API Reference#

Python module to interface with wrapped TetGen C++ code.

class tetgen.TetGen(*args)#

Bases: object

Input, clean, and tetrahedralize surface meshes using TetGen.

Parameters:

args (str | pyvista.PolyData | numpy.ndarray) – Either a pyvista surface mesh or a n x 3 vertex array and n x 3 face array.

Examples

Tetrahedralize a sphere using pyvista.

>>> import pyvista
>>> import tetgen
>>> sphere = pyvista.Sphere(theta_resolution=10, phi_resolution=10)
>>> tgen = tetgen.TetGen(sphere)
>>> nodes, elem = tgen.tetrahedralize()
>>> tgen.grid.plot(show_edges=True)

Tetrahedralize a cube using numpy arrays.

>>> import numpy as np
>>> import tetgen
>>> v = np.array(
...     [
...         [0, 0, 0],
...         [1, 0, 0],
...         [1, 1, 0],
...         [0, 1, 0],
...         [0, 0, 1],
...         [1, 0, 1],
...         [1, 1, 1],
...         [0, 1, 1],
...     ]
... )
>>> f = np.vstack(
...     [
...         [0, 1, 2],
...         [2, 3, 0],
...         [0, 1, 5],
...         [5, 4, 0],
...         [1, 2, 6],
...         [6, 5, 1],
...         [2, 3, 7],
...         [7, 6, 2],
...         [3, 0, 4],
...         [4, 7, 3],
...         [4, 5, 6],
...         [6, 7, 4],
...     ]
... )
>>> tgen = tetgen.TetGen(v, f)
>>> nodes, elems = tgen.tetrahedralize()
property grid#

Return a pyvista.UnstructuredGrid.

make_manifold(verbose=False)#

Reconstruct a manifold clean surface from input mesh.

Updates mesh in-place.

Requires pymeshfix.

Parameters:

verbose (bool, default: False) – Enable verbose output.

Examples

Create a mesh and ensure it’s manfold.

>>> import pyvista
>>> import tetgen
>>> sphere = pyvista.Sphere(theta_resolution=10, phi_resolution=10)
>>> tgen = tetgen.TetGen(sphere)
>>> tgen.make_manifold()
property mesh#

Return the surface mesh.

Returns:

Input surface mesh.

Return type:

pyvista.PolyData

Examples

Generate a tetgen.TetGen and return a pyvista.PolyData.

>>> import pyvista
>>> import tetgen
>>> sphere = pyvista.Sphere(theta_resolution=10, phi_resolution=10)
>>> tgen = tetgen.TetGen(sphere)
>>> tgen.mesh
PolyData (0x7fa3c97138e0)
  N Cells:    160
  N Points:   82
  N Strips:   0
  X Bounds:   -4.924e-01, 4.924e-01
  Y Bounds:   -4.683e-01, 4.683e-01
  Z Bounds:   -5.000e-01, 5.000e-01
  N Arrays:   0
plot(**kwargs)#

Display the input mesh.

See pyvista.plot() for available arguments.

Examples

Plot the input mesh.

