It can be said that an important research content of computer graphics is to generate pleasant realistic graphics by computer. Computer graphics is closely related to another subject-computer aided geometric design. In fact, graphics also takes curve and surface modeling technology and solid modeling technology that can express geometric scenes as its important research content. At the same time, the results of realistic graphics calculation are provided in the form of digital images, and computer graphics is closely related to image processing. The difference between graphics and images is becoming more and more blurred, but we still think there is a difference: images simply refer to the gray information in the form of bitmaps in computers.
The research content of computer graphics is very extensive, such as graphics hardware, graphics standards, graphics interaction technology, raster graphics generation algorithm, curve and surface modeling, solid modeling, realistic graphics calculation and display algorithm, as well as scientific calculation visualization, computer animation, natural scenery simulation, virtual reality and so on. As a graphics textbook for computer undergraduates and non-computer postgraduates, this book focuses on the related principles and algorithms of raster graphics generation, curve and surface modeling and realistic graphics generation. [3]
major constituent
Graphics are usually composed of geometric elements such as points, lines, surfaces and bodies, and non-geometric attributes such as gray level, color, line type and line width. From the point of view of composition elements, graphics are mainly divided into two categories. One is the geometric feature graphics that play a prominent role in composition, such as engineering drawings, contour maps, curved surface wireframes, etc. The other is the non-geometric characteristic graphics that play a prominent role in composition, such as light and shade diagram, light and shade diagram, realistic graphics and so on.
primary objective
One of the main purposes of computer graphics is to use computers to produce pleasing realistic graphics. Therefore, it is necessary to establish a geometric representation of the scene described by graphics, and then use some lighting model to calculate the lighting effects under the assumption of light source, texture and material properties. Therefore, computer graphics is closely related to another discipline-computer aided geometric design. In fact, graphics also focuses on curve and surface modeling technology and solid modeling technology that can represent geometric scenes. At the same time, the results of realistic graphics calculation are provided in the form of digital images, and computer graphics is closely related to image processing.
Conceptual difference
The difference between graphics and images is becoming more and more blurred, but there are still differences: images simply refer to the gray information in the form of bitmaps in computers, while graphics contain geometric attributes, or emphasize the geometric representation of scenes, which consists of geometric models and physical attributes of scenes.
Research scope
The research content of computer graphics is very extensive, such as graphics hardware, graphics standards, graphics interactive technology, raster graphics generation algorithm, curve and surface modeling, solid modeling, realistic graphics calculation and display algorithm, non-photorealistic rendering, scientific computing visualization, computer animation, natural scenery simulation, virtual reality and so on.
2 discipline history
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Ivan sutherland 1963, Ivan Sutherland published his doctoral thesis entitled "Sketchpad" at MIT, which marked the formal birth of computer graphics. It has a history of more than forty years. In the past, computers were mainly symbol processing systems. Since the appearance of computer graphics, computers can partly represent the function of human right brain, so the establishment of computer graphics is of great significance. Computer graphics has made great progress in the following aspects:
smartcad
The development of CAD also presents the trend of intelligence. As far as most popular CAD software is concerned, its main function is to support the drawing and output of engineering drawings in the subsequent stage of products, and the product design function is relatively weak. The most commonly used function of AutoCAD is interactive drawing. If you want to design a product, the most basic thing is to write a program in AutoLisp language, and sometimes it is inconvenient to write with other high-level languages. A new generation of intelligent CAD system can realize the whole process from conceptual design to structural design. For example, Sigraph design software developed by Siemens in Germany can realize the following functions: ① Sketch can be designed by computer from the beginning, and it is not necessary to input precise coordinate points in time and effort, and it can be modified at will. Once the structure is determined, a satisfactory drawing can be obtained by giving the correct size; ② The software has a relational data structure. When you change a part of a drawing, the relevant parts will automatically change, while when you modify a view, other views will automatically change, even a part drawing, other related part drawings and assembly drawings will automatically change. ③ In various professional fields, there are some common parts and standard parts. Therefore, we hope to have a parameter library. Sigraph can build its own library without programming, just draw a picture once; ④Sigraph can also realize the dynamic simulation of product design, which is used to observe whether the designed equipment is reasonable in actual operation, and so on. Another field of intelligent CAD is automatic input and intelligent recognition of engineering drawings. With the rapid popularization and application of CAD technology, factories and design institutes need to input thousands of long-term accumulated design drawings into computers quickly and accurately as technical data for new product development. For many years, the commonly used graphics input methods in CAD are interactive input of graphics digitizer and interactive input of mouse and keyboard, which can not meet the urgent demand of a large number of drawings input in engineering. Therefore, the automatic drawing input method based on photoelectric scanner has become a new topic explored by CAD workers at home and abroad. However, the intelligent recognition of engineering drawings involves high-tech contents such as computer hardware, computer graphics, pattern recognition and artificial intelligence, which makes the research work more difficult. Automatic input and intelligent recognition of engineering drawings are two inseparable processes. After drawing paper is input into the computer through the scanner handle, a dot matrix image is formed. In CAD, only vector graphics can be edited, which requires converting dot matrix images into vector graphics. These tasks are automatically completed by computers, which brings many problems, such as: ① Intelligent recognition of images; ② Character extraction and recognition; ③ The establishment of graphic topological structure and the understanding of graphics; ④ Practical post-processing methods and so on. Both the National Natural Science Foundation and the 863 Program Fund are supporting the research in this field, and some softwares in this field have been put into practice at home and abroad, such as RVmaster in the United States, VPmax in Germany, and products from Tsinghua University and Northeastern University. But the effect is not ideal. Did not achieve the expected results.
