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gMesh.py
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gMesh.py
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# -*- coding: utf-8 -*-
"""
Created on Wed Apr 4 14:33:23 2018
@author: ian
"""
from modelfunc import myerror
import matplotlib.pyplot as plt
import numpy as np
elSize = {1: 2, 2: 3, 3: 4}
class gMesh:
# nodes
def __init__(self, expFile=None, meshType='Triangle'):
self.nNodes, self.nElements = 0, 0
self.nodeValues = []
self.nodes, self.elements = [], []
self.nNVal, self.nEVal = 0, 0
self.nodeIndex, self.elIndex = [], []
self.meshpy = None
self.elementType = []
self.tag, self.group = [], []
self.meshtype = meshType
if expFile is not None:
self.readExp(expFile)
def readGmshHeader(self, gmshFile):
''' read gmsh header, return pointer to start of nodes'''
try:
fpGmsh = open(gmshFile, 'r')
except Exception:
myerror(f'error opening gmsh input file {gmshFile}')
for line in fpGmsh:
if '$Nodes' in line:
return fpGmsh
myerror(f'Reached end of {gmshFile} with no $Nodes found')
def readGmshNodes(self, fpGmsh):
''' read nodes from a gmsh file '''
try:
nNewNodes = int(fpGmsh.readline().strip())
except Exception:
myerror('readGmshNodes: cannot parse nLines')
#
nodeIndex, nodesRead = len(self.nodeIndex), 0
for line in fpGmsh:
nodeData = [eval(x) for x in line.split()]
self.nodes.append(nodeData[1:3])
self.nodeValues.append(nodeData[3])
nodeIndex += 1 # Increment node index and append
self.nodeIndex.append(nodeIndex)
nodesRead += 1 # Increment node counter
if nodesRead == nNewNodes:
print(f'Read {nodesRead} nodes')
self.nNodes += nodesRead
break
self.nodes = np.array(self.nodes)
print(self.nodes.shape)
if nodesRead != nNewNodes:
myerror(f'readGmshNodes: expected {nNewNodes} nodes read '
f'{nodesRead}')
if '$EndNodes' not in fpGmsh.readline():
myerror(f'readGmshNodes: expected $EendNodes')
def readGmshElements(self, fpGmsh):
''' read elements from a gmsh file '''
try:
print(f'{fpGmsh.readline()}')
nNewElements = int(fpGmsh.readline().strip())
except Exception:
myerror('readGmshElements: cannot parse nLines')
#
elIndex, elRead = len(self.elIndex), 0
for line in fpGmsh:
elData = [eval(x) for x in line.split()]
self.elements.append(elData[5:])
self.elementType.append(elData[1])
self.tag.append(elData[3])
self.group.append(elData[4])
elIndex += 1 # Increment el index and append
self.elIndex.append(elIndex)
elRead += 1 # Increment el counter
if elRead == nNewElements:
print(f'Read {elRead} elements')
self.nElements += elRead
break
if elRead != nNewElements:
myerror(f'readGmshElements: expected {nNewElements} nodes read '
f'{elRead}')
if '$EndElements' not in fpGmsh.readline():
myerror(f'readGmshNodes: expected $EndElements')
def readGmsh(self, gmshFile):
'''Read gmsh file'''
fpGmsh = self.readGmshHeader(gmshFile)
self.readGmshNodes(fpGmsh)
self.readGmshElements(fpGmsh)
def getNewTag(self):
''' Get a new incremental tag '''
if len(self.tag) == 0:
return 1 # First tag
else:
return self.tag[-1] + 1 # Increment last tag
def gmshHeader(self, gmshFile):
''' Open gmsh file and write header'''
# open file
try:
fpGmsh = open(gmshFile, 'w')
except Exception:
myerror(f'error opening gmsh output file {gmshFile}')
# Header info
print('$MeshFormat', file=fpGmsh)
print('2.2 0 8', file=fpGmsh)
print('$EndMeshFormat', file=fpGmsh)
return fpGmsh
def writeGmshNodes(self, fpGmsh):
''' write node data '''
print('$Nodes', file=fpGmsh)
print(self.nNodes, file=fpGmsh)
#
for i in range(self.nNodes):
print(f'{self.nodeIndex[i]:10} {self.nodes[i][0]:15.5f} '
f'{self.nodes[i][1]:15.5f} 0.0 ', file=fpGmsh)
print('$EndNodes', file=fpGmsh)
def writeGmshElements(self, fpGmsh):
''' write node data '''
print('$Elements', file=fpGmsh)
print(self.nElements, file=fpGmsh)
for i in range(self.nElements):
# [rint(self.elements[i])
if self.elementType[i] > 1:
group = 1000
else:
group = self.elIndex[i]
print(f'{self.elIndex[i]:8} {self.elementType[i]:3} 2 '
f'{self.tag[i]:4} {self.group[i]:6} '
f'{"".join([f"{x:10}" for x in self.elements[i]])}',
file=fpGmsh)
print('$EndElements', file=fpGmsh)
def toGmsh(self, gmshFile):
''' Write msh in gmsh format '''
#
# init
fpGmsh = self.gmshHeader(gmshFile)
# Nodes
self.writeGmshNodes(fpGmsh)
#
# Elements
self.writeGmshElements(fpGmsh)
#
fpGmsh.close()
def plotMesh(self, nodes=True, elements=True):
''' plot mesh - very slow mostly for debugging'''
fig, ax = plt.subplots(1, 1)
#
i = 0
ax.plot(self.nodes[:,0], self.nodes[:,1], 'k.')
for myEl in self.elements:
#print(self.nodes[myEl,:])
kk=np.array(myEl)-1
xy = self.nodes[kk, :]
#print(xy.shape)
ax.plot(xy[:,0], xy[:,1],'r-')
i+=1
if i == 1000 :
break
# print(myEl)
#
# print(xy[:,0], xy[:,1])
plt.show()