This plugin uses the features of the meshio Python module to allow GiD import/export the mesh in all formats supported by this module.
The module is written in python, but GiD uses Tcl as main scripting language. The Tohil package is the bridge to allow its use.
The plugin is placed at
<GiD>\plugins\Import\meshio
and like the rest of plugins is automatically loaded from Tcl when GiD starts.
It add to the Files Import/Export menus a new “meshio” item.
to import meshes the Python file gid_meshio.py define for example a function my_meshio_read_mesh
import numpy as np
import meshio
def my_meshio_read_mesh(filename):
#to avoid that numpy truncate the printed representation of its arrays
np.set_printoptions(threshold=np.inf)
mesh=meshio.read(filename)
return [mesh.points,mesh.cells,mesh.cells_dict]
and the Tcl file meshio.tcl invoke the import of this file in the Python interpreter to have defined the function, and then call the function to obtain the mesh data independently of the mesh file format read.
set filename_python [file join [gid_filesystem::get_folder_standard plugins] Import/meshio/gid_meshio.py] GiD_Python_Import_File $filename_python ... set m [GiD_Python_Call gid_meshio.my_meshio_read_mesh $filename_mesh] ...
Here GiD_Python_Import_File is an auxiliary proc (see <GiD>\scripts\gid_python.tcl) that decorate the tohil syntax and basically do
package require tohil
tohil::import $module_name
And GiD_Python_Call is like an alias of the command tohil::call
then the variable m has the data that define a collection of meshes (element type, coordinates of nodes and element connectivities), and this data is processed at Tcl level to have the desired final data.
this is the code of the proc that create GiD meshes from a file in a format supported by the meshio Python module:
proc MeshIo::Init { } {
variable meshio_num_nodes_per_cell
variable meshio_gid_element
#linear and serendipit
set meshio_num_nodes_per_cell(vertex) 1
set meshio_num_nodes_per_cell(line) 2
set meshio_num_nodes_per_cell(triangle) 3
set meshio_num_nodes_per_cell(quad) 4
set meshio_num_nodes_per_cell(quad8) 8
set meshio_num_nodes_per_cell(tetra) 4
set meshio_num_nodes_per_cell(hexahedron) 8
set meshio_num_nodes_per_cell(hexahedron20) 20
set meshio_num_nodes_per_cell(hexahedron24) 24
set meshio_num_nodes_per_cell(wedge) 6
set meshio_num_nodes_per_cell(pyramid) 5
#quadratic
set meshio_num_nodes_per_cell(line3) 3
set meshio_num_nodes_per_cell(triangle6) 6
set meshio_num_nodes_per_cell(quad9) 9
set meshio_num_nodes_per_cell(tetra10) 10
set meshio_num_nodes_per_cell(hexahedron27) 27
set meshio_num_nodes_per_cell(wedge15) 15
set meshio_num_nodes_per_cell(wedge18) 18
set meshio_num_nodes_per_cell(pyramid13) 13
set meshio_num_nodes_per_cell(pyramid14) 14
#degree 3
set meshio_num_nodes_per_cell(line4) 4
