BOWMAN D., HODGES L.: User Interface Constraints for Immersive Virtual Environment Applications. Technical Report GIT-GVU-95-26, Georgia Institute for Technology, 1995. 2  Home/Search   Document Details and Download   Summary   Related Articles   Check

....a number of advantages. Real time head tracked stereoscopic view improves the understanding of shape and spatial relationships. Spatial direct manipulation improves the accessibility to 3 D objects in a quick and intuitive way. For the last decade, a number of immersive modelers have been developed[3, 4, 5, 6]. However, most of them are only able to construct the shape of virtual objects, not to describe their behavior or geometric constraints. We have developed a new method for imposing geometric constraints on virtual objects within an immersive modeler. This method provides a number of geometric ....

....intuitive and e#cient way for designing 3 D objects, immersive modeling has attracted much attention because of its advantages explained in the next section. For the last decade, a number of immersive modeling systems have been developed; for example, VLEGO [4] the Conceptual Design Space (CDS) [5], and the Chapel Hill Immersive Modeling Program (CHIMP) 6] However, most of these systems support only constructing 3 D shapes, not imposing geometric constraints on the 3 D shapes. 2.1 Immersive Modeling Immersive modeling is a technique to design 3 D objects in an immersive virtual ....

D. A. Bowman and L. F. Hodges: "User Interface Constraints for Immersive Virtual Environment Applications, " Graphics, Visualization and Usability Center Technical Report, GIT-GVU-95-26, 1995.

....has a number of advantages. Real time head tracked stereoscopic view improves the traderstanding of shape and spatial relationships. Direct manipulation improves the accessibility to 3 D objects in a quick and intuitive way. For the last decade, a number of immersive modelers have been developed [3, 4, 5, 6], though most of them are only able to construct the shape of virtual objects, not to describe their behavior or geometric constraints. We focus on geometric constraints among a set of properties of reactive 3 D objects as the first step, since most real objects have geometric constraints on ....

....intuitive and efficient way for designing 3 D objects, immersive modeling has attracted much attention because of its advantages explained in the next section. For the last decade, a number of immersive modeling systems have been developed; for example, VLEGO [4] the Conceptual Design Space (CDS) [5], and the Chapel Hill Immersive Modeling Program (CHIMP) 6] However, most of these systems support only constructing 3 D shapes, not imposing geometric constraints on the 3 D shapes. 1. Immersive Modeling Immersive modeling is a technique to design 3 D objects in an immersive virtual ....

Bowman, D. A. and Hodges, L. F., "User Interface Constraints for Immersive Virtual Environment Applications," Graphics, Fisualization and Usability Center Technical Report, GIT-G[7J-95-26, 1995.

....tools must be very reliable to encourage the users to play and not frustrate them with a non working interface. We had to introduce a new graphical element to the system serving as an interface for the game relevant communication between the IP and the users. Game pads. Bowman and Hodges [1] proposed that the guidelines of Norman [2] should be applied to interaction objects in virtual environments (VE) The game pads we have used in the installation satisfy all four criteria which are: affordance, feedback, constraints and good mappings. To satisfy the affordance criteria, the ....

....the user interface was understood by almost all users. We have shown that it is possible to realize an advanced interaction scheme in an immersive virtual environment, which is well adopted by everyday users, satisfying all four interface design requirements described by Bowman and Hodges [1] and realizing a stable and reliable 12 setup to simulate a mouse input without requiring the user to handle any input device. The idea of using this advanced interface as an input for games originated from the environment in which the system was installed. The playful interaction between ....

Doug A. Bowman and Larry F. Hodges. User interface constraints for immersive virtual environment applications. Technical Report 95-26.

....objects within a virtual environment has a number of advantages such as a real time stereoscopic view of a 3 D scene and spatial manipulation for 3 D objects. In the last decade, a number of immersive modelers using virtual reality techniques have been developed for rapid prototyping of 3 D objects[1, 2, 3, 4]. However, most of existing immersive modelers are only able to construct the shape of objects. Nowadays, the term 3 D computer graphics design implies not only geometric modeling, but also creating geometric constraints, kinetic constraints, animation, behavior and physical properties. Therefore, ....

Bowman, D. A. and Hodges, L. F.: "User Interface Constraints for Immersive Virtual Environment Applications, " Graphics, Visualization and Usability Center Technical Report GIT-GVU-95-26, Georgia Institute of Technology, 1995.

....the device out. For a pair of scissors, the size of the holes limits the number of ngers that can be tted into each hole, so the user doesn t have to try the scissors out with di erent numbers of ngers in each hole. For an application the use of constraints within virtual environments, see [6]. 3. Mappings. Constraints and a ordances help to create a mapping for the user between object nature and required action. Putting the ngers in the holes is a logical conclusion of a look at the nature of the scissors. A conceptual model of the scissors can t be formulated if the user can t see ....

Bowman, D.A., and Hodges, L.F., User Interface Constraints for Immersive Virtual Environment Applications , Technical Paper , Graphic, Visualization and Usability Center, College of Computing, Georgia Institute of Technology.

....the full range of haptic feedback. The Virtual Tricorder [Wloka, 1995] is an example of this idea, whereby a 3D mouse is used as the principal input device, and given a representation in the virtual world, corresponding to its physical size, shape, etc. Allowing the constrained movement of objects [Bowman, 1995] is another method that helps solve the problem of accurately placing objects inside a virtual environment. Constrained movement means allowing the object only to move in a certain direction at any given time. For example, the user may choose to constrain the object to move only along the x axis, ....

