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Conceptual design and analysis using computer graphics
Micro display-processor components A L Thomas (University of Durham, U K y This paper briefly outlines the design' and application of two potential display processor components in future computeraided design systems. Most of the applications derive from the high-speed graphics facilities with automatic hidden-line" removal - however some depend on an overlap testing procedure which can be used both in interactive design systems and in computer controlled manufacturing systems.
Conceptual design and analysis using computer graphics D H McMurtry (IBM GP Department, USA) A methodology for conceptual design and analysis using computer graphics is presented. It discusses how a master layout can be used most effectively as a method for organizing the data. The traditional problems of creating and using master layouts are discussed. The applications of structural and tolerance analyses are presented. The ramifications on project organization and management are discussed. The human factors of designer productivity, project schedules and rate of engineering change are presented. The implications of computer graphics on manufacturing are briefly discussed. David H MeMurtry: BASe (University of Toronto), MS (Stanford University) currently Development Engineer, Printer Products, IBM, has worked in the areas of optical character recognition, barcode scanning, disc and tape drive memories, holography, mechanical analysis and as headquarters technical advisor.
Digitizing line drawings using a standard TV camera R Gray (Lloyd's Register of Shipping, UK) and C Besant (Imperial College, UK) The transcription of data from line drawings to a computer-readable media using manually operated techniques is both tedious and time-consuming. Although automatic systems have been developed which can overcome most of the difficulties associated with this problem, they have hitherto been relatively expensive. The semi-automatic digitizing system described in this paper achieves adequate accuracy for many purposes at relatively modest COSt.
Software filters for graphical output and interaction A C Kilgour (University of Glasgow, UK) The idea of 'software filters' (processes whose output is a transformation of their input) was first introduced by Ritchie and Thomson in connection with the UNIX operating system. This paper discusses the application of this idea to the design of graphical output systems. The implications for device independence and distributed systems are assessed, and the effects of allowing for graphical interaction are investigated. The implementation of a
82
system based on this approach is also described.
A C Kilgour has been lecturer in Computing Science at Glasgow University since 1974. Prior to that he worked as a technical programmer with ICL, and as Research Associate specializing in graphics systems with the CAD Project at Edinburgh University.
The primary role of the computer in the design process is to provide a means of recording the design, and subsequently of extracting information from the record. The choice of technique for recording geometry depends on the characteristics of the component and the nature of the information subsequently required about it. This paper reviews the principal techniques currently in use with particular emphasis on these two aspects.
Decentralized device driver for a digitizer
Curve and surface representations for
F J Mahrl and J Weiss (Institute fuer
Bezier B-spline systems
Datenverarbeitung, Austria)
P J Hartley and C J Judd (Lanchester
Polytechnic, UK)
Based on the requirements for a graphic system, this paper defines a device-independent interface for the input direction. We intended an utmost conformity with the German Graphical Kernal System (GKS) which is most likely going to be accepted as DIN-standard. As we are dealing with a decentralized system, a second important aspect besides standardization is the user aid. Its decentralization results in substantial relief for the host computer. An implementation combining both aspects which was realized in the Research Project for Graphical Data Processing of the Technical University in Vienna is presented.
The Bezier approach to the computeraided design of surfaces, using interactive design of curves to construct surface sections, can be implemented using spline curves just as well as the original polynomial curves, and with some advantages. In this paper we consider some problems that arise when a Bezier system is formulated and describe possible solutions for a splinebased system. Another aspect which is sometimes important is the quality of the parametrization. We shall briefly consider factors which contribute to producing good parametrization.
Franz J Mahrl: studied computer science at the Technical University Vienna (final stadium). Presently serving in the Austrian army, where he works in the main computer centre.
P J Hartley is a senior lecturer in the Department of Mathematics, Lanchester Polytechnic, specializing in numerical analysis.
Dipl Ing Johann Weiss: studied technical mathematics (with specialization in data processing) at the Technical University of Vienna. He has five years experience of Graphic System Implementation with Siemens in Munich. Since 1977 he has been project manager of the Graphic Research Project at the Technical University Vienna.
