EasyAnim for MBDyn

History and Background

EasyAnim is a free visualization tool initially developed by Olivier Verlinden (Olivier DOT Verlinden AT fpms DOT ac DOT be), Faculté Polytechnique de Mons, to serve as a lightweight visualization tool for the multibody symbolic analysis tool EasyDyn.

As one of the drawbacks of MBDyn has always been the lack of a graphical user interface, EasyAnim has been used for a while as a simple visualization tool. Recently, the need for more specific visualization capabilities, and the lack of continuing support from the original Authors of EasyAnim, suggested to take over the project at Politecnico di Milano.

So we branched out of EasyAnim's main project and, thanks to its GPL license, we are now continuing development on our own. We are doing this focusing on the needs of MBDyn, in the hope that our development may be of use also to other users of EasyAnim and of other multibody analysis software.

One caveat: EasyAnim is built on top of the V library, which was a very nice attempt to provide a platform-independent, easy-to-use support for graphical user interfaces. Unfortunately, that project seems to be lagging a bit behind; however, for EasyAnim's needs, its functionalities seem to be just fine, thus the overall architecture. This library aims at providing complete support for most Un*x-like and Windows platforms. Since Windows is not currently used by MBDyn developers, compatibility of our development with Windows is not guaranteed, as we do not have resources to take care of it. Users and developers that need to use EasyAnim with Windows are encouraged to check and complete the support for Windows and contribute it back to the project.

Download

The V library
- download version 1.90 from sourceforge: v-1.90.tar.gz (a cached copy is available here ).
- you'll need this additional archive: v-1.90a-patch.tar.gz (a cached copy is available here as well).
- also, with recent versions of gcc you'll need this small patch .

EasyAnim
- the original EasyAnim (currently 1.3) from Faculté Polytechnique de Mons can be downloaded here (a cached copy is available here ).
- a patch for a pre-release of our modified version, that applies to EasyAnim 1.3, is available here .
- as an alternative, you can download a complete archive of our pre-release version of EasyAnim here .

Extra packages
- to generate MPEG movies EasyAnim uses ffmpeg; it is currently distributed with GNU/Linux by some distributions. However, it could be easily adapted to use different packages; if you have special needs, or if you implement support for other packages, please drop us a note (possibly with a patch).

Building EasyAnim

The V library
- unpack v-1.90.tar.gz (note: it unpacks in a weird directory: home/vgui)
- unpack v-1.90a-patch.tar.gz (will overwrite some files in v-1.90)
- apply v-1.90-notUsedVar.patch by executing
```
	patch -p0 < v-1.90-notUsedVar.patch
```
- follow instructions to build and install it.
EasyAnim
- unpack EasyAnim-1.3.tgz
- change directory to EasyAnim-1.3 and apply EasyAnim-1.3-ando-M.m.b.patch by executing
```
	cd EasyAnim-1.3
	patch -p0 < EasyAnim-1.3-ando-M.m.b.patch
```
  (replace M, m and b with major, minor and bugfix of the patch).
- follow instructions in EasyAnim-1.3/README to build the application. Note that there is no configure or other standard Un*x-like automatic configuration system. One may be provided in the future, but in that case it will not likely be portable to Windows...

Jinwei Shen provides some tips about building/installing EasyAnim on Debian [cached].

Use of EasyAnim

The original EasyAnim, as of version 1.3, allowed to load models (the .vol file), play simulation results referring to that model (the .van file) and play complex mode shapes either in native or in Universal File format.

The version from Politecnico di Milano added more flexibility in the model definition, while preserving full compatibility with existing .vol files.

Additional features include the possibility to generate images (.ppm), movies (.mpg) and to visualize analyses online, reading the motion information from a data stream (either LOCAL or INET sockets).

To format the output of an MBDyn analysis as required by EasyAnim, use the mbdyn2easyanim.sh script. It is installed in MBDyn's bin/ directory. It requires awk, a standard Unix stream processing utility.

After executing an analysis with MBDyn, run the script with the output file name without extension as the only argument. For example:

	mbdyn -f inputfile -o outputfile
	mbdyn2easyanim.sh outputfile

The script usually expects to find the files .log and .mov, and generates a .vol file containing the description of the model and a .van file containing the positions of the nodes for the duration of the simulation. If the .mov file is not present, no .van file is generated.

The script can generate extra items according to default patterns that exploit the amount of information in the .log file. To alter this behavior one could hack the .log file (undocumented, though; please read MBDyn's code for the purpose), or add some simple awk scripting that alters the way the .log file is handled. In detail, one can define extra items, like nodes, edges and sides, that are relative to the existing ones and thus do not require dedicated motion information. Examples will be provided in MBDyn's distribution, as long as the scripting to define those entities freezes, and helper functions will be provided as well.

The figures below present few snapshots of a tiltrotor semi-span wind-tunnel model as resulting from the plain use of the mbdyn2easyanim.sh script.

This link points to a few movies obtained from MBDyn simulations by means of different tools, including the modified version of EasyAnim.

Development

Future development will address:

the capability to handle node orientations, by reading the angular parameters that define the orientation of nodes and displaying triads as appropriate;
the capability to display entity labels;
better interaction with MBDyn (e.g. launch MBDyn from the GUI);
the capability to perform most visualization tasks with the mouse, like zooming, moving and rotating the view and so.

If you wish to cooperate, you have suggestions or you found bugs, please mail a message to the mbdyn-devel@mbdyn.org mailing list (you must subscribe first; go to mailing lists for details).

Maintained by mbdyn@aero.polimi.it