《电子工程师手册》学习资料（英文版）Chapter 91 Computer Graphics

Rozansk,EP.“ Computer Graphics” The Electrical Engineering Handbook Ed. Richard C. Dorf Boca raton crc Press llc. 2000

Rozanski, E.P. “Computer Graphics” The Electrical Engineering Handbook Ed. Richard C. Dorf Boca Raton: CRC Press LLC, 2000

91 Computer graphics 91. 2 Graphics Hardware Hard Copy Technologies. Display Technologies. Standard RT. Other Display Technologi Packages.General Purpose Librarie Programming. Plotting and Page Description Evelyn P Rozanski Rochester Institute of Technology 91.4 Conclusion 91.1 Introduction The term computer graphics refers to the generation, representation, manipulation, processing, and display of data by a computer. Computer-generated images may be real or imagined, animated or still, two-dimensional (2-D)or three-dimensional (3-D). Today most computers, particularly those in the PC, Macintosh, or workstation categories, have graphics capability. Their central components are a graphical display device, usually a cathode ray tube(Crt), and one or more input devices(e.g, keyboard, mouse, digitizer, data glove) Output devices include laser printers or video or such other displays as goggles or " ey es” as in the case of ual reality system Computer graphics encompasses a wide variety of applications. It has expanded its scope from the mundane business/presentation graphics to placing desktop publishing at everyone's fingertips. Highly interactive real time systems are used in flight simulators where the display represents changes in the scene or landscape. In engineering, computer-aided design(CAD)systems allow users to create, store, manipulate, and test objects and designs. Fully integrated systems allow standard component parts libraries to be incorporated into a productProduct design and drafting information is fed into manufacturing operations via numerical control interfaces. Other engineering applications that make extensive use of graphics include very large scale integration Graphics has emerged as the vehicle for visualizing physical phenomena and the volume visualization of complex datasets[ Purgathofer and Schonhut, 1989: Vince, 1990; Kaufmen et al., 1996]. Some examples inclu the medical modeling of the anatomy and MRIs [Kaufmen et al., 1996. One application simulates laboratory testing of a new friction material for disc brakes and visualizes temperature distribution of the brakes'ability to conduct or absorb heat[Purgathofer and Schonhut, 1989]. In mathematics, BB Mandelbrot defined the geometry of fractals Fractals, geometrical self-similar objects with fractional dimension, form a powerful tool for generating objects that resemble natural phenomena such as mountains, trees, and coastlines [de ruiter, 1988: Mandelbrot, 1982 In the world of animation, the computer has taken the drudgery out of transforming and redrawing objects of letting the puter transform one image to another by generating all the in-between image.g,aprocess It has enhanced cell animation as well as produced glitzy Hollywood special effects such as morphing One of the most spectacular uses of graphics is in the area of virtual reality(VR). This technology, which uses high-resolution graphics terminals and head-mounted displays(HMD)or eyephones, provides the user c 2000 by CRC Press LLC

© 2000 by CRC Press LLC 91 Computer Graphics 91.1 Introduction 91.2 Graphics Hardware Hard Copy Technologies • Display Technologies • Standard CRT • Other Display Technologies 91.3 Graphics Software Engineering Software Packages • General Purpose Libraries and Packages • Solid Modeling Packages • Object-Oriented Programming • Plotting and Page Description Languages • Interaction 91.4 Conclusion 91.1 Introduction The term computer graphics refers to the generation,representation, manipulation, processing, and display of data by a computer. Computer-generated images may be real or imagined, animated or still, two-dimensional (2-D) or three-dimensional (3-D).Today most computers, particularly those in the PC,Macintosh, or workstation categories, have graphics capability. Their central components are a graphical display device, usually a cathode ray tube (CRT), and one or more input devices (e.g., keyboard, mouse, digitizer, data glove). Output devices include laser printers or video or such other displays as goggles or “eyephones” as in the case of some virtual reality systems. Computer graphics encompasses a wide variety of applications. It has expanded its scope from the mundane business/presentation graphics to placing desktop publishing at everyone’s fingertips. Highly interactive real￾time systems are used in flight simulators where the display represents changes in the scene or landscape. In engineering, computer-aided design (CAD) systems allow users to create, store, manipulate, and test objects and designs. Fully integrated systems allow standard component parts libraries to be incorporated into a product. Product design and drafting information is fed into manufacturing operations