*The design of a general drafting system Paul Richens (Applied Research of Cam-
bridge, UK) For many years ARC has been developing computer systems for architects and planners. Characteristically these consist of a suite of programs sharing a 3D model of the physical world, be it a building, the surface of the ground, the profiles of a motorway, or the land-use structure of the countryside. A major output of these systems has been drawings. Often the production of drawings is the major use. But producing drawings by manipulating a complex model can be unnecessarily hard work. It would be easier to model the drawing, detached from the underlying physical reality. GDS is the result of applying the advanced techniques developed for 3D physical models to the problems of drawing. It can be used on its own,or as a backend to a sophisticated modeller.
C J Judd is a research student in the same department working on the computeraided design of surfaces.
The spline functions of (2n+1)th degree with the coefficients expressed by even order derivatives X Zhen-xiang (Peking Institute of Aeronautics and Astronautics, The Peoples Republic of China) In this paper a method of constructing splines of (2n+1)th degree is advanced. This method is simple in its rules and convenient in computation. Given the position vectors Pi (i=1,2 . . . . . m) of m points, through which the spline function of degree (2n+1) in parametric form is
Pi(t) = _'~--0 [Pi(2J)(0)-f2j+l (t)+ p-~.(2j) (1) g2j+l (t)], ( O ~ t ~ l , i=2,3 . . . . .
m),
where ~.(2/)(0) and ~ 2' Pi (1)(1) are t~e vector derivatives of the (2j)th order_~f Pi(t} at t=0 and t=l respectively, and Pi(0J=~._I, ~ Pi0( )(1)=~ .. The blending functions f2j+l(t) and g2j+l (t) are polynomials of (2j+1)th degree of t, connected by the relations f2j+l (t)=g2j+l (1-t), (/=0,1,2,...,n).
GEOMETRIC DESIGN A review of computer techniques for representation of geometry
There exist g2j+l (t)=g2/-1 (t),
R S Davies (Computer Aided Design Centre,
g2j+l (0)=g2/+1 (1)=0,
UK)
g, (t)=t.
(/=1,2 ..... n),
c o m p u t e r - a i d e d design
Conceptual design and analysis using computer graphics D H McMurtry (IBM GP Department, USA) A methodology for conceptual design and analysis using computer graphics is presented. It discusses how a master layout can be used most effectively as a method for organizing the data. The traditional problems of creating and using master layouts are discussed. The applications of structural and tolerance analyses are presented. The ramifications on project organization and management are discussed. The human factors of designer productivity, project schedules and rate of engineering change are presented. The implications of computer graphics on manufacturing are briefly discussed. David H MeMurtry: BASe (University of Toronto), MS (Stanford University) currently Development Engineer, Printer Products, IBM, has worked in the areas of optical character recognition, barcode scanning, disc and tape drive memories, holography, mechanical analysis and as headquarters technical advisor.
Digitizing line drawings using a standard TV camera R Gray (Lloyd's Register of Shipping, UK) and C Besant (Imperial College, UK) The transcription of data from line drawings to a computer-readable media using manually operated techniques is both tedious and time-consuming. Although automatic systems have been developed which can overcome most of the difficulties associated with this problem, they have hitherto been relatively expensive. The semi-automatic digitizing system described in this paper achieves adequate accuracy for many purposes at relatively modest COSt.
Software filters for graphical output and interaction A C Kilgour (University of Glasgow, UK) The idea of 'software filters' (processes whose output is a transformation of their input) was first introduced by Ritchie and Thomson in connection with the UNIX operating system. This paper discusses the application of this idea to the design of graphical output systems. The implications for device independence and distributed systems are assessed, and the effects of allowing for graphical interaction are investigated. The implementation of a
82
system based on this approach is also described.
A C Kilgour has been lecturer in Computing Science at Glasgow University since 1974. Prior to that he worked as a technical programmer with ICL, and as Research Associate specializing in graphics systems with the CAD Project at Edinburgh University.
