计算机图形学（英文影印版）

.　　2d eye coordinates
　　2d screen coordinates
　appearance
　　color
　　textures
　　depth buffering
　the viewing process
　　different implementation, same result
　graphics cards
　a basic opengl program
　　the structure of the mai n o function on opengl
　　model space
　　modeling transformation
　　3d world space
　　viewing transformation
　　3d eye space
　　projections
　　2d eye space
　　2d screen space
　　the science in the program
　　appearance
　　another way to see the program
　opengl extensions
　summary
　opengl glossary for the chapter
　questions
　exercises
　experiments
chapter 1: viewing and projection
introduction
　fundamental model of viewing
　definitions
　　setting up the viewing environment
　　defining the projection
　　view volumes
　　the orthographic projection
　　the perspective projection
　　calculating the perspective projection
　　clipping on the view volume
　　defining the window and viewport
　some aspects of managing the view
　　hidden surfaces
　　double buffering
　stereo viewing
　viewing and visual communication
　implementation of viewing and proiection in opengl
　　defining a window and viewport
　　reshaping the window
　　defining a viewing environment
　　defining a perspective projection
　……
chapter 2: principles of modeling
chapter 3: implementing modeling in opengl
chapter 4: mathematics for modeling
chadter 5: color and blending
chapter 6: lighting and shading
chapter 7: events and interactive programming
chapter 8: texture mapping
chapter 9: graphical problem solving in science
chapter 10: rendering and the rendering pipeline
chapter 11: dynamics and animation
chapter 12: high-performance graphics techniques
chapter 13: interpolation and spline modeling
chadter 14: nonpolygon graphics
chapter 15: hardcopy
references and resources
appendix
index

.　　creates an image from that geometry so that the problem can be seen
　　uses the image to understand the problem or the model and to try to understand a possible solution
　　Figure 1 Computer graphics in the problem-solving process.
　　The image that represents a problem can be made in many ways. One of the classic uses of images in problem solving is simply to sketch an image--a diagram or picture--to communicate the problem to a colleague so it can be discussed informally. (It is folk wisdom that restaurants are not happy to see a group of scientists or mathematicians come to dinner because they write diagrams on the tablecloth!) But an image can also be made with computer graphics, and this is especially useful when it is important to share the idea with a larger audience. If the model per-mits it, this image may be an animation or an interactive display so that the problem can be ex-amined more generally than a single image would permit. That image, then, can be used by the problem solver or the audience to gain a deeper understanding of the model and hence of the problem, and the problem can be refined iteratively and a more sophisticated model created, and the process can continue.
　　This process is the basis for all of the discussions in Chapter 9 on graphical problem solv-ing in the sciences, but it may be applied to more general application areas. In allowing us to bring the visual parts of our brain and our intelligence to a problem, computer graphics gives us a powerful tool to think about the world. In the words of Mike Bailey of Oregon State University,computer graphics gives us a"brain wrench" that magnifies the power of our mind, just as a phys-ical wrench magnifies the power of our hands.
　　Overview of the Book ..
　　This book is a textbook for a beginning computer graphics course for students who have a good programming background, equivalent to a full year of programming courses. We use C as the pro-gramming language in our examples because it is the most common language for developing ap-plications with OpenGL, though the course could use C++ and extend some of the processes here into an object-oriented approach. The book can be used by students with no previous computer graphics experience and with less mathematics experience and advanced computer science studies than the traditional computer graphics course. Because we focus on graphics programming rather than on algorithms and techniques, we have fewer instances of data structures and other computer science techniques. This means that this text can be used for a computer graphics course that can be taken earlier in a student's computer science studies than the traditional graphics course, or for self-study by anyone with a sound programming background. In particular, this book can be used as a text for a computer graphics course at the community college level.
　　Many, if not most, of the examples in this book are taken from sources in the sciences, and we include a chapter that discusses several kinds of scientific and mathematical applications of computer graphics. This emphasis makes this book appropriate for courses in computational sci-ence or for computer science programs that want to develop ties with other science programs on campus, particularly programs that want to provide science students with a background that will support development of computational science or scientific visualization work. It has been tempt-ing to use the word visualization somewhere in the title of this book, but we would reserve that word for material that is primarily focused on the science with only a sidelight on the graphics;because we reverse that emphasis, the role of scientific visualization is in the application of the computer graphics.
