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Position Aiding: HTC Vive

MVN allows for position aiding with HTC Vive. With the feature, the MVN fusion engine combines the Motion Tracker data from the Motion Capture System (Link or Awinda) and the HTC Vive position tracking to improve the global position. This can be extended to multiple systems, improving the multi-actor alignment and optimizing the workflow. The Position Aiding can be viewed live as well as HD processed after recording. It can be used in the following Scenarios:

- Single Level: Actor is moving on a single plane

- Multi Level: Actor is moving on more than one plane (e.g. jumping on a table, walking stairs

- No Level: Actor has no contacts with the environment (e.g. skating, cycling). No contacts are used in this Scenario, which might result in foot slide. For no foot slide, use the Single or Multi Level Scenario)

 

This article helps you to set up a recording with HTC Vive Position Aiding.

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

 

1. Vive Hardware Placement

The Vive Hardware can be used in multiple locations on the body for position aiding. The Segment closest to the location of the Hardware will be most accurate. So, if you are most interested in Hand location, for example, if you are recording a high five between actors, it is advised to place the Vive Trackers on the forearms of the actors. 

Below you can find an overview of the locations you can mount the Vive Hardware on. 

Vive Hardware Locations
mceclip7.png Tracker

Pelvis

Right Fore Arm 

Left Fore Arm

Right Lower Leg

Left Lower Leg

mceclip6.png Headset  Head
mceclip5.png Controller 

Right Hand

Left Hand

 

A description of the exact placement of the Hardware can be found below. 

 

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Place the Vive Tracker just above Pelvis Motion Tracker

 

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Place the Vive Tracker at 1/2 of the forearm (halfway from wrist to elbow) on the outer side of the arm in n-pose.

 

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Place the Vive Tracker at 1/3 of the lower leg (one-third from the ankle to the knee) on the outer side of the arm in n-pose.

 

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Place the headset on the head, as if you are playing a virtual reality game

 

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Hold the controller in your hand as if you are holding it, playing a game.

 

2. Set up Session

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

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3. Make sure that the system is Ready for all operations. 

 

4. In the Motion Capture Configuration window go to the Position tab. 

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5. Open the 3D Position Aiding drop-down menu and select HTC Vive. 

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6. A list will appear of all Vive Hardware to use for Position Aiding.

 

7. You can use multiple Vive Trackers / Controllers / Headset per actor, which all contribute to determining the position of the actor. For all hardware you want to use for Position Aiding, select a Location. 

In the TrackerID drop-down menu, select the Vive Tracker ID to attach to this actor. 

NOTE: To check TrackerID, see the HTC Vive Setup Guide

mceclip1.png

 

NOTE: An octagon mceclip12.png will appear on the avatar to indicate the Status and Location of the Vive Tracker:

mceclip12.png (Green): Vive Ready and receiving position data

mceclip13.png (Yellow): Vive Tracker ready but not receiving position data from at least two Vive Base Stations. Check SteamVR if the Tracker is in the Play Area

mceclip11.png (Black): No Vive Tracker detected: Turn on the Tracker and make sure it is paired in SteamVR

 

NOTE:  In general, the pelvis mounted Vive tracker is used for root motion Position Aiding. Choose ForeArm or Lower Leg if the motion capture data requires more position accuracy for that segment. You can also combine multiple segments. 

 

NOTE: You can also check the hardware status of the Vive Hardware by pressing the Wrench Tool icon in the Motion Capture Configuration window. mceclip4.png

  mceclip3.png 

8. Press Ok

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By default, the avatar will be shown in the scene Viewport and the XY-Position of the Vive Hardware in the color of the system is shown in a graph. 

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3. Calibration

 1. Follow the regular calibration procedure inside the bounds of the Vive Play Area: 

Link
Awinda

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Typically, MVN will reset the Axis and Position based on the Vive data. In some cases, if there is not enough data collected, MVN indicates "System is not yet configured correctly for Vive data, please perform an Axis Reset. 

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2. Walk around inside the bounds of the Vive Play Area. 

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3. MVN will automatically detect the movement. Keep on walking around until the process bar is completed. 

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4. Reset Position

If the position of the system with Position Aiding is off, for example, if you are recording with multiple Position Aided systems or when your combining Position Aiding with Object Tracking, there are two things you can do, Dribbling, or Move Character to Origin. Both are explained below.  

 

4.1 Dribbling

Every actor can dribble on the spot. By lifting your feet from the ground, you constantly making new contacts with the floor, this will update the position and after a few seconds, it will align back with the Vive position.  

