P2.5.3 N-shell faces in jts-curve (OV-P2 / Bar 2)

[grootstebozewolf]

Stacked on cursor/p252-n-string-nodes-16dd @ b983f6a (draft #23, P2.5.2 N-string nodes). Do not merge this into #7. This is OV-P2 / Bar 2, not OV-P1. Does not merge #12 / #13 / #15 / #16 / #17 / #18 / #19 / #20 / #23 / #7. Does not push to feature/sfa-curve-rgr or master. P2.5.5 is not started.

Sentence

The noder is the named-miss suite, one assembly rule at a time. P2.1 nodes, P2.2 overlap-as-edge, P2.3 bite vs hole, P2.4 two-hole, hole-on-diameter, P2.5.2 N-string nodes. This rung assembles faces of N shells from that node set + those edges. Densify is never a noder. Snap-rounding is P2.5.4, not this rung: if the walk needs snap-rounding, stamp and stop. Core SegmentString / Noder is P2.5.5, 74 files, LOCKED.

What this is

P2.5.3: package-private CurveSegmentFaces in org.locationtech.jts.operation.overlayng.curve.

• faces(Geometry[]) / faces(List<List<CurveSegmentString>>, scale)
• Collects the P2.5.2 all-pairs node set and P2.2 shared-edge ends
• Splits each string at those points
• Walks next-outgoing at each node (leave-angle order)
• Returns closed rings (or null). The complementary outer ring (area = sum of the interiors) is dropped so the product is the bounded faces.

N=2 recovers the existing pair-kit faces (CAP + XOR components, count and area). A 0-node containment or a same-circle special case falls back to those kits. OverlayNG stays binary — this is the arrangement product, not an N-ary public overlay. If a pair among the N is wired as binary overlay, the existing kits stay in charge of CAP/CUP/SUB/XOR.

MIXED / pinch / holed Geometry-level stays null. Hole rings are walked as strings, as in P2.3/P2.4. A coincident leave-angle at a node (tangent pinch) is snap-rounding (P2.5.4): faces returns null with that reason. No HotPixel / ScaledNoder / core SegmentString.

No public API. Name is OverlayNGCurve.

Pins

N=2 recovers pair kits (area- and count-identical CAP+XOR):

• R1.5 two-disc lens + crescents
• R1.6-2 disc vs plain
• H-SHELL-2 two-shell lens
• H-FOUR / H-SHELL-N
• H-SHELL-N-ODD (walk stamps the tangent; pair-kit fallback recovers the rings)
• H-SAME-CIRCLE sectors (HALF_DISC × HALF_RIGHT)

Named nulls unchanged:

• H-SHELL-N-MIXED, H-ANNULUS-TANGENT, TOUCH-ext
• H-SHELL-HOLE-X Geometry-level holed pair

New N≥3 pin (existing fixtures only):

• HALF_DISC × HALF_HANGING × STADIUM_FOUR: nine bounded faces, union area 25.5π − LENS + 2, named triple / lens-sides / stadium strip / ears / hanging remainder. Permutation-identical. String-group API matches.
• HALF_DISC × HALF_HANGING × STADIUM_ODD: tangent leave-angles — stamped null (P2.5.4, not this rung).

What this is not

• Not P2.5.4 robustness / snap-rounding
• Not P2.5.5 core SegmentString / Noder (74-file blast)
• Not a merge into feature/sfa-curve-rgr / PR SFA/SQL-MM curve awareness: Curve rename, arc-aware operations, OverlayNGCurve ratchet (#1195 RGR series) #7 / locationtech master
• Not CC-NEST-ANNULUS / R1.6-honesty / H-DISC leftover overlay kits (P2.5.0)
• Not Apollonius / LEC (LEC point-site candidate completeness (NTS.Proofs 474) #22 is a different lane)
• Does not rewrite P2.1–P2.5.2 pair noder results

Verify

mvn -pl modules/curve -am test -DfailIfNoTests=false -Dcheckstyle.skip=true -Dpmd.skip=true \
  -Dtest=CurveSegmentStringTest,CompoundCurveShellOverlayTest,CircularArcOverlayTest,CircularDiscOverlayTest,CircularDiscPolygonOverlayTest,CircularLineOverlayTest,OverlayNGCurvePhase0Test,OverlayNGCurveRatchetTest,OverlayNGCurvePerfGateTest
bash dev/check-no-curved.sh
mvn -pl modules/curve checkstyle:check
mvn -pl modules/curve pmd:check

All green after this revision:

• CurveSegmentStringTest 24 / 0 (N=2 faces recover pair-kit CAP+XOR; MIXED / pinch / holed stay null; N=3 HALF_DISC × HALF_HANGING × STADIUM_FOUR is nine named faces; N≥3 tangent stamps null)
• CompoundCurveShellOverlayTest 27 / 0 (P2.1–P2.5.2 / HOLE-OUTER unchanged)
• CircularArcOverlayTest 11 / 0
• CircularDiscOverlayTest 12 / 0
• CircularDiscPolygonOverlayTest 7 / 0
• CircularLineOverlayTest 7 / 0
• OverlayNGCurvePhase0Test 19 / 0
• OverlayNGCurveRatchetTest 50 / 0
• OverlayNGCurvePerfGateTest 82 / 0 (15% slack)
• Naming-guard OK; Checkstyle 0 violations; PMD check on jts-curve succeeded

Slack stays 15%. Overlay name is OverlayNGCurve. No new public API. No noder was written in jts-core. P2.5.5 was not started.