Art and design
The development of computer art
1952. electronic abstract painting, this waveform diagram. The use of analog computers in La Poske in the United States marked the beginning of computer art (earlier than the formal establishment of computer graphics). The development of computer art can be divided into three stages.
Representative works: 1960 Wiuiam Ferrter designed the dynamic simulation of ergonomics experiment for Boeing Company, simulating various situations of pilots in the plane; 1963 Kenneth Kronorton's printer works naked. 1967 the return box of GTG group in Japan.
The first World Computer Art Exhibition in London-"Cybernetics Treasure 1" marks the beginning of worldwide research and application. With the gradual maturity of computer and computer graphics technology, some universities began to offer related topics, and some CAD application systems and achievements appeared. The 3D modeling system came into being and gradually improved.
Representative works: 1983 Fractal Mountain designed by Richerd Voss, IBM Research Institute, USA (you can find the knowledge about "fractal" on the website "fractal channel HRTP: TT fractal1.126.tom").
Personal computer graphics system has gradually matured, and a large number of commercial art (design) software has been listed; Desktop creative systems represented by Apple MAC and graphics system software are widely accepted, and CAD has become an important part in the field of art design.
Representative works: 1990 interactive graphic work Easy to Read by Jeffrey Shaw.
Computer design science
(Computer Design)
Including environmental design (architecture, automobile), visual communication design (packaging) and product design.
The application of CAD in art can be divided into three levels.
Computer animation art
1. Historical Review
The development of computer animation technology is closely related to the development of many other disciplines. The latest achievements in computer graphics, computer painting, computer music, computer-aided design, film technology, television technology and computer software and hardware technology have all played a very important role in promoting the research and development of computer animation technology. In 1950s and 1960s, most computer paintings were done on printers and plotters. Until the end of 1960s, computer art creation appeared by using the characteristics of computer display dot matrix and carefully designing patterns.
Since the 1970s, computer art has begun to flourish and mature. 65438-0973, "The First International Computer Art Exhibition" was held in Sony Corporation in Tokyo. Since 1980s, the development speed of computer art has far exceeded people's imagination. At the SIGGRAPH annual meeting, which represents the highest level of computer graphics research, wonderful computer art works emerge one after another. In addition, in the list of Oscar winners during this period, movies made with computer special effects frequently appear on the list, which has a great feeling of leaving me alone. In China, the first computer art seminar and exhibition was held in Beijing from 65438 to 0995. It summarizes the development of computer art in China and plays an important role in promoting the future work.
Toy story 2. Movie special effects
An important application of computer animation is to make movie stunts. It can be said that the development of film stunts and computer animation are complementary. From 65438 to 0987, Milla Lab, led by Tallman and his wife, a famous computer animation expert, produced a seven-minute computer animation "Meet Montreal", which reproduced the elegance of international movie star Marilyn Monroe. 1988, who framed Roger rabbit in American movies? The perfect combination of two-dimensional animated characters and real actors is jaw-dropping and breathtaking, and computer animation is widely used. 199 1 The American film Terminator II: The End of the World shows wonderful computer technology. In addition, there are Jurassic Park, The Lion King, Toy Story and so on.
3. Domestic situation
China's computer animation technology started late. 1990 1 1 Asian Games, the computer three-dimensional animation technology was used for the first time to produce the titles of related TV programs. Since then, computer animation technology has developed rapidly in domestic film and television production, and the popularity of 3D animation computer software represented by 3D Studio and 2D graphic design software represented by Photostyler and Photoshop has promoted the application of computer animation technology in China. In 2006, Universal Digital produced the first 3D animated film Mobius Ring in China.
