The AnyMoCap Framework

The AnyMoCap model is an effort to create a simple and unified framework for doing any kind of mocap analysis with the AnyBody Modeling System.

../_images/anymocap.jpg

Features

  • Adapts to any Mocap protocol
  • Optimization of marker locations and anthropometrics.
  • Support Marker based (C3D) and inertial based (BVH) input.
  • Support for standard force plates: (Types 1-4) plus more.
  • Prediction of ground reaction forces
  • Easy setup with multiple trials and subjects

Over determinate kinematic analysis

Musculoskeletal models that use Motion capture data are different from other types of models found the AMMR. Most importantly, MOCAP models usually require an over-determinate kinematic solver to handle the excess in information that the optical markers provide.

The over-determinate solver in AMS works great, but it can only find velocities and accelerations numerically. That has some performance issue when running inverse dynamics analysis. To overcome the problem, the MOCAP analysis is split into a two-step procedure, as illustrated on the figure below:

../_images/anymocap_flow.png

Figure 1: The framework of the AnyMoCap model. Analysis is split into three steps. Parameter identification, Marker tracking, Inverse dynamic analysis.

The over determinate kinematic analysis solves the model for positions, and writes joint angles to a a set of files. These joint angles can then be used with the determinate kinematic solver in the inverse dynamic analysis.

See also

The AnyBody tutorials, and the lesson on using the AnyMoCap model

AnyMoCap examples

The following gallery shows different examples using the AnyMoCap framework.

Note

The Multi trial MoCap model is likely the best starting point when working with many trials/subjects from a MoCap experiment.

Get started

The easiest way to get started, is to adapt one the example application above.

A typical application using the AnyMoCap framework will look something like this:

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 #include "../libdef.any"

 #path MOCAP_TRIAL_SPECIFIC_DATA "TrialSpecificData.any"
 #path MOCAP_SUBJECT_SPECIFIC_DATA "SubjectSpecificData.any"
 #path MOCAP_LAB_SPECIFIC_DATA "LabSpecificData.any"

 // Include the AnyMoCap Framwork
 #include "<ANYMOCAP_MODEL>"

You can place this main file anywhere on your computer as long the libdef.any file points to model repository (AMMR) you want to use.

Caution

It is recommended not to place working models inside the AMMR folder. Copy the example elsewhere before using.

Model structure

When loading the AnyMoCap model the following layout shows up in the model tree:

../_images/model-structure.png

Description of Model folders

Top-level model structure
Folder name Description
ModelSetup Contains contains all the machinery of the AnyMoCap Frame.
HumanModel Contain the Human model used. This is constructed automatically by the AnyMoCap framework.
Main.EnvironmentModel Contains the model parts which are not part of the Human model. (e.g. force plate and environment)
Studies Contains the three studies ParameterIdentification, MarkerTracking, and InverseDynamicStudy. See figure 1.
DrawSettings Contains visual and color settings for the model.
RunParameterIdentification Operation to run the Parameter Identification study and save the results.
RunAnalysis Operation to 1. load the optimized parameters (scaling and marker positions), 2. run marker tracking and finally 3. run inverse dynamics analysis, 4. save results to and HDF5 file for later replay.
LoadAndReplay This loads any previously saved data and starts the replay operation.

Options and settings

The Main.ModelSetup folder contains the main machinery of the AnyMoCap framework. It is controlled by a number of settings both #define/#path switches and variables which can be set directly. For example:

#define MOCAP_INPUT_DATA_TYPE "C3D"

Main.ModelSetup.TrialSpecificData.LastFrame = 240;

The following two sections gives an overview of the settings available:

Paths settings and switches

Path settings and switches are usually prefixed by MOCAP_ to indicate that they are specific to the AnyMoCap framework.