via numerical control interfaces. Other engineering applications that make extensive use of graphics include very large scale integration (VLSI) and solid modeling. Graphics has emerged as the vehicle for visualizing physical phenomena and the volume visualization of complex datasets [Purgathofer and Schonhut, 1989; Vince, 1990; Kaufmen et al., 1996]. Some examples include the medical modeling of the anatomy and MRIs [Kaufmen et al., 1996]. One application simulates laboratory testing of a new friction material for disc brakes and visualizes temperature distribution of the brakes’ ability to conduct or absorb heat [Purgathofer and Schonhut, 1989]. In mathematics, B. B. Mandelbrot defined the geometry of fractals. Fractals, geometrical self-similar objects with fractional dimension, form a powerful tool for generating objects that resemble natural phenomena such as mountains, trees, and coastlines [de Ruiter, 1988; Mandelbrot, 1982]. In the world of animation, the computer has taken the drudgery out of transforming and redrawing objects. It has enhanced cell animation as well as produced glitzy Hollywood special effects such as morphing, a process of letting the computer transform one image to another by generating all the in-between images. One of the most spectacular uses of graphics is in the area of virtual reality (VR). This technology, which uses high-resolution graphics terminals and head-mounted displays (HMD) or eyephones, provides the user Evelyn P. Rozanski Rochester Institute of Technology

with a stereo view of a virtual world and an ability to navigate through it. These systems have a tracking device to determine the position of the user and devices, such as data gloves, for inputting commands [Thomas and Stuart, 1992]. Applications include simulation and architecture. Research in the area of computer graphics has centered on all aspects of hardware, software, and algorithm development. Some of these areas are Object-oriented environments: Design of programming languages, tools, databases, user interfaces, and animation [ Purgathofer and Schonhut, 1989; Cunningham et al., 1992; de Ruiter, 1988] 2. Virtual reality: The design of system architecture, the creation and integration of component hardwares, the creation of software, the building of virtual environments, the development of real-world applica ions, and the study of philosophical and human perceptual issues [Stuart, 1992] 3. Scientific visualization: Graphics software solutions, practical implementations, user interfaces, high resolution hard copy, data representation and metafiles [Purgathofer and Schonhut, 1989 4. Algorithmic design: Ray tracing [Straber, 1987 5. Hardware design: Workstation architectures, support for geometric modeling[Straber, 198 6. Color models and manipulation [Purgathofer and Schonhut, 1989 7. Page description languages(PDLs): PostScript interpreters[ Purgathofer and Schonhut, 1989 8. CAD and solid modeling: VLSI, data exchange, geometric modeling [de Ruiter, 1988; Purgathofer and Schonhut, 1989] 91.2 Graphics Hardware Computer graphics systems comprise several different output components in which to display computer-generated mages. These components are classified into two groups:(1)hard copy technologies and (2)display technologies. Hard Copy Technologies Hard copy technologies include printers, pen plotters, electrostatic plotters, laser printers, ink-jet plotters, thermal transfer plotters, and film recorders [Foley et al, 1996. These devices use either a raster or vector style of drawing. The raster style uses discrete dots, and the vector style uses a continuous drawing motion. Each display device is distinguished by its dot size and the number of dots per inch, known as addressability. The loser the dots, the smoother the image. The smaller the dot, the finer the detail. Resolution is related to dot size and is the number of distinguishable lines per inch. This may vary in the horizontal and vertical directions. High-resolution devices have fine detail, smooth lines, and crisp images. Color may be achieved in several ways, depending on the device. Some devices use multicolored ribbons with single print heads, multiple print heads with different ribbons, or overstriking to combine colors. Other devices use color pens, spray(e.g, ink jet), toner (e.g, laser printer, electrostatic plotters), or pigment from colored wax paper(e.g, thermal transfer) The hard copy devices vary in color and intensity levels, addressability, dot size, cost, image quality, and speed. The laser printer is becoming the most common, high-quality output device in this category [Foley et al., 1996 Display Technologies Displays are, for the most part, characterized by their responsiveness to a changing image. As with the hard copy technologies, display technologies vary greatly with respect to performance and cost. Guidelines for comparisons are based on the following characteristics: power consumption, screen size, depth, weight, rug- gedness, brightness, addressability, contrast, intensity levels per dot, viewing angle, color capability, and relative cost Standard crT The most common component of graphics displays has been the CRT, which is used in televisions. The CRT is composed of five parts: (1)the electron gun, which when heated emits electrons at an appropriate rate;(2) the control grid, which regulates the flow of electrons;( 3)the focusing system, which concentrates the beam e 2000 by CRC Press LLC

