"""
Read a BREP solid
=================

BREP is OpenCASCADE's native shape serialization, the format every
OCCT-backed tool (FreeCAD, build123d, cadquery) can round-trip
losslessly. No openly licensed real-world ``.brep`` corpus exists, so
this example takes a *real* STEP part, the NIST AM Bench 2022 LPBF
bridge specimen (public domain, https://doi.org/10.18434/mds2-2607),
serializes it to BREP, and reads it back into
:class:`pyvista.PolyData`.

Why this matters: BREP is the canonical handoff between OCCT-aware
tools. Tessellation parameters surface up through ``read_brep`` so you
can trade mesh density for geometric fidelity.
"""

# %%
# Load the real STEP part and serialize it to BREP.

from pathlib import Path
import tempfile

import pyvista as pv

import pyvista_cad
from pyvista_cad.examples import downloads

src = pyvista_cad.read_step(downloads.step_part_path()).combine().extract_surface()
brep_path = Path(tempfile.mkdtemp()) / 'part.brep'
pyvista_cad.write_brep(src, brep_path)

# %%
# Read the BREP back. ``linear_deflection`` controls the mesher.

poly = pyvista_cad.read_brep(brep_path, linear_deflection=0.1)
poly

# %%
# Render CAD-friendly: faces coloured by elevation, topological edges
# overlaid, triangle-mesh edges hidden.

poly['elevation'] = poly.points[:, 2]

pl = pv.Plotter()
pl.cad.add(poly, scalars='elevation', cmap='plasma')
pl.show()