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Understanding the HeadTracking API

Introduction

Fire phone features Dynamic Perspective Sensors, cameras and motion sensors, that work with the software to recognize and track the user’s head. The HeadTracking API gives games and other apps a way to access this head-tracking data. The HeadTracking API provides the data as an event containing the following pieces of information:

  • The timestamp of the event.
  • Whether the software currently detects the user's face and is actively tracking the user's head.
  • The position of the head relative to the screen orientation of the phone, as X, Y, and Z coordinates.
  • The angle at which the head is inclined (rotated around the z axis) relative to the screen orientation of the phone.

Note: The content on this page applies to the Java version of the HeadTracking API. To learn about the native-code version of this API, see Understanding the Native-Code HeadTracking API.

Getting Head-Tracking Data

The HeadTracking API offers two ways to obtain head-tracking events, as a listener and by polling. If your app uses head-tracking events as they occur, it can register as a listener and receive head-tracking events as the system makes the information available. If your app requires access to head-tracking data on its own schedule, it creates an empty HeadTrackingEvent object and passes it to the HeadTrackingPoller.sample() method to be filled with the latest head-tracking data.

In either case, the app can then extract the head-tracking data from the fields of the HeadTrackingEvent object.

Power-Saving Features

The HeadTracking API also offers the following ways to manage power consumption:

  • You can pause head tracking when you are not using it.
  • You can choose different fidelity settings for the head tracking data. A lower fidelity implies lower battery consumption.
  • You can choose a data filter that uses cameras and motion sensors on the phone to track the head, or you can choose a data filter that uses cameras alone and so uses less power.