surface.boundary: surfaces through boundary curves and curve networks (#763) (#2129)

* feat(geom): surfaces through curve networks, and spline spaces to build them

Adds spline_space (clamped B-spline spaces, Hermite interpolation, exact
embedding by Bézier degree elevation and knot insertion, a monotone cubic
for reparameterising) and network (loft, Coons and Gordon surfaces through
curves in one or two directions, with G1/G2 cross-boundary conditions
against a neighbouring face). Part of #763.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* feat(kernel): boundary surfaces from sketch curves, 3D curves and edges

kernel::boundary_network turns sketch chains, 3D sketch polylines and edge chains
into network curves, gives G1 frames of the faces along open edges
(EdgeFaces), builds the B-spline face (sides split at chain vertices so a
join shares the body's edges) and joins it into a surface body by stitching.
G2 is refused for now (not supported yet). Part of #763.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* fix(kernel): second derivatives of B-spline surfaces in the vendored truck-geometry

BSplineSurface::uuder and vvder multiplied the second differences by p
instead of p·(p − 1), as BSplineCurve::der2 does, so every surface of
degree p ≥ 3 (NURBS too, through its homogeneous surface) reported
1/(p − 1) of its second derivative: a cubic surface's curvature read as
half. This is why a G2 boundary surface on a cylinder measured half the
curvature it carries (#763). New tests hold both to finite differences
for degrees 2 to 5.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* feat(kernel): G2 boundary surfaces against a body's face

The network always carried the face's curvature across a G2 edge; the
refusal came from measuring it with truck's halved surface second
derivatives (fixed in the previous commit). EdgeFaces now reads the
face's second fundamental form from the exact second derivatives
instead of differencing the normal. A new test holds the curvature
across a cylinder's edge to the cylinder's within 0.1%, also with a
sheared far curve; G3 is refused (a network holds up to G2).

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* test(kernel): a boundary patch with straight corners measures its own area

A stadium's arcs meet its lines at 180°, so the Coons patch is singular
at its corners. From such a corner the reference mesher's boundary walk
ran onto the B-spline's extrapolation past its domain (a planar spline
passes through every point of its plane there), and the face measured
289 mm² for its 158.5 (#763). The vendored mesher's bounded projection
(nearest_projection, #2043) keeps the walk on the domain; this holds it
there, by the faces, the measuring mesh and the display mesh. The
display path (#1653) was never affected.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* feat(geom,kernel): three-sided boundary surfaces (one side collapsed to a point)

A network curve may be a PointCurve: the apex where the two sides beside
it meet. The curves through it cross it at the point itself, its row of
the net collapses there, and the kernel's face leaves that side out of
its loop (three edges, one vertex at the apex). One point per patch, as
a side; refused elsewhere, when it moves, or with a continuity
condition. Tests: a triangle and a quarter disc filled flat with their
analytic areas (40 mm², 25π), by geom and by the kernel's faces and
meshes.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* feat(doc): boundary surfaces through curve networks and loops of three or four

FeatureKind::SurfaceNetwork saves a network as `u` and `v` curves, each
a sketch chain (planar or 3D), a chain of a body's edges with an
optional G1/G2 continuity, or a point (the apex of a three-sided
patch), and an `operation` that can join the surface into the body of
its edges. A SurfaceBoundary of three or four sketch curves, refused
until now, builds as the flat Coons patch of its loop (three collapse
the side opposite the first curve). The format change is one pending
file; feature-walk goldens record the new variant's sketches, bodies
and points.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* feat(engine): surface.boundary through loops of three or four and curve networks

The command keeps its loop form (two to four curves of one sketch; three
and four now build the flat patch of the loop, crown refused there) and
gains a network form: `u` and `v`, each curve a sketch curve id, a
{sketch?, curves} chain (planar or 3D), a {body, edges, continuity?}
edge chain (g1/g2 with the face beside it) or a {point} for a
three-sided patch, with `operation` new or join. Edits may move between
the two forms (timeline.redefine accepts the command now that it has a
dialog).

Tests: analytic areas of loop patches and of a hyperbolic paraboloid
bounded by four 3D lines (every mesh vertex on z = xy/10), a loft
across two sketches, G1 and G2 measured across a cylinder's edge with
inspect.continuity (angle < 0.1°; curvature jump 1e-16 with G2 against
0.027 with G1), 26 hostile networks refused without panicking, and u/v
added to hostile_params_never_panic.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* feat(ui): Boundary Surface dialog

Curves and Cross curves take sketch curves and edges (picks that meet
end to end in one sketch or body are one chain); Continuity and
Operation (New Body or Join). Two to four sketch curves of one sketch
with nothing across are the loop patch; anything else is a network.
Edit Feature brings either back (per-side orders, crown and stations
the dialog does not show are kept). Strings in en, ja and zh.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* docs: ROADMAP M8 and the bridge patch's notes for boundary networks (#763)

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* test(oracle): a boundary surface through a loop, thickened (#763)

