Abstract: User interaction with a device is sensed using a three-dimensional imaging system. The system preferably includes a library of user profiles and upon acquiring a three-dimensional images of a user can uniquely identify the user, and activate appliances according to user preferences in the user profile. The system can also use data from the acquired image of the user's face to confirm identity of the user, for purposes of creating a robust biometric password. Acquired three dimensional data can measure objects to provide automated, rapid and accurate measurement data, can provide image stabilization data for cameras and the like, and can create virtual three-dimensional avatars that mimic a user's movements and expressions and can participate in virtual world activities. Three-dimensional imaging enables a user to directly manipulate a modeled object in three-dimensional space.