In the following brief reviews, it is my intent to be as accurate as possible in my descriptions of the capabilities of the packages with respect to rigid body dynamics with intermittent unilateral contact. If you find errors, disagree with my assessment, know of any packages that I've missed, or know that some of the packages listed are no longer available, please let me know.

Multibody Simulation Packages that can Handle Rigid Bodies with Unilateral Contacts

• Abdula
  Francios Faure's Abdula can do some pretty amazing animations; up to 64,000 frictionless spheres dropped into a bowl. The simulation method is not published, but is related to the "optimization-based animation" of Schmidl and Milenkovic. Abdula is no longer being improved as Francios is developing a more general and flexible library.
  Updated 2/1/02.
• Adams
  "Adams Solver" solves rigid body contact problems with a penalty method. It exhibited problems typical of penalty methods. For example, I tried rolling a faceted approximation of a uniform sphere on a plane and had to try many parameter settings before Solver returned a solution approximating the known exact solution.
  Updated 11/10/01.
• AERO
  Refers to itself as a physically-based animation system. This software uses a penality method to calculate the contact forces. It also uses a "fixed set of bodies instead of triangular meshes." Complementarity theory and Baraff's method are mentioned as worthy goals that are not implemented.
  Updated 1/31/02.
• Animats
  The Falling Bodies software takes a spring/damper approach with a Featherstone-type approach to articulated characters, but with very careful handling of the details. It slows down on difficult collisions, but eventually grinds its way through them.
  Updated 11/10/02.
• Cinema 4D Dynamics
  This software imulates rigid body systems and other flexible systems like cloth. Only $500. This package seems to be an equal (on paper) to "Total Havok." Excellent videos. There is no information about the method used for rigid body dynamics.
  Updated 2/2/02.
• Dance
  This is a multibody dynamics simulator based on SD/Fast and targetted at animation applications. It appears as though rigid-rigid contacts are supported through "actuator plug-ins," which can be implemented as a penalty method.
  Updated 1/31/02.
• Havok Hardcore
  A dynamics engine geared toward rigid body dynamics for real-time virtual environments. The package "Total Havok" adds flexible bodies and fluid dynamics. The demos are as impressive as any I've seen, but there is no indication of the simulation method used.
  Updated 2/3/02.
• LMS DADS
  A full-blown commercial package similar to MDI Adams. Intermittent contacts are handled, but I don't yet know the method used. However, there is mention of using DAE methods for integration, which implies that they manage contact state transistions by monitoring contact forces (as Haug did in the original DADS package).
  Updated 1/30/02.
• Open Dynamics Engine
  Free software still under development from Russell Smith who worked at Math Engine. The method of integration is based on complementarity formulations of Stewart/Trinkle and Anitescu/Potra. The solver is based on Baraff's pivoting method. Collisions are handled following Mirtich's method.
  Updated 1/29/02.
• Siconos Platform
  This software was developed for general non-smooth dynamical systems, including multi-rigid-body systems with unilateral contacts. Time-stepping is based on subproblems formulated in the form of a complementarity problem. The code has been released under the Gnu Public Licence.
  Updated 12/11/07.
• Simulation and Active Interfaces
  A rigid body dynamics engine developed by Arachi.com that is based on the algorithms of Featherstone (dynamics with bilateral constraints), Mirtich (collision impulse response), and Baraff (contact transitions e.g., sticking to sliding). A haptic interface allows real-time interaction with a virtual enviroments as long as the number of degrees of freedom and number of steady contacts is not too large.
  Updated 3/16/02.
• Umbra
  Umbra is a general simulation and visualization environment developed by Fred Oppel and Eric Gottlieb at Sandia National Laboratories. It contains a rigid body dynamics module developed by Eric Gottlieb with technical guidance from Florian Potra and Jeff Trinkle. The time-stepping algorithm is based on the Stewart-Trinkle LCP formulation (in terms of velocities and impulses). All the videos on this web page were produced with Umbra. Even though there is currently no impact law is implemented, bouncing behavior can be observed in the animations. This is simply a side effect of the constraint stabilization in the Stewart-Trinkle algorithm. Many enhancements are underway.
  Updated 12/23/02.
• visual Nastran 4D
  Formerly Working Model. The integration method for rigid body dynamics is a penalty method. Even though it probably exhibits the usual problems that plague penalty methods, vN4D ran right "out of the box" on a problem in which three parts with about 1500 facets each were dropped onto a plane such that they would collide with each other. The API does not provide access to contact point locations and normals, but is schedule to in the next release - Q1 of 2002.
  Updated 9/25/01.
• Vortex
  Specialized for rigid body dynamics with unilateral, frictional contacts. However, dry friction does not obey Coulomb's Law. There are three choices, zero friction, infinite friction, and "box" friction. Box friction is simple limits on the tangential force values in two directions - no dependency on the normal load. A first-order semi-implicit time-stepper is used. The contact constraints are likely to be formulated as a complementarity problem, since it is possible to get a warning about cycling during constraint solution. The solver is at least partially based on algorithms to solve complementarity problems. The demos are impressive.
  Updated 1/28/02.