Case 83: four sketch curves (a square's three sides and a half circle
for its top) make one boundary surface, thickened 2 mm; analytic values
from tools/oracle-analytic/cases_surfaces.py (V = 2A, area 2A + 2P,
centroid by moments). Recipes gain boundary_surface, thicken and remove.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

* refactor: boundary surfaces, review cleanups

Project onto the face once per derivative evaluation (the frame is
passed to natural() and reused by scale()), keep each track's
finite-difference step instead of rescanning its table, export the
kernel's edge-pick and chain caps and the default station count for
the engine, doc and dialog to share, map TooLarge spline errors to
KernelError::TooLarge, reuse the engine's operation parser, and skip
the dialog's sketch lookup when the picks are no loop.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LGeCa5jWWdroMWvXxN3LLM

---------

Co-authored-by: jyviko <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>
Co-authored-by: bherbruck <[email protected]>

ROADMAP.md

@@ -53,7 +53,7 @@ PCB / Package, Render, Animation, Simulation, Manufacture/CAM, Drawings.
 | M5 | Persistent naming of faces and edges (docs/book/src/dev/naming.md): faces named from their exact kernel-reported history (sketch curve sides, caps, revolve sections, primitive sides, blends, shell inner walls, pattern/mirror copies; split pieces told apart by the faces around them, lumps of a cut body named after their faces), edges by their faces; fillets/chamfers, sketches on faces, shell/draft/offset/replace faces, hole placements, joint origins and face appearances resolve by name first and warn when the entity split or vanished: done. sheet metal edges by base sketch line and flange side, shell inner faces, sweep and loft roles: done. kernel-reported face history: done (merged faces answer to every name; operations without history yet fall back to geometric names, flagged unverified; format 14 keeps older designs' geometric names). Left: history through sheet metal, plastic, surface and emboss features; FaceSource certificates through history | in progress | 20 |
 | M6 | UI depth: selection feedback and origin (done), timeline editing (done: hover and selection highlight modifier faces, including fillets and chamfers; edit feature, history marker drag, dependency-checked single and multi-item reorder, suppress, rename, delete with dependents, re-resolved references; redefining selections refreshes persistent edge/face references while retaining feature identity and dimension names; optional compact named left feature history with rollback bar, multi-selection and persistent folders above the parts browser), right-docked dialogs (done), live previews for every feature dialog (done), keyboard-first commands with on-canvas value boxes and sketch inline dimensions (done), drag manipulators with automatic join/cut (done: extrude incl. two sides, fillet, shell, hole depth, move, pattern spacing, revolve rotator; taper handle open), dark theme (done), right-click menu with Repeat (done), measure tool (done), section analysis (done), selection filter (done), drag-solve of sketch points (done); appearance controls now preserve body/face/component targeting, named transparent looks, reuse/search and override removal; preferences | in progress | 6 |
 | M7 | Thin extrude (walls along open or closed curves: centre, inside, outside or two sides; mitred corners, crossing walls joined; #721), sweep, loft (incl. to a point), rib and web (to next / depth), emboss (planar faces and exact radial emboss/deboss of bounded orthogonal profiles on complete exterior cylinders/sleeves), thread (cosmetic, and modelled M3–M20 outside and inside: the ISO profile screwed in as a faceted cut), coil (smooth B-spline helical walls), pipe, pattern on path, patterns of bodies and components, replace face (parallel), align, remove, feature copy/paste: done. Unique eligible cylindrical targets are inferred for new Emboss features. Left: general curved-face emboss and exact (unfaceted) modelled threads | in progress | 12 |
-| M8 | Surface workspace (#772). Done: Patch (sketch regions; edge loops filled G0, plus `crown`), Stitch, Thicken (planes and cylinders), Extend (straight edges of planar surfaces), Trim (by a plane or a face), Delete Face (healing), Boundary Fill, zebra/draft/curvature-map analysis, Surface Extrude/Revolve/Sweep/Loft from open and closed curves, Offset, Unstitch and Reverse Normal; the continuity-driven core (`kernel/src/bridge.rs`, G0–G3 Hermite rows) with **Blend** (`surface.blend`, #764), **Match** (`surface.match`), **Boundary** (`surface.boundary`, #763 — two boundaries exact, three/four refused pending a Gregory-type corner), **Fair** (`surface.fair`, CV fairing), **continuity analysis** (`inspect.continuity`, #770; a toolbar tool with edge markers and a legend, and curvature combs along face isocurves) and a multi-section **loft** with per-end continuity and crown. Also in the Class-A pass: G1…G4 blend curves in the sketch, chord and variable-radius fillets on curved edges (with honest refusals where the fit cannot hold), and a G2 corner patch where filleted edges meet (kernel; the command refuses until the patch's sections can be sewn to the blends' contacts). Left: bias/form-factor fillet sections (design recorded), a Gregory-type corner, surface Fillet between separate surface bodies (#769), Ruled (#762), Untrim (#761), curved-face Extend (#760), loft guide rails (#201; sweep guide rails and two-rail sweeps are done, #771), and every remaining #757–#772 item | deferred | — |
