What is Simbody?

Simbody is a high-performance, industrial-grade open source C++ library providing sophisticated treatment of articulated multibody systems with special attention to the needs of biomedical simulation. It is useful for predictive dynamic simulations of diverse biological systems such as neuromuscular biomechanical models (https://simtk.org/home/opensim) and coarse-grained biomolecular modeling (https://simtk.org/home/rnatoolbox). It is also well suited to related simulation domains such as robotic and avatar simulation and control, and provides real time capabilities that make it useful for interactive scientific simulations as well as virtual worlds and games.

Simbody uses a minimal coordinate recursive formulation of the equations of motion, providing computation of system dynamics to machine precision with O(N) computational complexity for N interconnected bodies. Arbitrary adjoined constraints, contact modeling, and advanced numerical methods provide fast, robust simulation for any mechanical or biomechanical system from machines and vehicles to human skeletons and macromolecules.

Simbody is part of the SimTK biosimulation toolkit originating from Simbios, the NIH National Center for Physics-Based Simulation of Biological Structures at Stanford, funded under the NIH Roadmap for Medical Research, grant U54 GM072970. Related tools include

• Molmodel (https://simtk.org/home/molmodel), a C++ API for constructing coarse-grained, Simbody-based internal coordinate models of macromolecules like proteins and RNA, and

• OpenMM (https://simtk.org/home/openmm), a GPU-accelerated high-performance numerical library for efficient calculation of molecular force fields. OpenMM may be used standalone or through Molmodel.

Simbody is hosted on the simtk.org biosimulation community site, at https://simtk.org/home/simbody and is a community resource available for unrestricted academic, commercial, government, and personal use.

Simbody was conceived and initially implemented by Michael Sherman (Sherm), with substantial contributions from Peter Eastman, both of the Simbios Center at Stanford. Many others have contributed to the software, support, and documentation and we invite well-engineered community contributions.