Add gmsh-import, pybind2.2 ctor for Mesh

libsrc/meshing/python_mesh.cpp

@@ -431,6 +431,17 @@ DLL_HEADER void ExportNetgenMeshing(py::module &m)
   py::class_<Mesh,shared_ptr<Mesh>>(m, "Mesh")
     // .def(py::init<>("create empty mesh"))
 
+    .def(py::init( [] (int dim)
+                   {
+                     auto mesh = make_shared<Mesh>();
+                     mesh -> SetDimension(dim);
+                     SetGlobalMesh(mesh);  // for visualization
+                     return mesh;
+                   } ),
+         py::arg("dim")=3         
+         )
+
+    /*
     .def("__init__",
          [](Mesh *instance, int dim)
                            {
@@ -439,7 +450,7 @@ DLL_HEADER void ExportNetgenMeshing(py::module &m)
                            },
            py::arg("dim")=3
           )
-
+    */
     
     .def("__str__", &ToString<Mesh>)
     .def("Load",  FunctionPointer 

python/CMakeLists.txt

@@ -2,7 +2,7 @@ configure_file(__init__.py ${CMAKE_CURRENT_BINARY_DIR}/__init__.py @ONLY)
 
 install(FILES
         ${CMAKE_CURRENT_BINARY_DIR}/__init__.py
-        meshing.py csg.py geom2d.py stl.py gui.py NgOCC.py
+        meshing.py csg.py geom2d.py stl.py gui.py NgOCC.py read_gmsh.py
         DESTINATION ${NG_INSTALL_DIR_PYTHON}/${NG_INSTALL_SUFFIX}
         COMPONENT netgen
         )

python/read_gmsh.py

@@ -0,0 +1,73 @@
+from netgen.meshing import *
+
+def ReadGmsh (filename):
+    f = open(filename, 'r')
+
+    mesh = Mesh(dim=3)
+    
+    pointmap = { }
+    facedescriptormap = { } 
+                         
+    
+    while True:
+        line = f.readline()
+        if line == "": break
+            
+        if line.split()[0]=="$Nodes":
+            num = int(f.readline().split()[0])
+            print ("reading",num,"nodes")
+            for i in range(num):
+                line = f.readline()
+                nodenum,x,y,z = line.split()[0:4]
+                pnum = mesh.Add (MeshPoint(Pnt(float(x),float(y),float(z))))
+                pointmap[int(nodenum)] = pnum
+
+        if line.split()[0]=="$Elements":
+            num = int(f.readline().split()[0])
+            print ("reading",num,"elements")
+            
+            for i in range(num):
+                line = f.readline().split()
+                elmnum = int(line[0])
+                elmtype = int(line[1])
+                numtags = int(line[2])
+                tag1 = int(line[3])
+                    
+                if elmtype == 2:   # 3-node trig
+                    num_nodes = 3
+                elif elmtype == 3: # 4-node quad
+                    num_nodes = 4
+                elif elmtype == 4: # 4-node tet
+                    num_nodes = 4
+                else:
+                    print ("element type", elmtype, "not implemented")
+                    
+                nodenums = line[3+numtags:3+numtags+num_nodes]
+                nodenums2 = [ pointmap[int(nn)] for nn in nodenums ]
+
+
+                if elmtype in [2,3]:  # 2d elements
+
+                    # generate facedescriptor for boundary conditon number,
+                    # first tag is used as bc-number
+                    # element index maps into facedescriptor array
+                    if tag1 in facedescriptormap.keys():
+                        fdindex = facedescriptormap[tag1]
+                    else:
+                        fd = FaceDescriptor(bc=tag1)
+                        fdindex = mesh.Add(fd)
+                        facedescriptormap[tag1] = fdindex
+                    
+                    mesh.Add (Element2D(fdindex, nodenums2))
+                    
+                if elmtype == 4:  # 4-node tet
+                    nodenums2 = [ pointmap[int(nn)] for nn in nodenums ]
+                    mesh.Add (Element3D(tag1, [nodenums2[0],nodenums2[1],nodenums2[3],nodenums2[2]]))
+                print (nodenums2)
+    # print (mesh)
+    # print (pointmap)
+
+    return mesh
+    
+# ReadGMSH ("test.gmsh")
+