Difference between revisions of "Template:HMD Setup"

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Use the ray-based [[Rigid_Body_Properties#Default_General_Settings|tracking algorithm]]. The tracking algorithm setting determines which protocol to use for solving the rigid body in Motive. This algorithm is recommended because it allows tracking to be less susceptible to marker occlusions and solves rigid bodies more robustly without introducing trajectory gaps. This is more suitable for tracking the HMDs since even minor occlusions can acutely affect the experience.
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'''Passive Markers'''
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:Use the ray-based [[Rigid_Body_Properties#Default_General_Settings|tracking algorithm]] for HMDs with passive markers. This algorithm is recommended because it allows tracking to be less susceptible to marker occlusions and solves rigid bodies more robustly without introducing trajectory gaps. This is more suitable for tracking the passive marker HMDs since even minor occlusions can acutely affect the experience.
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'''Active Markers'''
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:Use the marker-based [[Rigid_Body_Properties#Default_General_Settings|tracking algorithm]] for HMDs using active marker clips. Ray-based tracking is not supported for active markers, but active markers themselves already provide stable tracking from its [[Active Marker Tracking|unique illumination patterns]], so marker-based tracking will provide stable tracking.
 
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Revision as of 12:46, 7 March 2018

HMD Tracking Setup


Setup and optimize the motion capture volume as explained in the Getting Started guide or the Hardware Setup documentations. If you plan to install any obstacles (e.g. walls) within the capture volume, make sure they are non-reflective, and place and orient the cameras so that every corner is thoroughly captured by multiple cameras. For typical rigid body tracking, attach the rigid body markers as instructed from the Rigid Body Tracking page.

General Setup Steps

  1. Attach the markers on the HMD
  2. Create a rigid body asset
  3. Calibrate the Pivot Point of the rigid body
  4. Configure the rigid body settings

Marker Attachment

Passive Markers

Attachment

When attaching retroreflective markers, make sure markers are securely attached and readily captured by the cameras. For attaching the markers, we recommend using our 20 mm wide and 30 mm tall M4 threaded plastic marker bases with Acrylic adhesives, available at the webstore, to attach the markers onto the HMD.

Placement

A markered HMD will be defined as a rigid body in Motive. When placing markers, make sure the placement asymmetry is respected in the arrangement within the HMD. Also, the marker arrangements between multiple HMDs must be incongruent. For more details, read about marker placement from the Rigid Body Tracking page.

Active Markers

Attachment & Placement

With the HMD bracket, simply attach the active marker bracket onto an CV1 HMD and use the active markers on it to define a rigid body.

Info2.png

When using the OptiTrack Active Marker Kit, active markers are actively labeled individually from their own unique illumination patterns, and only the matching active markers get contributed to the rigid body solve. The biggest benefit from the individual labeling is that markers can be placed in perfectly symmetrical placements among multiple rigid body assets.

  • Putting the HMD bracket on
  • When detaching the bracket from the HMD, first pull up the two latches behind the bracket and slowly pull it from the top.

Oculus Positional Tracker (Rift sensors)

  • When using an OptiTrack motion capture system to provide a solution for tracking Oculus HMD, avoid connecting its positional tracker, the Rift sensor, to the host PC.
  • When the tracker is connected, IR LEDs on the connected HMD will illuminate, and it could interfere negatively with the IR tracking of the motion capture system.
  • When Oculus tracker is not recognized by the computer, an error message may appear but you should be able to ignore the error message (Critical Error - can't find the sensor) and proceed without the tracker.

Create an HMD Rigid Body

In Motive, select the markers that are attached on the HMD and create a rigid body (Hotkey: CTRL + T) as you would do for other rigid bodies. Once the rigid body is created, select the asset and open the Properties pane. The following settings need to be configured for HMD tracking.

Rigid body properties for the HMD asset.

Deflection

Deflection setting is the tolerable distance, in millimeters, that a rigid body marker may deviate from its expected position before it is unlabeled and unassociated with the rigid body. The deflection is set to 4 mm by default. For HMD tracking applications, we recommended lowering this value to 3 or 2. This will reduce the amount of computation required for labeling, and overall latency may be reduced.

Tracking Algorithm

The tracking algorithm setting determines which protocol to use for solving the rigid body in Motive.

Passive Markers

Use the ray-based tracking algorithm for HMDs with passive markers. This algorithm is recommended because it allows tracking to be less susceptible to marker occlusions and solves rigid bodies more robustly without introducing trajectory gaps. This is more suitable for tracking the passive marker HMDs since even minor occlusions can acutely affect the experience.

