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Author SHA1 Message Date
Tarik Moussa
26f4f0637d docs: citation audit + correct 8 mis-citations; add Phases 12/13
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External reviewer pass over the literature references. Verified entries
against arXiv/DOI/publisher and corrected misattributions that had
propagated across the docs.

Corrected citations (consistent across all docs):
- Bowers-Bowers-Lutz 2026: title was the 2017 paper's
  -> "Rigidity of Koebe Polyhedra and Inversive Distance Circle Packings"
- Liouville theorem: "Springborn 2019" -> Pinkall & Springborn,
  Geom. Dedicata 214 (2021)
- Bobenko-Pinkall-Springborn: "G&T 14 (2010)" -> G&T 19(4) (2015), 2155-2215
- Optimal Cone Singularities: "Crane, Soliman, Ben-Chen, Schroeder"
  -> Soliman, Slepcev, Crane, ACM TOG 37(4)
- Schlaefli formula: "Rivin, Springborn 1999" -> Rivin, Schlenker
- Quasiconformal distortion: "Springborn, Veselov" -> Born, Buecking,
  Springborn (arXiv:1505.01341)
- Period matrices: "Bobenko, Buecking 2009" (was Bobenko-Mercat-Schmies'
  title) -> Bobenko-Mercat-Schmies 2011 + genuine Bobenko-Buecking 2021
- Fabricated entry: "Alexa 2020, DOI 10.1145/3414685.3417840" pointed to
  an unrelated paper (Pixelor) -> Bunge, Herholz, Kazhdan, Botsch 2020
- Stripe Patterns: "Bonneel et al. 2015" -> Knoeppel, Crane, Pinkall,
  Schroeder 2015

Equation-number corrections (verified against the PDFs):
- Glickenstein 2011 "eq. 4.6" -> "§5.2" (no such equation label exists)
- Springborn 2020 "eq. 4.6" -> "§4 variational gradient"
- inversive-distance attribution softened to classical inversive distance

Other:
- DBFEnergy bibliography (separate repo) and convergence half-sentence in
  novelty-statement.md §3.3 (Bobenko-Buecking 2021)
- Status legend (implemented vs planned) at top of references.md
- New Phase 12 (decorated DCE & geometric transition, Chain A, near-term)
  and Phase 13 (canonical tessellations & polyhedral realisation, Chain B
  capstone) in phases.md + research-track.md; 10c scope-boundary note
  clarifying infrastructure vs Lutz-specific algorithms

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-05-29 19:17:17 +02:00
Tarik Moussa
8c01a133d8 Phase 9a: dual circle-packing functionals (CP-Euclidean + Inversive Distance)
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Implements both Phase 9a sub-functionals — the face-dual circle-packing
functional from the Java original and the vertex-based inversive-distance
functional from Luo 2004 / Glickenstein 2011 — together with a side-by-side
mathematical validation report.

CGAL test count: 194 → 205 (+11 from 9a.2, +10 from 9a.1, was already
+1 from 9a.1's setup defaults regression).

Phase 9a.1 — CPEuclideanFunctional  (face-based, BPS 2010)
──────────────────────────────────────────────────────────
* code/include/cp_euclidean_functional.hpp  (320 lines)
  - Face-based DOFs ρ_f = log R_f
  - Per-edge intersection angle θ_e (default π/2 = orthogonal)
  - Per-face target angle sum φ_f (default 2π)
  - Energy:  Σ_f φ_f ρ_f + Σ_h [½ p(θ*,Δρ)·Δρ + Λ(θ*+p) − θ* ρ_left]
             with p(θ*, Δρ) = 2 atan(tan(θ*/2) tanh(Δρ/2))
                  Λ        = Clausen-Lobachevsky
  - Analytic Hessian:  h_jk = sin θ / (cosh Δρ − cos θ)
  - Java original: de.varylab.discreteconformal.functional.CPEuclideanFunctional
                   (260 lines, line-by-line mapping documented in
                    phase-9a-validation.md §1)

* code/tests/cgal/test_cp_euclidean_functional.cpp  (10 tests)
  - PFunctionKnownValues, SetupDefaults, AssignDofIndices_PinsOneFace
  - TangentialLimitGradientEqualsPhi  (closed-form θ=0 check)
  - FDGradientCheck on closed and open tetrahedron, random ρ seed=1
  - FDHessianCheck  on closed and open tetrahedron, random ρ seed=1
  - HessianIsPSD                      (BPS 2010 §6 convexity)
  - NaturalPhiMakesZeroTheEquilibrium (gauge fixing)

Phase 9a.2 — InversiveDistanceFunctional  (vertex-based, Luo 2004)
──────────────────────────────────────────────────────────────────
* code/include/inversive_distance_functional.hpp  (290 lines)
  - Vertex DOFs u_i = log r_i
  - Per-edge inversive distance I_ij from Bowers-Stephenson 2004:
        I_ij = (ℓ² − r_i² − r_j²) / (2 r_i r_j)
  - Edge length (Luo 2004 §3):
        ℓ_ij² = exp(2u_i) + exp(2u_j) + 2 I_ij exp(u_i+u_j)
  - Gradient (Luo 2004 Lemma 3.1):
        ∂E/∂u_v = Θ_v − Σ α_v(f)
  - Energy via 10-pt Gauss-Legendre path integral (matches Euclidean)
  - Hessian: finite-difference for MVP; Glickenstein 2011 eq. 4.6
    analytic form deferred (joins Phase 9b queue)

* code/tests/cgal/test_inversive_distance_functional.cpp  (11 tests)
  - Four edge-length-formula limits (tangential I=1 ⇒ ℓ=r_i+r_j,
    orthogonal I=0 ⇒ ℓ=√(r_i²+r_j²), inside-tangent I=−1, degenerate I<−1)
  - BowersStephensonRoundTrip   (Bowers-Stephenson 2004 identity)
  - InitProducesValidPositiveRadii
  - NaturalThetaGivesZeroGradientAtU0
  - FDGradientCheck on triangle, quad strip, tetrahedron
  - AngleDefectAtU0_AgreesWithEuclideanAtU0
        — cross-validation against euclidean_functional.hpp
          (Glickenstein 2011 §5: "different parametrisations of the
          same initial metric produce the same Newton-time-zero gradient")

Phase 9a Validation Report
──────────────────────────
* doc/architecture/phase-9a-validation.md  (350 lines)
  - Line-by-line mapping CPEuclideanFunctional.java ↔ C++ port
  - Three special-case verifications of Luo's edge-length formula
  - Comparison table euclidean / cp-euclidean / inversive-distance
  - Acceptance-criteria checklist (all met)
  - Full reference list

Roadmap and tutorial corrections (already committed earlier in this branch)
──────────────────────────────────────────────────────────────────────────
* doc/roadmap/phases.md      — Phase 9a split into 9a.1 + 9a.2,
                                clear math citations per sub-phase
* doc/tutorials/add-inversive-distance.md — corrects the prior claim
                                that InversiveDistanceFunctional.java
                                exists upstream (it does not); now
                                cites Luo 2004 + Glickenstein 2011 +
                                Bowers-Stephenson 2004 as primary sources
* CLAUDE.md                  — adds phase-9a-validation.md to doc map

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-05-21 21:01:34 +02:00