set meshio_num_nodes_per_cell(triangle10) 10
set meshio_num_nodes_per_cell(quad16) 16
set meshio_num_nodes_per_cell(tetra20) 20
set meshio_num_nodes_per_cell(wedge40) 40
set meshio_num_nodes_per_cell(hexahedron64) 64
#degree 4
set meshio_num_nodes_per_cell(line5) 5
set meshio_num_nodes_per_cell(triangle15) 15
set meshio_num_nodes_per_cell(quad25) 25
set meshio_num_nodes_per_cell(tetra35) 35
set meshio_num_nodes_per_cell(wedge75) 75
set meshio_num_nodes_per_cell(hexahedron125) 125
#degree 5
set meshio_num_nodes_per_cell(line6) 6
set meshio_num_nodes_per_cell(triangle21) 21
set meshio_num_nodes_per_cell(quad36) 36
set meshio_num_nodes_per_cell(tetra56) 56
set meshio_num_nodes_per_cell(wedge126) 126
set meshio_num_nodes_per_cell(hexahedron216) 216
#degree 6
set meshio_num_nodes_per_cell(line7) 7
set meshio_num_nodes_per_cell(triangle28) 28
set meshio_num_nodes_per_cell(quad49) 49
set meshio_num_nodes_per_cell(tetra84) 84
set meshio_num_nodes_per_cell(wedge196) 196
set meshio_num_nodes_per_cell(hexahedron343) 343
#degree 7
set meshio_num_nodes_per_cell(line8) 8
set meshio_num_nodes_per_cell(triangle36) 36
set meshio_num_nodes_per_cell(quad64) 64
set meshio_num_nodes_per_cell(tetra120) 120
set meshio_num_nodes_per_cell(wedge288) 288
set meshio_num_nodes_per_cell(hexahedron512) 512
#degree 8
set meshio_num_nodes_per_cell(line9) 9
set meshio_num_nodes_per_cell(triangle45) 45
set meshio_num_nodes_per_cell(quad81) 81
set meshio_num_nodes_per_cell(tetra165) 165
set meshio_num_nodes_per_cell(wedge405) 405
set meshio_num_nodes_per_cell(hexahedron729) 729
#degree 9
set meshio_num_nodes_per_cell(line10) 10
set meshio_num_nodes_per_cell(triangle55) 55
set meshio_num_nodes_per_cell(quad100) 100
set meshio_num_nodes_per_cell(tetra220) 220
set meshio_num_nodes_per_cell(wedge550) 550
set meshio_num_nodes_per_cell(hexahedron1000) 1000
set meshio_num_nodes_per_cell(hexahedron1331) 1331
#degree 10
set meshio_num_nodes_per_cell(line11) 11
set meshio_num_nodes_per_cell(triangle66) 66
set meshio_num_nodes_per_cell(quad121) 121
set meshio_num_nodes_per_cell(tetra286) 286
#linear and serendipit
set meshio_gid_element(vertex) point
set meshio_gid_element(line) line
set meshio_gid_element(triangle) triangle
set meshio_gid_element(quad) quadrilateral
set meshio_gid_element(tetra) tetrahedra
set meshio_gid_element(hexahedron) hexahedra
set meshio_gid_element(wedge) prism
set meshio_gid_element(pyramid) pyramid
#quadratic
set meshio_gid_element(line3) line
set meshio_gid_element(triangle6) triangle
set meshio_gid_element(quad8) quadrilateral
set meshio_gid_element(quad9) quadrilateral
set meshio_gid_element(tetra10) tetrahedra
set meshio_gid_element(hexahedron20) hexahedra
set meshio_gid_element(hexahedron27) hexahedra
set meshio_gid_element(wedge15) prism
set meshio_gid_element(pyramid13) pyramid
...
