When directly manipulating 3D objects in an immersive environment we cannot normally achieve the accuracy and control that we have in the real world. This reduced accuracy stems from hand instability. We present PRISM, which dynamically adjusts the C/D ratio between the hand and the controlled object to provide increased control when moving slowly and direct, unconstrained interaction when moving rapidly. We describe PRISM object translation and rotation and present user studies demonstrating their effectiveness. In addition, we describe a PRISM-enhanced version of ray casting which is shown to increase the speed and accuracy of object selection.

We present a novel text input interface for immersive virtual environments called CTD, or "Connect the Dots". The CTD interface is a small virtual panel containing a grid of dots the user can connect to form alphanumeric characters using a hand held stylus. Coupled with a physical paddle or desk for force feedback, the CTD provides an intuitive text input interface similar to using a pen and paper.

A significant benefit of an immersive virtual environment is that it provides users the ability to interact with objects in a very natural, direct way; often realized by using a tracked, hand-held wand or stylus to grab and position objects. In the absence of force feedback or props, it is difficult and frustrating for users to move their arms, hands, or fingers to precise positions in 3D space, and more difficult to hold them at a constant position, or to move them in a uniform direction over time. The imprecision of user interaction in virtual environments is a fundamental problem that limits the complexity of the environment the user can interact with directly. We present PRISM (precise and rapid interaction through scaled manipulation), a novel interaction technique which acts on the user's behavior in the environment to determine whether they have precise or imprecise goals in mind. When precision is desired, PRISM dynamically adjusts the control/ display ratio which determines the relationship between physical hand movements and the motion of the controlled virtual object, making it less sensitive to the user's hand movement. In contrast to techniques like Go-Go, which scale up hand movement to allow long distance manipulation; PRISM scales the hand movement down to increase precision. We present the results of a user study which shows that PRISM significantly out-performs the more traditional direct manipulation approach.