"""Grouper: true sections of the built model (read-only): the meshes cut by planes Y = const (or X = const), drawn as (x, z)
segments per object, for checking clearances by eye. Writes JSON for gr_section_plot.py (plain Python + PIL).
    blender.exe -b Tender_Grouper.blend --python build/gr_section.py -- y=-2.70 y=-2.65 x=0.45 out=<json>"""
import bpy, sys, json
import numpy as np
args = sys.argv[sys.argv.index("--") + 1:]
cuts = [(a[0], float(a[2:])) for a in args if a[:2] in ("y=", "x=")]
out = [a[4:] for a in args if a.startswith("out=")][0]
dg = bpy.context.evaluated_depsgraph_get()
res = {}
for o in bpy.data.objects:
    if o.type != 'MESH' or o.name.startswith("UCX_") or o.hide_render:
        continue
    ev = o.evaluated_get(dg)
    me = ev.to_mesh()
    me.calc_loop_triangles()
    M_ = np.array(ev.matrix_world)
    V = np.array([v.co[:] for v in me.vertices] or [[0, 0, 0]])
    V = (np.c_[V, np.ones(len(V))] @ M_.T)[:, :3]
    T = np.array([t.vertices[:] for t in me.loop_triangles] or [[0, 0, 0]])
    ev.to_mesh_clear()
    for ax, val in cuts:
        ai = 1 if ax == "y" else 0
        d = V[:, ai] - val
        segs = []
        dt = d[T]
        cross = (np.sign(dt).max(1) > 0) & (np.sign(dt).min(1) < 0)
        for tri in T[cross]:
            pts = []
            for a, b in ((0, 1), (1, 2), (2, 0)):
                da, db = d[tri[a]], d[tri[b]]
                if (da > 0) != (db > 0):
                    t = da / (da - db)
                    p = V[tri[a]] + (V[tri[b]] - V[tri[a]]) * t
                    pts.append(p)
            if len(pts) == 2:
                if ax == "y":
                    segs.append([round(pts[0][0], 4), round(pts[0][2], 4), round(pts[1][0], 4), round(pts[1][2], 4)])
                else:
                    segs.append([round(pts[0][1], 4), round(pts[0][2], 4), round(pts[1][1], 4), round(pts[1][2], 4)])
        res.setdefault("%s=%.3f" % (ax, val), {})[o.name] = segs
json.dump(res, open(out, "w"))
print("SECTION OK", list(res.keys()))