Connectivity for C3D10 element does not follow the right hand rule

[BoyangChenFEM]

Hello Ihor ,

In the writer.py:

dic = {
'S6': [1, 3, 5, 2, 4, 6],
'S8': [1, 3, 5, 7, 2, 4, 6, 8],
'C3D10': [1, 3, 5, 10, 2, 4, 6, 7, 8, 9],
'C3D15': [1, 3, 5, 10, 12, 14, 2, 4, 6, 11, 13, 15, 7, 8, 9],
'C3D20': [1, 3, 5, 7, 13, 15, 17, 19, 2, 4, 6, 8, 14, 16, 18, 20, 9, 10, 11, 12],
}

The connectivity for C3D10 (maybe also for the other quadratic elements) shows clock-wise orientation when seen from the top, this may be due to the fact that the UNV convention seems to follow the clock-wise orientation, please see the example 118.unv:
2411
1 1 1 11
0.0000000000000000E+00 0.0000000000000000E+00 0.0000000000000000E+00
2 1 1 11
1.0000000000000000E+00 0.0000000000000000E+00 0.0000000000000000E+00
3 1 1 11
5.0000000000000000E-01 8.0000001192092896E-01 0.0000000000000000E+00
4 1 1 11
5.0000000000000000E-01 3.0000001192092896E-01 8.0000001192092896E-01
5 1 1 11
5.0000000000000000E-01 0.0000000000000000E+00 0.0000000000000000E+00
6 1 1 11
7.5000000000000000E-01 4.0000000596046448E-01 0.0000000000000000E+00
7 1 1 11
2.5000000000000000E-01 4.0000000596046448E-01 0.0000000000000000E+00
8 1 1 11
2.5000000000000000E-01 1.5000000596046448E-01 4.0000000596046448E-01
9 1 1 11
7.5000000000000000E-01 1.5000000596046448E-01 4.0000000596046448E-01
10 1 1 11
5.0000000000000000E-01 5.5000001192092896E-01 4.0000000596046448E-01
-1
-1
2412
1 118 2 1 7 10
1 7 3 6 2 5 8 10
9 4

But Abaqus C3D10 follows counter-clockwise orientation, so I think that the connectivity should be [1, 5, 3, 10, 6, 4, 2, 7, 9, 8]?

[imirzov]

unv2ccx is written for Calculix, not for Abaqus - some differences could exist between those solvers. Sorry, I do not have much time to read and recall my old codes. If you think you're right - please, attach some images with conversion results - it should reveal the problem.

[imirzov]

And, please, bring some light to consequences of finite-element facet normal inversion.