Field visualization flipped relative to eps preview (origin='lower' vs origin='upper' in viz.field)

[4ndrebar]

Description

When using legume.viz.field, the field visualization appears vertically flipped relative to the expected layout (as seen in the structure or EPS preview).

Expected vs. Actual

This discrepancy is especially visible when the structure is not vertically symmetric. Here's a comparison:

Expected (matches geometry):

Actual (flipped vertically):

Minimal working example

import numpy as np
import legume

# Initialize the lattice and the PhC
def wg(
    phc_periods: int = 8,
    index: int = 3,
    lattice_constant: float = 337,
    radius: float = 92,
    stack_height: float = 450,
    background_index: float = 1.45,
    semiconductor_index: float = 3.34,
):
    _radius = radius / lattice_constant
    _stack_height = stack_height / lattice_constant
    cell_center = (0, -(phc_periods) * np.sqrt(3) / 4)
    lattice = legume.Lattice([1, 0], [0, -2 * cell_center[1]])
    phc = legume.PhotCryst(lattice, eps_l=background_index**2, eps_u=background_index**2)

    top_phc = [
        legume.Circle(
            eps=background_index**2,
            x_cent=0.5 * ((period + 1) % 2),
            y_cent=period * np.sqrt(3) / 2 + cell_center[1],
            r=_radius
        )
        for period in range(phc_periods) if period != index
    ]

    phc.add_layer(d=_stack_height, eps_b=semiconductor_index**2)
    phc.add_shape(top_phc)
    return phc

phc = wg()
path = phc.lattice.bz_path([np.array([np.pi / 2, 0]), np.array([np.pi, 0])], [2])

gme = legume.GuidedModeExp(phc, gmax=4.01)
options = {
    'gmode_inds': [2, 4],
    'numeig': 2,
    'verbose': False
}
gme.run(kpoints=path['kpoints'], **options)

# Field visualization
_ = legume.viz.field(
    gme,
    field='e',
    kind=2,
    mind=0,
    z=0.5,
    component='y',
    val='abs'
)

Proposed fix

To correct the flipped field image, I locally modified line 1294 in viz.py:

Original:
origin='lower'

Modified:
origin='upper'

This change makes the field plot align with the EPS geometry.

Environment

legume version: legume.version = 1.0.2

Python version: python --version = 3.13.5

Full Conda environment: conda_env.txt