On a B-spline face the export now takes each edgeuse's UV trim exactly as
SMLib holds it (EDGEUSE_NURBS_*): the face's parameters are SMLib's, so the
trim is the pcurve, reversed exactly (knots t -> a + b - t) where the
edgeuse runs against its edge, its knots mapped onto the edge record's
parameter where that is an affine image of SMLib's (identity for spline
edges, as_line's map for NURBS lines, the C side's map for lines), and its
end knots set to the edge interval where they differ by rounding (within
the schema's 1e-9 slack, else an error). Changed: export.rs `curves`
(per-edge TrimMap), new `trims`, `mapped`, `Face::given`,
`Edge::trim_map`, the face loop in `native_ordered`, `pcurves`,
`outer_area`.
Analytic faces and circle/ellipse edges keep brep::pcurve: SMLib keeps an
analytic face's trims on its internal rational B-spline (SmCylinder.h:
"the map from one to the other is not linear") and a circle's on its NURBS
parameter, neither an exact B-spline in the record's angle parameters.
brep::pcurve::EdgeUse gains `given`, a producer's exact pcurve taken as it
is (structure and interval checked, moved by whole periods with its loop,
never refitted). Existing construction sites (STEP reader, tests, truck
adapter) pass `given: None`; the existing tests change only for the new
field.
Built, clippy-clean and tested on 4b2c0eaf before the rebase onto
kernel-smlib/no-truck (not built: base in progress).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt
jyviko
667cd33560