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LPVR-CAD combines input from an optical tracking source with data from an IMU attached or built-into the head mounted display. For the combiner to be able to fuse the information from both sources they need to be in the same coordinate system. Pose data from the optical tracking system is transformed into headset IMU coordinates. After the fusion the resulting pose data is transformed back into the global coordinate system and output to the 3D engine. An overview of the signal flow is shown in the diagram below. Transformations are marked in blue.
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LPVR-DUO adds another combiner, the so-called differential combiner in front of the default combiner. For the system to operate inside a car, car rotation and head rotation need to be separated. The differential combiner takes as input the HMD IMU data and combines it with gyroscope and accelerometer information from the platform IMU. The operation takes place in the IMU coordinate system. The block diagram below shows an overview of the signal flow.
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