fdtdx.circular_brush

def circular_brush(
    diameter: float,
    size: int | None = None,
) -> jax.Array:
    """Creates a circular binary mask/brush for morphological operations.

    Args:
        diameter (float): Diameter of the circle in grid units.
        size (int | None, optional): Optional size of the output array. If None, uses ceil(diameter) rounded
            up to next odd number.

    Returns:
        jax.Array: Binary array containing a circular mask where True indicates points
        within the circle diameter.
    """
    if size is None:
        s = math.ceil(diameter)
        if s % 2 == 0:
            s += 1
        size = s
    xy = jnp.stack(jnp.meshgrid(*map(jnp.arange, (size, size)), indexing="xy"), axis=-1) - jnp.asarray((size / 2) - 0.5)
    euc_dist = jnp.sqrt((xy**2).sum(axis=-1))
    # the less EQUAL here is important, because otherwise design may be infeasible due to discretization errors
    mask = euc_dist <= (diameter / 2)
    return mask