}
proc MeshIo::ReadPreUnstructuredMesh { filename } {
set fail 0
variable meshio_gid_element
variable meshio_num_nodes_per_cell
MeshIo::Import_gid_meshio_py ;#to load in python the file gid_meshio.py to define its python functions before be called
set m [GiD_Python_Call gid_meshio.my_meshio_read_mesh $filename]
set nodes_coordinates [lindex [MeshIo::PythonArrayToTclList [lindex $m 0]] 0]
#e.g.[lindex $m 1] == {<meshio CellBlock, type: triangle, num cells: 156, tags: []>}
set meshio_element_types_and_connectivities [MeshIo::PythonArrayToTclList [lindex $m 2]]
set layer [GiD_Layers get to_use]
set offset_nodes [GiD_Info mesh MaxNumNodes]
set offset_elements [GiD_Info mesh MaxNumElements]
set last_element_id $offset_elements
#better use GiD_MeshPre_Create with same syintax as GiD_MeshPost (and some day could be implemented to be faster in C++)
set num_nodes [llength $nodes_coordinates]
set node_ids [objarray new_from_to intarray [expr $offset_nodes+1] [expr $offset_nodes+$num_nodes]]
set vertices [objarray new doublearray [expr $num_nodes*3]]
set i 0
foreach node $nodes_coordinates {
foreach value $node {
objarray set $vertices $i $value
incr i
}
}
foreach {meshio_element_type meshio_connectivities} $meshio_element_types_and_connectivities {
set element_type ""
set element_num_nodes 0
if { [info exists meshio_gid_element($meshio_element_type)] } {
set element_type $meshio_gid_element($meshio_element_type)
set element_num_nodes $meshio_num_nodes_per_cell($meshio_element_type)
} else {
W "element $meshio_element_type not supported"
continue
}
set elements [lindex $meshio_connectivities 0]
set num_elements [llength $elements]
set element_ids [objarray new_from_to intarray [expr $last_element_id+1] [expr $last_element_id+$num_elements]]
set element_vertex_indices [objarray new intarray [expr $num_elements*$element_num_nodes]]
set i 0
foreach element $elements {
foreach node_id $element {
objarray set $element_vertex_indices $i [expr $node_id+$offset_nodes+1]
incr i
}
}
set zero_based_array 0
GiD_MeshPre_Create $element_type $element_num_nodes $node_ids $vertices $element_ids $element_vertex_indices $zero_based_array $layer
incr last_element_id $num_elements
}
return $fail
}
For the import feature GiD is invoking from its Tcl code functions of Python files and modules like meshio and numpy.
For the export feature it is implemented in two alternative ways:
For Tcl-like programmers, with most code in Tcl
For Pyhton-like programmers: with most code in Python
Note that only the second approach is bi-directional and will invoke from Python Tcl commands (of the GiD interpreter) importing in Python the tohil module
Ask to GiD its current mesh data with Tcl, and process this data with Tcl code to reach the format expected by the Python meshio function and then call a Python function that create a meshio.Mesh and write it to file with the desired format.
From Tcl call some Python code that ask GiD mesh information calling Tcl commands and process this data with Python to create a meshio.Mesh and write it to file with the desired format.
The implementation of 1. is something like this
meshio.tcl (big code)
proc MeshIo::Init { } {
variable meshio_element_name
...
set meshio_element_name(point,1) vertex
set meshio_element_name(line,2) line
set meshio_element_name(triangle,3) triangle
set meshio_element_name(quadrilateral,4) quad
set meshio_element_name(tetrahedra,4) tetra
set meshio_element_name(hexahedra,8) hexahedron
set meshio_element_name(prism,6) wedge
set meshio_element_name(pyramid,5) pyramid
#quadratic
set meshio_element_name(line,3) line3
set meshio_element_name(triangle,6) triangle6
set meshio_element_name(quadrilateral,8) quad8
set meshio_element_name(quadrilateral,9) quad9