© 2000 by CRC Press LLC with a stereo view of a virtual world and an ability to navigate through it. These systems have a tracking device to determine the position of the user and devices, such as data gloves, for inputting commands [Thomas and Stuart, 1992]. Applications include simulation and architecture. Research in the area of computer graphics has centered on all aspects of hardware, software, and algorithm development. Some of these areas are 1. Object-oriented environments: Design of programming languages, tools, databases, user interfaces, and animation [Purgathofer and Schonhut, 1989; Cunningham et al., 1992; de Ruiter, 1988]. 2. Virtual reality: The design of system architecture, the creation and integration of component hardwares, the creation of software, the building of virtual environments, the development of real-world applica￾tions, and the study of philosophical and human perceptual issues [Stuart, 1992]. 3. Scientific visualization: Graphics software solutions, practical implementations, user interfaces, high￾resolution hard copy, data representation and metafiles [Purgathofer and Schonhut, 1989]. 4. Algorithmic design: Ray tracing [Straber, 1987]. 5. Hardware design: Workstation architectures, support for geometric modeling [Straber, 1987]. 6. Color models and manipulation [Purgathofer and Schonhut, 1989]. 7. Page description languages (PDLs): PostScript interpreters [Purgathofer and Schonhut, 1989]. 8. CAD and solid modeling: VLSI, data exchange, geometric modeling [de Ruiter, 1988; Purgathofer and Schonhut, 1989]. 91.2 Graphics Hardware Computer graphics systems comprise several different output components in which to display computer-generated images. These components are classified into two groups: (1) hard copy technologies and (2) display technologies. Hard Copy Technologies Hard copy technologies include printers, pen plotters, electrostatic plotters, laser printers, ink-jet plotters, thermal transfer plotters, and film recorders [Foley et al., 1996]. These devices use either a raster or vector style of drawing. The raster style uses discrete dots, and the vector style uses a continuous drawing motion. Each display device is distinguished by its dot size and the number of dots per inch, known as addressability. The closer the dots, the smoother the image. The smaller the dot, the finer the detail. Resolution is related to dot size and is the number of distinguishable lines per inch. This may vary in the horizontal and vertical directions. High-resolution devices have fine detail, smooth lines, and crisp images. Color may be achieved in several ways, depending on the device. Some devices use multicolored ribbons with single print heads, multiple print heads with different ribbons, or overstriking to combine colors. Other devices use color pens, spray (e.g., ink jet), toner (e.g., laser printer, electrostatic plotters), or pigment from colored wax paper (e.g., thermal transfer). The hard copy devices vary in color and intensity levels, addressability, dot size, cost, image quality, and speed. The laser printer is becoming the most common, high-quality output device in this category [Foley et al., 1996]. Display Technologies Displays are, for the most part, characterized by their responsiveness to a changing image. As with the hard copy technologies, display technologies vary greatly with respect to performance and cost. Guidelines for comparisons are based on the following characteristics: power consumption, screen size, depth, weight, rug￾gedness, brightness, addressability, contrast, intensity levels per dot, viewing angle, color capability, and relative cost. Standard CRT The most common component of graphics displays has been the CRT, which is used in televisions. The CRT is composed of five parts: (1) the electron gun, which when heated emits electrons at an appropriate rate; (2) the control grid, which regulates the flow of electrons; (3) the focusing system, which concentrates the beam