+| M8 | Surface workspace (#772). Done: Patch (sketch regions; edge loops filled G0, plus `crown`), Stitch, Thicken (planes and cylinders), Extend (straight edges of planar surfaces), Trim (by a plane or a face), Delete Face (healing), Boundary Fill, zebra/draft/curvature-map analysis, Surface Extrude/Revolve/Sweep/Loft from open and closed curves, Offset, Unstitch and Reverse Normal; the continuity-driven core (`kernel/src/bridge.rs`, G0–G3 Hermite rows) with **Blend** (`surface.blend`, #764), **Match** (`surface.match`), **Boundary** (`surface.boundary`, #763 — two sketch curves exact with G0–G3, three or four as the flat patch of their loop, and curve networks: Coons and Gordon surfaces through sketch, 3D-sketch or edge curves, a point for a three-sided side, G1/G2 against the faces along one direction's edges, joined into their body on request; G1/G2 on two sides that meet at a corner waits for the Gregory-type corner), **Fair** (`surface.fair`, CV fairing), **continuity analysis** (`inspect.continuity`, #770; a toolbar tool with edge markers and a legend, and curvature combs along face isocurves) and a multi-section **loft** with per-end continuity and crown. Also in the Class-A pass: G1…G4 blend curves in the sketch, chord and variable-radius fillets on curved edges (with honest refusals where the fit cannot hold), and a G2 corner patch where filleted edges meet (kernel; the command refuses until the patch's sections can be sewn to the blends' contacts). Left: bias/form-factor fillet sections (design recorded), a Gregory-type corner, surface Fillet between separate surface bodies (#769), Ruled (#762), Untrim (#761), curved-face Extend (#760), loft guide rails (#201; sweep guide rails and two-rail sweeps are done, #771), and every remaining #757–#772 item | deferred | — |
 | M9 | Components and assemblies: New Component / Create Components from Bodies, active component, per-component origin/bodies/sketches/timeline entries, occurrences with transforms, Copy/Paste vs Paste New, nested Browser tree with visibility and isolate; Ground, Move/Copy of occurrences, joints (rigid, revolute, slider, cylindrical, pin-slot, planar, ball) by joint origins with limits and Drive Joints, closed kinematic loops (four-bar, slider-crank: the loop's other joints follow the driven one on its branch, and driving stops where a loop can no longer close), cams (`joint.cam`: a revolute cam drives a slider or revolute follower along a closed sketch profile or the cam's edges, knife, roller or flat followers, worked out again when the profile changes; drives, studies, closed loops, contact sets), As-built Joint, Rigid Group, Contact Sets (driving and motion studies stop where bodies in a set would pass through each other), Motion Study (joint values keyed along a timeline, playback, export of occurrence positions as JSON/CSV), motion analysis (joint values and a point's path charted over a study as value, velocity and acceleration; the parts that collide along a study, with the steps where they do), Exploded views (automatic or by hand, shown without changing placements); interference, per-component physical properties; STEP with assembly structure; URDF export for robot simulators (links with meshes, mass and inertia; joint chains whose values match Drive Joints; docs/urdf.md). Physical properties now measure material-aware component/occurrence placements, descendants and repeated instances, including pending moves and body reassignment offsets; contact geometry and automatic exploded centres respect those offsets. Groundwork done: component tree, occurrences with transforms (instances, Paste New), world placement, active component as authoring frame, ground, Capture/Revert Position, moving bodies and sketches. UI: ASSEMBLE panel dialogs for New Component, Joint (snaps on faces, edges, circles and vertices; animated motion preview; offsets, flip, limits), As-built Joint, Joint Origin, Rigid Group, Drive Joints (live slider), Motion Link, Cam and Interference (overlaps shown red); joints in the timeline and the Browser | in progress | 32 |
 | M10 | Sheet metal: flange (base, edge, contour), hem, unfold/refold, convert, flat pattern + DXF, rules: done. PLASTIC enclosure subset: Boss, Rib, Web, Lip/Groove, Snap Fit, Rest, Plastic Rules (library, edit, assign; rule draft and clearance as feature defaults): done, tested against hand-computed geometry. UI: SHEET METAL and PLASTIC tabs in Fusion's layout with dialogs (live preview, Edit Feature, pre-selection) for Flange, Hem, Unfold/Refold, Convert, Sheet Metal Rules, Create Flat Pattern (flat view with bend lines, bend table CSV/JSON and DXF export with exact circle/arc/line cutouts), Boss, Lip/Groove, Snap Fit, Rest, Manage and Assign Plastic Rules; Fold (bend along a sketch line); flanges meeting at a corner closed at any angle with the rule's gap; edge flanges with their own angle and height per edge in one feature; corner reliefs (notch, round, rectangular, tear) chosen by the rule; Convert to Sheet Metal from a solid or shelled body by its bend edges (flat faces, sharp bends) | in progress | 36 |
 | M11 | 2D drawings | deferred | — |