Proposal for an Orientation Sensor

[charlespetzold]

An orientation sensor combines data from the accelerometer and magnetometer to provide a complete orientation of the device in 3D space. This information is vital for VR and AR applications. One common usage is a "night sky" astronomy program.

On iOS, this information is available from the Device Motion subset of the CMMotionManager API.

On Android, it's the SensorType.RotationVector subset of the SensorManager API.

On UWP, it's the OrientationSensor class.

I think OrientationSensor is probably the best name for the class in Xamarin.Essentials, and distinguishes it from an Orientation API that might only provide portrait and landscape orientation.

A description of an orientation in 3D space is sometimes given in Euler angles; in roll, pitch, and yaw; or as a 3D rotation matrix. However, all three platforms provide a quaternion, and this is probably the simplest for the Xamarin.Essentials API. (System.Numerics includes a Quaternion type that can be used for this.)

In fact, it is extremely easy to create OrientationSensor classes using the Accelerometer classes as a guide. (In fact, I've already done it.) Rather than passing three numbers to the shared partial class, you pass four, and then set an Orientation property of type Quaternion.

From what I can determine, the three platforms are consistent in the relationship of the quaternion to the orientation of the device (as long as you hold a UWP tablet in portrait mode). So in that sense, it's simpler than the Accelerometer!

Although the quaternion might be frightful to some people, it's convertible into other types. For example, the System.Numerics.Matrix4x4 class has a CreateFromQuaternion method. Plus, we can write documentation that describe how to use it. (I wrote several orientation-sensor samples for MSDN Magazine several years ago, and I'd love to port them to Forms + Essentials.)

[mattleibow]

This sounds like a nice API, and I feel a game coming on...

[charlespetzold]

Let me know if you want a PR with the implementation!

[mattleibow]

Create a PR and we will start commenting!