Simbody is a high-performance, open-source toolkit for science- and engineering-quality simulation of articulated mechanisms, including biomechanical structures such as human and animal skeletons, mechanical systems like robots, vehicles, and machines, and anything else that can be described as a set of rigid bodies interconnected by joints, influenced by forces and motions, and restricted by constraints. Simbody includes a multibody dynamics library for modeling motion in generalized/internal coordinates in O(n) time. This is sometimes called a Featherstone-style physics engine.
Simbody provides a C++ API that is used to build domain-specific applications; it is not a standalone application itself. For example, it is used by biomechanists in OpenSim, by roboticists in Gazebo, and for biomolecular research in MacroMoleculeBuilder (MMB). Here's an artful simulation of several RNA molecules containing thousands of bodies, performed with MMB by Samuel Flores:
Read more about Simbody at the Simbody homepage.
Simple example: a double pendulum
Here's some code to simulate and visualize a 2-link chain:
#include "Simbody.h"
using namespace SimTK;
int main() {
// Define the system.
MultibodySystem system;
SimbodyMatterSubsystem matter(system);
GeneralForceSubsystem forces(system);
Force::Gravity gravity(forces, matter, -YAxis, 9.8);
// Describe mass and visualization properties for a generic body.
Body::Rigid bodyInfo(MassProperties(1.0, Vec3(0), UnitInertia(1)));
bodyInfo.addDecoration(Transform(), DecorativeSphere(0.1));
// Create the moving (mobilized) bodies of the pendulum.
MobilizedBody::Pin pendulum1(matter.Ground(), Transform(Vec3(0)),
bodyInfo, Transform(Vec3(0, 1, 0)));
MobilizedBody::Pin pendulum2(pendulum1, Transform(Vec3(0)),
bodyInfo, Transform(Vec3(0, 1, 0)));
// Set up visualization.
Visualizer viz(system);
system.addEventReporter(new Visualizer::Reporter(viz, 0.01));
// Initialize the system and state.
State state = system.realizeTopology();
pendulum2.setRate(state, 5.0);
// Simulate for 20 seconds.
RungeKuttaMersonIntegrator integ(system);
TimeStepper ts(system, integ);
ts.initialize(state);
ts.stepTo(20.0);
}
See Simbody's User Guide for a step-by-step explanation of this example.
Features
- Wide variety of joint, constraint, and force types; easily user-extended.
- Forward, inverse, and mixed dynamics. Motion driven by forces or prescribed motion.
- Contact (Hertz, Hunt and Crossley models).
- Gradient descent and interior point optimizers.
- A variety of numerical integrators with error control.
- Visualizer, using OpenGL.
You want to...
- install Simbody.
- use Simbody in your own program.
- view API documentation.
- learn the theory behind Simbody.
- extend Simbody.
- get support at the Simbody forum.
- report a bug or suggest a feature.
Dependencies
Simbody depends on the following:
- cross-platform building: CMake 2.8.6 or greater
- compiler: Visual Studio 2010 or 2013 (Windows only), gcc (typically on Linux), or Clang (typically on Mac)
- linear algebra: LAPACK and BLAS
- visualization (optional): FreeGLUT, Xi and Xmu
- API documentation (optional): Doxygen 1.7.2 or later
Installing
Simbody works on Windows, Mac, and Linux. For Windows, you must build from source. For Mac and Linux, you can use a package manager or build from source. In this file, we provide instructions for 4 different ways of installing Simbody:
- Windows: build from source using Microsoft Visual Studio
- Mac: install with Homebrew
- Ubuntu: install with apt-get
- UNIX (Mac, Linux): build from source using gcc or Clang with Makefile's
These are not the only ways to install Simbody, however. For example, on a Mac, you could use CMake and Xcode.
Windows and Visual Studio
Get the dependencies
We give the linear algebra dependencies to you, and Windows comes with the visualization dependencies.
- Download and install Microsoft Visual Studio. If using an Express (free) version, use Visual Studio Express 2013 for Windows Desktop or Visual C++ 2010 Express.
