the index calculation in mpm_fan_rotation.py

[commatrixs]

hi zhijie,

Thanks for sharing your code! I noticed that the you use 'nn = (i+1)(j+1)-1' to calculation index at line 127 of the file 'mpm_fan_rotation.py'. I think this code can only partially fill matrices. For example, in the diagonal matrix, only the 1st, 2nd, 3rd, 4th, 6th, and 9th elements on the diagonal are updated. Maybe it should be modified to 'nn = i3 + j'