#path settings for AnyMoCap.
Settings Description Default
MOCAP_TRIAL_SPECIFIC_DATA Path to a file with trial specific data. This file is include within the Main.ModelSetup.TrialSpecificData folder. None
MOCAP_SUBJECT_SPECIFIC_DATA Path to a file with subject/session specific data. This file is include within the Main.ModelSetup.SubjectSpecificData folder. None
MOCAP_LAB_SPECIFIC_DATA Path to a file with laboratory specific data (i.e. data common for the whole model or experimental setup. This file is include within the Main.ModelSetup.LabSpecificData folder. None
MOCAP_C3DSETTINGS A file with setting for the C3D file. None
MOCAP_BVHSETTINGS A file with setting for the C3D file. None
MOCAP_EXTRA_DRIVERS_FILE A file with user defined extra drivers. Additional drivers are useful/necessary in some cases where the marker protocol doesn’t provide enough information to specify all degrees of freedom. Hence, these drivers complement a specific driver protocol. This file is included in Main.ModelSetup.MoCapExtraDrivers None
MOCAP_MARKER_PROTOCOL_FILE A file with the definition of the marker protocol. This file is included in Main.ModelSetup.MoCapDrivers None
BODY_MODEL_CONFIG_FILE A file with the body model configuration. None
MOCAP_FORCE_PLATE_FILE A file with the definition of the force plates. None
MOCAP_C3D_DATA_PATH Path to folder where C3D files are stored. Main file directory
ANYMOCAP_MODEL_PATH Path to the AnyMoCap framework. The AnyMoCap implementation in the AMMR
ANYBODY_PATH_OUTPUT Path to where output files are saved. The main file directory
TEMP_PATH Path to where temporary files are saved (joint angles etc.) ANYBODY_PATH_OUTPUT
#define settings for AnyMoCap.
Setting Description Default value
MOCAP_INPUT_DATA_TYPE Data type (“C3D”, “BVH”) used by the AnyMoCap application. “C3D”
MOCAP_CREATE_PARAMETER_ID_SHORTCUT Setting for creating the Main.RunParameterIdentification shortcut operation . ON
MOCAP_OUTPUT_FILENAME_PREFIX Prefix added to all output files from the model. “”
MOCAP_PARAMETER_FILE_PREFIX Prefix for the parameter identfication files. Can be usefull to set explicitly in special cases where subjects share a common parameter file. MOCAP_OUTPUT_FILENAME_PREFIX
MOCAP_USE_GRF_PREDICTION Switch to indicate that the model uses Ground Reaction Force (GRF) prediction. It will ensure that the AnyMoCap framework uses the appropriate settings. (e.g. recruited actuators as weak residuals on the pelvis. OFF
MOCAP_FILTER_JOINT_ANGLES Switch to enable extra low pass filtering of the output from the Marker tracking. Useful in some cases where other drivers (e.g. joint limits) cause high accelerations in the output from Marker tracking. OFF
MOCAP_HIDE_UPPERBODY Switch hide the upper body (Thorax, neck, arms and skull). OFF
MOCAP_HUMAN_GROUND_RESIDUALS The type of Human Ground residuals (Hand of God) used. Possible values are “Pelvis”, “Thorax”, “PelvisWeak”. “PelvisWeak” is default when using GRF prediction. “Pelvis”

Configurable variables

The Main.ModelSetup folder contains all the machinery of the AnyMoCap framework. It has three important subfolder (TrialSpecificData, SubjectSpecificData and LabSpecificData).

../_images/model-setup-structure.png

These three folders contain variables specific to the application but also has a few variables which can be assigned directly by the user.

Variables in the Main.ModelSetup.TrialSpecificData folder which can be overridden.
Main.ModelSetup.TrialSpecificData Description Default value
TrialFileName Name of the current trial. This is usually used for naming output files and locating the input c3d files (c3d filename without the extension) Name of the main-file directory
LoadParametersFrom List of trial names from which the scaling and optimized marker postions are loaded from. {TrialFileName}
FirstFrame First frame of the C3D/BVH file to use as starting frame in the analysis First frame in the C3D/BVH file
LastFrame The last frame of the C3D/BVH file to use in the analysis Last frame in the C3D/BVH
tStart Specifies the start time of the analysis. Setting this overides FirstFrame Calculated based on FirstFrame
tEnd Specifies the end time of the analysis. Setting this overides LastFrame Calculated based on LastFrame
nStep Number of time steps used in the analysis. (Note that the number of time-steps in the inverse dynamic analysis will be 4 less than this values) Calculate based on tStart/tEnd
Variables in the Main.ModelSetup.LabSpecificData folder which can be overridden.
Main.ModelSetup.LabSpecificData Description Default value
Gravity Specifies the gravity vector in global reference frame. {0,0,-9.81}
LowPassFilterSettings Folder with filter settings used for markers and analog (force) data.  
.MarkerFilterCutOffFrequency The lowpass cutoff frequency used for the marker data. 5.0
.MarkerFilterOrder The filter order used when low pass filtering the marker data. Note: Since the filter is applied as a zero phase filter (filtfilt or forward/backward filter) the effective filter order is the double of this value. 2
.ForceFilterCutOffFrequency The lowpass cutoff frequency used for the force/analog data. 12.0
.ForceFilterOrder The filter order used when low pass filtering the force/analog data. Note: Since the filter is applied as a zero phase filter (filtfilt or forward/backward filter) the effective filter order is the double of this value. 2

More resources

This section contains further documentation on the AnyMoCap framework.