摘要:

AbstractThis paper presents a system for constructing collaborative design applications based on distributed augmented reality. Augmented reality interfaces are a natural method for presenting computer‐based design by merging graphics with a view of the real world. Distribution enables users at remote sites to collaborate on design tasks. The users interactively control their local view, try out design options, and communicate design proposals. They share virtual graphical objects that substitute for real objects which are not yet physically created or are not yet placed into the real design environment.We describe the underlying augmented reality system and in particular how it has been extended in order to support multi‐user collaboration. The construction of distributed augmented reality applications is made easier by a separation of interface, interaction and distribution issues. An interior design application is used as an example to demonstrate the advantages of our appro

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0003.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAugmented reality involves the use of models and their associated renderings to supplement information in a real scene. In order for this information to be relevant or meaningful, the models must be positioned and displayed in such a way that they align with their corresponding real objects. For practical reasons this alignment cannot be known a priori, and cannot be hard‐wired into a system. Instead a simple, reliable alignment or calibration process is performed so that computer models can be accurately registered with their real‐life counterparts.Wedescribe the design and implementation of such a process and we show how it can be used to create convincing interactions between real and virtual obje

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0015.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractTime lag and image jittering are the main reasons for destroying the feeling of reality in most virtual environments. They cause motion sickness because human beings are simply not used to unrealistically generated feedback. This paper proposes advanced software methods that greatly reduce these unwanted effects: a new improved two‐step prediction method for better head tracking, an image deflection technique to reduce remaining error and a new software configuration that allows the full use of available hardware capabilities. Our improved prediction technique reduces prediction error by 50% in comparison to standard methods. The image deflection allows to extend the prediction distance by 100% while keeping the error below a tolerable leve

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0029.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDoes the modern commercial Graphical User Interface constrain the developer of graphics applications into certain interaction styles? This paper looks at the Microsoft Windows environment as an example, with particular reference to the question of interaction modes, screen real‐estate and visual appearance. The concept of syntax channelling is introduced to help analyse the problem of modality, and the question of button‐down versus button‐up dragging is debated in the context of a range of commercial applications, and possible consequences for upper limb disorder. A Windows application developed by the author involving the implementation of a variety of innovative interfacing techniques is pres

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0043.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMany of the reported developments in the design of virtual spaces or visualisation systems are based on improvements in technology, either physical devices or algorithms for achieving realistic renderings within real‐time constraints. While this experimental approach produces a wealth of empirical results, it operates largely without a sound underlying theory that can be used to design systems that will effectively support users in real‐world domains. One of the main problems is that these sophisticated technologies rely on, but rarely assess, the cognitive abilities of the user. This paper introduces a new approach to modelling human‐system interaction. A syndetic model combines a formal expression of system behaviour with an approximate representation of cognitive resources to allow reasoning about the flow and utilisation of information within the combined system. The power of the approach to provide insight into novel interaction techniques is illustrated by developing a syndetic model of a gesture‐driven user in

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0055.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMany ways of communications are used between human and computer, while using gesture is considered to be one of the most natural way in a virtual reality system. Because of its intuitiveness and its capability of helping the hearing impaired or speaking impaired, we develop a gesture recognition system. Considering the world‐wide use of ASL (American Sign Language), this system focuses on the recognition of a continuous flow of alphabets in ASL to spell a word followed by the speech synthesis, and adopts a simple and efficient windowed template matching recognition strategy to achieve the goal of a real‐time and continuous recognition. In addition to the abduction and the flex information in a gesture, we introduce a concept of contact‐point into our system to solve the intrinsic ambiguities of some gestures in ASL. Five tact switches, served as contact‐points and sensed by an analogue to digital board, are sewn on a glove cover to enhance the functions of a traditional dat

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0067.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper shows how to construct a rational Bezier model of a swept surface that interpolatesNframes (i.e., N position/orientation pairs) of a fixed rational space curve c(s) and maintains the shape of the curve at all intermediate points of the sweep. Thus, the surface models an exact sweep of the curve, consistent with the given data. The primary novelty of the method is that this exact modeling of the sweep is achieved without sacrificing a rational representation for the surface. Through a simple extension, we also allow the sweeping curve to change its size through the sweep. The position, orientation, and size of the sweeping curve can change with arbitrary continuity (we use C2continuity in this paper). Our interpolation between frames has the classical properties of Bezier interpolation, such as the convex hull property and linear precision.This swept surface is a useful primitive for geometric design. It encompasses the surface of revolution and extruded surface, but extends them to arbitrary sweeps. It is a useful modeling primitive for robotics and CAD/CAM, using frames generated automatically by a moving robot or tool.

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0077.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractTriangular B‐splines surfaces are a tool for representing arbitrary piecewise polynomial surfaces over planar triangulations, while automatically maintaining continuity properties across patch boundaries. Recently, Alfeld et al. [1] introduced the concept of sphericalbarycentric coordinateswhich allowed them to formulate Bernstein‐Bézier polynomials over the sphere.In this paper we use the concept of spherical barycentric coordinates to develop a similar formulation for triangular B‐splines, which we callspherical triangular B‐splines. These splines defined over spherical triangulations share the same continuity properties and similar evaluation algorithms with their planar counterparts, but possess none of the annoying degeneracies found when trying to represent closed surfaces using planar parametric surfaces. We also present an example showing the use of these splines for approximating spherical scatte

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0089.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractModeling a curve through minimizing its energy yields an overall smooth curve. A common way to model shape features is to perform the minimization subject to a number of interpolation constraints. This way of modeling is attractive because the designer is not bothered with the precise representation of the curve (e.g. control points). However, local shape specification by means of interpolation constraints is very limited. On the other hand, local deformation by repositioning control points is powerful but very laborious, and destroys the minimal energy property. In this paper, deform operators are introduced for 3D curve modeling that have built‐in energy terms that have an intuitive effect. These operators allow local shape modification and do justice to the energy minimization way of modelin

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0097.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractVolume rendering is a key technique in scientific visualization that lends itself to significant exploitable parallelism. The high computational demands of real‐time volume rendering and continued technological advances in the area of VLSl give impetus to the development of special‐purpose volume rendering architectures. This paper presents and characterizes three recently developed volume rendering engines which are based on the ray‐casting method. A taxonomy of the algorithmic variants of ray‐casting and details of each ray‐casting architecture are discussed. The paper then compares the machinefeatures and provides an outlook onfuture developments in the area of volume rendering

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1995.cgf143_0111.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY