Protractor3D: A Closed-Form Solution to Rotation-Invariant 3D Gestures

Protractor 3D is a gesture recognizer that extends the 2D touch screen gesture recognizer Protractor [8] to 3D gestures. It inherits many of Protractor's desirable properties, such as high recognition rate, low computational and low memory requirements, ease of implementation, ease of customization, and low number of required training samples. Protractor 3D is based on a closed-form solution to finding the optimal rotation angle between two gesture traces involving quaternions. It uses a nearest neighbor approach to classify input gestures. It is thus well-suited for application in resource-constrained mobile devices. We present the design of the algorithm and a study that evaluates its performance.