strut-based lattice generation

[mehbah]

Hi Microgen support team,

Thank you for sharing this helpful tool!

I am currently working on generating strut-based lattices and noticed that it is possible to create a unit cell and replicate it in three dimensions, as demonstrated in the octet-truss example in the documentation. This example references a 'test_octet.dat' file, which specifies the cylinders required to construct a single octet-truss unit cell.

Are there other .dat files available for different unit cells, such as simple cubic, BCC, or FCC structures? Alternatively, could you assist me in generating such files?

Kind regards,
Mehran

[kmarchais]

Hello @mehbah, thank you for your interest in microgen.

We don't have other .dat files for this but you don't really need it, you can do it in python directly.
Here is a little script to generate a cubic structure:

# /// script
# requires-python = ">=3.9"
# dependencies = [
#     "microgen",
# ]
# ///

from microgen import fuse_shapes, repeat_shape, Rve, Cylinder

import pyvista as pv
import cadquery as cq

from pathlib import Path

# orientation: Euler angles in degrees in the XZX convention
c1 = Cylinder(height=1, radius=0.05, center=(0, 0, 0), orientation=(0, 0, 0)).generate()
c2 = Cylinder(height=1, radius=0.05, center=(0, 0, 0), orientation=(0, 0, 90)).generate()
c3 = Cylinder(height=1, radius=0.05, center=(0, 0, 0), orientation=(0, 90, 90)).generate()

result = fuse_shapes(shapes=[c1, c2, c3], retain_edges=False)
result = repeat_shape(result, rve=Rve(dim=(1, 1, 1)), grid=(3, 3, 3))

file_path = Path(__file__).parent / "result.stl"

cq.exporters.export(result, str(file_path))

pv.read(file_path).plot()

It will generate the following structure

Then you can modify the script to generate the shapes you need.
If you have any question, request or suggestion, feel free to share it here.

[kmarchais]

For the orientation you can use scipy to go from the rotation system you want (any euler convention, quaternions, matrix) to the XZX system.

from scipy.spatial.transform import Rotation as R

R.from_euler("XYZ", [0, 90, 0], degrees=True).as_euler("XZX", degrees=True)
>>> [-90.  90.  90.]

[chemiskyy]

@mehbah just make sure you use the "ZXZ" convention instead of "XZX" as the rotation of objects in micron use this convention.

from scipy.spatial.transform import Rotation as R

R.from_euler("XYZ", [0, 90, 0], degrees=True).as_euler("ZXZ", degrees=True)
>>> [-90.  90.  90.]

[mehbah]

Thank you so much for your help—I truly appreciate it! I was able to generate the lattices successfully.

However, I’ve encountered something that’s a bit confusing. Sometimes the XZX convention gives me the correct rotation, and other times the ZXZ convention seems to work instead.

[kmarchais]

We are currently making changes to be able to use scipy rotations which should make it more convenient.