>>> import pyvista
>>> import tetgen
>>> sphere = pyvista.Sphere(theta_resolution=10, phi_resolution=10)
>>> tgen = tetgen.TetGen(sphere)
>>> tgen.plot()
tetrahedralize(plc=True, psc=0.0, refine=0.0, quality=True, nobisect=False, cdt=0.0, cdtrefine=7.0, coarsen=0.0, weighted=0.0, brio_hilbert=1.0, flipinsert=0.0, metric=0.0, varvolume=0.0, fixedvolume=0.0, regionattrib=0.0, insertaddpoints=0.0, diagnose=0.0, convex=0.0, nomergefacet=0.0, nomergevertex=0.0, noexact=0.0, nostaticfilter=0.0, zeroindex=0.0, facesout=0.0, edgesout=0.0, neighout=0.0, voroout=0.0, meditview=0.0, vtkview=0.0, vtksurfview=0.0, nobound=0.0, nonodewritten=0.0, noelewritten=0.0, nofacewritten=0.0, noiterationnum=0.0, nojettison=0.0, docheck=0.0, quiet=0.0, nowarning=0.0, verbose=0.0, vertexperblock=4092.0, tetrahedraperblock=8188.0, shellfaceperblock=2044.0, supsteiner_level=2.0, addsteiner_algo=1.0, coarsen_param=0.0, weighted_param=0.0, fliplinklevel=-1.0, flipstarsize=-1.0, fliplinklevelinc=1.0, opt_max_flip_level=3.0, opt_scheme=7.0, opt_iterations=3.0, smooth_cirterion=1.0, smooth_maxiter=7.0, delmaxfliplevel=1.0, order=1.0, reversetetori=0.0, steinerleft=100000.0, unflip_queue_limit=1000.0, no_sort=0.0, hilbert_order=52.0, hilbert_limit=8.0, brio_threshold=64.0, brio_ratio=0.125, epsilon=1e-08, facet_separate_ang_tol=179.9, collinear_ang_tol=179.9, facet_small_ang_tol=15.0, maxvolume=-1.0, maxvolume_length=-1.0, minratio=2.0, opt_max_asp_ratio=1000.0, opt_max_edge_ratio=100.0, mindihedral=0.0, optmaxdihedral=177.0, metric_scale=1.0, smooth_alpha=0.3, coarsen_percent=1.0, elem_growth_ratio=0.0, refine_progress_ratio=0.333, switches=None, bgmeshfilename='', bgmesh=None)#

Generate tetrahedrals interior to the surface mesh.

Returns nodes and elements belonging to the all tetrahedral mesh.

The tetrahedral generator uses the C++ library TetGen and can be configured by either using a string of switches or by changing the underlying behavior using optional inputs.

Should the user desire more control over the mesh tetrahedralization or wish to control the tetrahedralization in a more pythonic manner, use the optional inputs rather than inputting switches.

Parameters:

  • quality (bool, optional) – Enables/disables mesh improvement. Enabled by default. Disable this to speed up mesh generation while sacrificing quality. Default True.

  • minratio (double, default: 2.0) –

    Maximum allowable radius-edge ratio. Must be greater than 1.0 the closer to 1.0, the higher the quality of the mesh. Be sure to raise steinerleft to allow for the addition of points to improve the quality of the mesh. Avoid overly restrictive requirements, otherwise, meshing will appear to hang.

    Testing has showed that 1.1 is a reasonable input for a high quality mesh.

  • mindihedral (double, default: 0.0) –

    Minimum allowable dihedral angle. The larger this number, the higher the quality of the resulting mesh. Be sure to raise steinerleft to allow for the addition of points to improve the quality of the mesh. Avoid overly restrictive requirements, otherwise, meshing will appear to hang.

    Testing has shown that 10 is a reasonable input

  • verbose (int, default: 0) – Controls the underlying TetGen library to output text to console. Users using iPython will not see this output. Setting to 1 enables some information about the mesh generation while setting verbose to 2 enables more debug output. Default is no output

  • nobisect (bool, default: False) –

    Controls if Steiner points are added to the input surface mesh. When enabled, the surface mesh will be modified.

    Testing has shown that if your input surface mesh is already well shaped, disabling this setting will improve meshing speed and mesh quality.

  • steinerleft (int, default: 100000) –

    Steiner points are points added to the original surface mesh to create a valid tetrahedral mesh. Settings this to -1 will allow tetgen to create an unlimited number of steiner points, but the program will likely hang if this is used in combination with narrow quality requirements.

    The first type of Steiner points are used in creating an initial tetrahedralization of PLC. These Steiner points are mandatory in order to create a valid tetrahedralization

    The second type of Steiner points are used in creating quality tetra- hedral meshes of PLCs. These Steiner points are optional, while they may be necessary in order to improve the mesh quality or to conform the size of mesh elements.

  • order (int, default: 2) – Controls whether TetGen creates linear tetrahedrals or quadradic tetrahedrals. Set order to 2 to output quadradic tetrahedrals.