set meshio_element_name(tetrahedra,10) tetra10
set meshio_element_name(hexahedra,20) hexahedron20
set meshio_element_name(hexahedra,27) hexahedron27
set meshio_element_name(prism,15) wedge15
set meshio_element_name(pyramid,13) pyramid13
}
proc MeshIo::TclObjarrayToPythonArrayPoints { node_xyzs } {
set points ""
lassign $node_xyzs xs ys zs
set num_nodes [objarray length $xs]
for {set i_node 0} {$i_node<$num_nodes} {incr i_node} {
set x [objarray get $xs $i_node]
set y [objarray get $ys $i_node]
set z [objarray get $zs $i_node]
append points "\[$x,$y,$z\],"
}
return "\[$points\]"
}
proc MeshIo::TclObjarrayToPythonArrayConnectivities { element_num_nodes connectivities } {
set cells ""
set num_elements [expr [objarray length $connectivities]/$element_num_nodes]
set i 0
for {set i_element 0} {$i_element<$num_elements} {incr i_element} {
set node_ids [list]
for {set i_node 0} {$i_node<$element_num_nodes} {incr i_node} {
lappend node_ids [objarray get $connectivities $i]
incr i
}
append cells "\[[join $node_ids ,]\],"
}
return "\[$cells\]"
}
proc MeshIo::WritePreUnstructuredMesh { filename } {
variable meshio_element_name
MeshIo::Import_gid_meshio_py ;#to load in python the file gid_meshio.py to define its python functions before be called
# coordinates
lassign [GiD_Info mesh nodes -array] node_ids node_xyzs
set max_id_nodes [objarray get $node_ids end]
set num_nodes [objarray length [lindex $node_xyzs 0]]
set new_node_ids ""
set nodes_renumbered_for_meshio 0
if { $max_id_nodes != $num_nodes } {
set nodes_renumbered_for_meshio 1
set new_node_ids [objarray new_from_to intarray 0 [expr $num_nodes-1]]
}
set points [MeshIo::TclObjarrayToPythonArrayPoints $node_xyzs]
set cells "\["
foreach element_type {linear triangle quadrilateral tetrahedra pyramid prism hexahedra } {
set elements_data [lindex [GiD_Info mesh elements $element_type -array2] 0]
if { [llength $elements_data] } {
lassign $elements_data element_type_ret element_ids connectivities materials
set num_elements_block [objarray length $element_ids]
if { $num_elements_block } {
if { $nodes_renumbered_for_meshio } {
objarray renumber $connectivities $node_ids $new_node_ids
} else {
objarray incr $connectivities -1 ;#meshio is zero based
}
set some_element_id [objarray get $element_ids 0]
set element_num_nodes [llength [GiD_Mesh get element $some_element_id connectivities]]
set meshio_etype $meshio_element_name($element_type,$element_num_nodes)
append cells "(\"$meshio_etype\",[MeshIo::TclObjarrayToPythonArrayConnectivities $element_num_nodes $connectivities]),"
}
}
}
append cells "\]"
set result [GiD_Python_Call gid_meshio.my_meshio_write_mesh $points $cells $filename]
return 0
}
gid_meshio.py (small code)
import meshio
def my_meshio_write_mesh(points,cells,filename):
#trick, use ast.literal_eval to convert from string to list representation
import ast
points=ast.literal_eval(points)
cells=ast.literal_eval(cells)
mesh=meshio.Mesh(points,cells)
result=mesh.write(filename)
return result
The implementation of 2. is something like this
meshio.tcl (small code)
proc MeshIo::WritePreUnstructuredMesh2 { filename } {
MeshIo::Import_gid_meshio_py ;#to load in python the file gid_meshio.py to define its python functions before be called
set result [GiD_Python_Call gid_meshio.my_meshio_write_mesh2 $filename]
return 0
}
gid_meshio.py (big code)
import numpy as np
import tohil
import meshio
#to create functions and variables for all tcl available ones
tcl=tohil.import_tcl()
gid_to_meshio_type = {
"sphere,1":"vertex",
"point,1":"vertex",
"line,2":"line",
"triangle,3":"triangle",
"quadrilateral,4":"quad",
"tetrahedra,4":"tetra",
"hexahedra,8":"hexahedron",
"prism,6":"wedge",
"pyramid,5":"pyramid",
#quadratic
