First Person Camera Setup
=========================

The actor framework supports a special first-person camera setup that places
the camera inside the actual player model's head and can be controlled by
mouse as well as by matching the eye position of a virtual reality HMD.

The model's head, neck and optionally also the upper part of the spine will
be posed to realistically follow the direction the player is looking.

For virtual reality, however, Unity's InputTracking component will update
the position of the active camera in response to the movements of the player's
head, thus active camera must not be a child of the model's head, neck or
upper spine bones -- otherwise there would be a cylic dependency.
  

Recommended Camera Setup
------------------------

PlayerDude (HeadPoser, MouseLookHeadController, VirtualRealityHeadController)
 + Rig
   + Spine
     + Chest
       + Neck
         + Head
           + EyePosition
     + CameraRoot
       + EyeCamera

The "MouseLookHeadController" needs to be configured to copy the EyePosition
transform to the EyeCamera.
 
- When the game runs in "Controller" mode, the mouse will move the Chest,
  Neck and Head bones around and the EyeCamera will be placed whereever
  the EyePosition ends up. The VirtualRealityHeadController will not
  do any work.

- When the game runs in "Virtual Reality" mode, the HMD will update
  the position of the EyeCamera itself and the VirtualRealityHeadController
  will make the Chest, Neck and Head bones follow the EyeCamera position.
  The MouseLookHeadController will do nothing.