Lighthouses for the HTC Vive

HTC Vive is a virtual reality system that can be used to play games, watch movies or interact with virtual environments. It is a hardware setup that includes the headset, two controllers and two tracking cameras (also known as lighthouses). The system is powered by a computer and connected through cables to allow it to track the position of the headset and controllers. A base station is needed to synchronise the tracking with the computer and it can be positioned anywhere in the room.

The current state-of-the-art VR systems are the Vive Pro and the Valve Index. Both use the same tracking camera technology but have different architectures and software for positioning. They also have slightly different working principles.

Unlike other VR systems, the Vive does not require external cameras to function as it uses its own infrared laser emitter units called ‘lighthouses’. These are placed around the tracked area to limit and correct the build-up in error from dead reckoning based on inertial measurements. This is done at a rate of 120 Hz. When the view of one or both lighthouses is lost, the headset stops updating its position and orientation based on inertial measurements.

To investigate the accuracy of the lighthouses, static 3D positions were measured with the system in a controlled environment. Recorded X-Z positions for each grid point fell along a regular grid and recorded height varied smoothly across the tracking space. However, the reported Y axis tilt differed significantly from the expected values for a physically level headset. The results suggest that the second generation of lighthouses, like their predecessors, may be reporting measurement locations with reference to a tilted plane.