Second Lawson variant from HyperIdealConvergenceTest...WithBranchPoints.
- make_lawson_branch_points(): base + STELLAR subdivision (Java StellarLinear)
via CGAL Euler::add_center_vertex — a centre vertex per quad fan-connected to
its 4 corners (6 centres, 24 triangles, 36 edges). The 6 centres are IDEAL
vertices (b=0, v_idx=-1); θ_e=π on the 12 base edges, θ_e=π/2 on the 24 spokes.
- BranchPointsGoldenVector_JavaXVal: newton_hyper_ideal converges to the Java
golden (per symmetry class @1e-4):
original vertices → 1.3169579
base edges → 2.2924317
spoke edges → 0 (the π/2 spokes collapse to ideal)
Key insight: Java's index-based θ split (first 12 edges π, rest π/2) is
geometric — base edges vs stellar spokes — so the symmetry shortcut applies.
createLawsonHyperelliptic() NOT ported: needs a reader for the Java
conformal-data XML (lawson_curve_source.xml) + a port of
HyperIdealHyperellipticUtility, and its golden vector is not class-symmetric.
Documented as a deferred task.
243/243 cgal tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Ports the Java HyperIdealConvergenceTest (Lawson square-tiled) — the strongest
remaining @Ignore'd oracle (a hard-coded converged solution from a historical
x86 PETSc run).
- make_lawson_square_tiled(): builds the genus-2 base (4 vertices, 12 edges,
6 quads) via the low-level CGAL Surface_mesh half-edge API (add_edge +
set_target/set_next/set_face/set_halfedge), since the multi-edges (≥2 edges
per vertex pair) make add_face / OFF / polygon-soup impossible. Then
triangulate_faces → 12 triangles, 18 edges (12 original + 6 diagonals).
BuildsValidGenus2Mesh: is_valid + V=4/F=12/E=18 + χ=−2.
- ConvergenceGoldenVector_JavaXVal: Θ_v=2π, θ_e=π/2 (12 original edges),
θ_e=π (6 diagonals); newton_hyper_ideal converges (from x0=1.0, unconstrained)
to the Java golden vector:
vertices → 1.1462158341786262
original → 1.7627471737467797
aux → 2.633915794495759
asserted per symmetry class @1e-5 (robust to DOF ordering).
The perfect symmetry of the golden vector means any consistent one-diagonal
triangulation reproduces the three values, so the external jtem Triangulator
choice need not be replicated. Resolves the Tier-3 item from PR #29's analysis.
242/242 cgal tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
