Unified Gesture-Based Interaction Techniques for Object Manipulation and Navigation in a Large-Scale Virtual Environment Yusuke Tomozoe* Takashi Machida*+ Kiyoshi Kiyokawa*+ and Haruo Takemura*+ *Graduate School of Information Science and Technology, Osaka University + Cybermedia Center, Osaka University
[email protected], {machida, kiyo, takemura}@ime.cmc.osaka-u.ac.jp
Manipulation of virtual objects and navigation are common operations in a large-scale virtual environment. In this paper, we propose a few gesture-based interaction techniques that can be used for both object manipulation and navigation. Unlike existing methods, our techniques enable a user to perform these two types of operations flexibly with a little practice in identical interaction manners by introducing a movability property attached to every virtual object.
movability properties are set in advance, and a user is also able to flip each value by using a keyboard in the current implementation. With the movability property, an operation for an unmovable object is considered as a navigation command, and the same operation for a movable object is considered as a manipulation command. For example, pushing back a cup on a table moves the cup further from the user, while pushing back a wall moves the user backward. Visual feedback is provided to show the user whether the object is movable or unmovable.
1. Introduction
3. Functions of our system
Manipulation of virtual objects and navigation are often necessary in a large-scale virtual environment [1]. Most VR systems support direct manipulation of virtual objects within reach. It is often useful to support remote object manipulation for those out of reach as well. On the other hand, navigation is another essential interaction in a large-scale virtual environment. One of the main advantages of using a virtual reality system is that a user can see and examine three-dimensional data from an arbitrary viewpoint. Most VR systems allow a user to change the viewpoint and viewing direction in real-time. Most interaction techniques for navigation and remote object manipulation have been developed independently. But they are similar to each other in a sense that a user changes relative position and orientation between the user and objects. So, it is expected that if a user can perform these two functions in an identical manner, he/she will be able to remember commands and use the system more easily.
We propose three kinds of gesture-based operations according to the distances from a user to target objects. By combining these operations, a user can perform object manipulation and navigation in a large-scale virtual environment flexibly with a little practice.
Abstract
3.1. Short range operation We simply employ a direct manipulation technique for a target object within reach. If the target object is movable, user can grab and move it. On the other hand, if the grabbed object is unmovable, the user’s position moves Wave Away
Movable Object (cone)
Wave Away
2. Basic idea for unifying commands The basic idea to unify interaction techniques for remoteobject manipulation and navigation is very simple. That is, each virtual object in the scene is set to either movable or unmovable. For example, books, cars, or bottles are likely to be movable. On the other hand, ground planes, tall buildings or walls are likely to be unmovable. Default
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Proceedings of the 2004 Virtual Reality (VR’04) 1087-8270/04 $ 20.00 IEEE
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Beckon
Unmovable Object (wall)
Beckon
Figure 1. String-shot manipulation
Movable Object (cone)
(a)
(b)
(c)
Unmovable Object (wall) (d)
Figure 2. Skewer manipulation according to the movement of the user’s hand.
3.2. Middle range operations 3.2.1. String-shot. “String-shot” is an interaction technique for a remote target that is out of reach but within view. Similarly to a ray-casting technique, a user can shoot a string (a line segment) toward arbitrary objects by a pointing gesture. The string is hooked to the target and the user can change the relative distance between him/her and the object by beckoning or waving away. The length of the string also changes like a rubber band to visualize the distance. Figure 1 shows a few screenshots of the string-shot operation on a movable object and a unmovable object.
4. Conclusions and future work
3.2.2. Skewer. “Skewer" is another interaction technique for remote object manipulation and navigation. A user can grab a stick which was made in a string-shot operation. After grabbing the stick a user can move and rotate the hooked object around the user, or the viewpoint around the object. Figure 2 shows some screenshots of skewer operations on a movable and an unmovable object.
Our unified techniques are expected to require less practice time and cognitive load compared with conventional separated techniques, especially when both object manipulation and navigation are frequently performed. A tunnel-window not only contributes to perform remote manipulation but also reduce the required numbers of navigation. For example, a user can move objects among distant locations without locomotion by making multiple windows. On the other hand, our techniques may be hard to use in a complex environment where line of sights are limited. Another technique such as a world-in-miniature can be combined for such a case. Future work includes conducting rigorous user studies and development of geometrically constrained operations for more precise manipulations.
3.3 Long range operation Interaction techniques mentioned above are only available for a target within view. We propose a “Tunnelwindow”, a novel versatile interaction technique for a variety of long range operations. A “Tunnel-window” is created at an arbitrary location by specifying a diagonal line in space. A user can change the viewpoint in the window by the techniques mentioned above, and jump into the window to teleport to the scene (move the viewpoint instantly). Further more, a user can move a remote object in a single window, and move an object between multiple windows and/or the local scene by using “Direct manipulation”, “String-shot”, and “Skewer” techniques.
Proceedings of the 2004 Virtual Reality (VR’04) 1087-8270/04 $ 20.00 IEEE
(e)
Figure 3. Manipulations in a tunnel-window Figure 3 shows a few manipulation examples of a tunnelwindow technique. Figure 3-(a) shows direct manipulation of a remote object in a tunnel-window. Figure 3-(b) shows a string-shot operation (beckoning) of a remote object. Figure 3-(c) shows a skewer operation (swinging) of another. These examples show remote manipulations at a local place. A tunnel-window also supports manipulations between inside and outside the frame. Figure 3-(d) shows a beckoning operation that moves an object from a remote place to the local place seamlessly. Tunnel-windows can be created as many as needed, and allow a user to move objects between them. In figure 3-(e), a user is moving a remote object from one tunnel-window to another.
References [1] Doug A. Bowman, David Koller and Larry F. Hodges, “A Methodology for the Evaluation of Travel Techniques for Immersive Virtual Environments,” Virtual Reality Research Development and Applications, Vol.3, No.2, pp.120-131, 1998.
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