complex have to be accurately represented in the mesh.
MC	either a model of the concept MeshCriteria_3 or a model of MeshCriteriaWithFeatures_3 if the domain has exposed features.
NamedParameters	a sequence of Named Parameters

Parameters

domain	the domain used to create the c3t3 parameter. It is the sole link through which the domain to be discretized is known by the mesh generation algorithm.
criteria	specifies the size and shape requirements for mesh tetrahedra and surface facets. These criteria form the rules which drive the refinement process. All mesh elements satisfy those criteria at the end of the refinement process. In addition, if the domain has features, the argument criteria provides a sizing field to guide the discretization of 1-dimensional exposed features.
np	an optional sequence of Named Parameters among the ones listed below:

Optional Named Parameters

Feature preservation options If the domain is a model of MeshDomainWithFeatures_3, 0 and 1-dimensional features can be taken into account while generating the mesh. The following two named parameters control this option: parameters::features(domain) parameters::no_features() Default: parameters::features(domain)
Topological options (manifoldness) In order to drive the meshing algorithm and ensure that the output mesh follows a desired topological criterion, three named parameters control this option: parameters::manifold() parameters::manifold_with_boundary() parameters::non_manifold() Note that the meshing algorithm cannot generate a manifold surface if the input surface is not manifold. Default: parameters::non_manifold()
Lloyd optimization lloyd_optimize_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_lloyd() parameters::lloyd_optimize_mesh_3() Default: parameters::no_lloyd()
ODT optimization odt_optimize_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_odt() parameters::odt() Default: parameters::no_odt()
Mesh perturbation perturb_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_perturb() parameters::perturb() Default: parameters::perturb()
Mesh exudation exude_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_exude() parameters::exude() Default: parameters::exude()

Note that regardless of which optimization processes are activated, they are always launched in the order that is a suborder of the following (see user manual for further details): ODT-smoother, Lloyd-smoother, perturber, and exuder.

Beware that optimization of the mesh is obtained by perturbing mesh vertices and modifying the mesh connectivity and that this has an impact on the strict compliance to the refinement criteria. Though a strict compliance to mesh criteria is guaranteed at the end of the Delaunay refinement, this may no longer be true after some optimization processes. Also beware that the default behavior does involve some optimization processes.

See also

refine_mesh_3()

exude_mesh_3()

perturb_mesh_3()

lloyd_optimize_mesh_3()

odt_optimize_mesh_3()

odt_optimize_mesh_3()

template<typename C3T3 , typename MeshDomain , typename NamedParameters = CGAL::parameters::Default_named_parameters>

Mesh_optimization_return_code CGAL::odt_optimize_mesh_3	(	C3T3 &	c3t3,
		const MeshDomain &	domain,
		const NamedParameters &	np = parameters::default_values()
	)

#include <CGAL/odt_optimize_mesh_3.h>

The function odt_optimize_mesh_3() is a mesh optimization process based on the minimization of a global energy function.

In odt_optimize_mesh_3(), the minimized global energy may be interpreted as the \( L^1\)-norm of the error achieved when the function \( x^2\) is interpolated on the mesh domain using a piecewise linear function which is linear in each mesh cell.

The optimizer odt_optimize_mesh_3() works in iterative steps. At each iteration, mesh vertices are moved into positions that bring to zero the energy gradient and the Delaunay triangulation is updated. Vertices on the mesh boundaries are handled in a special way so as to preserve an accurate representation of the domain boundaries.

Template Parameters

C3T3	a model of the concept MeshComplex_3InTriangulation_3
MeshDomain	a model of the concept MeshDomain_3
NamedParameters	a sequence of Named Parameters

Parameters

c3t3	the initial mesh and is modified by the algorithm to represent the final optimized mesh.
domain	the domain used to create the c3t3 parameter
np	an optional sequence of Named Parameters among the ones listed below:

Optional Named Parameters

time_limit is used to set up, in seconds, a CPU time limit after which the optimization process is stopped. This time is measured using Real_timer. The default value is 0 and means that there is no time limit. Type: double Precondition: time_limit >= 0 Default: 0
max_iteration_number sets a limit on the number of performed iterations. The default value of 0 means that there is no limit on the number of performed iterations. Type: std::size_t Default: 0
convergence is a stopping criterion based on convergence: the optimization process is stopped, when at the last iteration, the displacement of any vertex is less than a given percentage of the length the shortest edge incident to that vertex. The parameter convergence gives the threshold ratio. Type: double Precondition: 0 <= convergence <= 1 Default: 0.02
freeze_bound is designed to reduce running time of each optimization iteration. Any vertex that has a displacement less than a given percentage of the length of its shortest incident edge, is frozen (i.e. is not relocated). The parameter freeze_bound gives the threshold ratio. Type: double Precondition: 0 <= freeze_bound <= 1 Default: 0.01
do_freeze completes the freeze_bound parameter. If it is set to true, frozen vertices will not move anymore in next iterations. Otherwise, at each iteration, any vertex that moves, unfreezes all its incident vertices. Type: bool Default: true

