Vicon ProCalc Generating VSKs Tutorial
- Former user (Deleted)
- Dev Ops
- Gisela Roberts
About this tutorial
ProCalc 1.3 and later enables you to generate subject-specific Vicon Skeleton (VSK) files based on calculations specified within a ProCalc variables scheme. This tutorial explains how to do this and the benefits of this approach.
This tutorial uses as a Vicon Skeleton Template (VST) file that is based on version 2.3 of the python Conventional Gait Model ( see About the Conventional Gait Model 2.3). The segments are the same but the knee joint type was changed from a 1-degree-of-freedom (hinge) joint to a 3-degree-of-freedom (ball) joint. If you want to use a different VST, make sure all joint types are set to ball joints (see Updating the joints in the VST).
The goal of this tutorial is to:
- Learn how to build a biomechanical model that can be used to generate a VSK
- Learn how to generate a VSK if you already have a suitable, existing ProCalc variables scheme
About VSK/VST files
The Vicon VSK/VST file format is primarily used in the Vicon Nexus software to specify labeling skeleton templates. The labeling skeleton contains a set of relationships between motion-captured markers and an underlying skeletal structure, which Vicon Nexus uses to automatically label (auto-label) markers. Users of Vicon Nexus select a template (VST), and then scale/calibrate the template to the current subject that is being captured (which generates a corresponding VSK file), so that the auto-labeler can do its job.
The VST/VSK file format is a generic format that can be used to specify any relationship between markers and segments, including those that define biomechanical models – in other words, where the segments’ positions estimate anatomical segments. ProCalc enables you to specify the marker-segment relationships that are normally used in a biomechanical model in the VST/VSK file format without having to manually edit a text file. Instead, you generate a VSK from a model that is defined in ProCalc.
Generating a VSK from ProCalc has two major benefits:
- When you set up a customized biomechanical model in ProCalc, you can use the same model for labeling.
- You can improve the labeling for any VST, or generate real-time kinematics.
Important
Some of the default VST files that are supplied with Nexus use a 1‑degree-of-freedom (hinge) joint at the knee. Before using the VSK with ProCalc as described in this tutorial, replace the 1-degree-of-freedom joint with a 3-degree-of-freedom (ball) joint. For more information, see Updating the joints in the VST.
About the data for this tutorial
To follow this tutorial, navigate to C:\Program Files\Vicon\ProCalc\Help and unzip the ProCalc Tutorials Data file. Choose a path or directory that has sufficient read/write permissions and that you can remember and access easily (e.g. C:\Users\Public\Documents\Vicon). If you have completed a ProCalc tutorial in the past, you may have already completed this step.
For this tutorial, we will use the Generating VSKs session. Within this folder, there is one trial (Static.c3d), two ProCalc schemes and a VST file (see About the files for this tutorial).
To access the trials in ProCalc, your hierarchy must look like the following example, though the specific path will depend on where you extracted your data.
About the files for this tutorial
This tutorial folder features other files that must be moved to the appropriate folders. With ProCalc closed, copy the files from the session folder into the following locations:
| File name | Description | Location |
|---|---|---|
|
GeneratingVSKs.vst |
Labeling skeleton template | C:\Users\Public\Documents\Vicon\Nexus2.x\ModelTemplates |
| GeneratingVSKs.InputParamScheme | Input parameters scheme | C:\Users\Public\Documents\Vicon\Eclipse\InputParamSchemes |
| GeneratingVSKs.VarScheme | Variables scheme | C:\Users\Public\Documents\Vicon\Eclipse\VariableSchemes |
These files contain complete information for this tutorial, so you can follow the instructions without having to enter additional data.