 

4.2 Move Character to Origin

Alternatively, you can use Move Character to Origin. This will put the avatar in the position based on the Vive Data. 

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*NOTE: In the above picture the Tracker has been made visible for clarity. The tracker will not be visible by default in Position Aiding mode. However, you can make it visible by enabling the same tracker in Object Tracking.  

 

1. Select all systems in the Navigator that have to be reset. Multiple systems can be selected at the same time. 

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2. For all selected systems, have the actors stand in Npose

3. Go to Tasks > Move Character to Origin (Shortkey: Ctrl + 0)

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NOTE: If using Position Aiding, the position of the right heel of the avatar will not be reset to 0.0 as is the case without Position Aiding. 

 

4. With Position Aiding, this will update the position of the Avatar to match the position of the Vive Hardware. 

mceclip11.png
*NOTE: In the above picture the Tracker has been made visible for clarity. The tracker will not be visible by default in Position Aiding mode. However, you can make it visible by enabling the same tracker in Object Tracking.  

 

4.3 Reset Axis

If the heading of the system with Position Aiding is off, for example, if you are recording with multiple Position Aided systems or when your combining Position Aiding with Object Tracking, you can perform an axis reset to align the heading. 

 

1. Select all systems in the Navigator that have to be reset. Multiple systems can be selected at the same time. 

mceclip14.png

2. For all selected systems, have the actors stand in Npose

3. Go to Tasks > Axis Reset  (Shortkey: Ctrl + Alt + A)

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4. For all selected systems, have the actors stand walk around inside the bounds of the Vive Play Area. 

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5. MVN will automatically detect the movement. Keep on walking around until the process bar is completed. 

mceclip13.png

 

5. Recording

After calibration, you are ready to record. 
1. Make sure you are in the bounds of the Vive Play Area. 
2. Press record mceclip18.png

mceclip16.png

 

3. Press Stop Recording mceclip17.png to stop the recording. 
4. After recording, MVN will create the following file type(s):

- .mvn file: contains the Position Aided Motion Capture Data

mceclip5.png

- .mvno file: contains the positional and rotational data from the Objects (only created if Object Tracking was enabled during the session, see Object Tracking: HTC Vive)

mceclip3.png

- .mvns file: contains the Mocap Data and Objects Data combined in a session (only created if Object Tracking was enabled during the session). 

mceclip4.png

More info on file types can be found in MVN File Types

 

TIP: The Vive data (Position and Rotation) can be found under the segment that the Vive Hardware was attached to. In this example: Segments > Right Fore Arm > External Data

mceclip20.png

 

6. HD Reprocess

6.1 Reprocess file

1. Open a file in MVN with Vive position data included. 
2. Go to the reprocessing window by clicking the gears icon mceclip17.png

mceclip22.png

 

3. Make sure to select Use HTC Vive

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4. Press Start and Close to Process the file and close this window. 

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After processing the Xsens Fusion engine has combined the MVN Motion Capture data with the Vive position data resulted in Position aided Motion Capture data (.mvn file). This data can be exported like any other .mvn file: Exporting data from MVN

 Untitled_Project.gif

 

NOTE: If you want the Motion Capture data without Position Aiding, Reprocess the file again, this time selecting No External Position. 

 

6.2 Remap or disable Segments

If some data from the Vive hardware turns out to be of less quality or not useful or if you made a mistake during setup, selecting the wrong segment, you can correct this in Processing.

1. Go to the reprocessing window by clicking the gears icon mceclip17.png

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2. Make sure to select Use HTC Vive

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3. By default, MVN has the Vive Hardware mapped to the segment(s) selected during setup. You can check this by enabling Show data mapping. 

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4. If you want to change the Mapped Segment or disable the use of specific Vive Data, double right-click on the segment. 

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You can choose

- Don't use: disable data for this Segment

- Reset to default: Reset to the Segment that was selected during setup

- Remap to > Segment: Select the segment to remap the data to. 

 

7. Exporting

The recorded MVN-files with Position Aiding data can be exported to all filetypes a regular MVN-file can be exported to.  

More info on exporting can be found in Exporting Data from MVN

 

8. Streaming

The Motion Capture session with Position Aiding can also be streamed. This has to be enabled in the Network Streamer: Go Options > Network Streamer

mceclip21.png

For setting up a network stream to a specific 3rd party software check: Network Streamer in MVN

 

 

 

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