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OptiTrack Active Marker Tracking

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Main PageOptiTrack Active Marker Tracking


Page Scope

This page provides instructions on how to set up and use OptiTrack's active marker solution for active labeling in Motive. Note that this setup workflow is specific only to the pre-programmed OptiTrack active marker kit which consists of the Base Station and the Tags. This guide will not work with third-party active LEDs.



Overview[edit]



Our active solution allows synchronized tracking of active LED markers using an OptiTrack camera system. The solution consists of the Base Station, the Tags, and the Active LED markers, and it requires an Ethernet camera system (Prime series or Slim 13E) with the eSync 2 synchronization hub. Once everything is setup, the Base Station becomes the sync master for both the camera system and the active markers. It sends out sync signals via RCA output and radio frequency waves allowing precise synchronization between camera shutters and illumination of the Active LED markers. The synchronized illumination allows labeling of individual markers in Motive.

Info2.png

  • The active solution works with Ethernet camera systems (Prime series and Slime 13E cameras) only. Integration with USB camera systems (Flex series) is not supported.
  • Currently, the Base Station can only send out 180 Hz sync signal.

Active Labeling[edit]

When tracking the active markers using our solution, the markers are labeled individually from their unique illumination patterns, and only the correctly labeled active markers get contributed to the rigid body solve. The largest benefit of individual marker labeling is that the markers can be placed in a perfectly symmetrical arrangement among multiple rigid body assets.

In Motive, each of the actively labeled markers is assigned with a marker ID less than 5000. Marker IDs can be monitored from the 3D viewport when the Marker Labels is checked under the visual aids options.

  • Active markers on a gun controller
  • Active markers reconstructed in Motive

Required Components[edit]



Name Image
eSync 2 Synchronization Hub

The synchronization hub for the camera system.

ESync2Pic.png
Base Station

Used as the sync master for both the active LED markers and the camera system. It sends out sync signals via RCA output and RF emitter for synchronizing the eSync and the Tags.

Warning: Power the Base Station through PoE connection to the switch. Do NOT plug the PoE and power adaptor at the same time'

BaseStation.png
Tag

The Tags receive RF signals from the Base Station and correspondingly synchronizes illumination of connected active LED markers.

Tag.png
Active LEDs

Emits 850 nm IR light. 4 active LEDs in each bundle and up to two bundles can be connected to each Tag.

(8 Active LEDs (4(LEDs/set) x 2 set) per Tag)

Size: 5 mm (T1 ¾) Plastic Package, half angle ±65°, typ. 12 mW/sr at 100mA

ActiveLEDs.png

Sync Setup[edit]



Follow the below steps for synchronizing and tracking the active markers in Motive.

eSync 2 and Base Station[edit]

Setup Steps[edit]

  1. Connect the eSync 2 to the camera network using an Ethernet cable.
  2. For powering the Base Station, connect it to one of the ports on the PoE switch. Do not use the DC input to power the base station.
  3. Connect the eSync 2 and the Base Station. Use an RCA cable to connect the output port (white) of the Base station into the Input 3 port on the eSync. You will need to use an RCA-BNC adaptor (included with the eSync 2) to do this.
  4. Open Motive
  5. [Motive] Go to the synchronization pane.
  6. [Motive > Synchronization] Use the dropdown menu to switch to the Custom Synchronization mode.
  7. [Motive > Custom Synchronization] Set the Input Source to Reserved. (The Base Station should be connected to the Input 3 port of the eSync, but the Reserved setting corresponds to an alternative mode of operation specific to the BaseStation).
  8. [Motive > Custom Synchronization] Click Apply. Now the cameras will be synchronized to the signal from the Base Station (master) which will also synchronize the active markers.
Example setup of 9 Prime cameras, the eSync 2, and the Base Station

Info2.png

Base Station Signal

The Base Station sends out radio frequency waves for synchronizing the active markers. The following is the specification of the RF signal:
  • RF: 802.15.4 @ 2.4 GHz
  • Channel 20

Tag + Active Markers[edit]

Setup Steps[edit]

  1. Once the Base Station and the eSync are set by following the above steps; now you can setup the active markers.
  2. If not already assembled, assemble the Tag, wires, and LED markers together. This step will not be necessary if you purchased pre-assembled Tags.
  3. Power the Tag. Use a micro USB cable to connect the Tag to a power source.
  4. Once powered, you will see the LEDs illuminating in red.

Tag Power[edit]

Each Tag requires power from a micro USB cable. The power requirement is between 2.7V - 5.5V measured at 100mA @ 5V with all LEDs on for every frame.

Motive Configuration[edit]

  1. Now that the hardware components and the synchronization configurations are set up, the last step is to tell Motive that it needs to look for active markers. This can be done in the Application Settings pane.
  2. [Motive > Application Settings] Under the General tab > Misc, there is a setting named Active Marker Labeling. This must be set to True in order to reconstruct the active markers. Once this setting is enabled, it will be indicated on the 3D viewport that Motive is tracking active markers.
  3. [Motive > Devices pane] For tracking active markers, set the camera exposure slightly higher compared to when tracking passive markers. This will make the markers more visible to the cameras.
ActiveMarker InMotive.png


Rigid Body Assets[edit]



Now that both the hardware and software components are set up for tracking active markers, the corresponding rigid body assets must be defined from active marker reconstructions in Motive. The process is exactly same as how it would be done with the passive markers. Simply select the active markers and create a rigid body. Then the active marker definitions will be saved for each asset, and Motive will know exactly which active markers are included in which rigid body assets.

Read through the Rigid Body Tracking page for more information on rigid body assets in Motive.


Active LED HMD bracket[edit]


Mounting[edit]

The HMD brackets ship with the active LEDs and the Tags attached to enclosures that can get clipped onto the HMD. To attach the bracket, first slide the bottom of the bracket onto the HMD and then clip the top, as shown in the image below.
HMDBracket.png

Detaching[edit]

When detaching the bracket from the HMD, first pull up the two latches behind the bracket and slowly pull it from the top.
HMDBracketDetach.png


Troubleshooting[edit]



› Q : The synchronization pane indicates that the camera system is synchronized to the Base Station. However, the active markers are flickering from both the 3D viewport and 2D camera views in Motive.

A: First of all, make sure the Application Settings is configured for tracking active markers. If the flickering of markers persists, it indicates the camera system and active LED markers are incorrectly synchronized. This usually occurs when power cycling the Base Station or when synchronization settings are altered in Motive. You can fix this by power cycling the Tags.

› Q : In the Synchronization pane, no input signal is detected.

A: Make sure the sync output (white) of the base station is connecting to the Input 3 of the eSync 2. Then, Motive must be configured to sync to the Reserved source.