- Download and install CMake.
- If you want to build API documentation, download and install Doxygen as well.
Download the Simbody source code
- Method 1: Download the source code from https://github.com/simbody/simbody/releases. Look for the highest-numbered release, click on the .zip button, and unzip it on your computer. We'll assume you unzipped the source code into
C:/Simbody-source
. - Method 2: Clone the git repository.
-
Get git. There are many options: Git for Windows (most advanced), TortoiseGit (intermediate; good for TortoiseSVN users), GitHub for Windows (easiest).
-
Clone the github repository into
C:/Simbody-source
. Run the following in a Git Bash / Git Shell, or find a way to run the equivalent commands in a GUI client:$ git clone https://github.com/simbody/simbody.git C:/Simbody-source $ git checkout Simbody-3.4
-
In the last line above, we assumed you want to build a released version. Feel free to change the version you want to build. If you want to build the latest development version ("bleeding edge") of Simbody off the master branch, you can omit the
checkout
line.
-
Configure and generate project files
- Open CMake.
- In the field Where is the source code, specify
C:/Simbody-source
. - In the field Where to build the binaries, specify something like
C:/Simbody-build
, just not inside your source directory. This is not where we will install Simbody; see below. - Click the Configure button.
- Choose a "generator" that corresponds to the Visual Studio you're using. For Visual Studio 2013, select Visual Studio 12. To build as 64-bit, select an option that ends with Win64.
- Click Finish.
- Where do you want to install Simbody on your computer? Set this by changing the
CMAKE_INSTALL_PREFIX
variable. We'll assume you set it toC:/Simbody
. If you choose a different installation location, make sure to use yours where we useC:/Simbody
below. - Play around with the other build options:
BUILD_EXAMPLES
to see what Simbody can do. On by default.BUILD_TESTING
to ensure your Simbody works correctly. The tests take a long time to build, though. If you need to build Simbody quickly, maybe turn this off. On by default.BUILD_VISUALIZER
to be able to watch your system move about! If building on a cluster, you could turn this off. On by default.BUILD_STATIC_LIBRARIES
builds the three libraries as static libraries, whose names will end with_static
.BUILD_TESTS_AND_EXAMPLES_STATIC
if tests or examples are being built, creates statically-linked tests/examples. Can take a while to build, and it is unlikely you'll use the statically-linked libraries.BUILD_TESTS_AND_EXAMPLES_SHARED
if tests or examples are being built, creates dynamically-linked tests/examples. Unless you know what you're doing, leave this one on.
- Click the Configure button again. Then, click Generate to make Visual Studio project files.
Build and install
-
Open
C:/Simbody-build/Simbody.sln
in Visual Studio. -
Select your desired Solution configuration from the drop-down at the top.
- Debug: debugger symbols; no optimizations (more than 10x slower). Library names end with
_d
. - Release: no debugger symbols; optimized.
- RelWithDebInfo: debugger symbols; optimized. Bigger but not slower than Release; choose this if unsure.
- MinSizeRel: minimum size; optimized.
You at least want release libraries (the last 3 count as release), but you can have debug libraries coexist with them. To do this, go through the full installation process twice, once for each configuration.
- Debug: debugger symbols; no optimizations (more than 10x slower). Library names end with
-
Build the project ALL_BUILD by right-clicking it and selecting Build.
-
Run the tests by right-clicking RUN_TESTS and selecting Build.
-
Install Simbody by right-clicking INSTALL and selecting Build.
Play around with examples
- Make sure your configuration is set to a release configuration (e.g., RelWithDebInfo).
- Right click on one of the targets whose name begins with
Example -
and select Select as Startup Project. - Type Ctrl-F5 to start the program.
Set environment variables and test the installation
If you are only building Simbody to use it with OpenSim, you can skip this section.
- Allow executables to find Simbody libraries (.dll's) by adding the Simbody
bin/
directory to yourPATH
environment variable.- In the Start menu (Windows 7) or screen (Windows 8), search
environment
. - Select Edit the system environment variables.