Computer animation has a wide range of applications. In addition to making film and television works, it has important applications in scientific research, visual simulation, electronic games, industrial design, teaching and training, photo simulation, process control, graphic painting, architectural design and many other aspects, such as military tactical simulation.
Visualization of scientific calculation
Visualization of scientific computing is a new technology proposed and developed by developed countries in the late 1980s. It transforms the data in the process and result of scientific calculation into geometric figures and image information, which is displayed on the screen and processed interactively, and becomes a powerful tool to discover and understand various phenomena in the process of scientific calculation.
1987 In February, the National Science Foundation held the first visualization conference of scientific computing in Washington. The meeting agreed that "the application of graphics and image technology to scientific computing is a brand-new field." Scientists not only need to analyze the calculated data obtained by the computer, but also need to understand the changes of the data in the process of computer processing. The conference named this technology "Visualization in Scientific Computing". Scientific computing can be regarded as the combination of graphics generation technology and image understanding technology, which can understand the image data sent to the computer and generate graphics from complex multidimensional data. It involves the following independent fields: computer graphics, image processing, computer vision, computer-aided design and interactive technology. Scientific calculation can be divided into three levels according to its functions: (1) post-processing of result data; (2) Real-time tracking processing and display of the result data; (3) Real-time display and interactive processing of the result data.
Visualization status quo
This is a research project of the National Aeronautics and Space Administration (Ames) Research Center, which includes two virtual screens connected to a supercomputer. The distributed virtual environment is used to realize three-dimensional unsteady flow field. Two people working together can share the same flow field data from different viewpoints and observation directions in an environment.
This is a research project of National Supercomputer Application Center (NCSA). This is a software for studying atmospheric fluids in an interactive distributed environment. PHTHFINDER studies storms through several related models.
Dynamic display of cardiac CT data
This is also the research project of NCSA, which uses remote parallel computing resources and volume rendering technology to realize the dynamic display of ct scanning three-dimensional data field. Its specific content is to display the dynamic image of the dog's heartbeat cycle.
Dynamic model visualization
This is a research project of Northwestern University, which can display complex temporal and spatial transient images when unheated gas burns. The flame is located between two concentric cylinders. Combustible mixed gas is injected from the inner cylinder, and the substances produced by combustion are sent out through the outer cylinder.
The University of Illinois at Chicago has developed a visual billion application software implemented on workstations and supercomputers. Its content is an interactive three-dimensional display of a seven-week-old human embryo, reconstructed from the data obtained by the National Museum of Health and Medicine. This project demonstrates the possibility of remote access to human morphological data and distributed computing in network resources. America will also visualize the whole human body. They sliced two volunteers (a man and a woman). The man was cut into 1780 pieces with a thickness of about 1 mm, and the woman was cut into 5400 pieces with a thickness of about 0.3 mm, with a large amount of data. To sum up, there are the following points:
Aerodynamics, mathematics, medical imaging and other fields. The technical level of scientific computing visualization is developing from post-processing to real-time tracking and interactive control.
VR（Virtual Reality）
Gibson's "virtual reality"-the word was first put forward by jaron lanier, the founder of the American Jet Propulsion Laboratory (VPL), and was called "artificial reality" in Myron Kruger's experiments in the early 1970s. In William Gibson's science fiction Neuremanccr published in 1984, it is also called "Cyberspaee". Virtual reality, also known as virtual environment, is a high-tech developed by NASA and military departments for simulation. It uses computer graphics generator, position tracker, multi-function sensor and controller to effectively simulate actual scenes and situations, so that observers have a real immersive feeling. Virtual environment consists of hardware and software. The hardware part mainly includes: sensor, Efeeter, and special hardware connecting sensor and impressionism to generate simulated physical environment. The software that uses virtual reality technology to generate virtual reality environment needs to complete the following three functions: establishing the shape and dynamic model of actors and objects; Establish the interaction between objects and the surrounding environment determined by Newton's law of motion; Describe the content characteristics of the surrounding environment
Virtual reality refers to a virtual three-dimensional space generated by a computer in real time. This space can be a microscopic world as small as molecules and atoms, a macroscopic world as large as celestial bodies, or a living space similar to the real society. It can confuse people, so it is also called virtual reality. Users can walk freely in this three-dimensional space, observe at will, and interact with the virtual scene through some devices. Interaction is multi-channel and natural. It can be a gesture, a look, an expression to convey information. In this environment, users see realistic images generated by computers, hear sounds in the virtual environment, and their bodies feel the force of feedback from the virtual environment, thus creating an immersive feeling.