The primary role of the computer in the design process is to provide a means of recording the design, and subsequently of extracting information from the record. The choice of technique for recording geometry depends on the characteristics of the component and the nature of the information subsequently required about it. This paper reviews the principal techniques currently in use with particular emphasis on these two aspects.
Decentralized device driver for a digitizer
Curve and surface representations for
F J Mahrl and J Weiss (Institute fuer
Bezier B-spline systems
Datenverarbeitung, Austria)
P J Hartley and C J Judd (Lanchester
Polytechnic, UK)
Based on the requirements for a graphic system, this paper defines a device-independent interface for the input direction. We intended an utmost conformity with the German Graphical Kernal System (GKS) which is most likely going to be accepted as DIN-standard. As we are dealing with a decentralized system, a second important aspect besides standardization is the user aid. Its decentralization results in substantial relief for the host computer. An implementation combining both aspects which was realized in the Research Project for Graphical Data Processing of the Technical University in Vienna is presented.
The Bezier approach to the computeraided design of surfaces, using interactive design of curves to construct surface sections, can be implemented using spline curves just as well as the original polynomial curves, and with some advantages. In this paper we consider some problems that arise when a Bezier system is formulated and describe possible solutions for a splinebased system. Another aspect which is sometimes important is the quality of the parametrization. We shall briefly consider factors which contribute to producing good parametrization.
Franz J Mahrl: studied computer science at the Technical University Vienna (final stadium). Presently serving in the Austrian army, where he works in the main computer centre.
P J Hartley is a senior lecturer in the Department of Mathematics, Lanchester Polytechnic, specializing in numerical analysis.
Dipl Ing Johann Weiss: studied technical mathematics (with specialization in data processing) at the Technical University of Vienna. He has five years experience of Graphic System Implementation with Siemens in Munich. Since 1977 he has been project manager of the Graphic Research Project at the Technical University Vienna.
*The design of a general drafting system Paul Richens (Applied Research of Cam-
bridge, UK) For many years ARC has been developing computer systems for architects and planners. Characteristically these consist of a suite of programs sharing a 3D model of the physical world, be it a building, the surface of the ground, the profiles of a motorway, or the land-use structure of the countryside. A major output of these systems has been drawings. Often the production of drawings is the major use. But producing drawings by manipulating a complex model can be unnecessarily hard work. It would be easier to model the drawing, detached from the underlying physical reality. GDS is the result of applying the advanced techniques developed for 3D physical models to the problems of drawing. It can be used on its own,or as a backend to a sophisticated modeller.
C J Judd is a research student in the same department working on the computeraided design of surfaces.
The spline functions of (2n+1)th degree with the coefficients expressed by even order derivatives X Zhen-xiang (Peking Institute of Aeronautics and Astronautics, The Peoples Republic of China) In this paper a method of constructing splines of (2n+1)th degree is advanced. This method is simple in its rules and convenient in computation. Given the position vectors Pi (i=1,2 . . . . . m) of m points, through which the spline function of degree (2n+1) in parametric form is
Pi(t) = _'~--0 [Pi(2J)(0)-f2j+l (t)+ p-~.(2j) (1) g2j+l (t)], ( O ~ t ~ l , i=2,3 . . . . .
m),
where ~.(2/)(0) and ~ 2' Pi (1)(1) are t~e vector derivatives of the (2j)th order_~f Pi(t} at t=0 and t=l respectively, and Pi(0J=~._I, ~ Pi0( )(1)=~ .. The blending functions f2j+l(t) and g2j+l (t) are polynomials of (2j+1)th degree of t, connected by the relations f2j+l (t)=g2j+l (1-t), (/=0,1,2,...,n).
GEOMETRIC DESIGN A review of computer techniques for representation of geometry
There exist g2j+l (t)=g2/-1 (t),
R S Davies (Computer Aided Design Centre,
g2j+l (0)=g2/+1 (1)=0,
UK)
g, (t)=t.
(/=1,2 ..... n),
c o m p u t e r - a i d e d design