图形学第1章(孔令德编).ppt

* * * * * * * * * 修改图形：实际是修改显示文件中的某些绘图命令。 随机扫描所绘制的图形只能是单线条图形。 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * /tfi/exhibits/sutherland.html Dr. Ivan E. Sutherland was a pioneering researcher in computer graphics. His doctoral work on a software-hardware combination called SketchpadO represents a seminal innovation in thinking about computer graphics. Dr. Sutherlands work laid part of the foundation necessary for the development of todays Graphical User Interfaces. Effectively, Sutherlands Sketchpad is the grandfather of the Graphical User Interface. At a time when cathode ray tube monitors were themselves a novelty, Dr. Ivan Sutherlands 1963 software-hardware combination, Sketchpad, enabled users to draw points, line segments and circular arcs on a cathode ray tube with a light pen. In addition Sketchpad users could assign constraints to whatever they drew and specify relationships among the segments and arcs. The diameter of arcs could be specified, lines could be drawn horizontally or vertically, and figures could be built up from combinations of elements and shapes. Figures could be copied, moved, rotated, or resized and their constraints were preserved. Sketchpad also included the first window-drawing program and clipping algorithm which made possible the capability of zooming in on objects while preventing the display of parts of the object whose coordinates fall outside the window. The development of the Graphical User Interface, which is ubiquitous today, has revolutionized the world of computing, bringing to large numbers of discretionary uses the power and utility of the desk top computer. Several of the ideas first demonstrated in Sketchpad are now part of the computing environments used by millions in scientific research, in business applications, and for recreation. These ideas include: 1) the concept of the internal hierarchic structure of