Returns

a value of type CGAL::Mesh_optimization_return_code which is:

• CGAL::TIME_LIMIT_REACHED when the time limit is reached.
• CGAL::MAX_ITERATION_NUMBER_REACHED when odt_optimize_mesh_3() stops because it has performed max_iteration_number iterations.
• CGAL::CONVERGENCE_REACHED when odt_optimize_mesh_3() stops because the convergence criterion is achieved.
• CGAL::ALL_VERTICES_FROZEN when all vertices have been frozen, when the do_freeze parameter is set to true.
• CGAL::CANT_IMPROVE_ANYMORE when odt_optimize_mesh_3() stops because most vertices have been frozen, and no better convergence can be reached.

Example

// 100 iterations of ODT-smoothing
odt_optimize_mesh_3(c3t3,
                    domain,
                    parameters::max_iteration_number = 100,
                    parameters::convergence = 0);

See also

CGAL::Mesh_optimization_return_code

CGAL::make_mesh_3()

CGAL::refine_mesh_3()

CGAL::exude_mesh_3()

CGAL::perturb_mesh_3()

CGAL::lloyd_optimize_mesh_3()

perturb_mesh_3()

template<typename C3T3 , typename MeshDomain , typename NamedParameters = CGAL::parameters::Default_named_parameters>

Mesh_optimization_return_code CGAL::perturb_mesh_3	(	C3T3 &	c3t3,
		const MeshDomain &	domain,
		const NamedParameters &	np = parameters::default_values()
	)

#include <CGAL/perturb_mesh_3.h>

The function perturb_mesh_3() is a mesh optimizer that improves the quality of a Delaunay mesh by changing the positions of some vertices of the mesh.

The perturber tries to improve the dihedral angles of the worst cells in the mesh degree by degree: the step number n is considered as successful if after this step the worst tetrahedron of the mesh has a minimal dihedral angle larger than n degrees. The perturber exits if this is not the case.

Template Parameters

C3T3	a model of the concept MeshComplex_3InTriangulation_3
MD	a model of the concept MeshDomain_3
NamedParameters	a sequence of Named Parameters

Parameters

c3t3	the initial mesh, modified by the algorithm to represent the final optimized mesh
domain	the domain used to create the c3t3 parameter
np	an optional sequence of Named Parameters among the ones listed below:

Optional Named Parameters

time_limit is used to set up, in seconds, a CPU time limit after which the optimization process is stopped. This time is measured using the Real_timer class. The default value is 0 and means that there is no time limit. Type: double Precondition: time_limit >= 0 Default: 0

sliver_bound is designed to give, in degrees, a targeted lower bound on dihedral angles of mesh cells. The function perturb_mesh_3() runs as long as steps are successful and step number sliver_bound (after which the worst tetrahedron in the mesh has a smallest angle larger than sliver_bound degrees) has not been reached. The default value is 0 and means that there is no targeted bound: the perturber then runs as long as steps are successful. Type: double Precondition: 0 <= sliver_bound <= 180 Default: 0

Returns

a value of type CGAL::Mesh_optimization_return_code which is:

• CGAL::BOUND_REACHED when the targeted bound for the smallest dihedral angle in the mesh is reached.
• CGAL::TIME_LIMIT_REACHED when the time limit is reached.
• CGAL::CANT_IMPROVE_ANYMORE when the perturbation process stops because the last step is unsuccessful.

Example

// Perturb until every dihedral angle of the mesh is >= 10 degrees
// No time bound is set
perturb_mesh_3(c3t3,
               domain,
               parameters::sliver_bound = 10);

See also

CGAL::Mesh_optimization_return_code

CGAL::make_mesh_3()

CGAL::refine_mesh_3()

CGAL::exude_mesh_3()

CGAL::lloyd_optimize_mesh_3()

CGAL::odt_optimize_mesh_3()

Examples

Mesh_3/mesh_implicit_domains.cpp, Mesh_3/mesh_implicit_domains_2.cpp, Mesh_3/mesh_implicit_ellipsoid.cpp, and Mesh_3/mesh_optimization_example.cpp.

refine_mesh_3()

template<typename C3T3 , typename MeshDomain , typename MeshCriteria , typename NamedParameters = CGAL::parameters::Default_named_parameters>

void CGAL::refine_mesh_3	(	C3T3 &	c3t3,
		const MeshDomain &	domain,
		const MeshCriteria &	criteria,
		const NamedParameters &	np = parameters::default_values()
	)

#include <CGAL/refine_mesh_3.h>

The function refine_mesh_3() is a 3D mesh generator.

It produces simplicial meshes which discretize 3D domains.

The mesh generation algorithm is a Delaunay refinement process followed by an optimization phase. The criteria driving the Delaunay refinement process may be tuned to achieve the user needs with respect to the size of mesh elements, the accuracy of boundaries approximation, etc.