Active Markers

Use the marker-based tracking algorithm for HMDs using active marker clips. Ray-based tracking is not supported for active markers, but active markers themselves already provide stable tracking from its unique illumination patterns, so marker-based tracking will provide stable tracking.

Streaming ID

The User Data value for each rigid body is used as an identification number to reference the rigid body in external applications. Log this value for each rigid body (including the HMD(s)) in the scene. This number will be used to associate the assets in the client applications using the plugin devices.

Min Marker Count

This setting may need to be modified when tracking HMDs with passive markers. To prevent the swapping of the rigid body definition, set this setting to 4. When tracking multiple HMDs, there could be limitations to a variety of unique marker arrangements that could be achieved. If this value is set to a lower value, a set of three markers on an HMD may be congruent to another set in a different HMD, and the rigid body definitions may be switched in Motive.

Calibrate Rigid Body Pivot Point

After the rigid body definition have been created for the HMD, the position and orientation of the rigid body pivot point need to be carefully adjusted for HMD tracking:

  • The pivot point is placed on the bridge of the nose; specifically, right at the midpoint between two eyes.
  • Orientation axes of the rigid body should precisely align with the physical HMD component.
  • Uncalibrated HMD rigid body definition. The pivot point is not positioned nor oriented properly.
  • Calibrated HMD rigid body definition. x-axis forward for UE4 integration.


Manually Calibrating the HMD Pivot Point

In general, you will be utilizing the HMD calibration tool for precisely positioning and orienting the HMD rigid body. However, if, for some reason, you want to manually position the pivot point without using the HMD Calibration feature, follow the instruction on this page: Manually Calibrating the HMD Pivot Point.

HMD Calibration Tool

Info2.png

Rigid body pivot can be easily calibrated using the HMD Calibration tool. Supported only for Oculus HMD models only. Does not work with GearVR.

Using the HMD Calibration Tool (Passive Markers)

Calibration of HMDs with passive markers utilizes both the OptiTrack mocap system and the Oculus Tracker for precisely calculating the location of the pivot point of an Oculus HMD. When using this feature, both systems must be tracking the HMD rigid body.

  1. Connect the Oculus Tracker and have the Oculus software running in the background.
  2. Launch Motive.
  3. [Motive] Create a rigid body asset from the markers on the oculus HMD. Read: Creating Rigid Body.
  4. [Motive] Open the Trackables pane. Tools → Trackables → HMD Calibration tab
  5. [Motive] Select the HMD rigid body. Under Detected Type, it should indicate Custom RigidBody.
  6. [Motive → Trackables pane] Set the desired number of sample counts (Default: 750) and the desired orientation.
  7. [Motive → Trackables pane] Press start to initiate the sampling process.
  8. [Motive → Trackables pane] During calibration, make sure both the mocap system and the Oculus Tracker is tracking the HMD.
  9. [Motive → Trackables pane] Once it starts collecting the samples, point the HMD towards the Tracker and slowly rotate it and sample different orientations.
  10. [Motive → Trackables pane] When it finishes collecting samples, it will display the offset distance, in mm, between pivot point position detected by oculus and the motion capture system.
  11. [Motive → Trackables pane] If the results are satisfying, press Apply to calibrate the HMD rigid body.


Using the HMD Calibration Tool (Active HMD Clips)

You can also use the HMD Calibration feature to easily calibrate the pivot point of the active marker HMD clips.

  1. First of all, make sure Motive is configured for active marker tracking.
  2. In Live mode, select the active markers on the HMD clip and define a rigid body.
  3. Under Tools tab open the Trackables pane and access the HMD calibration tab.
  4. Hold the selected rigid body at the center of the capture volume so that as many cameras as possible can clearly capture the markers on the HMD clip.
  5. Select the active HMD clip rigid body in Motive.
  6. Make sure Detected Type shows up as OptiTrack Active HMD clip.
  7. Under the Samples Counts entry, assign a number of sample frames that you wish to capture for calibration
  8. Select the desired orientation of the rigid body. You can select from +Z forward (Unity), +X forward (Unreal), or -Z forward (Native)
  9. Press Start to start the calibration process.
  10. Slowly rotate the HMD to collect samples in diverse orientations.
  11. Once all necessary samples are collected, it will report the calibration result.
  12. If everything looks good, press Apply Calibration, and the HMD rigid body pivot point will be calibrated to given orientation.