- Click Environment Variables....
- Under System variables, click Path, then click Edit.
- Add
C:/Simbody/bin;
to the front of the text field. Don't forget the semicolon!
- In the Start menu (Windows 7) or screen (Windows 8), search
- Allow Simbody and other projects (e.g., OpenSim) to find Simbody. In the same Environment Variables window:
6. Under User variables for..., click New....
7. For Variable name, type
SIMBODY_HOME
. 8. For Variable value, typeC:/Simbody
. - Changes only take effect in newly-opened windows. Close any Windows Explorer or Command Prompt windows.
- Test your installation by navigating to
C:/Simbody/examples/bin
and runningSimbodyInstallTest.exe
orSimbodyInstallTestNoViz.exe
.
Layout of installation
How is your Simbody installation organized?
bin/
the visualizer and shared libraries (.dll's, used at runtime).doc/
a few manuals, as well as API docs (SimbodyAPI.html
).examples/
src/
the source code for the examples.bin/
the examples, compiled into executables; run them!simmath/
source code for examples of Simbody's SimTKmath library.
include/
the header (.h) files; necessary for projects that use Simbody.lib/
"import" libraries, used during linking.share/
CMake files that are useful for projects that use Simbody.
Mac and Homebrew
If using a Mac and Homebrew, the dependencies are taken care of for you.
With this method, Simbody is built with C++11 (the -std=c++11
compiler flag). Thus, any projects you build on top of Simbody must also use C++11. See issue #125.
Install
-
Install Homebrew.
-
Open a terminal.
-
Add the Open Source Robotics Foundation's list of repositories to Homebrew:
$ brew tap osrf/simulation
-
Install the latest release of Simbody.
$ brew install simbody
To install from the master branch instead, append
--HEAD
to the command above.
Where is Simbody installed?
Simbody is now installed to /usr/local/Cellar/simbody/<version>/
, where <version>
is either the version number (e.g., 3.4
), or HEAD
if you specified --HEAD
above.
Some directories are symlinked (symbolically linked) to /usr/local/
, which is where your system typically expects to find executables, shared libraries (.dylib's), headers (.h's), etc. The following directories from the Simbody installation are symlinked:
include/simbody -> /usr/local/include/simbody
lib -> /usr/local/lib
share/doc/simbody -> /usr/local/share/doc/simbody
Layout of installation
What's in the /usr/local/Cellar/simbody/<version>/
directory?
include/simbody/
the header (.h) files; necessary for projects that use Simbody.lib/
shared libraries (.dylib's), used at runtime.cmake/simbody/
CMake files that are useful for projects that use Simbody.pkgconfig/
pkg-config files useful for projects that use Simbody.simbody/examples/
the examples, compiled into executables; run them!
libexec/simbody/
thesimbody-visualizer
executable.share/doc/simbody/
a few manuals, as well as API docs (SimbodyAPI.html
).examples/
source code for the examples.
Ubuntu and apt-get
You can currently get Simbody via the Open Source Robotics Foundation's Debian repositories. We are currently working on getting Simbody directly into the Debian repositories. apt-get
will take care of getting the necessary dependencies.
With this method, Simbody is built with C++11 (the -std=c++11
compiler flag). Thus, any projects you build on top of Simbody must also use C++11. See issue #125.
Install
-
Setup your computer to accept software from packages.osrfoundation.org. This step depends on your version of Ubuntu. For more detailed instructions, see OSRF's installation instructions.
-
12.04:
sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu precise main" > /etc/apt/sources.list.d/gazebo-latest.list'
-
13.10:
sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu saucy main" > /etc/apt/sources.list.d/gazebo-latest.list'
-
-
Install Simbody.
$ sudo apt-get update $ sudo apt-get install libsimbody-dev
Layout of installation
Simbody is installed into the usr/
directory.
usr/include/simbody/
the header (.h) files; necessary for projects that use Simbody.usr/lib/
shared libraries (.so's), used at runtime.cmake/simbody/
CMake files that are useful for projects that use Simbody.pkgconfig/
pkg-config files useful for projects that use Simbody.
usr/libexec/simbody/
thesimbody-visualizer
executable.usr/share/doc/simbody/
a few manuals, as well as API docs (SimbodyAPI.html
).
