Introducing: Computer Graphics Chapter 1

Chpater 1 -- Introducing: Computer Graphics2 n Computer Graphics is a branch of Computer Science, but its appeal reaches far beyond it. u In its short lifetime, computer graphics has attracted some of the most creative people in the world to its fold. u They come from all disciplines -- art, science, music, … u In fact, since the excitement and diversity of computer graphics can best be conveyed by consideration of its applications, let us take a look at several in more detail.

Chpater 1 -- Introducing: Computer Graphics3 1. A Few Uses of Computer Graphics n Computer graphics is used today in many different areas of industry, business, government, education, and entertainment. n The list is enormous, and is growing rapidly as computers with graphics capabilities become commodity products. n Here is a brief look at some of these areas:

Chpater 1 -- Introducing: Computer Graphics4 n User Interfaces n Interactive plotting in business, science, and technology

Chpater 1 -- Introducing: Computer Graphics5 n Cartography n Medicine

Chpater 1 -- Introducing: Computer Graphics6 n Computer-aided drafting and design n Multimedia textbooks

Chpater 1 -- Introducing: Computer Graphics7 n Simulation and animation for scientific visualization and entertainment.

Chpater 1 -- Introducing: Computer Graphics8 2. A Brief History of Computer Graphics n This book concentrates on fundamental principles and techniques that were derived in the past and are still applicable today -- and generally will be applicable in the future. n It is easier to chronicle the changes in hardware than software, since hardware changes have had a greater influence on how the field has developed. Thus we will begin with hardware.

Chpater 1 -- Introducing: Computer Graphics9 2.1 Output Technology n Two basic display types u Vector displays and u Raster displays n Both are based on Cathode Ray Tubes (CRT’s) which we will see in Chapter 4.

Chpater 1 -- Introducing: Computer Graphics10 n Vector displays were developed in the mid- sixties and in common use until the mid eighties. u Characters were made up of a sequence of vectors or strokes. This technique was also called a random scan

Chpater 1 -- Introducing: Computer Graphics11 n Raster displays were developed in the early seventies. u it was based on television technology, and contributed more to the growth of the field than any other technology.

Chpater 1 -- Introducing: Computer Graphics12 u The complete image on a raster display is formed from the raster, which is a set of horizontal scan lines, each a row of individual pixels

Chpater 1 -- Introducing: Computer Graphics13 u Since, in the raster system the entire grid of pixels must be stored explicitly, the availability of inexpensive solid-state random-access memory (RAM) for bitmaps in the early seventies was the breakthrough needed to make raster graphics the dominant hardware technology. u Other Defs: F bitmap F pixmap F frame buffer

Chpater 1 -- Introducing: Computer Graphics14 n Advantages of raster over vector: u lower cost u the ability to fill areas with solid colors or patterns. n Disadvantages: u The discrete nature of pixel representation. This produces jagged lines (aliasing) u Scan conversion is needed u Vector displays produce continuous smooth lines and curves.

Chpater 1 -- Introducing: Computer Graphics Input Technology n A wide range of input devices have been developed. n Basic: u keyboard, mouse, joystick, trackball,… n Advanced: u 3D input devices with high degrees of freedom, and ones with feedback.

Chpater 1 -- Introducing: Computer Graphics Software Portability and Graphics Standards n It used to be low-level and device dependent packages supplied by the vendor, making it very difficult to port the software. n We have now moved to high-level device independent packages, which allow much easier porting of software.

Chpater 1 -- Introducing: Computer Graphics17 n Graphics Software Standards: u CORE -- 3D Core Graphics Systems -- a specification produced by an ACM SIGGRAPH committee in u GKS - Graphical Kernel System -- (1985) cleaned up and implemented the 2D portion of CORE. u GKS-3D (1988) -- implemented CORE’s 3D portions. F Permitted the grouping of primitives (such as lines, polygons, and character strings -- and their attributes) into collections. F These collections could not be nested.

Chpater 1 -- Introducing: Computer Graphics18 u PHIGS - Programmers Hierarchical Interactive Graphics System (1988) F PHIGS also supports a retained database of structures, and automatically updated the screen when the database had been altered. u PHIGS+ (1992) F added features for photorealistic rendering. u Other standards F Postscript F X-Windows F OpenGL F PEX u The copyright of this book.

Chpater 1 -- Introducing: Computer Graphics19 3. The Advantage of Interactive Graphics u Graphics provides one of the most natural means of communicating with a computer, F since our 2D and 3D pattern recognition abilities allow us to perceive and process data rapidly and efficiently. u Interactive computer graphics permits extensive, high-bandwidth user-computer interaction. F Such interactions significantly enhance our ability to understand data, to perceive trends, and to visualize real or imaginary objects.

Chpater 1 -- Introducing: Computer Graphics20 4. Conceptual Framework for Interactive Graphics n The high-level conceptual framework shown here can be used to describe almost any interactive graphics system

Chpater 1 -- Introducing: Computer Graphics21 n The three major parts of the framework are: u Application Modeling F Calculating what is to be displayed u Displaying the Model F Calling the graphics API routines u Interaction Handling F Handling user interaction, which will change the model, and therefore the display. F typically an event driven loop

Chpater 1 -- Introducing: Computer Graphics22 Summary n Graphical interfaces have replaced textual interfaces as the standard means for user- computer interaction. n Until the late eighties, the bulk of computer- graphics applications dealt with 2D objects; 3D applications were relatively rare.

Chpater 1 -- Introducing: Computer Graphics23 n The spectacular progress of VLSI semiconductor technology also led to the explosive growth of 3D accelerators and 3D applications. n Images and animations are no longer merely illustrations in science and engineering -- they have become part of the content of science and engineering and are influencing how scientists and engineers conduct their daily work.