A long term goal of the Simbios center is to produce an open source simulation toolkit, which we're now calling "SimTK Core". The idea is to enable biology-oriented application programmers to exploit high quality physics-based simulation in their work, analogous to the way Kitware's open source visualization tookit VTK enables them to exploit high quality visualization. Although this has so far been a background effort for Simbios, as an enabling technology it has the potential to make a substantial long term contribution to biomedical computation.

Phase I of the SimTK Core will enable applications of "Multibody Biology"; that is, models whose components can be treated as interconnected rigid

bodies. That includes a multi-scale spectrum of biomedical applications from neuromuscular biomechanics simulations of human movement to coarse-grained models of biopolymer structure formation. It does not include systems best modeled using continuum methods, such as fluid/tissue interactions, which we hope to address in Phase II. The SimTK Core component Simbody (https://simtk.org/home/simbody), built on several lower SimTK Core layers, provides the needed multibody capability.

I will talk about the scope of multibody biology and Simbody, architecture of the SimTK Core, progress so far and future plans. I will encourage questions and discussion regarding specific uses of multibody biology in research. Finally, there is much work remaining and I will invite participation from willing and able contributors.