Poisson 's Ratio vs. Treatment for ductile Irons 0.25 Torsion 60-40-18 65-45-12 80-55-06 Treatment FIGURE 91. 1 An example of a figure generated on the Macintosh with Microsoft Excel 3.0, showing the effect of four different treatments on two different measured variables. Although this information could be presented in two dimensions, the 3-D illustration can be more intuitive and interesting into a fine point;(4)the deflection system, which directs the beam to the appropriate location; and(5)the phosphor screen, which glows when bombarded with the electron beam. The persistence of the phosphor is defined as the time from the removal of excitation to when the phosphorescence has decayed to 10% of the initial light output[ Foley et al., 1996]. Depending on the persistence of the phosphor used, the screen will need to be continually refreshed, or redrawn. Color is produced by laying triads of red-green-blue(rGB) phosphors on the screen and using three electron guns, one for each color, to excite the corresponding phosphor The raster CRT scans the image, one row at a time, from a matrix whose elements correspond to a pixel,or point on the screen. This matrix is referred to as the frame buffer and allows for a constant refresh rate, usually 60 times per second. Systems may also have more than one frame buffer(double buffer) to facilitate faster image generation. These displays include high resolution(1024 X 11280), SVGA(768 1024),NTSC (350 X 480) and HDTV (720 X 1280 and 1080 X 1920)[Baily et al., 1996]. In vector CRt displays, the picture is generated in a continuous sweep, much like tracing an image on paper. The refresh rate on the vector displays is a function of the complexity of the image. The result may be a noticeable flicker on the screen. Other Display technologies 1. Direct view storage tubes(DVST): These devices were the primary displays used in earlier systems. These vector drawing devices stored their images on a grid, which was continually bombarded with electrons n order to transfer the image to the screen. The advantage was that once the image was drawn, the refresh process took place independently of the complexity of the image, thereby producing a constant ge on the screen. The disadvantage of these systems was that no part of the image could be selectively erased without erasing the entire grid and resending the modified image to the display. 2. Liquid crystal display (LCD ) This device uses matrix addressing and refreshes the display one row at a time. Appropriate voltages are applied to the crystals, causing them to line up. They remain polarized not allowing light to pass through; light is absorbed, causing dark spots on the display. These devices 3. Plasma panels: These devices have an array of neon bulbs between glass plates, which may be turned on or off. While color is possible, it has not been commercially available. These devices excel in screen size, weight, ruggedness, and brightness characteristics but are generally high in cost. 4. Electroluminescent displays: These devices also use a grid-like structure for addressing elements. The light-emitting material, a zinc sulfide doped with manganese, is available in color. These devices have brightness characteristics but are high in cost. e 2000 by CRC Press LLC

© 2000 by CRC Press LLC into a fine point; (4) the deflection system, which directs the beam to the appropriate location; and (5) the phosphor screen, which glows when bombarded with the electron beam. The persistence of the phosphor is defined as the time from the removal of excitation to when the phosphorescence has decayed to 10% of the initial light output [Foley et al., 1996]. Depending on the persistence of the phosphor used, the screen will need to be continually refreshed, or redrawn. Color is produced by laying triads of red-green-blue (RGB) phosphors on the screen and using three electron guns, one for each color, to excite the corresponding phosphor. The raster CRT scans the image, one row at a time, from a matrix whose elements correspond to a pixel, or point on the screen. This matrix is referred to as the frame buffer and allows for a constant refresh rate, usually 60 times per second. Systems may also have more than one frame buffer (double buffer) to facilitate faster image generation. These displays include high resolution (1024 ¥ 11280), SVGA (768 ¥ 1024), NTSC (~350 ¥ 480) and HDTV (720 ¥ 1280 and 1080 ¥ 1920) [Baily et al., 1996]. In vector CRT displays, the picture is generated in a continuous sweep, much like tracing an image on paper. The refresh rate on the vector displays is a function of the complexity of the image. The result may be a noticeable flicker on the screen. Other Display Technologies 1. Direct view storage tubes (DVST): These devices were the primary displays used in earlier systems. These vector drawing devices stored their images on a grid, which was continually bombarded with electrons in order to transfer the image to the screen. The advantage was that once the image was drawn, the refresh process took place independently of the complexity of the image, thereby producing a constant image on the screen. The disadvantage of these systems was that no part of the image could be selectively erased without erasing the entire grid and resending the modified image to the display. 