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Object Tracking: HTC Vive

Tutorial: 

 

MVN allows for object tracking with HTC Vive. Vive Trackers can be mounted on all sorts of objects to track orientation and position. With this, it is possible to move multiple objects freely around the Vive play area and use the data to move virtual objects.

This article helps you to get set up for a recording with HTC Vive Object Tracking.

Before you start, make sure that have:
- Correctly set up your Xsens Motion Capture (Link or Awinda) system
- Correctly set up the HTC Vive: HTC Vive Setup Guide

NOTE: It is advised to use Vive Object tracking in combination with Vive Position Aiding (see Position Aiding: HTC Vive) for the best results. By default, SteamVR (Vive) and MVN systems have their own Coordinate system. With Vive Position Aiding the avatar is adapted to the SteamVR coordinate system. 

 

Required Means

Hardware

Item Version Amount
Xsens Link or Awinda

-

at least 1

Vive Pro SteamVR Base Station (No combination of versions) 

1.0 

2, more details: Vive play area

2.0 

2-4, depending on room scale (see below). More details: Using more than 2 Base Stations

Vive Tracker (No combination of versions)  1.0 1 per object
2.0 1 per object
Tracker strap / mount - 1 per Tracker
Base station mounts / clamps - 1 per Base Station

Software
- MVN Animate Pro / Analyze 2020.0
- Steam with SteamVR

 

1. Set up MVN Session

1.1 Set up Xsens MVN

 

1. Open MVN
2. Start a new Session by clicking the Blank Page icon (or go to File > Start Motion Capture)

mceclip1.png

 

3. Set up a system as normal (at least one online mocap system is required to record Object Tracking data)
4. In the Motion Capture Configuration window go to the Objects tab on the left side. 

mceclip0.png

 

4. Enable Object with the Objects toggle switch. 

mceclip0.png

NOTE: Available Vive TrackerID's will be shown in a List. To check TrackerID, see the HTC Vive Setup Guide.

 

5. Select the Tracker(s) to use for object tracking, and rename if required. 

mceclip0.png

 NOTE: An Object Vive Tracker may be in use by an MVN System (for Position Aiding). In that case, MVN will indicate which system is using that Vive Tracker. It is possible to use the Vive Tracker for Object Tracking and Position Aiding at the same time. 

image2020-3-11_15-59-52.png

 

6. Press Ok in the bottom right of the Motion Capture Configuration Window

You should see your avatar and the Vive Object Tracker in the viewport. 

 

NOTE: depending on the SteamVR setup, the tracker may appear above or below the MVN ground plane.  To adjust this, see HTC Vive Setup Guide

mceclip0.png

The Vive Trackers are represented by a Vive Tracker model with the name of the object above it. The orientation and position of this tracker will be displayed and updated live in the Viewport. 

 mceclip5.png

In the Navigator, an Objects item is available which contains all the Vive Object Trackers. Each Vive Object Tracker has Orientation and Position data. 

mceclip1.png

 

1.2 Manually Adjust floor height (optional)

In the Standing Only Room Setup (see HTC Vive Setup Guide), the floor height is adjusted to the headset location. Because there is only a virtual headset, the origin plane might my different than the actual floor. This can be corrected in 3rd party software after recording. Therefore, it can be useful to set 1 Vive Objects Tracker on the floor as a reference for later in 3rd party software. 
It is also possible to adjust the height of the floor manually. More information on how to manually change the floor height can be found in the HTC Vive Setup Guide.

 

2. Calibrate MVN System

 1. Follow the regular calibration procedure: 

Link
Awinda

mceclip2.png

 

3. Start Recording
Make sure the Vive Tracker is inside the play area. 

1. To start a recording, press the record button mceclip1.png

mceclip0.png

2. After the take, press the Stop Recording button to stop the recording mceclip2.png

After recording, MVN will create three file types:
- .mvn file: contains the Motion Capture data

mceclip5.png


- .mvno file: contains the positional and rotational data from the  Objects. This data can be exported to .fbx format: Exporting data from MVN

mceclip3.png


- .mvns file: contains the session data (Mocap data and Objects Data). 

mceclip4.png

 

4. Position Aiding

It is advised to use Vive Object tracking in combination with Vive Position Aiding (see Position Aiding: HTC Vive) for the best results. By default, SteamVR (Vive) and MVN systems have their own Coordinate system. With Vive Position Aiding the avatar is adapted to the SteamVR coordinate system. 

1. To play back the recorded session, open the .mvns file that was created. This will include the Mocap data and the Objects data. 

Below, the difference between using no Position Aiding (left) and using Position Aiding (right) is illustrated. The situation without Position Aiding is also what you can expect to see in live mode. This is because HTC Vive Position Aiding is only effective after HD reprocessing.

Object_Tracking_Comparison.gif

 

 

 

 

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