UNIX and Makefiles
These instructions are for building Simbody from source on either a Mac or on Ubuntu.
Get dependencies
On a Mac, the Xcode developer package gives LAPACK and BLAS to you via the Accelerate framework. Mac's come with the visualization dependencies.
On Ubuntu, we need to get the dependencies ourselves. Open a terminal and run the following commands.
- Get the necessary dependencies:
$ sudo apt-get install cmake liblapack-dev
- If you want to use the CMake GUI, install
cmake-qt-gui
. - For visualization (optional):
$ sudo apt-get install freeglut3-dev libxi-dev libxmu-dev
- For API documentation (optional):
$ sudo apt-get install doxygen
Get the Simbody source code
There are two ways to get the source code.
- Method 1: Download the source code from https://github.com/simbody/simbody/releases. Look for the highest-numbered release, click on the .zip button, and unzip it on your computer. We'll assume you unzipped the source code into
~/simbody-source
. - Method 2: Clone the git repository.
-
Get git.
- Mac: You might have it already, especially if you have Xcode, which is free in the App Store. If not, one method is to install Homebrew and run
brew install git
in a terminal. - Ubuntu: run
sudo apt-get install git
in a terminal.
- Mac: You might have it already, especially if you have Xcode, which is free in the App Store. If not, one method is to install Homebrew and run
-
Clone the github repository into
~/simbody-source
.$ git clone https://github.com/simbody/simbody.git ~/simbody-source $ git checkout Simbody-3.4
-
In the last line above, we assumed you want to build a released version. Feel free to change the version you want to build. If you want to build the latest development version ("bleeding edge") of Simbody off the master branch, you can omit the
checkout
line.
-
Configure and generate Makefiles
-
Create a directory in which we'll build Simbody. We'll assume you choose
~/simbody-build
. Don't choose a location inside~/simbody-source
.$ mkdir ~/simbody-build $ cd ~/simbody-build
-
Configure your Simbody build with CMake. We'll use the
cmake
command but you could also use the interactive toolsccmake
orcmake-gui
. You have a few configuration options to play with here.-
If you don't want to fuss with any options, run:
$ cmake ~/simbody-source
-
Where do you want to install Simbody? By default, it is installed to
/usr/local/
. That's a great default option, especially if you think you'll only use one version of Simbody at a time. You can change this via theCMAKE_INSTALL_PREFIX
variable. Let's choose~/simbody
:$ cmake ~/simbody-source -DCMAKE_INSTALL_PREFIX=~/simbody
-
Do you want to use C++11? By default, Simbody assumes yes. If you plan to use Simbody in a project that DOES use C++11, then you must build Simbody with C++11 as well. You can change this via the
SIMBODY_STANDARD_11
variable:$ cmake ~/simbody-source -DSIMBODY_STANDARD_11=off
-
Do you want the libraries to be optimized for speed, or to contain debugger symbols? You can change this via the
CMAKE_BUILD_TYPE
variable. There are 4 options:- Debug: debugger symbols; no optimizations (more than 10x slower). Library names end with
_d
. - Release: no debugger symbols; optimized.
- RelWithDebInfo: debugger symbols; optimized. Bigger but not slower than Release; choose this if unsure.
- MinSizeRel: minimum size; optimized.
