The HPU conducts the processing that integrates real world and data for augmented reality. All of the integration of environmental data and user input is handled by the HPU. This offloading frees processor resources of the Cherry Trail-based Intel Atom combined CPU/GPU for developers to use to augment the user's reality to greater effect.
The HPU receives information from the inertial measurement unit (IMU) which includes an accelerometer, gyroscope, and magnetometer and combines this with head tracking cameras that follow the user and their environment to augment the user's visual perspective with holographic 3D projections on its transparent lenses.
The processing of gestures and voice data is also handled by the HPU. According to Alex Kipman, HoloLens chief inventor, it integrates terabytes of information from the HoloLens's sensors in real time. This leaves many wondering just exactly what it's silicon is but details are yet unclear.