Vicon Nexus Real-Time Integration

Visual3D streams data in real time as Vicon Nexus processes incoming frames. During streaming, Visual3D can either save the incoming frames to a C3D file or capture a static trial directly from the live stream. It’s important to remember that Visual3D depends on Nexus for data streaming—Visual3D cannot replace Nexus in this workflow.

Capturing a static trial within Visual3D is especially useful when preparing for real-time digitizing or defining functional joints. Before starting the stream, in Nexus 2, make sure that a static trial is captured, and then have performed the labeling calibration to ensure auto-labelling in live mode is functional.

Purpose: This tutorial provides a step-by-step guide to streaming real-time data from Vicon Nexus to Visual3D, allowing users to take full advantage of Visual3D’s real-time processing and biofeedback features.

Before streaming in real time, Nexus must be running and the subject calibration trial must be labeled. This allows Nexus to label markers in “Live” mode.

1. Calibrating the Capture Volume

• Calibrate the capture volume based on Nexus's standard protocol.

2. Create the Session Folder

• Ensure that the appropriate session folder has been selected before capturing motion capture data. Seen below, the grey circle in the Data Management indicates that the session folder is being used.

• Ensure Live Mode is enabled before capturing data. The top of the screen will indicate the status—if the system is offline, it will display ‘No Trial’ or the current trial name.

• If unsure how to create the session folder, refer to Vicon's tutorial.

3. Creating a New Subject from a Labeling Skeleton Template

• Load the desired Vicon Labeling Skeleton Template (VST) (one provided by Vicon or a custom VST)
• Vicon Labeling Skeleton Template is a Vicon Nexus file type to describe the relationship between segments, joints, and marker sets.

4. Capture Static Calibration Trial (Ensure Live Mode is on)

• Capture a static trial.
• Return to the session folder and load the static calibration trial that was just previously captured.

5. Reconstruct the Static Calibration Trial

• To reconstruct the markers, on the Tool Bar click the Reconstruct button highlighted in red on the top left of the application or run the Reconstruct Pipeline seen on the right.

6. Auto Initialize Labeling Pipeline

• Select the Auto Initialize Labeling Pipeline in the dropdown under Current Pipeline.
• Run the first step of the pipeline individually (Auto Label Static Frame) to assess the labeling quality and correct any incorrect labels.
• Once satisfied, run the following two steps in the pipeline to scale the subject and create a Vicon Labeling Skeleton file(VSK) and to automatically label the markers.

7. Verify Labeling in Live Mode

• Go back to “Live” mode, with the subject in the capture volume to test that Nexus correctly auto labels the markers in real-time.
  

To create the segments in Visual3D, load a static trial into Visual3D and apply a model template (.mdh).

To load the static trial:
Option 1 - Load the static trial collected in Nexus during Step 1.
Option 2 - Collect a static trial in Visual3D.
Its recommended to use the static trial collected in Nexus (Option 1).

1. Import the Static File

• From the Model menu, select Create → Hybrid Model from C3D file.
• Select *Static.c3d* and click Open.
  

2. Apply the Model Template

• Go to Model → Apply Model Template and browse to necessary model template (.mdh)
  

1. Model Menu

• From the Model menu, select Create (Add Static Calibration File), then Hybrid Model from RealTime Streaming.
  

2. Define the name of the model

• Define the name of the model template.

3. Verify Settings

• Select the correct real-time system from the drop down menu and click start streaming.
• When prompted, specify the sampling frequency.
• When prompted, specify the IP address as the local host, 127.0.0.1 and port as 801.

4. Collect Static Calibration Trial

• While the subject is standing still, collect a static trial by either clicking Create Snapshot (Static Trial) to save the static trial in the workspace or Save Static File to Disk to save the static trial as a C3D file.
• Please note that closing the Real Time Model Building dialog box will stop the real time streaming and remove the markers from the 3D viewer. After closing this dialog, if the static trial does not appear in the 3D viewer, switch to the Workspace tab and back to the Models tab.
  

5. Apply the Model Template

• Go to Model → Apply Model Template and browse to necessary model template (.mdh)
  

1. Launch Visual3D

**2. Select the Real-time capture TAB **

3. Data Streaming in Nexus

• In the dialog box the plug in will be visible ______.dlls Click Vicon_Nexus_RT.
• A dialog box will appear to select the current Nexus System file. When using standard Nexus file structure, the system file should be located under: C:\ProgramData\Vicon\Nexus\Configurations\Systems\

Streaming data from Nexus is continuous, the streaming status is in the bottom left of the page. If streaming for a long duration, the labeling in Nexus may start to fail. In Nexus, clicking CTRL+R may improve the labeling.

It is very important that Nexus automatic labelling works properly in “Live” mode and identifies markers correctly. If the markers aren't correctly identified in Nexus, Visual3D can not process any real-time data.

After having created or loaded a model, and established connection with the system back in the Real-Time tab, it is then possible to compute any model based item through the real-time pipeline.

1. Compute Model Based Items via Pipeline Commands

• Open up: Model Based Data Computation under the Real-Time Pipeline
• Double click, Compute_Model_Based_Data
• Click Edit

Change the corresponding:

**Data Name:** Ankle
**Folder:** ORIGINAL
**Model Based Item Properties:** JOINT_ANGLE
**Segment:** Right Foot
**Reference Segment:** Right Shank

1. Graph Creation

• Click Add in the Real-Time Graphs section, and enter the following:
  

Data: LINK_MODEL_BASED::ORIGINAL::Ankle

The result should show a Real-Time stream that looks like the picture below.

Remember to save the Graph and RT Pipeline

Important Reminder: It is very important that Nexus automatic labeling works properly in “Live” mode and identifies markers correctly. If the markers aren't correctly identified in Nexus, Visual3D can not process any real-time data.