The optimization phase is a sequence of optimization processes, amongst the following available optimizers: an ODT smoothing, a Lloyd smoothing, a sliver perturber, and a sliver exuder. Each optimization process can be activated or not, according to the user requirements and available time. By default, only the perturber and the exuder are activated. Note that the benefits of the exuder will be lost if the mesh is further refined afterward.

Attention

The function template refine_mesh_3() may be used to refine a previously computed mesh, e.g.:

C3T3 c3t3 = CGAL::make_mesh_3<C3T3>(domain,criteria);
 
CGAL::refine_mesh_3(c3t3, domain, new_criteria);

Please note that we guarantee the result if and only if the domain does not change from one refinement to the next one.

Template Parameters

C3T3	either a model of the concept MeshComplex_3InTriangulation_3 or of MeshComplexWithFeatures_3InTriangulation_3 if MD is a model of MeshDomainWithFeatures_3. The type C3T3 is in particular required to provide a nested type C3T3::Triangulation for the 3D triangulation embedding the mesh. The vertex and cell base classes of the triangulation C3T3::Triangulation are required to be models of the concepts MeshVertexBase_3 and MeshCellBase_3 respectively.
MD	either a model of the concept MeshDomain_3 or of MeshDomainWithFeatures_3 if 0 and 1-dimensional features of the input complex have to be accurately represented in the mesh.
MC	either a model of the concept MeshCriteria_3 or a model of MeshCriteriaWithFeatures_3 if the domain has exposed features.
NamedParameters	a sequence of Named Parameters

Parameters

c3t3	the mesh to be refined that is modified by the refinement process. As the refinement process only adds points to the triangulation, all vertices of the triangulation of c3t3 remain in the mesh during the refinement process. c3t3 can be used to insert specific points in the domain to ensure that they will be contained in the final triangulation.
domain	the domain used to create the c3t3 parameter. It is the sole link through which the domain to be discretized is known by the mesh generation algorithm.
criteria	specifies the size and shape requirements for mesh tetrahedra and surface facets. These criteria form the rules which drive the refinement process. All mesh elements satisfy those criteria at the end of the refinement process. In addition, if the domain has features, the argument criteria provides a sizing field to guide the discretization of 1-dimensional exposed features.
np	an optional sequence of Named Parameters among the ones listed below. They control which optimization processes are performed and enable the user to tune the parameters of the optimization processes. Individual optimization parameters are not described here as they are internal types (see instead the documentation page of each optimizer). For each optimization algorithm, there exist two global functions that enable/disable the optimizer.

Optional Named Parameters

Topological options (manifoldness) In order to drive the meshing algorithm and ensure that the output mesh follows a desired topological criterion, three named parameters control this option: parameters::manifold() parameters::manifold_with_boundary() parameters::non_manifold() Note that the meshing algorithm cannot generate a manifold surface if the input surface is not manifold. Default: parameters::non_manifold()
Lloyd optimization lloyd_optimize_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_lloyd() parameters::lloyd_optimize_mesh_3() Default: parameters::no_lloyd()
ODT optimization odt_optimize_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_odt() parameters::odt() Default: parameters::no_odt()
Mesh perturbation perturb_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::no_perturb() parameters::perturb() Default: parameters::perturb()
Mesh exudation exude_mesh_3() can optionally be called after the meshing process. Two named parameters control this behavior: parameters::exude() parameters::no_exude() Default: parameters::exude()

The optimization parameters can be passed in arbitrary order. If one parameter is not passed, its default value is used. The default values are no_lloyd(), no_odt(), perturb() and exude(). Note that regardless of which optimization processes are activated, they are always launched in the order that is a suborder of the following (see user manual for further details): ODT-smoother, Lloyd-smoother, perturber, and exuder.

Beware that optimization of the mesh is obtained by perturbing mesh vertices and modifying the mesh connectivity and that this has an impact on the strict compliance to the refinement criteria. Though a strict compliance to mesh criteria is guaranteed at the end of the Delaunay refinement, this may no longer be true after some optimization processes. Also beware that the default behavior does involve some optimization processes.

See also

CGAL::make_mesh_3()

CGAL::parameters::manifold()

CGAL::parameters::manifold_with_boundary()

CGAL::parameters::non_manifold()

CGAL::exude_mesh_3()

CGAL::perturb_mesh_3()

CGAL::lloyd_optimize_mesh_3()

CGAL::odt_optimize_mesh_3()

CGAL::parameters::exude()

CGAL::parameters::no_exude()

CGAL::parameters::perturb()

CGAL::parameters::no_perturb()

CGAL::parameters::lloyd()

CGAL::parameters::no_lloyd()

CGAL::parameters::odt()

CGAL::parameters::no_odt()

Examples

Mesh_3/mesh_3D_gray_image_with_custom_initialization.cpp, Mesh_3/mesh_3D_image_with_custom_initialization.cpp, Mesh_3/mesh_polyhedral_domain.cpp, and Mesh_3/mesh_polyhedral_domain_sm.cpp.