Question How does Unity get the distance between the eyes for Hololens stereo rendering?

I have a use-case that involves remote rendering, this means I need the camera positions/rotation (cameraToWorldMatrix) for each eye.

I have tried several approaches which have all come up short, but Unity must know this information to do it's own stereographic render for each eye with the Hololens eye calibration data, for example, the interpupillary distance (horizontal offset between left and right eye pupil).

Approaches I have tried and results so far:

• MRTK GazeProvider, gives only a single center-eye gaze origin.
• Unity

  camera.stereoSeparation

  which comes back at 2.2cm (a constant set by MRTK somewhere, seems too small, with average IPD being 63mm for a male)
• Unity

  UnityEngine.SpatialTracking.PoseDataSource.TryGetDataFromSource(UnityEngine.SpatialTracking.TrackedPoseDriver.TrackedPose.LeftEye, ...

  which returns the left and right eye offset as zero.