Add Moco 3D tracking example with foot-ground contact #4008

nickbianco · 2025-01-31T21:34:19Z

Fixes issue #3960

Brief summary of changes

This change adds example3DWalking.cpp, an example that demonstrates how to create a simulation of walking tracking both kinematics and ground reaction forces using a contact model. This example lives inside the example3DWalking folder and relies on the existing reference data there, some of which was modified to accommodate the new example while still working for exampleMocoInverse and exampleMocoTrack. New reference files were added to allow adding contact forces to the model and for loading in marker weights based on an IKTaskSet.

The following minor additions are included in this PR which are incorporated in the new/updated examples:

Added ModelFactory::createResidualActuators and ModOpAddResiduals to make it easy to add a set of residual actuators to a model.
Updated ModelFactory::createReserveActuators and ModOpAddReserves with changes that make them compatible with the new residual utility methods.
Added convenience methods to MocoTrack to allow setting marker weights from a Set<MarkerWeight> or IKTaskSet.
Added a const-qualifier to IKTaskSet::createMarkerWeightSet.
Minor improvements and changes to exampleMocoInverse and exampleMocoTrack based on the updated reference data and the new utility methods.

Testing I've completed

WIP: testing all updated examples to make sure results are consistent across C++, Python, and Matlab.

Looking for feedback on...

I tried to check carefully that all updated examples are consistent with each other, but additional spot checking during review would be helpful.

CHANGELOG.md (choose one)

updated.

This change is

… examples

…p Moco problem to create initial guess

…r class

…dd other minor fixes

carmichaelong

awesome to have an example like this. looks good overall, just some minor comments

Reviewed 23 of 23 files at r1, all commit messages.
Reviewable status: all files reviewed, 9 unresolved discussions (waiting on @aymanhab)

Bindings/Python/examples/Moco/example3DWalking/exampleMocoTrack.py line 219 at r1 (raw file):

    problem = study.updProblem()

    # Set the control effort weights.

i wonder if this is a good place to be a little more explicit in the comments here to emphasize how this sets a weight of 0.1 for all controls except for the pelvis wiht a weight of 10 using a wildcard pattern (something of that nature)

OpenSim/Examples/Moco/example3DWalking/subject_walk_scaled_ContactForceSet.xml line 77 at r1 (raw file):

                <socket_half_space>/contactgeometryset/floor</socket_half_space>
                <!--The stiffness constant (i.e., plain strain modulus), default is 1 (N/m^2)-->
                <stiffness>306777.59999999998</stiffness>

nit: this and the left side have slightly different stiffness than the other contact spheres (~1.6 larger)

CHANGELOG.md line 76 at r1 (raw file):

- Remove unused, legacy `<defaults>` blocks in `.osim` and `.xml` files (#3986).
- Added `example3DWalking`, which demonstrates how to create a tracking simulation with foot-ground contact in Moco. (#4008)
- Added `ModelFactory::createResidualActuators` and `ModOpAddResiduals` to make it easy to add a set of residual actuators to a model. (#4008)

could also mention the change to the similar function for reserves so that folks know they can now set reserves and residuals separately along with this new function

Bindings/Java/Matlab/examples/Moco/example3DWalking/example3DWalking.m line 43 at r1 (raw file):

    % Set minimum muscle controls and activations to 0 (default is 0.01).
    actuators = model.updActuators();

can you use updMuscles() here?

Bindings/Java/Matlab/examples/Moco/example3DWalking/example3DWalking.m line 178 at r1 (raw file):

    % Construct the MocoTrack problem.
    track = MocoTrack();
    track.setName('track_walking');

can use studyName here

Bindings/Python/examples/Moco/example3DWalking/example3DWalking.py line 86 at r1 (raw file):

    # Construct the MocoTrack problem.
    track = osim.MocoTrack()
    track.setName('track_walking')

can use study_name here

Bindings/Python/examples/Moco/example3DWalking/example3DWalking.py line 237 at r1 (raw file):

# Set minimum muscle controls and activations to 0 (default is 0.01).
actuators = model.updActuators()

is it possible to use updMuscles() instead and then not have to use the if?

OpenSim/Examples/Moco/example3DWalking/subject_walk_scaled.osim line 14393 at r1 (raw file):

					<socket_parent_frame>/bodyset/toes_l</socket_parent_frame>
					<!--The fixed location of the station expressed in its parent frame.-->
					<location>0.0877793 0.0428623 0.0226433</location>

this isn't symmetric with marker R.Toe. intentional?

OpenSim/Examples/Moco/example3DWalking/subject_walk_scaled.osim line 14409 at r1 (raw file):

					<socket_parent_frame>/bodyset/toes_l</socket_parent_frame>
					<!--The fixed location of the station expressed in its parent frame.-->
					<location>0.00474658 0.0240174 -0.0659469</location>

this isn't symmetric with marker R.MT5. intentional?

nickbianco

Thanks for the detailed review @carmichaelong! I've addressed all of your comments.

Reviewable status: 15 of 23 files reviewed, 9 unresolved discussions (waiting on @aymanhab and @carmichaelong)

CHANGELOG.md line 76 at r1 (raw file):