engineering/mech/views.py grows the two remaining view kinds. A section's cut
faces come out of the same radial profile the silhouette does, so the hatched
area and the drawn outline are one calculation and cannot disagree: a solid
shaft's half-section loop measures exactly the sum of its segment rectangles,
and a bore closes the loop on itself rather than being hatched over.
ISO 6410's section convention falls out of the model rather than being special-
cased: an internal thread's radial_edit already raises the bore to the major
diameter, so the hatch stops there. ISO 128-3's rib rule is a flag on the
feature - a pocket marked no_section_hatch is drawn and left unhatched, while
the rest of the cut face is hatched with the part's ISO 128-50 material.
Four styles, each either implemented or refused by name with the alternative
rather than approximated: full and half on a longitudinal plane through a
revolved axis; full and revolved on a transverse plane (the annulus, flattened
at 2 degrees - 0.015% of the radius, stated in CIRCLE_SEGMENTS rather than
hidden); full and offset on a prismatic part, where through features split the
cut face and pockets reduce it to the remaining thickness. A plane that misses
the part, or that grazes an outline vertex so its crossings cannot be paired, is
refused instead of producing a guessed cut face.
Details scale a circular region of a parent view, emit the ISO 128-34 circle and
letter for the parent and the "A (5:1)" label for the detail itself, and report
every feature that falls outside the circle in omitted - the honesty rule again.
Three test assertions were corrected to the measured truth rather than the
engine bent to them, each verified by running the code:
* the ISO 6410 test asked for the whole cut-face loop's minimum to be the M20
major (r=10). It is not, and must not be: over the 5 mm that is drilled but
not threaded the loop closes on the real 16 mm drill (r=8). The loop is
((0,10),(0,25),(25,25),(30,25),(30,8),(30,8),(25,8),(25,10),(0,10)). The test
now pins both spans, which is the convention it meant to assert.
* the transverse-annulus areas were pinned at rel=2e-4. An inscribed regular
180-gon is exactly 1 - (n/2pi) sin(2pi/n) = 2.0307e-4 under the circle, so
2e-4 rejects the very flattening CIRCLE_SEGMENTS declares. The tolerance is
now 2.1e-4 and the test computes the deficit and pins it, so the number is
derived rather than guessed. CIRCLE_SEGMENTS' docstring now states both
figures: 0.015% radial (the 2 degree chord's sagitta) and 0.0203% of area.
* tests/test_mech_views.py pinned VIEW_KINDS == ("front","side","top"), which
this task deliberately grows. It now pins the three orthographic kinds as the
first three and the full five-kind tuple.
_is_longitudinal takes only the plane; the plan's signature also took the part
and never read it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
