Remeshing
OpenPisco provides a Python interface to the remeshing software mmg 1 with pre-and post-processing routines. Mmg allows to remesh
unstructured thetrahedral meshes (mmg3d)
surfacic triangular meshes (mmgs)
simplicial meshes in 2d (mmg2d)
The interface is available in the dedicated module OpenPisco.Unstructured.MmgMesher().
Overview
A set of parameters and options is provided by the user to drive the remeshing process :
hmin minimal desired element size
hmax maximal desired element size
hausd geometrical quality of surfaces
hgrad desired size variation between adjacent elements
-opnbdy preservation of internal simplicial elements of dimension 2
-nr desactivation of ridges detection
Starting from these global user requirements, mmg3d improves the mesh quality performing local mesh operations.
Two additional remeshing functionalities are available : level set conformal remeshing and classical adaptive remeshing.
Level set remeshing
OpenPisco.Unstructured.MmgMesher.MmgMesherActionLevelSet()
This functionality allows to generate an explicit mesh of an implicit domain. See also the web documentation 2 of mmg3d.
A set of parameters and options is provided by the user to drive the remeshing process :
-ls [isovalue] activation of the level set mode (the default isovalue is 0)
-rmc deletion of connected components whose volumic fraction is smaller than a given threshold
The level set split preserves initial subregions specified in the input mesh. Each subregion is splitted into two parts corresponding respectively to positive and negative parts of the level set. Thus, new mesh tags are added to the output
Outside3D dimension 3 elements belonging to the positive part of the level set
Inside3D dimension 3 elements belonging to the negative part of the level set
InterSurf triangles belonging to the level set conformal isosurface
InterBars bars belonging to the level set on the bounding box
The following minimal working examples illustrate the conformal remeshing using the Python API
Adaptive remeshing
OpenPisco.Optim.Criteria.Criteria.MmgMesherActionRemesh()
This routine performs mesh adaptation with respect to a given metric field. The metric (isotropic or anisotropic) is a size field defined at mesh nodes specifing the desired local size.
It is also possible to combine the mesh adaptation with the conformal remeshing in a sole remeshing operation. To do so, the user must provide a distance field with the option -ls and a metric field with the option -met .
The following function contains two minimal working examples of adaptive remeshing using the Python interface:
Required entities
Mesh entities which must be preserved during remeshing should be labeled with the keyword “Required”
RequiredVertices nodal tag
RequiredEdges element tag (bars)
RequiredTriangles element tag (triangles)
Elements of dimension 0 ( of type “Point0”) are automatically preserved during a remeshing operation.