You at least want release libraries (the last 3 count as release), but you can have debug libraries coexist with them. To do this, go through the full installation process twice, once for each configuration. It is typical to use a different build directory for each build type (e.g.,
~/simbody-build-debug
and~/simbody-build-release
). - Debug: debugger symbols; no optimizations (more than 10x slower). Library names end with
-
There are a few other variables you might want to play with:
BUILD_EXAMPLES
to see what Simbody can do. On by default.BUILD_TESTING
to ensure your Simbody works correctly. The tests take a long time to build, though. If you need to build Simbody quickly, maybe turn this off. On by default.BUILD_VISUALIZER
to be able to watch your system move about! If building on a cluster, you could turn this off. On by default.BUILD_STATIC_LIBRARIES
builds the three libraries as static libraries, whose names will end with_static
.BUILD_TESTS_AND_EXAMPLES_STATIC
if tests or examples are being built, creates statically-linked tests/examples. Can take a while to build, and it is unlikely you'll use the statically-linked libraries.BUILD_TESTS_AND_EXAMPLES_SHARED
if tests or examples are being built, creates dynamically-linked tests/examples. Unless you know what you're doing, leave this one on.
You can combine all these options. Here's another example:
$ cmake ~/simbody-source -DCMAKE_INSTALL_PREFIX=~/simbody -DCMAKE_BUILD_TYPE=RelWithDebInfo -DBUILD_VISUALIZER=off
-
Build and install
-
Build the API documentation. This is optional, and you can only do this if you have Doxygen.
$ make doxygen
-
Compile. Use the
-jn
flag to build usingn
processor cores. For example:$ make -j8
-
Run the tests.
$ ctest -j8
-
Install. If you chose
CMAKE_INSTALL_PREFIX
to be a location which requires sudo access to write to (like/usr/local/
, prepend this command with asudo
.$ make -j8 install
Just so you know, you can also uninstall (delete all files that CMake placed into CMAKE_INSTALL_PREFIX
) if you're in ~/simbody-build
.
$ make uninstall
Play around with examples
From your build directory, you can run Simbody's example programs. For instance, try:
$ ./ExamplePendulum
Set environment variables and test the installation
If you are only building Simbody to use it with OpenSim, you can skip this section.
-
Allow executables to find Simbody libraries (.dylib's or so's) by adding the Simbody lib directory to your linker path.
-
If your
CMAKE_INSTALL_PREFIX
is/usr/local/
, run:$ sudo ldconfig
-
If your
CMAKE_INSTALL_PREFIX
is neither/usr/
nor/usr/local/
(e.g.,~/simbody
'):-
Mac:
$ echo 'export DYLD_LIBRARY_PATH=$DYLD_LIBRARY_PATH:~/simbody/lib' >> ~/.bash_profile
-
Ubuntu:
$ echo 'export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:~/simbody/lib/x86_64-linux-gnu' >> ~/.bashrc
These commands add a line to a configuration file that is loaded every time you open a new terminal. If using Ubuntu, you may need to replace
x86_64-linux-gnu
with the appropriate directory on your computer. -
-
-
Allow Simbody and other projects (e.g., OpenSim) to find Simbody. Make sure to replace
~/simbody
with yourCMAKE_INSTALL_PREFIX
.-
Mac:
$ echo 'export SIMBODY_HOME=~/simbody' >> ~/.bash_profile
-
Ubuntu:
$ echo 'export SIMBODY_HOME=~/simbody' >> ~/.bashrc
-
-
Open a new terminal.
-
Test your installation:
$ cd ~/simbody/share/doc/simbody/examples/bin $ ./SimbodyInstallTest # or ./SimbodyInstallTestNoViz
Layout of installation
The installation creates the following directories in CMAKE_INSTALL_PREFIX
. The directory [x86_64-linux-gnu]
only exists if you're using a recent version of Ubuntu (e.g., 13.10) and did NOT install to /usr/local/
. Even in that case, the name of your directory may be different.
include/simbody/
the header (.h) files; necessary for projects that use Simbody.lib/[x86_64-linux-gnu]/
shared libraries (.dylib's or .so's), used at runtime.cmake/simbody/
CMake files that are useful for projects that use Simbody.pkgconfig/
pkg-config files useful for projects that use Simbody.simbody/examples/
the examples, compiled into executables; run them!
libexec/simbody/
thesimbody-visualizer
executable.share/doc/simbody/
a few manuals, as well as API docs (SimbodyAPI.html
).examples/
source code for the examples.