This release of Simbody includes a smoothed compliant contact model and a few bug fixes.

• The new SmoothSphereHalfSpaceForce provides a continuous and differentiable contact model, ideal for use with gradient-based optimization algorithms (PR #667).
• Fixes a memory issue with CPodes (PR #642).
• The new CMake variable INSTALL_DOCS controls whether docs are installed (PR #655).
• Fixes a bug with calculating constraint acceleration errors (PR #670).
• Fixes Pathname::getThisExecutablePath() for FreeBSD (PR #672).
• Fixes simbody-visualizer on macOS 10.15 Catalina when using high-DPI screens. Now, simbody-visualizer is an app bundle (simbody-visualizer.app) on Mac (PR #676).

This patch release is 3.6 with minor changes:

• Fixed a bug wherein a program may crash when using the visualizer if
  the visualizer window was closed manually.

This is the first release of Simbody that requires C++11, as much of the code base now takes advantage of C++11 features. The MinGW compiler is now supported, providing an alternative to Visual C++ on Windows. This release fixes a bug in MultibodyGraphMaker where massless bodies were handled incorrectly. The state's caching mechanism is now more fine-grained ("stage versions"), though this change should not affect users in this release.

If upgrading from 3.5, you may need to make minor changes to downstream code:

• SimTK::ClonePtr's equality comparison operator previously checked equality between the underlying objects, but now checks equality between pointers.
• Support for long double has been removed.
• Some methods in SimTK::ClonePtr and SimTK::ReferencePtr have been renamed.
• SimTK::Xml was changed from a class to a namespace.

Where possible, we have deprecated previous methods rather than removing them completely.

There were numerous smaller improvements to Simbody since the previous release, in build and installation, documentation, performance, bug fixes, and small enhancements. For details, see CHANGELOG.md.

For installation instructions, see README.md.
For API documentation, see https://simbody.github.io/simbody-3.6-doxygen/api/.
For information on contributing to the Simbody project, see CONTRIBUTING.md.

If you have questions or problems, please post to the Simbody Forum.

This patch release is 3.5.3 with minor changes:

• The source will now compile on macOS with Xcode 8 and SDK MacOSX10.12.sdk.

This patch release is 3.5.2 with minor changes:

• The source will now compile on Windows with Visual C++ 2015. It has also been tested with 2013 and should still work with 2010.

There are also bug fixes for two relatively obscure problems:

• SpatialInertia::shift() and calcCompositeBodyInertias() were not correct for non-zero center of mass offsets (issue #334).
• VectorIterator was causing unnecessary copying during mesh handling (issue #349).

Same as 3.5.1 except on 64 bit Windows which now has a patched version of Lapack that
addresses an obscure error handling problem that caused trouble for some OpenSim users. This release is intended to support OpenSim; there is no reason for Simbody users to upgrade from 3.5.1 although it is harmless to do so.

The change here is a patch to Lapack 3.4.2 (64 bit) to fix the bug discussed in Issue #177 and PR #342. There were two functions where convergence failures incorrectly caused an abort (XERBLA in Lapack-speak) that bubbled up to trash an IpOpt optimization that should have recovered. See discussion on Lapack forum: http://icl.cs.utk.edu/lapack-forum/viewtopic.php?f=13&t=4586. The patched Lapack DLL is binary compatible with the previous one, same functions and ordinals.

(This patch release fixed an installation problem but is otherwise identical to 3.5.)

Release 3.5 focused primarily on infrastructure for and prototyping of rigid contact and impact, and the development of examples showing how to perform task space control using Simbody. These two projects were supported by our DARPA research subcontract with Open Source Robotics Foundation, and were integrated with Gazebo. Further development for rigid contact is required for smooth integration into Simbody; this is planned for Simbody 4.0 and only the bravest among you should attempt to use rigid contact before then. The task space control examples TaskSpaceControl-UR10 and TaskSpaceControl-Atlas can be found in the Simbody examples directory.

Chris Dembia integrated Nikolaus Hansen's Covariant Matrix Adaptation Evolution Strategy (CMA-ES) global optimizer into Simbody's existing Optimizer class framework, and implemented a multithreading capability for it. This is ready to use and we would like feedback. Thanks to Nikolaus Hansen for allowing us to include this in Simbody under the Apache 2.0 license.

There were numerous smaller improvements to Simbody since the previous release, in build and installation, documentation, performance, bug fixes, and small enhancements. There are no known incompatibilities with previous release 3.4.1 and we highly recommend that you upgrade. For details, see CHANGELOG.md.

For installation instructions, see README.md.
For information on contributing to the Simbody project, see CONTRIBUTING.md.

If you have questions or problems, please post to the Simbody Forum.

This release is functionally similar to 3.3 but has had extensive changes to build and install, mostly affecting Linux and OSX systems. The behavior should now conform better to standards on those platforms, thanks to the hard work of @scpeters and @j-rivero at Open Source Robotics Foundation and @chrisdembia at Stanford.

There are a number of bug fixes but they will not be noticed by most users. The most numerically significant is that SimbodyMatterSubsystem::getTotalCentrifugalForces() now returns the correct result (see issue #112). There are several small new features and enhancements but they were targeted narrowly at specific use cases and are likely to affect only the people who were involved in their development.

If you run into problems with the build changes, please post to the Simbody forum.

This is the first release built for use in Open Source Robotic Foundation's Gazebo robot simulator and is also the version of Simbody that ships with OpenSim 3.2. It incorporates many fixes and enhancements prompted by the integration effort with OSRF, and a new Debian builder for smooth incorporation into the Gazebo build.

This is also a stable general purpose Simbody build.

Version 3.3.1 is a minor patch to 3.3 to fix some problems compiling with Visual Studio 12 (2013) on Windows. Otherwise it is unchanged from 3.3.

This is the version of Simbody that was packaged with OpenSim 3.1. You can read more about OpenSim here: http://opensim.stanford.edu.