simtk.org

Hi,

I'm running the default CustomActuator example in the OpenSim APIExamples directory with the visualizer turned on (Ubuntu 10.04 + OpenSim 3.1 + Simbody 3.1)and I see this strange behavior. Sometimes the example runs without any error with the visualizer running fine, but most of the time it results in the following error:

VisualizerGUI listenerThread: unrecoverable error:
SimTK Exception thrown at VisualizerGUI.cpp:2423:
Error detected by Simbody method listenForInput(): Unexpected command 137 received from VisualizerGUI. Can't continue.
(Required condition '!"unrecognized command"' was not met.)

Exiting

It would be helpful if someone could comment on what might be causing this. Thanks.

Regards,
Priyanshu

Hi, Priyanshu.

I don't think we have ever seen that error here. A few thoughts:

1) The VisualizerGUI is a standalone executable that is launched from the runtime library and has to be located. To do that it checks environment variables, guesses standard installation locations and so on. First it looks in the same directory as the currently executing program (the example that you are running). Then it tries bin subdirectories of environment variable locations OPENSIM_HOME, then SIMBODY_HOME, then SimTK_INSTALL_DIR. If it is possible that you have an out-of-date version of the VisualizerGUI lurking in one of those locations, that might explain the behavior.

2) I don't think we have built 3.1 on Ubuntu 10.04. The oldest we've tried is Ubuntu 12.04. I don't know of any reason it wouldn't work in 10.04 but that is a possibility since we haven't tried it.

Regards,
Sherm

Hi Michael,

Thanks for your suggestions. I checked the various locations you mentioned and just found the Simbody 3.1 version accessible through those paths. I also checked the various examples employing the visualizer in Simbody and found a similar behavior with some of the examples. For example, ChainExample does not execute properly and results in the error whereas ExampleGears run with absolutely no error. Also, the standalone VisualizerGUI runs fine.

Everything runs fine on Ubuntu 12.04. The reason I am sticking to 10.04 is due to RTAI patch which works with that version. I'm planning to use the visualizer for real-time rending of an actuated mechanism by running the control loop and visualizer on parallel threads. What is strange is the fact that the same code runs fine at the first time (almost always) and results in the error (sort of randomly in later executions). Thanks.

Regards,
Priyanshu

You probably thought of this already, but this could conceivably be a GPU driver problem. Also I have seen odd behavior due to emulated drivers such as come with virtual machines. Anyway you might check to see if there is an upgraded 10.04 driver for your board if you haven't done so already.

Sherm

Hi Michael,

Yes, it might be a driver problem. I'm using the latest proprietary NVIDIA driver which seems to be running fine for other applications. I'll look into switching to open-source nouveau driver and see if it helps. Thanks.

Regards,
Priyanshu