[Bug] Model Initalization Error with ScaleTool and MarkerSet

[alexbeattie42]

Problem

This is an edge case issue, but I wanted to shed some light on it in case anyone runs into a similar problem. I was writing some scripts to execute the ScaleTool iteratively to make models representing each participant in the data set.

I began with the sample marker set available in the Scale testing application. This file contains a <defaults> section although I cannot definitely determine what it is used for (if it is used at all).

I noticed a very strange error when writing the iterative code that the first iteration runs successfully and then all subsequent iterations fail with the following error:

[error] Property 'min_control' has an invalid value.
(details: Minimum control cannot be less than minimum activation).

        In Object 'glut_med1_r' of type Thelen2003Muscle.
        Thrown at Thelen2003Muscle.cpp:108 in extendFinalizeFromProperties().

Solution

I found that the short term solution is to completely remove the <defaults> tag and all of its children from the MarkerSet.xml file. This allows the ScaleTool to be executed repetitively without error.

Interestingly, if the "broken" file (with the <defaults> tag) is loaded at all during the programs lifetime, all subsequent calls will fail. Even when the "working" file is loaded later, it isn't enough to fix whatever the "broken" file broke. It seems that there is some kind of caching or memory management that is causing this.

Do you have any ideas on what could be causing this behavior @nickbianco @aymanhab?

Reproduction

The full reproduction code is available here.

I am using the gait2392_thelen2003muscle.osim model and a marker set corresponding to the Kuopio Gait Dataset. The issue may also persist with other models and marker sets but I have not tested that yet.

Code snippet

std::unique_ptr<OpenSim::Model> model;
    for (int i = 0; i < iterations; i++) {
        try {
            // Works fine
            std::cout << "\nInitializing Model Regularly!" << std::endl;
            std::string modelPath = 
                SimTK::Pathname::getAbsolutePathnameUsingSpecifiedWorkingDirectory(_pathToSubject, fileNameModel);
            model = std::make_unique<OpenSim::Model>(OpenSim::Model(modelPath));
            model->initSystem();
            std::string markerSetPath = 
                SimTK::Pathname::getAbsolutePathnameUsingSpecifiedWorkingDirectory(_pathToSubject, fileNameMarkerSetBroken);
            std::cout << "Loading marker set from: " << markerSetPath << std::endl;
            // This will work the first time around the loop but cause the error on all subsequent iterations
            OpenSim::MarkerSet markerSet(markerSetPath);
            model->updateMarkerSet(markerSet);
            std::cout << "[" << i << "] Iteration Completed!" << std::endl;
        }
        catch (const OpenSim::Exception& x)
        {
            std::cerr << x.what() << std::endl;
        } 
    }

[nickbianco]

@alexbeattie42 the issue is that Thelen2003Muscle has a minimum activation property which is set to 0.01 by default. The minimum control in the model file in the test is set to 0, which is invalid. A quick solution would be to set the minimum control to 0.01, or if this model is truly only used to test scaling, just remove the default components.