....by the user should produce a proportional output action in the system. Feedback is also a major factor contributing to a usable interface. The user should never be in doubt as to whether or not some action has been accomplished or not. Good feedback should naturally follow from good mappings [Bowman, 1995]. For example, in the virtual hand system, when an object has been successfully grabbed , its representation is changed by adding a semi transparent bounding sphere around the object being manipulated, and placing a set of x , y and zaxes onto the object. Feedback in the virtual hand system also ....

Doug A. Bowman and Larry F. Hodges, User Interface Constraints for Immersive Virtual Environment Applications, Graphics, Visualisation and Usability Centre, Georgia Institute of Technology, Technical Report TR95-26

....principles which apply to user interfaces are taken from a discussion of everyday artifacts that we use in our homes, schools, and offices. Since many virtual environments purport to represent a semi realistic world, it is perhaps even more important that interaction in VEs follow these guidelines (Bowman and Hodges, 1995). Norman identifies four characteristics of usable artifacts: affordances, constraints, good mappings, and feedback. Affordances refer to the properties of an object that inform the user of its purpose and the way it can be used. Constraints are 13 limitations on the use of an object that guide ....

....user to position objects correctly. Most of these methods use some type of constraints to reduce the number of degrees of freedom that must be controlled by the user, or to reduce the required precision on the part of the user. For example, one can constrain an object to move only in one dimension (Bowman and Hodges, 1995), model an object s collisions with other parts of the world (Kitamura, Yee, and Kishino, 1996) or place some intelligence in the object so that it naturally seeks to be aligned correctly with the world and other objects (Bukowski and Sequin, 1995) 5.2.2 Evaluation of Techniques There has been ....

Bowman, D. and Hodges, L. (1995). User Interface Constraints for Immersive Virtual Environment Applications. Graphics, Visualization, and Usability Center Technical Report GIT-GVU-95-26.

.... world (Nielsen, 1993) In our experience, however, we have found that natural metaphors are not appropriate for abstract commands, and that overuse of real world techniques can lead to system clutter and reduced user efficiency due to multiple metaphors and tools needed to perform various tasks (Bowman Hodges, 1995). A good deal of research into virtual menus has been performed (Bowman, 1996, Ferneau Humphries, 1995, Jacoby Ellis, 1992) The current approach borrows from the system described in (Angus Sowizral, 1995) in its use of the pen tablet metaphor. a. b. Figure 2. Two Interaction ....

.... the user to travel freely throughout the environment, either walking in two dimensions (constrained to a ground plane) or flying in all three dimensions (Mine, 1995) Often, however, users who have freedom of movement become lost or disoriented, or miss important features of the environment (Bowman Hodges, 1995). Since our system was not designed to allow users to examine every detail of the 3D model, we implemented a more constrained method of travel called the flying chair metaphor. Users sit in a physical chair (see Figure 4) with their feet above the ground so that the illusion of a flying chair ....

Bowman, D., & Hodges, L. (1995). User Interface Constraints for Immersive Virtual Environment Applications. Graphics, Visualization, and Usability Center Technical Report GIT-GVU-95-26.

.... that all interaction in the VE should be natural, or similar to the physical world [15] In our experience, however, we have found that natural metaphors are not appropriate for abstract commands, and that overuse of real world techniques can lead to system clutter and reduced user efficiency [5]. A good deal of research into virtual menus has been performed [4, 10, 12] Our approach is closest to that described in [1] In the Virtual Venue, the user holds a physical tablet, which is tracked in 3D space (Figure 2) In the VE, the user sees a virtual representation of the tablet, on which ....

....can mimic any 2D interface which can be controlled with a single button mouse, since users can click or drag on the physical 2D surface of the tablet. This physical feedback provides an important constraint: if the pen is touching the tablet, users are assured that a menu item will be selected [5]. Constrained Travel A second issue concerns the movement of users around the Virtual Venue. Most VR applications allow the user to travel freely throughout the environment, either walking in two dimensions (constrained to a ground plane) or flying in all three dimensions [14] Often, ....

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D. Bowman and L. Hodges, "User Interface Constraints for Immersive Virtual Environment Applications," Graphics, Visualization, and Usability Center Technical Report GIT-GVU-95-26, 1995.

....is a grabbing technique where a light ray extends from the user s hand. By intersecting an object with this ray and releasing the button, the object is attached to the ray (Figure 3) Users can then manipulate the object easily using wrist or arm motion. Ray casting has several drawbacks, however [1, 6]. First, it suffers from the lever arm problem, meaning that because objects are attached to the end of the ray, there is no simple method for rotating an object in place, except around the axis of the ray itself. Also, it lacks a method for controlling the object s distance from the user. Thus, ....

D. Bowman and L. Hodges. "User Interface Constraints for Immersive Virtual Environment Applications." Graphics, Visualization, and Usability Center Technical Report GITGVU -95-26, 1995.

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BOWMAN D., HODGES L.: User Interface Constraints for Immersive Virtual Environment Applications. Technical Report GIT-GVU-95-26, Georgia Institute for Technology, 1995. 2

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D. A. Bowman and L. F. Hodges. User interface constraints for immersive virtual environment applications. Technical Report GITGVU-9526, Graphics, Visualization, and Usability Center, Georgia Institute of Technology, Atlanta, 1995.

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Doug A. Bowman and Larry F. Hodges. User interface constraints for immersive virtual environment applications. In Proceedings of IEEE VRAIS, pages 35--38, 1997.

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D.A. Bowman and L.F. Hodges, User Interface Constraints for Immersive Virtual Environment Applications, Graphics, Visualization, and Usability Center Technical Report GIT-GVU-95-26, Georgia Institute of Technology, Atlanta, 1995.

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