b7e837815f
Closes the UX gap identified in the Phase-8b-Lite design discussion:
the four classical-DCE CGAL entries now optionally run their `*_layout()`
step internally if the caller supplies `CGAL::parameters::output_uv_map(pmap)`.
Before this PR, the workflow was:
auto res = CGAL::discrete_conformal_map_euclidean(mesh);
// ... user has to re-set up maps, re-pin vertex, then ...
auto layout = euclidean_layout(mesh, res.x, maps);
// ... and copy coordinates into a property map manually.
After this PR:
auto uv = mesh.add_property_map<Vertex_index, K::Point_2>("uv", ...).first;
CGAL::discrete_conformal_map_euclidean(
mesh, CGAL::parameters::output_uv_map(uv));
// ... uv now populated for every vertex.
Coverage
────────
* `discrete_conformal_map_euclidean` — `Point_2` per vertex.
* `discrete_conformal_map_spherical` — `Point_3` per vertex (on S²).
* `discrete_conformal_map_hyper_ideal` — `Point_2` per vertex (Poincaré disk).
CP-Euclidean and Inversive-Distance entries do not yet support
`output_uv_map` — face-based packing has no per-vertex UV concept, and
inversive-distance needs a dedicated layout routine that uses Luo's
edge-length formula (planned follow-up).
New named parameters (`code/include/CGAL/Conformal_map/internal/parameters.h`)
─────────────────────────────────────────────────────────────────────────────
* `output_uv_map(pmap)` — write coordinates into pmap after layout.
* `normalise_layout(bool)` — apply post-layout canonical normalisation
(PCA centroid for Euclidean, north-pole alignment for Spherical,
Möbius centring for Hyper-ideal).
Both follow the existing Phase-8a-MVP named-parameter convention.
Chained syntax (`.output_uv_map(...).normalise_layout(true)`) is not
yet supported — pass them one at a time.
Tests (5 new in test_cgal_phase8b_lite.cpp)
───────────────────────────────────────────
* `OutputUvMap_Euclidean_PopulatesPmap` — UVs are finite + non-trivial.
* `OutputUvMap_Spherical_PopulatesXyz` — every output on unit S².
* `OutputUvMap_HyperIdeal_PointsInPoincareDisk` — |p|² ≤ 1 if converged.
* `OutputUvMap_Absent_DoesNotRunLayout` — no parameter ⇒ no layout.
* `OutputUvMap_NormaliseLayout_TakesEffect` — both raw + norm calls
return finite UVs (named-parameter chaining limitation documented).
All five pass. Full CGAL suite: 232/232, 0 skipped (was 227).
doc/api/tests.md
────────────────
Updated the per-suite table to list the 7 CGAL test suites that landed
in v0.9.0 (8a MVP + 9a + 9b + 8b-Lite) but had not yet been added to the
canonical table. Total: 227 → 232. This brings the doc back in sync
with `ctest` output and unblocks future `scripts/check-test-counts.sh`
runs.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
conformallab++
C++17 reimplementation of ConformalLab — Stefan Sechelmann's Java research library for discrete conformal geometry (TU Berlin). The long-term goal is a CGAL package for discrete conformal maps.
Algorithmic foundation:
Stefan Sechelmann — Variational Methods for Discrete Surface Parameterization: Applications and Implementation, TU Berlin 2016. DOI: 10.14279/depositonce-5415 · CC BY-SA 4.0 · Java original · sechel.de
Status: v0.9.0 — Phases 1–9a complete, Phase 8b-Lite CGAL API surface. Newton solvers for five DCE models (Euclidean / Spherical / HyperIdeal / CP-Euclidean / Inversive-Distance), priority-BFS layout in ℝ²/S²/Poincaré disk, Gauss–Bonnet, tree-cotree cut graph, Möbius holonomy, period matrix (genus 1), fundamental domain, halfedge_uv texture atlas, JSON/XML serialisation, CLI app. Full test suite passing, 0 skipped — see doc/api/tests.md for the per-suite breakdown.
Quick start
git clone https://codeberg.org/TMoussa/ConformalLabpp && cd ConformalLabpp
# Fast tests — no system dependencies
cmake -S code -B build && cmake --build build --target conformallab_tests -j$(nproc)
ctest --test-dir build --output-on-failure
# CGAL tests headless (apt install libboost-dev / brew install boost)
cmake -S code -B build -DWITH_CGAL_TESTS=ON
cmake --build build --target conformallab_cgal_tests -j$(nproc)
ctest --test-dir build -R "^cgal\." --output-on-failure
# Full build with CLI + viewer (requires Wayland/X11 dev headers)
cmake -S code -B build -DWITH_CGAL=ON && cmake --build build -j$(nproc)
./bin/conformallab_core -i input.off -g euclidean -o layout.off -j result.json
# API documentation (requires doxygen: brew/apt install doxygen)
cmake --build build --target doc
open doc/doxygen/html/index.html
Minimal usage
#include "conformal_mesh.hpp"
#include "mesh_io.hpp"
#include "euclidean_functional.hpp"
#include "gauss_bonnet.hpp"
#include "newton_solver.hpp"
#include "layout.hpp"
using namespace conformallab;
ConformalMesh mesh = load_mesh("input.off");
EuclideanMaps maps = setup_euclidean_maps(mesh);
compute_euclidean_lambda0_from_mesh(mesh, maps);
// Assign DOFs — pin first vertex (gauge fix)
auto vit = mesh.vertices().begin();
maps.v_idx[*vit++] = -1;
int idx = 0;
for (; vit != mesh.vertices().end(); ++vit) maps.v_idx[*vit] = idx++;
// Natural equilibrium target: x* = 0 by construction
std::vector<double> x0(idx, 0.0);
auto G0 = euclidean_gradient(mesh, x0, maps);
for (auto v : mesh.vertices())
if (maps.v_idx[v] >= 0) maps.theta_v[v] -= G0[maps.v_idx[v]];
check_gauss_bonnet(mesh, maps);
NewtonResult res = newton_euclidean(mesh, x0, maps);
Layout2D layout = euclidean_layout(mesh, res.x, maps);
Documentation
| Getting started — build modes, single-test invocation, CLI, Docker | doc/getting-started.md |
| Pipeline API — all three geometries, holonomy, serialisation | doc/api/pipeline.md |
| Public headers — all public headers with descriptions | doc/api/headers.md |
| Test suites — per-suite breakdown and counts (single source of truth) | doc/api/tests.md |
| Extending — new functionals, geometry modes, porting from Java | doc/api/extending.md |
| Processing unit contracts — preconditions / provides table | doc/api/contracts.md |
| CGAL package design — Phase 8 target, YAML pipeline | doc/api/cgal-package.md |
| Architecture & pipeline diagram | doc/architecture/overall_pipeline.md |
| geometry-central comparison — shared core, demarcation, adoption candidates, scientific added value | doc/architecture/geometry-central-comparison.md |
| Design decisions — key architectural choices + rationale | doc/architecture/design-decisions.md |
| Project structure — directory tree + build targets | doc/architecture/project-structure.md |
| Discrete conformal theory — mathematical background for collaborators | doc/math/discrete-conformal-theory.md |
| Validation — known analytic results + how to verify them | doc/math/validation.md |
| Validation protocol — concrete commands with expected outputs | doc/math/validation-protocol.md |
| Tutorial: add a new functional — step-by-step Inversive-Distance port | doc/tutorials/add-inversive-distance.md |
| Declarative YAML pipeline — concept, token vocabulary, 5 examples | doc/concepts/declarative-pipeline.md |
| Geometry modes — Euclidean / Spherical / HyperIdeal comparison | doc/math/geometry-modes.md |
| References — all papers by module | doc/math/references.md |
| Software landscape — how conformallab++ relates to libigl, CGAL, geometry-central | doc/math/software-landscape.md |
| Novelty statement — unique features, target audience, what this is not | doc/math/novelty-statement.md |
| Complexity & scalability — O() analysis, measured timings on real meshes, HyperIdeal bottleneck | doc/math/complexity.md |
| Roadmap — Phases 1–10 | doc/roadmap/phases.md |
| Java parity table — what is ported, what is planned | doc/roadmap/java-parity.md |
| Contributing — language policy, test standards, release flow | doc/contributing.md |
| Claude Code context | CLAUDE.md |
Citing
If you use conformallab++ in your research, please cite it using the metadata
in CITATION.cff. GitHub and Codeberg show a "Cite this repository"
button that generates BibTeX and APA automatically.
The primary algorithmic source is:
Stefan Sechelmann — Variational Methods for Discrete Surface Parameterization: Applications and Implementation, TU Berlin 2016. DOI: 10.14279/depositonce-5415
Bugs & questions
- Bug reports / feature requests: Gitea Issues
- Code mirror (read-only): Codeberg
- Contact: Tarik Moussa · Tarik.moussa95@gmail.com
License
conformallab++ is released under the MIT License (see LICENSE).
Copyright © 2024–2026 Tarik Moussa.
The dissertation (Sechelmann 2016) is CC BY-SA 4.0.