"line,3":"line3",
"triangle,6":"triangle6",
"quadrilateral,8":"quad8",
"quadrilateral,9":"quad9",
"tetrahedra,10":"tetra10",
"hexahedra,20":"hexahedron20",
"hexahedra,27":"hexahedron27",
"prism,15":"wedge15",
"pyramid,13":"pyramid13",
}
def gid_points_to_meshio_points(node_xyzs):
xs,ys,zs=node_xyzs
num_nodes=len(xs)
points=np.empty((num_nodes,3))
for i_node in range(num_nodes):
points[i_node]=(float(xs[i_node]),float(ys[i_node]),float(zs[i_node]))
#points[:, 0] = xs[:]
#points[:, 1] = ys[:]
#points[:, 2] = zs[:]
return points
def gid_elements_to_meshio_cells(element_num_nodes,connectivities):
cells=[]
#operator // is for integer division
num_elements=len(connectivities)//element_num_nodes
i=0
for i_element in range(num_elements):
node_ids=[]
for i_node in range(element_num_nodes):
node_ids.append(connectivities[i])
i+=1
cells.append(node_ids)
return cells
def tohil_obj_array_int_to_numpy(items):
num_items=len(items)
numpy_array=np.empty(num_items,np.int64)
for i in range(num_items) :
numpy_array[i]=int(items[i])
return numpy_array
def numpy_renumber(connectivities,old_node_ids,new_node_ids):
fail=0
length_connectivities=len(connectivities)
length_old_ids=len(old_node_ids)
length_new_ids=len(new_node_ids)
if(length_old_ids==length_new_ids):
max_old_id=np.max(old_node_ids)
new_number=np.empty(max_old_id,np.int32)
for i in range(length_old_ids) :
new_number[old_node_ids[i]]=new_node_ids[i]
for i in range(length_connectivities) :
connectivities[i]=new_number[connectivities[i]]
else:
fail=1
return connectivities
def numpy_incr(connectivities,increment):
connectivities=connectivities+increment
return connectivities
#similar to my_meshio_write_mesh but asking GiD data from python and processing this data here
def my_meshio_write_mesh2(filename):
info_nodes=tuple(tcl.GiD_Info('mesh','nodes','-array'))
node_ids,node_xyzs=info_nodes
#tcl.W(node_ids)
#tcl.W(node_xyzs)
max_id_nodes=int(node_ids[-1])
num_nodes=len(node_ids)
nodes_renumbered_for_meshio=False
if (max_id_nodes != num_nodes):
nodes_renumbered_for_meshio=True
new_node_ids=np.arange(num_nodes)
points=gid_points_to_meshio_points(node_xyzs)
cells = []
for element_type in ['linear','triangle','quadrilateral','tetrahedra','pyramid','prism','hexahedra']:
info_elements=tuple(tcl.GiD_Info('mesh','elements',element_type,'-array2'))
if (len(info_elements)):
#tcl.W(info_elements)
elements_data=info_elements[0]
element_type_ret,element_ids_original,connectivities_original,materials=elements_data
element_ids=tohil_obj_array_int_to_numpy(tuple(element_ids_original))
connectivities=tohil_obj_array_int_to_numpy(tuple(connectivities_original))
num_elements_block=len(element_ids)
if (num_elements_block):
if (nodes_renumbered_for_meshio):
connectivities=numpy_renumber(connectivities,node_ids,new_node_ids)
else:
connectivities=numpy_incr(connectivities,-1)
some_element_id=element_ids[0]
element_num_nodes=len(tcl.GiD_Mesh('get','element',some_element_id,'connectivities'))
key=element_type+','+str(element_num_nodes)
meshio_etype=gid_to_meshio_type[key]
cells.append((meshio_etype,gid_elements_to_meshio_cells(element_num_nodes,connectivities)))
mesh=meshio.Mesh(points,cells)
result=mesh.write(filename)
return result
Note that in this case use python commands to call Tcl like these:
import tohil
tcl=tohil.import_tcl()
info_nodes=tuple(tcl.GiD_Info('mesh','nodes','-array'))
info_elements=tuple(tcl.GiD_Info('mesh','elements',element_type,'-array2'))
#tcl.W(node_ids) #to show information in a GiD message window for debug
element_num_nodes=len(tcl.GiD_Mesh('get','element',some_element_id,'connectivities'))
To know the syntax of GiD-Tcl added commands (like GiD_Info or GiD_Mesh) read the GiD Customization Manual: TCL AND TK EXTENSION