Random nonoverlapping spheres

Generate a reproducible collection of identical spheres in a uniform background. Sphere centres are proposed uniformly within the part of the box that keeps each sphere fully inside. Overlapping proposals are rejected; the generator raises an error if it cannot place every requested sphere within its attempt limit. This is sequential placement, rather than an equilibrium hard-sphere model.

The plotted medium samples material at voxel centres. Choose a spacing fine enough to resolve each sphere, and use small refractive index contrast for Born scattering.

Generated 12 nonoverlapping spheres with radius 40 nm.

import matplotlib.pyplot as plt
from bornsim import Grid
from bornsim.medium.random_spheres import RandomSphereMedium
from bornsim.units import ureg


grid = Grid(
    shape=(16, 16, 16),
    spacing=25 * ureg.nanometer,
)

medium = RandomSphereMedium(
    background_refractive_index=1.33,
    sphere_refractive_index=1.35,
    radius=40 * ureg.nanometer,
    sphere_count=12,
)

volume = medium.to_volume(
    grid=grid,
    seed=42,
)

figure = volume.plot_3d(
    backend="matplotlib",
    mode="voxels",
    field="refractive_index",
)

print(f"Generated {medium.sphere_count} nonoverlapping spheres with radius {medium.radius:~P}.")

plt.show()