Using an ODF

[atsushi-labo]

Hello,

Thank you to the developers of Neper for your great work.

I have a question regarding the tutorial "Using an ODF."
I understand that the number of elements in fr.msh must match the number of lines in odf.txt.

At the end of the fr.msh file, the Rodrigues vector is defined like this:

$ElsetOrientations
1 rodrigues:active
1 0.919953402851 1.412193625247 -0.358468593221
$EndElsetOrientations

The odf.txt file looks like this:

0.000000759253
9.942171443106
0.426465599961
…
(the number of lines equals the number of elements)

I have two questions:

Question 1

A Rodrigues vector is defined as:

r = n * tan(Θ / 2)

n = (n1, n2, n3): unit vector representing the rotation axis

Θ: rotation angle (in radians)

r = (r1, r2, r3): Rodrigues vector

Based on this definition, does the Rodrigues vector in fr.msh represent n, and do the values in odf.txt represent Θ?

Question 2

Would it be okay to arbitrarily change the Rodrigues vector part in fr.msh like this:

$ElsetOrientations
1 rodrigues:active
1 1.0 0.0 0.0
$EndElsetOrientations

and then set arbitrary values in odf.txt as well?