smbinterp/bin/parse_gmsh.py

#!/usr/bin/env python
import atexit
import os
import sys
import readline
import rlcompleter

historyPath = os.path.expanduser("~/.pyhistory")

def save_history(historyPath=historyPath):
  import readline
  readline.write_history_file(historyPath)

if os.path.exists(historyPath):
  readline.read_history_file(historyPath)

atexit.register(save_history)
del os, atexit, readline, rlcompleter, save_history, historyPath


import sys
import pickle
from itertools import combinations

import numpy as np

THREE_NODE_TRIANGLE = 2

class point(object):
  def __init__(self, xyz):
    self.index = index

    self.xyz    = xyz
    self.faces  = []

  def __getitem__(self, i):
    if isinstance(i, int):
      if   i == 0:
        return self.xyz[0]
      elif i == 1:
        return self.xyz[1]
      elif i == 2:
        return self.xyz[2]
      else:
        raise IndexError("there are only (x,y,z)")
    else:
      raise TypeError("only point.x and point[0] access allowed")

  def _getx(self):
    return self.xyz[0]
  x = property(_getx)
  def _gety(self):
    return self.xyz[1]
  y = property(_gety)
  def _getz(self):
    return self.xyz[2]
  z = property(_getz)

  def __str__(self):
    return '%s' % self.xyz
  __repr__ = __str__

class face(object):
  def __init__(self):
    self.neighbors = []
    self.points = []

if __name__ == '__main__':
  if len(sys.argv) != 2:
    print >> sys.stderr, "usage: %s <gmsh file>" % sys.argv[0]
    sys.exit(1)

  gmsh_file = open(sys.argv[1], 'r')


  gmsh_file.readline() # $MeshFormat
  format = gmsh_file.readline()
  gmsh_file.readline() # $EndMeshFormat

  gmsh_file.readline() # $Nodes

  node_count = int(gmsh_file.readline())

  points = []
  nppoints = np.zeros((node_count, 3))
  for i in xrange(node_count):
    cur_line = gmsh_file.readline()
    (index, x,y,z) = cur_line.split()
    index = int(index) - 1
    x     = float(x)
    y     = float(y)
    z     = float(z)

    nppoints[i][0] = x
    nppoints[i][1] = y
    nppoints[i][2] = z
    points.append(point(nppoints[i]))


  gmsh_file.readline() # $EndNodes
  gmsh_file.readline() # $Elements

  element_count = int(gmsh_file.readline())

  faceobjs        = {}
  neighbors       = {}

  for i in xrange(element_count):
    cur_line = gmsh_file.readline()
    cur_line = cur_line.split()
    cur_face_index, node_type, rest = (int(cur_line[0]),
                                       int(cur_line[1]),
                                       [int(j) for j in  cur_line[2:]])

    if(node_type == THREE_NODE_TRIANGLE):
      points_for_cur_face = [i-1 for i in rest[rest[0]+1:]]

      cur_face = face()

      for cur_point in points_for_cur_face:
        points[cur_point].faces.append(cur_face_index)

      cur_face.points       = points_for_cur_face

      faceobjs[cur_face_index] = cur_face
      edges = [tuple(sorted(i)) for i in combinations(points_for_cur_face, 2)]

      # edge is two points
      for edge in edges:
        if edge in neighbors:
          neighbors[edge].append(cur_face_index)
        else:
          neighbors[edge] = [cur_face_index]

  for k,v in neighbors.iteritems():
    if len(v) > 1:
      faceobjs[v[0]].neighbors.append(v[1])
      faceobjs[v[1]].neighbors.append(v[0])

  pickle.dump([(p[0], p[1], p[2]) for p in points], open('/tmp/points.p', 'w'))
  pickle.dump([f.points for f in faceobjs.itervalues()], open('/tmp/faces.p',  'w'))