@ ~ Computer Graphics, Volume 24, Number 4, August 1990 Rapid Controlled Movement Through a Virtual 3D Workspace Jock D. Mackinlay, Stuart K. Card, and George G. Robertson Xerox Palo Alto Research Center* Abstract Computer graphics hardware supporting real-time interac- tive 3D animation has the potential to support effective user interfaces by enabling virtual 3D workspaces. However, this potential requires development of viewpoint movement tech- niques that support rapid and controlled movement through workspaces. Rapid movement through large distances avoids wasted work time; controlled movement near target objects allows the user to examine and interact with objects in the workspace. Current techniques for viewpoint movement typ- icaUy use high velocities to cover distances rapidly, but high velocities are hard to control near objects. This paper de- scribes a new technique for targeted viewpoint movement that solves this problem. The key idea is to have the user indicate a point of interest (target) on a 3D object and use the distance to this target to move the viewpoint logarithlni- cally, by moving the same relative percentage of distance to the target on every animation cycle. The result is rapid mo- tion over distances that slows as the viewpoint approaches the target object. The technique can be used with 2D and multidimensional input devices. We also extend the tech- nique to move objects in the workspace. Cl:t Categories and Subject Descriptors: 1.3.6 [Com- puter Graphics]: Methodology and Techniques - Interaction techniques; D.2.2 [Software Engineering]: Tools and Tech- niques - User interfaces Additional Key Words and Phrases: Viewpoint move- ment, object movement, virtual reality, interactive graphics, 3D graphics, logarithmic motion, 3D workspaces 1 INTRODUCTION Advances in computer graphics hardware have enabled the practical realization of real-time interactive 3D animation systems. These systems have the potential to provide simu- lated 3D workspaces for user interaction with CAD/CAM, medical information, scientific visualization, "artificial real- ity", and general information access. An important require- *3333 Coyote Hill Road, Palo Alto, CA 94304, 415-494-4335, [email protected] Permission to copy without fee all or part of this material is granted provided that the copies arc not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. merit for such systems is a technique that allows the user to move the viewpoint (1) rapidly through large distances, (2) with such control that the viewpoint can approach very close to a target without collision. We call this the problem of rapid and controlled, targeted 3D viewpoint movement. This problem arises in large information spaces, such as for complex machine parts in a CAD system or in simulated landscapes. Large information spaces contain numerous ob- jects and/or highly detailed objects that require the user to move back and forth from global, orienting views to manip- ulate detailed information. Current techniques for moving the viewpoint are not very satisfactory for targeted viewpoint movement. Some tech- niques fail to support rapid movement because of inefficient interactions or movement trajectories. Techniques support- ing rapid movement either use coarse-grained scale factors for direct positioning of the viewpoint over large distances or use high velocities for flying the viewpoint rapidly through large distances. Coarse-grained scale factors do not allow fine-grained control and high velocity flight is difficult to control once a target object is reached. This paper describes a new, more effective technique for targeted 3D viewpoint movement. The key idea is to have the user select a 3D point of interest (the target) on the surface of an object. On each animation cycle, the user's viewpoint is moved the same relative percentage of the dis- tance to the target, resulting in an approach that is rapid for large distances, but logarithmically slower as the target becomes closer. Since the technique only requires the mouse or afaother 2D input device, it integrates with existing in- terfaces and work environments. It can also be used with multidimensional input devices. In the paper, we summarize current viewpoint movement techniques, describe the Point of Interest logarithmic movement technique, and show how the ideas can be extended to include general object move- ment. 2 3D VIEWPOINT MOVEMENT Developing an effective technique for 3D viewpoint move- ment is difficult for several reasons. One problem is the number of parameters to be controlled by the user. 3D viewpoint movement involves at least six degrees of free- dom: three dimensions for position and three dimensions for rotation. The actual number of parameters depends on the movement metaphor, which typically involves either the direct positioning of the viewpoint in the workspace or the flying of the viewpoint through the workspace. Direct posi- tioning metaphors typically involve a scale factor parameter for the input device and flying metaphors typically involve ©1990 ACM-0-89791 - 344-2/90/008/0171 $00.75 171SIGGRAPH '90, Dallas, August 6-10, 1990 velocity or direction parameters. Specialized tasks can in- volve additional viewpoint parameters (typically associated with the viewing matrix). For example, a cinematographic application might have a parameter for controlling the zoom of the field of view. Another problem is the type of viewpoint movement re- quired by a given task. We can distinguish at least four types of viewpoint movement for interactive 3D workspaces: General movement. Exploratory movement, such as walking through a simulation of an architec- tural design. Targeted movement. Movement with respect to a specific target, such as moving in to examine a detail of an engineering model. Specified coordinate movement. Movement to a precise position and