2. Liquid crystal display (LCD): This device uses matrix addressing and refreshes the display one row at a time. Appropriate voltages are applied to the crystals, causing them to line up. They remain polarized, not allowing light to pass through; light is absorbed, causing dark spots on the display. These devices are light in weight, rugged, and have a low power consumption, fair intensity, and low cost. 3. Plasma panels: These devices have an array of neon bulbs between glass plates, which may be turned on or off. While color is possible, it has not been commercially available. These devices excel in screen size, weight, ruggedness, and brightness characteristics but are generally high in cost. 4. Electroluminescent displays: These devices also use a grid-like structure for addressing elements. The light-emitting material, a zinc sulfide doped with manganese, is available in color. These devices have excellent brightness characteristics but are high in cost. FIGURE 91.1 An example of a figure generated on the Macintosh with Microsoft Excel 3.0, showing the effect of four different treatments on two different measured variables. Although this information could be presented in two dimensions, the 3-D illustration can be more intuitive and interesting

91.3 Graphics Software Software for scientific and engineering applications has changed dramatically in the past several years. In the 1970s and early 1980s, there were few graphics software tools available. Most of the engineering packages were in the CAD area. Many specific engineering applications required users to develop and implement programs to solve their problems. These programs were written in the Fortran or C programming languages using low level graphical commands or calls to some standard or quasi-standard(e.g, the CORe package) graphic utines. Most of these systems were developed for a mainframe computer environment. A trend begun in the late 1980s resulted in a change in computing hardware environments as well as in software approaches. Predominantly, the hardware platforms are PCs, microcomputers, and powerful Unix workstations, with most of these machines having excellent graphics capabilities. Software moved from code generation to customized stand-alone scientific and engineering software tools. Software development uses standard languages and graphical user interfaces for CH, C, Fortran, and Pascal, as well as more sophisticated languages such as JAVA, Hyper Text, Unix X11, Microsoft's Windows, and Post Script. The technical community is relying more and more on the increased power of computers to easily support software packages that manipulate complex data and represent them in a visual manner. Engineering Software Packages Several commercial scientific and engineering software packages have graphics functionality. It is difficult to distinguish graphics or visualization capabilities without discussing some of these packages. An excellent reference is found in the IEEE Spectrum Focus Report: Softwar These graphical application software packages fall into five categories 1. Logic simulation for application-specific integrated circuits(ASICs) Software in this area might display a schematic of a multigate ASIC from large functional building blocks. These blocks could represent a finite-state machine with several states and gates. Representative packages are Mentor Graphics'Auto- Logic, Cadence Design Systems' HDL Synthesizer and Optimizer, and Teradyne's Frenchip. HDL is a 2. Electromagnetic design and simulation Software in this area might simulate a printed-circuit board for a 32-bit-wide, 8-bit-byte reversal network. Multilayers of a board are displayed, with colors indicating current densities in lines. Representative systems are Hewlett-Packard's High Frequency Structure Sim- ulator(HFSS), a finite-element-based product having animation of field plots and conductor loss and 3-D full-wave solution and S-parameter output; Sonnet Software's"em"package with animation of conductor currents; and Compact Software's Microwave Explorer with X-Windows and OSF Motif raphical interfaces. 3. Data acquisition, analysis, display, and technical reporting. Systems in this area have compute-intensive analysis routines and enhanced visualization of data which capitalize on sharper display resolutions These packages could produce plots and graphs based on acquired data that are displayed in several windows at once; changes to one window could result in recalculation and updating of corresponding windows. Packages in this area frequently have support for standard languages and graphical user interfaces for C and Fortran as well as the Unix X1l interface or Microsofts windows. Representative packages are HP's VEE-Test; Design Sciences Math Type; DSP Development's DADiSP; National Instru- ments'Labwindows; Speakeasy Computing s Speakeasy Zeta, which features user-tailored graphical user interface and PostScript output; and Mihalisin Associates'Temple-Graph, which produces a color Post 4. Mathematical calculations and graphics for visualization Applications for these packages would be curve fitting, evaluation of integrals, statistical analysis, signal processing, and numerical analysis. Features include programmability in languages such as C, Fortran, and Pascal and 2-D and 3-D representations The leading package in this area is Mathematica by Wolfram Research, which is a general system and programming language for numerical, symbolic, and graphical computations in engineering, research, science,financial analysis, and education [Wolfram, 1991]. Other packages are Amtec Engineering Tecplot, Integrated Systems'Xmath, Math Works' Mathlab, Jandel Scientific's SigmaPlot, and NAGs Axiom. e 2000 by CRC Press LLC