  • bgmeshfilename (str, optional) – Filename of the background mesh.

  • bgmesh (pv.UnstructuredGrid) – Background mesh to be processed. Must be composed of only linear tetra. Cannot specify both bgmeshfilename and bgmesh.

Returns:

  • nodes (numpy.ndarray) – Array of nodes representing the tetrahedral mesh.

  • elems (numpy.ndarray) – Array of elements representing the tetrahedral mesh.

Examples

The following switches “pq1.1/10Y” would be:

>>> nodes, elems = tgen.tetrahedralize(
...     nobisect=True, quality=True, minratio=1.1, mindihedral=10
... )

Using the switches option:

>>> nodes, elems = tgen.tetrahedralize(switches="pq1.1/10Y")

Notes

There are many other options and the TetGen documentation contains descriptions only for the switches of the original C++ program. This is the relationship between tetgen switches and python optional inputs:

Switches of TetGen.

Option

Switch

Default

plc

'-p'

psc

'-s'

refine

'-r'

quality

'-q'

nobisect

'-Y'

cdt

'-D'

cdtrefine

'-D#'

coarsen

'-R'

weighted

'-w'

brio_hilbert

'-b'

flipinsert

'-L'

metric

'-m'

varvolume

'-a'

fixedvolume

'-a'

regionattrib

'-A'

insertaddpoints

'-i'

diagnose

'-d'

convex

'-c'

nomergefacet

'-M'

nomergevertex

'-M'

noexact

'-X'

nostaticfilter

'-X'

zeroindex

'-z'

facesout

'-f'

edgesout

'-e'

neighout

'-n'

voroout

'-v'

meditview

'-g'

vtkview

'-k'

vtksurfview

'-k'

nobound

'-B'

nonodewritten

'-N'

noelewritten

'-E'

nofacewritten

'-F'

noiterationnum

'-I'

nojettison

'-J'

docheck

'-C'

quiet

'-Q'

nowarning

'-W'

verbose

'-V'

Parameters of TetGen.

Option

Switch

Default

vertexperblock

'-x'

tetrahedraperblock

'-x'

shellfaceperblock

'-x'

supsteiner_level

'-Y/'

addsteiner_algo

'-Y//'

coarsen_param

'-R'

weighted_param

'-w'

opt_max_flip_level

'-O'

opt_scheme

'-O/#'

opt_iterations

'-O//#'

smooth_cirterion

'-s'

smooth_maxiter

'-s'

order

'-o'

reversetetori

'-o/'

steinerleft

'-S'

unflip_queue_limit

'-U#'

hilbert_order

'-b///'

hilbert_limit

'-b//'

brio_threshold

'-b'

brio_ratio

'-b/'

0.125.

epsilon

'-T'

1.0e-8.

facet_separate_ang_tol

'-p'

179.9.

collinear_ang_tol

'-p/'

179.9.

facet_small_ang_tol

'-p//'

15.0.

maxvolume

'-a'

-1.0.

maxvolume_length

'-a'

-1.0.

minratio

'-q'

0.0.

mindihedral

'-q'

5.0.

optmaxdihedral

'-o/#'

177.0.

metric_scale

'-m#'

1.0.

smooth_alpha

'-s'

0.3.

coarsen_percent

'-R1/#'

1.0.

elem_growth_ratio

'-r#'

0.0.

refine_progress_ratio

'-r/#'

0.333.
write(filename, binary=False)#

Write an unstructured grid to disk.

Parameters:

  • filename (str) –

    Filename of grid to be written. The file extension will select the type of writer to use.

    • ".vtk" will use the vtk legacy writer

    • ".vtu" will select the VTK XML writer

  • binary (bool, default: False) – Writes as a binary file by default. Set to False to write ASCII.

Examples

Write to a VTK file.

>>> tgen.write("grid.vtk", binary=True)

Notes

Binary files write much faster than ASCII, but binary files written on one system may not be readable on other systems. Binary can be used only with the legacy writer.

You can use utilities like meshio to convert to other formats in order to import into FEA software.

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