Virtual reality technology mainly studies how to simulate (construct) a three-dimensional graphic space with a computer and enable users to interact with the space naturally. It involves a lot of scientific knowledge, and the requirements for three-dimensional graphics processing technology are particularly high. Simple virtual reality system was used in the military field to train drivers as early as 1970s. After the 1980s, with the improvement of computer software and hardware technology, it was also attached importance and developed rapidly. It has been initially applied in aerospace, medicine, education, art, architecture and other fields. For example, in July of 1997, the NASA rover sojourner landed on Mars, which is about1900,000 kilometers away from the Earth. This car has no drivers crawling slowly on the surface of Mars. It is operated by engineers on earth through virtual reality system.
Virtual reality application
1. Two-handed spatial interface tool for brain surgery planning
The University of Virginia has launched a two-handed spatial interface tool called Netra, which can be used for brain surgery planning. According to the working environment and habits of brain surgeons, the system adopts a controller that looks like a human head. According to their own professional habits, brain surgeons can conveniently observe different parts of the human brain by rotating the controller of the external connector, and at the same time control the scanning well stripped from the surface of the human brain through the plane of the right hand control panel, so that the real image with color observation viewpoint can be displayed according to the main brain model generated by CT or strong magnetic vibration images.
2. Virtual environment is used to treat acrophobia.
A virtual reality system developed in Britain can produce the following virtual environments: ① transparent glass elevator, ② balcony of high-rise building, and @ Cable Bridge above fault. In order to increase the sense of reality, patients must stand in a special frame in addition to wearing a helmet-mounted display that can produce three-dimensional scenes. Adjusting the height of elevators, balconies and cable bridges can produce different degrees of stimulation.
3. Virtual wind tunnel
Kruger of the German National Information Technology Research Center and others have established a so-called "virtual wind successor" to replace the wind tunnel experiment (because the wind tunnel experiment is expensive and difficult to control). In the virtual wind tunnel, the simulation data comes from finite element programs running on supercomputers or high-performance workstations. Using the virtual wind tunnel, observers can easily observe given points and lines by wearing liquid crystal switch glasses, and can also conduct more detailed research by zooming in, which greatly facilitates people's research on the dynamic characteristics of objects.
4. Closed fighting trainer
Cctt (closed combat training device) is a simulation device developed by Masta Gurley and others for the US military, which is used for tanks and mechanized infantry to exercise on actual terrain. It is different from the usual virtual environment and simulator, and needs to build a large-scale complex virtual environment suitable for military training.
5. The application of virtual reality technology in architectural design
Virtual reality technology is also widely used in architectural design. Kruger and others showed their future buildings on the virtual working platform they invented. Architects get together, see the designed three-dimensional buildings through LCD glasses, and easily add or delete some buildings or other objects. At the same time, different light sources can be set through data gloves. Simulate sunlight and moonlight at different times. Observe the aesthetic feeling of the designed building in different light and its harmony with the overall environment.
geographical information system (GIS)
Geographic Information System (GIS) is a comprehensive information management system based on geographic graphics about population, mineral resources, forests, tourism and other resources. It has been widely used in developed countries, and it has also been widely studied and applied in China. In geographic information system, computer graphics technology is used to make high-precision graphs of various resources, including geographic map, topographic map, forest distribution map, population distribution map, mineral distribution map, meteorological map, water resources distribution map and so on. Geographic information system provides very effective support for managers and decision makers.
In a word, virtual reality technology is an interdisciplinary and comprehensive new technology. Therefore, its development will depend on the development and progress of related science and technology. The most basic requirement of virtual reality technology is the real-time reflection and authenticity of the scene. But generally speaking, real-time and authenticity are often contradictory.
User Interface(UI)
User interface is an important part of communication between people and computers in computer systems. In 1980s, the graphical user interface (GUD) based on WIMP (window, icon, menu and mouse) greatly improved the usability, learnability and effectiveness of computers, and quickly replaced the character interface represented by command behavior, becoming the mainstream of computer user interface. The user-centered system design idea, enhancing the naturalness of human-computer interaction and improving the efficiency and bandwidth of human-computer interaction are the research directions of user interface. So the concept of multi-channel user interface is put forward, which includes language, gesture input, head tracking, visual tracking, stereoscopic display, three-dimensional interactive technology, sensory feedback and natural language interface. It can be said that the surface of the human body is the man-machine interface. Any part of the human body should be a channel for man-machine dialogue. Virtual reality display is the key, which needs not only software implementation, but also hardware implementation. To sum up, the human-computer interaction channel of virtual reality can be divided into two aspects: the main sensory channel and the active working channel.
The development demand of virtual reality will certainly promote the development of various disciplines of computer graphics. Similarly, the development of virtual reality will also depend on the development of other disciplines, and the prospect of computer graphics is attractive. The situation is urgent (China is still relatively backward), but the gap can still be shortened through efforts.