Simple is a new (differentiable) physical engine based on recent progress on solving contact simulation and leveraging Pinocchio for fast dynamics computations and Coal for efficient collision detection. While first targetting robotics applications, Simple can be exploited in many other contexts: video games, system design, graphical animations, biomechanics, etc.

Simple is developed by the WILLOW team at Inria. The code associated with Simple has been released on May, 26th 2025 under the permissive BSD-3 license.

More features and improved efficiency will come soon. And as Jean de La Fontaine wrote: "Patience and time do more than strength or passion".

The following persons actively took part in the development of Simple:

• Justin Carpentier (Inria): core developer and project instigator
• Quentin Le Lidec (Inria): core developer
• Louis Montaut (Inria): core developer
• Joris Vaillant (Inria): core developer
• Yann de Mont-Marin (Inria): core developer
• Ajay Sathya (Inria): feature contributor
• Fabian Schramm (Inria): feature contributor

External contributions are more than welcome. If you have contributed to the development of Simple, feel free to add your name.

Simple is built on active research around understanding and enhancing physical simulation. Interested readers can learn more about the algorithmic and computational foundations of Simple by reading these publications:

• Le Lidec, Q., Montaut, L. & Carpentier, J. (2024, July). From Compliant to Rigid Contact Simulation: a Unified and Efficient Approach. In RSS 2024-Robotics: Science and Systems.
• Montaut, L., Le Lidec, Q., Petrik, V., Sivic, J., & Carpentier, J. (2024). GJK++: Leveraging Acceleration Methods for Faster Collision Detection. IEEE Transactions on Robotics.
• Sathya, A., & Carpentier, J. (2024). Constrained Articulated Body Dynamics Algorithms. IEEE Transactions on Robotics.
• Montaut, L., Le Lidec, Q., Bambade, A., Petrik, V., Sivic, J., & Carpentier, J. (2023, May). Differentiable collision detection: a randomized smoothing approach. In 2023 IEEE International Conference on Robotics and Automation (ICRA).
• Le Lidec, Q., Jallet, W., Montaut, L., Laptev, I., Schmid, C., & Carpentier, J. (2023). Contact models in robotics: a comparative analysis. IEEE Transactions on Robotics.
• Montaut, L., Le Lidec, Q., Petrik, V., Sivic, J., & Carpentier, J. (2022, June). Collision Detection Accelerated: An Optimization Perspective. In Robotics: Science and Systems (RSS 2O22).
• Carpentier, J., Budhiraja, R., & Mansard, N. (2021, July). Proximal and sparse resolution of constrained dynamic equations. In Robotics: Science and Systems (RSS 2021).
• Carpentier, J., & Mansard, N. (2018, June). Analytical derivatives of rigid body dynamics algorithms. In Robotics: Science and systems (RSS 2018).