Graphics Programming using OpenGL（使用OpenGL图形编程）.pdfVIP

Graphics Programming using OpenGL Why OpenGL? • Device independence • Platform independence – SGI Irix, Linux, Windows • Abstractions (GL, GLU, GLUT) • Open source • Hardware-independent software interface • Support of client-server protocol • Other APIs – OpenInventor (object-oriented toolkit) – DirectX (Microsoft), Java3D (Sun) Brief Overview of OpenGL OpenGL is a software interface that allows the programmer to create 2D and 3D graphics images. OpenGL is both a standard API and the implementation of that API. You can call the functions that comprise OpenGL from a program you write and expect to see the same results no matter where your program is running. OpenGL is independent of the hardware, operating, and windowing systems in use. The fact that it is windowing-system independent, makes it portable. OpenGL program must interface with the windowing system of the platform where the graphics are to be displayed. Therefore, a number of windowing toolkits have been developed for use with OpenGL. OpenGL functions in a client/server environment. That is, the application program producing the graphics may run on a machine other than the one on which the graphics are displayed.The server part of OpenGL, which runs on the workstation where the graphics are displayed, can access whatever physical graphics device or frame buffer is available on that machine. OpenGLs rendering commands, however are primitive. You can tell the program to draw points, lines, and polygons, and you have to build more complex entities upon these. There are no special-purpose functions that you can call to create graphs, contour plots, maps, or any of the other elements we are used to getting from old standby programs”. With OpenGL, you have to build these things up yourself. With OpenGL any commands that you execute are executed immediat