Filters usage ¶

Filters allow picking only the mesh elements satisfying to a specific condition or a set of conditions. Filters can be used to create or edit mesh groups, remove elements from the mesh, control mesh quality by different parameters, etc.

Several filtering criteria can be combined together by using logical operators AND and OR. In addition, a filtering criterion can be reverted using logical operator NOT.

Mesh filters can use the functionality of mesh quality controls to filter mesh nodes / elements by a specific characteristic (Area, Length, etc).

This page provides a short description of the existing mesh filters, describes required parameters and gives simple examples of usage in Python scripts.

See also: Quality Controls

Table of contents

Aspect ratio ¶

filters 2D mesh elements (faces) according to the aspect ratio value:

element type should be SMESH.FACE
functor type should be SMESH.FT_AspectRatio
threshold is floating point value (aspect ratio)

# Aspect ratio
# This script demonstrates various usages of filters

# create mesh
from mechanic import *

# get faces with aspect ratio > 2.5
filter = smesh_builder.GetFilter(SMESH.FACE, SMESH.FT_AspectRatio, SMESH.FT_MoreThan, 2.5)
ids = mesh.GetIdsFromFilter(filter)
print("Number of faces with aspect ratio > 2.5:", len(ids))

# get faces with aspect ratio > 1.5
filter = smesh_builder.GetFilter(SMESH.FACE, SMESH.FT_AspectRatio, '>', 1.5, mesh=mesh)
ids = filter.GetIDs()
print("Number of faces with aspect ratio > 1.5:", len(ids))

# copy the faces with aspect ratio > 1.5 to another mesh;
# this demonstrates that a filter can be used where usually a group or sub-mesh is acceptable
filter.SetMesh( mesh.GetMesh() ) # - actually non necessary as mesh is set at filter creation
mesh2 = smesh_builder.CopyMesh( filter, "AR > 1.5" )
print("Number of copied faces with aspect ratio > 1.5:", mesh2.NbFaces())

# create a group (Group on Filter) of faces with Aspect Ratio < 1.5
group = mesh.MakeGroup("AR < 1.5", SMESH.FACE, SMESH.FT_AspectRatio, '<', 1.5)
print("Number of faces with aspect ratio < 1.5:", group.Size())

# combine several criteria to Create a Group of only Triangular faces with Aspect Ratio < 1.5;
# note that contents of a GroupOnFilter is dynamically updated as the mesh changes
crit = [ smesh_builder.GetCriterion( SMESH.FACE, SMESH.FT_AspectRatio, '<', 1.5, BinaryOp=SMESH.FT_LogicalAND ),
         smesh_builder.GetCriterion( SMESH.FACE, SMESH.FT_ElemGeomType,'=', SMESH.Geom_TRIANGLE ) ]
triaGroup = mesh.MakeGroupByCriteria( "Tria AR < 1.5", crit )
print("Number of triangles with aspect ratio < 1.5:", triaGroup.Size())

# get range of values of Aspect Ratio of all faces in the mesh
aspects = mesh.GetMinMax( SMESH.FT_AspectRatio )
print("MESH: Min aspect = %s, Max aspect = %s" % ( aspects[0], aspects[1] ))

# get max value of Aspect Ratio of faces in triaGroup
grAspects = mesh.GetMinMax( SMESH.FT_AspectRatio, triaGroup )
print("GROUP: Max aspect = %s" % grAspects[1])

# get Aspect Ratio of an element
aspect = mesh.FunctorValue( SMESH.FT_AspectRatio, ids[0] )
print("Aspect ratio of the face %s = %s" % ( ids[0], aspect ))