kernel::sew builds an arc edge, and the wall an extruded arc sweeps, with truck's
three-point arc (circumcentre, then a turn about it). On a very flat arc that
construction ends off its own vertex: a 12 mm chord with a 0.08 um sagitta (a 225 m
radius) ends about 1e-6 mm short of it, and the planar face holding the arc, 1238 mm
from the origin, fails with "cannot attach a plane to a wire that is not on one plane".
truck's plane fit takes the sum of the wire's control points as its centre, so a gap
of that size is scaled by a distance of the order of the coordinates and tilts the
estimated normal beyond the fit's 1e-6 flatness tolerance.
Arcs whose sagitta is under 1% of the half chord are now built as their exact rational
quadratic (apex 2/(1-t^2) along the bow, weight (1-t^2)/(1+t^2), t the sagitta over the
half chord), for edges and for the extruded walls on them. Deeper arcs keep truck's
construction.
Co-authored-by: NOWN-DEV <257771410+NOWN-DEV@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
