"""
Custom tessellation deflection
==============================

OCCT's ``BRepMesh_IncrementalMesh`` exposes a linear and angular
deflection knob. Coarser deflection yields fewer triangles; finer
deflection yields smoother curves. ``read_step``, ``read_brep``,
``read_fcstd``, and the build123d / cadquery bridges all forward
these knobs.

The part is a real M3 nyloc lock nut from the FreeCAD parts library
(CC-BY 3.0, FreeCAD-library contributors). Its helical thread and
chamfers are exactly the curved features the deflection knob
resolves, so the triangle count moves with the setting.
"""

# %%

import pandas as pd
import pyvista as pv

import pyvista_cad
from pyvista_cad.examples import downloads

# %%
# Tessellate the same real FCStd part at three deflection settings.

fcstd = downloads.fcstd_nut_path()
settings = [
    ('coarse', 0.5, 1.0),
    ('medium', 0.1, 0.5),
    ('fine', 0.02, 0.2),
]
meshes = {
    name: pyvista_cad.read_fcstd(fcstd, linear_deflection=lin, angular_deflection=ang)
    .combine()
    .extract_surface()
    for name, lin, ang in settings
}

pd.DataFrame(
    [
        {'setting': name, 'linear': lin, 'angular': ang, 'triangles': meshes[name].n_cells}
        for name, lin, ang in settings
    ]
)

# %%
# Side by side with the camera locked across views.

pl = pv.Plotter(shape=(1, 3))
for i, name in enumerate(['coarse', 'medium', 'fine']):
    pl.subplot(0, i)
    mesh = meshes[name]
    mesh['z'] = mesh.points[:, 2]
    pl.add_mesh(mesh, scalars='z', cmap='inferno', show_edges=True, edge_color='black')
pl.link_views()
pl.show()