Assembly constraint solver for Kindred Create. Combines a numerical multibody dynamics engine (OndselSolver) with a GNN-based constraint prediction layer.

Components

OndselSolver (C++)

Numerical assembly constraint solver using multibody dynamics. Solves joint constraints between rigid bodies using a Newton-Raphson iterative approach. Used by FreeCAD's Assembly workbench as the backend solver.

Source: OndselSolver/
Entry point: OndselSolverMain/
Tests: tests/, testapp/
Build: CMake

Theory: MbDTheory

Building

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

ML Solver Layer (Python)

Graph neural network that predicts constraint independence and per-body degrees of freedom. Trained on synthetic assembly data generated via the pebble game algorithm, with the goal of augmenting or replacing the numerical solver for common assembly patterns.

Core library: solver/
Data generation: solver/datagen/ (pebble game, synthetic assemblies, labeling)
Model architectures: solver/models/ (GIN, GAT, NNConv)
Training: solver/training/
Inference: solver/inference/
FreeCAD integration: freecad/
Configuration: configs/ (Hydra)

Setup

pip install -e ".[train,dev]"
pre-commit install

Usage

make help          # show all targets
make dev           # install all deps + pre-commit hooks
make test          # run tests
make lint          # run ruff linter
make check         # lint + type-check + test
make data-gen      # generate synthetic data
make train         # run training
make export        # export model

Docker is also supported:

docker compose up train       # GPU training
docker compose up test        # run tests
docker compose up data-gen    # generate synthetic data

Repository structure

kindred-solver/
├── OndselSolver/       # C++ numerical solver library
├── OndselSolverMain/   # C++ solver CLI entry point
├── tests/              # C++ unit tests + Python tests
├── testapp/            # C++ test application
├── solver/             # Python ML solver library
│   ├── datagen/        # Synthetic data generation (pebble game)
│   ├── datasets/       # PyG dataset adapters
│   ├── models/         # GNN architectures
│   ├── training/       # Training loops
│   ├── evaluation/     # Metrics and visualization
│   └── inference/      # Runtime prediction API
├── freecad/            # FreeCAD workbench integration
├── configs/            # Hydra configs (dataset, model, training, export)
├── scripts/            # CLI utilities
├── data/               # Datasets (not committed)
├── export/             # Model packaging
└── docs/               # Documentation

License

OndselSolver: LGPL-2.1-or-later (see LICENSE) ML Solver Layer: Apache-2.0