摘要:

AbstractA new approach for the animation of articulated figures is presented. We propose a system of articulated motion design which offers a full combination of both direct and inverse kinematic control of the joint parameters. Such an approach allows an animator to specify interactively goal‐directed changes to existing sampled joint motions, resulting in a more general and expressive class of possible joint motions. The fundamental idea is to consider any desired‐joint space motion as a reference model inserted into the secondary task of an inverse kinematic control scheme. This approach profits from the use of half‐space Cartesian main tasks in conjunction with a parallel control of the articulated figure called the coach‐trainee metaphor. In addition, a transition function is introduced so as to guarantee the continuity of the control. The resulting combined kinematic control scheme leads to a new methodology of joint‐motion editing which is demonstrated through the improvement of a functional model of huma

ISSN:0167-7055    

DOI:10.1111/1467-8659.1140189

出版商:Blackwell Science Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractConstructive Solid Geometry (CSG) defines the shape of objects, i.e. the inside and the outside regions of objects, but it does not define the material properties of the space in the interior of objects. The definition is ambiguous. There are points of space lying in several primitives, which can consist of different materials. When visualizing transparent objects this ambiguity leads to strange results, which are not consistent with the CSG modelling scheme and must therefore be eliminated. This work describes how an unambiguous model can be built by asymmetric CSG‐operators and how correct refraction and shading on material boundaries can be established by separating surface properties from material properties. This separation leads to a consistent view of CSG modelling also concerning materials and surfaces. Ray tracing CSG trees and the shading model are influenced by these asymmetric operators. We introduce an applied classification scheme to handle the requirements of the new operator definitio

ISSN:0167-7055    

DOI:10.1111/1467-8659.1140203

出版商:Blackwell Science Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWhilst providing images of excellent quality, ray tracing is a computationally intensive task. The first part of this paper compares the speed‐up achieved in ray tracing using various space subdivision algorithms and discusses the implications of implementing the algorithms on parallel processing systems. The second part addresses the problem of building the data structure within the rendering process, a situation which occurs when the rendering process is parallelised and dynamic scenes are rendered. Greater performance can be achieved with dynamic structure building compared to creation of the structure prior to rendering. The dynamic building algorithm proposed reduces the building time and storage cost of space subdivision structures, and decreases the data structure creation‐render cycle time, thus enhancing image parallelism performa

ISSN:0167-7055    

DOI:10.1111/1467-8659.1140213

出版商:Blackwell Science Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWindow management systems are now used extensively for user interfaces to computer systems. In particular, X11 has come to dominate the workstation market as a widely accepted industry standard on many different hardware platforms. However, no formal standard currently exists for this window system, both in terms of an international standards body (although this is being addressed), and in terms of a precise (mathematical) specification of what the interface is intended to do. This paper advocates the use of a formal notation to describe such an important system to avoid ambiguity and undesired or unintended variations between different implementations of the same system.Theformal notation used for demonstration purposes, Z, is based on set theory, and has been developed at the Programming Research Group in Oxford.

ISSN:0167-7055    

DOI:10.1111/1467-8659.1140221

出版商:Blackwell Science Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe convex differences tree (CDT) representation of a simple polygon is useful in computer graphics, computer vision, computer aided design and robotics. The root of the tree contains the convex hull of the polygon and there is a child node recursively representing every connectivity component of the set difference between the convex hull and the polygon. We give an O(nlogK + Klog2n) time algorithm for constructing the CDT, where n is the number of polygon vertices and K is the number of nodes in the CDT. The algorithm is adaptive to a complexity measure defined on its output while still being worst case efficient. For simply shaped polygons, where K is a constant, the algorithm is linear. In the worst case K = O(n) and the complexity is O(nlog2n). We also give an O(nlogn) algorithm which is an application of the recently introduced compact interval tree data structure.

ISSN:0167-7055    

DOI:10.1111/1467-8659.1140235

出版商:Blackwell Science Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA new algorithm for clipping lines against rectangular windows is described. It is suitable for computations in both object space (floating point arithmetic) and image space (integer arithmetic). The algorithm is compared with other object and image space algorithms and shown to be superior for small windows.

ISSN:0167-7055    

DOI:10.1111/1467-8659.1140241

出版商:Blackwell Science Ltd    

年代:1992

数据来源: WILEY