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: Phase 7 complete. Newton solver for all three geometries (Euclidean / Spherical / HyperIdeal), 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. 170 CGAL tests + 36 non-CGAL tests.

---

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

---

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 24 headers with descriptions	doc/api/headers.md
Test suites — 28 suites, 170 tests, individual counts	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
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
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

---

License

conformallab++ is released under the MIT License (see LICENSE).
The dissertation (Sechelmann 2016) is CC BY-SA 4.0.