　　The book is organized along fairly traditional lines, treating projection, viewing, modeling,rendering, lighting, shading, and many other aspects of the field. These are all structured into the scene graph, a construct that is extremely useful to help the programmer organize scenes. There is also an emphasis on the graphics pipeline to produce images. Besides the basic techniques of creating images, the book has an emphasis on using computer graphics to address real problems and to communicate results effectively to the viewer. As we move through this material, we de-scribe a full range of general concepts and techniques in computer graphics and show how the OpenGL API provides the graphics programming tools that implement these principles and tech-niques. Our goal is to give the student both an understanding of graphics concepts and skill in us-ing a graphics APl (application programming interface) to implement graphics operations and create effective images for communicating with a viewer. We are mindful of the limitations of a single course, so while we also outline or sketch the algorithms and principles that lie behind the way the techniques are implemented, we do not develop these as fully as a more theoretical text would. Your instructor will provide these in more detail if he or she finds it useful to do so.
　　We have tried to match the sequence of chapters in the book to the sequence we would ex-pect to be used in a beginning computer graphics course, and in some cases the presentation of one chapter will depend on your knowing the content of an earlier chapter. However, in other cases it will not be critical that earlier chapters have been covered. It should be pretty obvious if other chapters are assumed, and we may make that assumption explicit in some chapters. As-suming that the course will want to cover interactive graphics, we believe that all the chapters through Chapter 7 on interaction should be covered (though the mathematics chapter, Chapter 4,may be treated as a reference), as well as Chapter 10 on the graphics pipeline. Beyond that, the chapters are relatively independent, and you may choose them as you will.
　　The book focuses on computer graphics programming with a graphics APl and in particu-lar uses the OpenGL API to implement the basic concepts that it presents. Each chapter includes a general discussion of a topic in graphics as well as a discussion of the way the topic is handled in OpenGL. However, another graphics APl might also be used, with the OpenGL discussion serving as an example of the way an API could work. Many of the fundamental algorithms and tech-niques that are at the root of computer graphics are covered only at the level they are needed to understand questions of graphics programming. This differs from most computer graphics text-books that place a great deal of emphasis on understanding these algorithms and techniques. We recognize the importance of these for persons who want to develop a deep knowledge of the sub-ject and suggest that a second graphics course can provide that knowledge. We believe that the experience provided by API-based graphics programming will help you understand the impor-tance of these algorithms and techniques as they are developed and will equip you to work with them more fluently than if you met them with no previous background.
　　This book includes several features that are not found in most beginning textbooks. These features support a course that fits the current programming practice in computer graphics. The discussions in this book focus on 3D graphics and almost completely omit uniquely 2D tech-niques. It has been traditional for computer graphics courses to start with 2D graphics and move up to 3D because some of the algorithms and techniques have been easier to grasp at the 2D level,but without that concern it is easier to begin by covering 3D concepts and discuss 2D graphics as the special case where all the modeling happens in the X-Y plane.
　　Modeling is a very fundamental topic in computer graphics, and there are many different ways that one can model objects for graphical display. This book uses the standard beginning ap-proach of focusing on polygon-based modeling because that approach is supported by OpenGL and most other graphics APIs. The discussion on modeling in this book places an important em-
　　phasis on the scene graph as a fundamental tool in organizing the work needed to create a graph-ics scene. The concept of the scene graph allows the student to design the transformations,geometry, and appearance of a number of complex components such that they can be implemented quite readily in code, even if the graphics API itself does not support the scene graph directly. This is particularly important for hierarchical modeling, but it also'provides a unified design approach to modeling and has some very useful applications for placing the eyepoint in the scene and for managing motion and animation.
　　A key feature of this book is an emphasis on using computer graphics to create effective vi-sual communication. This recognizes the key role that computer graphics has taken in develop-ing an understanding of complex problems and in communicating this understanding to others,from small groups of working scientists to the general public. This emphasis is usually missing from computer graphics textbooks, although we expect that most instructors include this some-how in their courses. The discussion of effective communication is integrated throughout several of the basic chapters in the book, because it is an important consideration in graphics modeling,viewing, color, and interaction. We believe that a systematic discussion of this subject will help prepare students for more effective use of computer graphics in their future professional lives,whether this is in technical areas in computing or is in areas where there are significant applica-tions of computer graphics.
