A configuration you use when you just want to track faces using the device's front camera.
A face tracking configuration detects the faces that can be seen in the device’s front camera feed. When ARKit detects a face, it creates an ARFaceAnchor object that provides information about the face’s position and orientation, its topology, and features that describe facial expressions.
The ARFaceTrackingConfiguration class provides no methods or properties, but supports all properties inherited from its superclass ARConfiguration. Additionally, when you enable the lightEstimationEnabled setting, a face tracking configuration uses the detected face as a light probe and provides an estimate of directional or environmental lighting (an ARDirectionalLightEstimate object).