Encyclopedia of Computer Science and Technology

106 computer industryso on). By creating a hierarchy of arm, hand, fingers a transformation(scaling or rotation) of one object can be propagatedto its dependent objects (see animation). In manycases graphics are created from real-world objects that havebeen digitally photographed or scanned, and then manipulated(see image processing).In most scenes the relationships between graphicalobjects are also important. Modern graphics modeling programsuse a virtual “camera” to indicate the position andangle from which the graphics are to be viewed. In renderingthe scene, the Painter’s Algorithm can be used to sortobjects and draw closer surfaces on top of farther ones, asa painter might paint over the background. Alternatively,the Z-buffer algorithm stores depth information for eachpixel to determine which ones are drawn. This techniquerequires less calculation (because surfaces don’t need tobe sorted), but more memory, since the depth of each pixelmust be stored.Within a scene, the effects of light (and its absence,shadows) must be realistically rendered. A simple techniquecan be used to calculate an overall light level for anobject based on its angle in relation to the light source,plus a factor to account for ambient and diffuse light in theenvironment. The Gouraud shading technique can be usedto smooth out the artifacts caused by the simple flat shadingmethod. Another technique, Phong shading, can morerealistically reproduce highlights (the sharp image of a lightsource being reflected within a surface). But the most realisticlighting effects are provided through ray tracing, whichinvolves tracing how representative vectors (representingrays of light) reflect from or refract through various surfaces.However, ray tracing is also the most computationallyintensive lighting technique.Several techniques can be used to give objects morerealistic surfaces. Texture mapping can be used to “paint”a realistic texture (perhaps scanned from a real-worldobject) onto a surface. For example, pieces in a chess gamecould be given a realistic wood grain or marble texture.This can be further refined through bump mapping, whichcalculates variations in the texture at each point based onlight reflections.Applications and TradeoffsThe most graphics-intensive applications today are games,multimedia programs, and scientific visualization or modelingapplications. Because of the impact graphics have onusers’ perception of games and multimedia programs, developersspend a high proportion of their resources on graphics.Critics often complain that this is at the expense ofcore program functions. The software in turn places a highdemand on user hardware: The contemporary “multimedia-ready”PC has a video card that includes special “videoaccelerator” hardware to speed up the display of graphicsdata and a video memory buffer of 256 MB or more.Complex 3D graphics with lighting, shading, and texturesmay have to be displayed at a relatively low resolution(such as 640 × 480) because of the limitations of the mainprocessor (which performs necessary calculations) and thevideo card. However as processor speed and memory capacitycontinue to increase, many computer graphics now rivalvideo and even film in realistic detail.Further ReadingACMSIGGRAPH. [graphics special interest group] Availableonline. URL: http://www.siggraph.org/. Accessed June 24,2007.Computer Graphics World. [magazine] Available online. URL:http://www.cgw.com/ME2/Default.asp. Accessed June 24,2007.Govil-Pai, Shalini. Principles of Computer Graphics: Theory andPractice Using OpenGL and Maya. New York: Springer, 2005.Jones, Wendy. Beginning DirectX 10 Game Programming. Boston:Thomson Course Technology PTR, 2007.computer industryThe U.S. computer industry began with the marketing of theUnivac, designed by J. Presper Eckert and John Mauchly inthe early 1950s. The first computers were made one at a timeand only as ordered, and the market for the huge, expensivemachines was thought to be limited to government agenciesand the largest corporations. However, astute marketing bySperry-Univac, Burroughs, and particularly, InternationalBusiness Machines (see ibm) convinced a growing numberof companies that modern data processing facilities wouldbe essential for managing their growing and increasinglycomplex business (see mainframe).The mainframe market was controlled by a handful ofvendors who typically provided the complete computer system(including peripherals such as printers) and a long-termservice contract. (Eventually, third-party vendors began tomake compatible peripherals.) Companies that could notafford their own computers began to contract with servicebureaus for their data processing needs, such as payrollprocessing.By the 1960s, transistorized circuitry was replacingthe vacuum tube, and somewhat smaller machines becamepracticable (see minicomputer). While these computerswere the size of a desk, not a desktop, models such as DigitalEquipment Corporation’s PDP series and competitionfrom companies such as Data General provided computingpower for engineers and scientists to use in factories andlaboratories. During the 1970s, the dedicated word processingmachine marketed by the Wang Corporation beganthe digital transformation of the office. By the end of thatdecade, the first general-purpose desktop microcomputerswere marketed. The Apple II made a modest inroad intobusiness, fueled by VisiCalc, the first spreadsheet program.This new market attracted the attention of IBM, viewedby many microcomputer enthusiasts as a dinosaurlike relicof the mainframe age. Uncharacteristically, IBM managementgave the developers of their personal computer (PC)project free rein, and the result was the IBM PC introducedin 1981. The machine had two major advantages. One wasthe IBM name itself, which was comforting to executivescontemplating a bewildering new technology. The otherwas that IBM (again, uncharacteristically) had followedApple’s lead in designing their PC with an “open architecture,”meaning that third-party manufacturers could mar-