Originally posted by **sbmse007** August 9, 2023
Hello,
I have been trying to generate 3D columnar hexagonal grains. I followed the "hex_grain_growth_2D_eldrforce.i" input file. However, when I am converting the file into 3D, I am always getting the following error:
```
"*** ERROR ***
The following error occurred in the object "hex_ic", of type "PolycrystalHex".
PolycrystalHex requires a square or cubic number depending on the mesh dimension".
```
In the 2D version, putting op_num = 3 as well as grain_num = 36 in the '"PolycrystalHex" user object works fine.
Moreover, I can eliminate the above mentioned error if I use op_num = 8 and grain_num = 8. But the grain structure is not a perfect hexagon as in 2D. It will be very helpful if anyone can provide me with some suggestions.
Discussed in https://github.com/idaholab/moose/discussions/25155