© 2000 by CRC Press LLC 91.3 Graphics Software Software for scientific and engineering applications has changed dramatically in the past several years. In the 1970s and early 1980s, there were few graphics software tools available. Most of the engineering packages were in the CAD area. Many specific engineering applications required users to develop and implement programs to solve their problems. These programs were written in the Fortran or C programming languages using low￾level graphical commands or calls to some standard or quasi-standard (e.g., the CORE package) graphical routines. Most of these systems were developed for a mainframe computer environment. A trend begun in the late 1980s resulted in a change in computing hardware environments as well as in software approaches. Predominantly, the hardware platforms are PCs, microcomputers, and powerful Unix workstations, with most of these machines having excellent graphics capabilities. Software moved from code generation to customized stand-alone scientific and engineering software tools. Software development uses standard languages and graphical user interfaces for CH, C, Fortran, and Pascal, as well as more sophisticated languages such as JAVA, HyperText, Unix X.11, Microsoft’s Windows, and PostScript. The technical community is relying more and more on the increased power of computers to easily support software packages that manipulate complex data and represent them in a visual manner. Engineering Software Packages Several commercial scientific and engineering software packages have graphics functionality. It is difficult to distinguish graphics or visualization capabilities without discussing some of these packages. An excellent reference is found in the IEEE Spectrum Focus Report: Software. These graphical application software packages fall into five categories: 1. Logic simulation for application-specific integrated circuits (ASICs). Software in this area might display a schematic of a multigate ASIC from large functional building blocks. These blocks could represent a finite-state machine with several states and gates. Representative packages are Mentor Graphics’ Auto￾Logic, Cadence Design Systems’ HDL Synthesizer and Optimizer, and Teradyne’s Frenchip. HDL is a hardware description language. 2. Electromagnetic design and simulation. Software in this area might simulate a printed-circuit board for a 32-bit-wide, 8-bit-byte reversal network. Multilayers of a board are displayed, with colors indicating current densities in lines. Representative systems are Hewlett-Packard’s High Frequency Structure Sim￾ulator (HFSS), a finite-element-based product having animation of field plots and conductor loss and 3-D full-wave solution and S-parameter output; Sonnet Software’s “em” package with animation of conductor currents; and Compact Software’s Microwave Explorer with X-Windows and OSF Motif graphical interfaces. 3. Data acquisition, analysis, display, and technical reporting. Systems in this area have compute-intensive analysis routines and enhanced visualization of data which capitalize on sharper display resolutions. These packages could produce plots and graphs based on acquired data that are displayed in several windows at once; changes to one window could result in recalculation and updating of corresponding windows. Packages in this area frequently have support for standard languages and graphical user interfaces for C and Fortran as well as the Unix X.11 interface or Microsoft’s Windows. Representative packages are HP’s VEE-Test; Design Science’s MathType; DSP Development’s DADiSP; National Instru￾ments’ LabWindows; Speakeasy Computing’s Speakeasy Zeta, which features user-tailored graphical user interface and PostScript output; and Mihalisin Associates’ Temple-Graph, which produces a color Post￾Script output link to Mathematica. 4. Mathematical calculations and graphics for visualization. Applications for these packages would be curve fitting, evaluation of integrals, statistical analysis, signal processing, and numerical analysis. Features include programmability in languages such as C, Fortran, and Pascal and 2-D and 3-D representations. The leading package in this area is Mathematica by Wolfram Research, which is a general system and programming language for numerical, symbolic, and graphical computations in engineering, research, science, financial analysis, and education [Wolfram, 1991]. Other packages are Amtec Engineering’s Tecplot, Integrated Systems’ Xmath, MathWorks’ Mathlab, Jandel Scientific’s SigmaPlot, and NAG’s Axiom