thread_display_tests sewed its M10 and M12 threads from cubic Bezier pieces approximating
helices, which lie about 1e-5 mm off the core and crest cylinders. No exact (same-parameter)
pcurve exists on the cylinder for such an edge, and SolidCraft's pcurves are exact B-splines
only. Sewing refused the core face ("no exact pcurve of a B-spline on a spline surface"). Truck
had fitted one. The thread feature makes its helices exactly, with SMLib's screw sweep, so the
test now does the same: the ISO ridge's section is screw-swept and joined to the core cylinder.
The section reaches a tenth of a pitch into the core along its flanks. ridge_volume is still the
thread's exact volume, and both display tests run unchanged, from the body as made and after a
STEP round trip. Imported edges that lie off their surfaces stay refused; they are Repair Part's
job.
The quality check's sag is now measured at the surface point nearest each triangle's centre.
Before, it was read at the mean of the corners' parameters. A closed surface's parameters are
kept within one period, so a triangle across the core's seam had corners a period apart, and
their mean read 6.27 mm off a triangle that lies on the surface.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
jyvikoandClaude Opus 5.5
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