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Manually Calibrating the HMD Pivot Point

Pivot Point Position

For best virtual experiences, the pivot point of the HMD rigid body, in Motive, needs to be positioned on the midpoint between two eyes, of the user when the HMD is put on. To locate this, use the side and top-center landmark markers as references. For more information on adjusting rigid body pivot points, please read through the Rigid Body Tracking page.

1. Set the pivot point over the landmark marker. Use the Set Pivot Point to Selected Marker feature to assign the pivot point to the marker. This will set the elevation of the pivot point along the eye-level.


  • Top view: Rigid body pivot point is assigned to the left landmark marker.
  • Side view: Now both the landmark marker and the pivot point is positioned along the user's eye-level elevation.


2. Place the pivot point at the midpoint between the two markers. Enable Two Marker Distance visual aid Viewport16.png from the perspective pane, and select the two landmark markers in Motive. This will provide a distance between two markers. Then, using this information, translate the pivot point laterally by half of the distance so that it is placed right on the midpoint between two markers.

Translating the pivot point by half of the measured distance to place it at the midpoint.

3. Translate the pivot point along the z-axis using the translation tool. For the most accurate position, you may need to physically measure the sagittal, z-axis, distance from the landmark marker to the root of nose, and apply the measured offset.

  • Pivot point translated along the z-axis
  • Perspective view of the adjusted pivot point position.


Orientation

Now that you have translated the pivot point, you need to make detailed adjustments to the orientation using the orientation transformation tool. For best results, align the two front markers along the x-axis grid and roughly center the rigid body along the z-axis grid. Then, check to make sure that each of the rigid body orientation axes is parallel to the grids lines in Motive. If there is any deviation, apply rotation to adjust the offset. If needed, transparency of the axes and the grids can be adjusted from the Application settings.

  • In Unreal Engine: the X-axis of the HMD rigid body must be directed forward.
  • In Unity: the Z-axis of the HMD rigid body must be directed forward.
  • Slight offset in the rigid body orientation.
  • After Adjusting, the rigid body orientation axes are precisely aligned with the global axes of Motive

Info2.png

Tip: Once you have the rigid body asset for the HMD configured, you can export the asset into a TRA file for future uses. Importing the TRA file (e.g. CV1.tra) will load the rigid body (HMD) asset and make it available for use; however, the marker placement must remain unchanged in order to re-load previously created rigid bodies.

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