The purpose of this presentation is to show a possible classification of 3D user interaction methods, develop a taxonomy, and to describe how to use and implement several techniques. The input devices are restricted to the ubiquitous 2D mouse and keyboard, and the futuristic 3D trackers and control buttons. This provides for a wide range of input possibilities and allows us to compare 2D versus 3D methods while greatly restricting the set of possible input devices.

Classification of Interaction Techniques: a taxonomy

In trying to develop a taxonomy, we can divide the top-level into two user interaction methods:

• World Navigation or Camera-Centered:
• used to move the viewer (camera) through a virtual environment
• transformations are applied to the camera system
• Object Manipulation or Object-Centered:
• used to properly position, orient, and resize objects in the scene
• transformations are applied to the objects

Interaction methods can be further classified in each grouping by the type of transformations applied. The following camera or object transformations are sufficient to implement most techniques:

• Translation
• Rotation
• Scaling

The techniques are further subdivided by how the transformations are applied:

• Position controlled: the user sets a unique transformation with an input device and the it is applied only once.
• Rate controlled: transformations are applied continuously and incrementally; the user simply specifies the rate.
• Intertial: the user can impart momentum on an object or the viewer. The last transformation before termination of the interaction method is applied continuously or until interrupted by another transformation. This can be applied to both position and rate control methods.