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A Varjo Headset
ART optical tracking system in an in-vehicle configuration (e.g. Smarttrack 3)
An external LPMS-IG1 IMU that is fixed to the vehicle frame (“reference “platform IMU”)
A PC running Varjo Base that powers the VR/AR experience
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In order to use LPVR-DUO we need to connect the various parts and we need to calibrate the orientation of the reference platform IMU that is mounted to the vehicle. For the following settings we give the line numbers in the default configuration.
In order to receive data from DTrack the port number configured on line 7 needs to match the one configured in DTrack. The default configuration uses port number 5000 which is also the default for DTrack.
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If you have already calibrated the headset tracking body (see above), you should now be able to now use the headset with DTrack tracking. It should also react to motion of the reference platform IMU. Though as long as the reference platform IMU is not calibrated, this motion should not make much sense.
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Follow this tutorial to install and run the vehicle-fixed LPMS-IG1 IMU. If you are using LPVR-DUO for Varjo with the ART SmartTrack and our provided IMU holder, you should be done at this step. If you are using another setup, please follow the steps below.
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| title | Manual Calibration Procedure |
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In a first step the orientation of the internal coordinate system of the vehicle fixed IMU and the optical tracking system needs to be defined. For this purpose, attach an optical marker to the enclosure of the IMU and create a new rigid body in the optical tracking software. To activate the calibration features of LPVR, click on Show Additional Features on the LPVR configuration page.
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 Image AddedActivate the automatic pivot point calibration by selecting the optical tracking system (“DTrack” or “my_art”) in the absolute source field with rigid body id tracking idand the vehicle fixed IMU (“Platform IMU” or “reference_imu”) in the imu source field. Clicking Find Rotation will start the calibration process. During the calibration process, slowly rotate the IMU with attached optical marker within the view of the optical tracking system. Pause the rotation from time-to-time to allow for some internal processing. After the calibration process is finished the result will be output below the calibration feature dialog. The output quaternion needs to be manually inserted into referenceToOpticalQuat.
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platform IMU to the vehicle in the intended location with the optical marker still attached. Make sure that it is visible to DTrack. We now need to read the orientation quaternion from Varjo Bases log files and enter them as referenceOrientationQuat around line 59 of the configuration. Accessing the Varjo Base log files takes a few steps which we detail below. Open Diagnostics from the Support menu in Varjo Base
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 Image AddedEnter the log folder, out of the files named tracking_<number>.log select the latest one and open it. Near its end search for lines similar to this
20210120 15:16:31.156 --- [Varjo::Tracking::PluginUtilityAPI::WriteLogMessage] PLUGIN: [INFO] new pose: q = {"w":0.9913584114738726,"x":0.1302836073262127,"y":0.006246731684853627,"z":-0.013979051208529776} pos = {"x":-1.1893610000000001,"y":0.831757,"z":-0.936706} Replace the contents of referenceOrientationQuat in the configuration web page with the values of q in the log file, i.e. {"w":0.9913584114738726,"x":0.1302836073262127,"y":0.006246731684853627,"z":-0.013979051208529776} in this example. After the above procedure the optical marker can be detached from the
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platform IMU should now not be moved anymore. The system should now be sufficiently calibrated for operation. You should now be able to display content fixed to the vehicle coordinate system. E.g. when you drive a curve in a vehicle and keep looking straight ahead, objects in VR/AR should not change their position and orientation. |