I looked into “read_gmsh.py” and found node ordering of Netgen is not similar to Gmsh.
if elmtype in trigs:
ordering = [i for i in range(3)]
if elmtype == trig6:
ordering += [4,5,3]
if elmtype in quads:
ordering = [i for i in range(4)]
if elmtype == quad8:
ordering += [4, 6, 7, 5]
if elmtype in tets:
ordering = [0,1,2,3]
if elmtype == tet10:
ordering += [4,6,7,5,9,8]
elif elmtype in hexes:
ordering = [0,1,5,4,3,2,6,7]
if elmtype == hex20:
ordering += [8,16,10,12,13,19,15,14,9,11,18,17]
elif elmtype in prisms:
ordering = [0,2,1,3,5,4]
if elmtype == prism15:
ordering += [7,6,9,8,11,10,13,12,14]
elif elmtype in pyramids:
ordering = [3,2,1,0,4]
if elmtype == pyramid13:
ordering += [10,5,6,8,12,11,9,7]
The mesh ordering of Gmsh can be found in the following.
Gmsh node ordering
Are there any documents on the node ordering of Netgen, such as Gmsh?
It might be complicated because Netgen would support higher elements than 2nd order elements.