　　This book also places a good deal of emphasis on creating interactive displays. Most com-puter graphics textbooks cover interaction and the creation of interactive graphics. Historically this was a difficult area to implement because it involved writing or using specialized device driv-ers, but with the growing importance of OpenGL and other graphics APIs this area has become much more common. Because we are concerned with effective communication, we believe it is critically important to understand the role of interaction in communicating information with graphics. Our discussion of interaction includes a general treatment of event-driven program-ming and covers the events and callbacks used in OpenGL, but it also discusses the role of inter-action in creating effective communications. This views interaction in the context of the task that is to be supported, not just the technology being studied, and thus integrates it into the overall context of the book.
　　You will probably notice that the figures in this book are not as sophisticated as those in most computer graphics texts. This is deliberate. We believe that if we are talking about creating graphical communications with the level of OpenGL that the book presents, we should make the figures with this same level. We hope that you will find these "homemade" figures effective and that perhaps you may be challenged to create illustrations of your own that may well be better
　　than ours.
　　This book's approach, discussing computer graphics principles without covering the details of the algorithms and mathematics that implement them, differs from those of most computer graphics textbooks that place a much larger emphasis on understanding these graphics algorithms and techniques. We recognize the importance of these ideas for persons who want to develop a deep knowledge of the subject and suggest that a second graphics course can provide that knowl-edge. We believe that the experience provided by APl-based graphics programming will help the student understand the importance of these algorithms and techniques as they are developed and will equip someone to work with them more fluently than if they were covered with no computer graphics background.
　　Outcomes
　　When you have finished with a computer graphics course based on this book, we believe that you should have the following knowledge or skills:
　　An understanding of how graphical information is represented to a graphics system and en-coded by the system to create images
　　An understanding of how to organize graphical information in a program in order to create images with a graphics API
　　An understanding of how to use events in a graphics system to create interactive graphics displays
　　An understanding of the issues involved in making images that communicate effectively to a viewer
　　Skill at using the OpenGL graphics APl to create effective images
　　We hope that you will have applied the principles and skills you are learning to an area where computer graphics makes an important contribution, and that you will understand what that contribution is. We support this for the sciences but recognize that there are many other ar-eas where this is also the case. If a course uses this text with an application area other than the sciences, the author would like to hear of it.
　　Credits
　　The initial development of this project was supported by National Science Foundation grant DUE-9950121. All opinions, findings, conclusions, and recommendations in this work are those of the author and do not necessarily reflect the views of the National Science Foundation. The au-thor also gratefully acknowledges sabbatical support from California State University Stanislans and thanks the San Diego Supercomputer Center (SDSC), most particularly Mike Bailey (now at Oregon State University) for hosting the sabbatical where this work was started and for pro-viding significant assistance with both visualization and science content. Kris Stewart of San Diego State University, Angela Shiflet of Wofford College, Rozeanne Steckler and Kim Baldridge of SDSC, and lan Littlewood of CSU Stanislaus provided helpful contributions to the chapter on graphics in the sciences. Sam Rebelsky of Grinnell College provided helpful com-ments. Sampson Asare of the University of Botswana, Petros Mashwama of the University of Swaziland, and Marcelo Zuffo of the University of Sao Paolo gave the author opportunities to use early versions of the manuscript in workshops. Several of the author's students at CSU Stanis-laus and San Diego State University provided important examples and insight for this project.Ken Brown was particulary helpful with several figures and concepts in this manuscript. The author also thanks his students Mike Dibley, Ben Eadington, Jordan Maynard, and Virginia Muncy for their contributions through examples.
　　The author also wishes to thank the many reviewers who have looked at early stages of the book. They gave help at many levels, from general concepts to very detailed suggestions and cor-rections. To the extent that this book is successful, my students and colleagues and the reviewers get much of the credit; if anything in the book is not successful, that comes back to the author.
　　Steve Canningham
　　Coralville, Iowa ...