geotofenics.py

#!/usr/bin/env python3
"""
Created on Wed Jun 3 20:42:08 2020

Usage: ./geotofenics.py filename.geo

    Note: A new file called 'filename.geo.xml' will be created if all goes 
    well. Make sure you don't have a file with the same name you want to keep
    before running this.
         
    EXPORTING FROM SOLIDWORKS SIMULATION
    ------------------------------------
    1. Create your desired geometry in Solidworks. The model
       can be a part or an assembly. If it is an asssembly, each part will
       be stored in the mesh file as a domain. This is done by tagging 
       the elements with integers, starting from zero. 
    2. Choose Simulation->New Study->Thermal
    3. Right-click Mesh->Create Mesh...
    4. Choose your resolution (Mesh Parameters)
    5. From the menu at the top Simulation->Export
    6. From the "Save as" type menu, you MUST select Simulation files (*.geo)
    7. IMPORTANT. CLick on Options and select "Export FEM only" 
    8. Save to a file WITHOUT a space in the name
 
    READING IN FENICS AND VISUALIZE
    ------------------------------------
    This script is particularly useful for multi-domains (i.e., multi-parts)
    geometries. To import the generated mesh in fenics and visualize the 
    geometry with the various domains do something like (assuming 
    output_mesh.xml was generated by this script)
    
    from fenics import *
    from dolfin import *
    
    mesh = Mesh("output_mesh.xml")
    mf = MeshFunction("size_t", mesh, 3, mesh.domains())
    domains_file =  File('output_mesh.pvd') 
    domains_file << mf

    Then, open output_mesh.pvd with Paraview and see the geometry and the 
    various domains.
    
    This script was tested with
    - Fenics/Dolfin 2019.1.0
    - Solidworks 2019 Education Edition
    - Python 3.6.10 on Ubuntu
    
@author: Alberto Corrias (Github: albertocorrias)
"""
import sys

if (len(sys.argv) != 2):
    raise Exception('Only filename expected. Usage: ./geotofenics.py filename.geo')

sw_filename = sys.argv[1]
output_xml_filename = sw_filename + '.xml';

try:
    input_sw_file = open(sw_filename, "r")
except:
    print('ERROR: Unable to open input file ' + sw_filename)
    exit();

try:    
    output_file = open(output_xml_filename, "w")
except:
    print('ERROR: Unable to open putput file')
    exit();
    
#Headers and footers
header = '<?xml version="1.0"?> \n \
<dolfin xmlns:dolfin="http://fenicsproject.org"> \n \
<mesh celltype="tetrahedron" dim="3"> \n';

footer = '<data /> </mesh> \n \
</dolfin>\n'
output_file.write(header);
#########################

#First sweep just to count elements, nodes and number of domains (parts)
nodes=0;
elems = 0;
domain_tags = []
for line in input_sw_file:
    if (line.find('ND')!=-1) and (line.find('FND')==-1) and (line.find('DND')==-1):
        #This is a "node" line
        nodes = nodes + 1
    if (line.find('EL,')!=-1):
        #This is an "element" line
        split_line = line.split();
        tag_for_element = int(split_line[3].strip(','))
        if tag_for_element not in domain_tags:
            domain_tags.append(tag_for_element)#Store unique element tag
        elems = elems + 1
input_sw_file.close()

#other headers and footers based on mesh size
node_string_header = '<vertices size="' + str(nodes) + '">\n';
output_file.write(node_string_header)
node_string_footer = '</vertices> \n'
elem_string_header = '<cells size="' + str(elems) + '">\n'
elem_string_footer = '</cells> \n'

num_domains = len(domain_tags)
domain_string_header = '  <domains> \n \
<mesh_value_collection name="f" type="uint" dim="3" size="' + str(elems) + '">\n'
    
domain_string_footer = '</mesh_value_collection> \n </domains>';
  

#Reopen the file and re-loop to get nodes and elements
input_sw_file = open(sw_filename, "r")   

node_counter=0;
elem_counter = 0;
elem_domain_pairs = [[],[]] #This will be used for domains later
nodes_used = []
for line in input_sw_file:
    if (line.find('ND')!=-1) and (line.find('FND')==-1) and (line.find('DND')==-1):
        #This is a "node" line
        split_line = line.split()
        
        xml_node_line = '<vertex index="' + str(node_counter)+ \
        '" x="' + str(split_line[2]) +\
        '" y="' + str(split_line[3]) +\
        '" z="' + str(split_line[4]) +'" />\n'
        
        output_file.write(xml_node_line)
        node_counter = node_counter + 1
        
    if (line.find('EL,')!=-1):
        #This is an "element" line
        if (elem_counter==0):
            output_file.write(node_string_footer)
            output_file.write(elem_string_header)
            
        split_line = line.split();
        
        #note that we need to subtract 1 from the node number
        #as Solidworks counts from 1
        xml_elem_line = '<tetrahedron index="'+str(elem_counter) +\
        '" v0="' + str(int(split_line[5])-1) +\
        '" v1="' + str(int(split_line[6])-1) +\
        '" v2="' + str(int(split_line[7])-1) +\
        '" v3="' + str(int(split_line[8])-1) + '" />\n'
        if (int(split_line[5])-1) not in nodes_used:
            nodes_used.append(int(split_line[5])-1)
        if (int(split_line[6])-1) not in nodes_used:
            nodes_used.append(int(split_line[6])-1)
        if (int(split_line[7])-1) not in nodes_used:
            nodes_used.append(int(split_line[7])-1)
        if (int(split_line[8])-1) not in nodes_used:
            nodes_used.append(int(split_line[8])-1)
        output_file.write(xml_elem_line)

        #store element  - domain pairs for later
        tag_for_element = int(split_line[3].strip(','))-1
        elem_domain_pairs[0].append(elem_counter)
        elem_domain_pairs[1].append(tag_for_element)
        
        elem_counter = elem_counter + 1

input_sw_file.close()
output_file.write(elem_string_footer)

print (node_counter, '   ', len(nodes_used))
#Add domains info before closing
output_file.write(domain_string_header)
for el_idx in elem_domain_pairs[0]:
    domain_element_string = '<value cell_index="' + str(el_idx) +\
    '" local_entity="0" value="'+str(elem_domain_pairs[1][el_idx])+'" />\n'
    
    output_file.write(domain_element_string)

output_file.write(domain_string_footer)
#Footers and close
output_file.write(footer)
output_file.close();