Computer Graphics

What is computer graphics?
Computer graphics means drawing pictures on a computer screen. What's so good about that? Sketch something on paper—a man or a house—and what you have is a piece of analog information: the thing you draw is a likeness or analogy of something in the real world. Depending on the materials you use, changing what you draw can be easy or hard: you can erase pencil or charcoal marks easily enough, and you can scrape off oil paints and redo them with no trouble; but altering watercolors or permanent markers is an awful lot more tricky. That's the wonder of art, of course—it captures the fresh dash of creativity—and that's exactly what we love about it. But where everyday graphics is concerned, the immediacy of art is also a huge drawback. As every sketching child knows too well, if you draw the first part of your picture too big, you'll struggle to squeeze everything else on the page.... and what if you change your mind about where to put something or you want to swap red for orange or green for blue? Ever had one of those days where you rip up sheet after sheet of spoiled paper and toss it in the trash?

That's why many artists, designers, and architects have fallen in love with computer graphics. Draw a picture on a computer screen and what you have is a piece of digital information. It probably looks similar to what you'd have drawn on paper—the ghostly idea that was hovering in your mind's eye to begin with—but inside the computer your picture is stored as a series of numbers. Change the numbers and you can change the picture, in the blink of an eye or even quicker. It's easy to shift your picture around the screen, scale it up or down, rotate it, swap the colors, and transform it in all kinds of other ways. Once it's finished, you can save it, incorporate it into a text document, print it out, upload it to a web page, or email it to a client or work colleague—all because it's digital information.

FILM VERSUS DIGITAL IMAGERY

Computer graphics is the art of using computer technology to create visual images from data. One way to understand this is to contrast film and digital photography. With a film camera a roll of film is loaded into the camera. To make a picture the camera exposes some halide silver crystals on one small piece of film at a time to light. When the entire roll has been used, it may be taken to a professional who processes the film with chemicals and then shines light through the film onto light-sensitive paper. An image soon appears on the paper and a print is created.

Unlike film cameras, a digital camera does not use film. It has a minicomputer inside that records light onto a two-dimensional array of points. Each of these points is then assigned a digital value. In general all digital devices work on the same principle. The source may be light from the natural world or a piece of paper, or an image created on the computer. Each digital device turns the source input into an array of digital values. To better understand this, one needs to look more closely at how computers work.

THE BINARY SYSTEM

Computers use a binary system consisting of 1s and 0s. Conceptually this works like an on/off switch. To describe an image in black and white, white can be assigned the value "0" and black the value "1." If one takes a black-and-white image and superimposes a series of rows and columns onto it, then at each intersection of a row and column one has a point. Each point can then be assigned a value of "0," white, or "1," black. Now there is an array of 0s and 1s that taken together represent an image. Every value, that is, every 0 or 1, requires a bit of storage. An image as described above is said to have a bit depth of 1, because it takes 1 bit (either a 1 or 0) to describe any point on the image.

If one wants an image to contain shades of gray between black and white, one need more bits. If one uses 2 bits, there are four possible combinations of 1 and 0

	1960s	1970s	1980s	1990s	2000s
Computer technology	Programs are run in batch mode using punch cards. Text characters are used to create pictures. Printers can only print whole characters not individual dots.	Mid 1970s: First personal computers appear. Monitors display white text against a green background the result of a P1 phosphor from a cathode ray tube. Monitors are called CRTs or greenscreens. Graphics resolution is low, around 128 × 48 dots per screen.	1981: IBM introduces the first color PC. The CGA monitor is capable of displaying 4 colors using a combination of red, green, and blue. 1984: Apple Macintosh is introduced. Color graphics are possible, but computer memory is limited. 1987: 256 colors and a resolution of 720 dots × 400 dots are possible.	The number of colors a PC monitor can display jumps from 256 to 16.7 million. PCs can use 3D graphics. 1994: the World Wide Web becomes available to the public and provides another channel for computer graphics use.	LCD monitors become popular. PC Graphics Processing Units (GPU) deliver 25 times the 3D graphics performance of the 1990s.
Video	Manufacturers of video games experiment with computer graphics in games such as Pong.		Video games have advanced to virtual reality and role playing. In business virtual reality technology is used to evaluate and modify product designs.		Users interact with games through realtime 3D graphical representations of users.
Movies/TV		1977: Star Wars incorporates 3D computer graphics into the film.	1984: The Last Starfighter displays the first photorealistic computer graphic images in a feature film. 1988: Who Framed Roger Rabbitcombines computer animation characters with live humans.	1991: Toy Storybecomes the first computer animated full-length film. 3D computer graphics are used in cartoons on TV and in animated movies.	High Definition digital televisions (HDTV) become popular. Shark Taleuses global illumination to render realistic shadows and reflections.
Modeling			Early 1980s: CAD systems using 2D floor planning and rudimentary modeling are available. Late 1980s: CAD systems offer 3D rendering and walkthrough capabilities. 1989: Simulation and visualization programs become available. CAT scan technology which allows physicians to see graphical representations of soft tissue aid in diagnosis and treatment of abnormalities. 3D models of the human body are used for virtual surgery and training.	Photographs are integrated with CAD drawings. CAD/CAM programs are used to design, assemble and test new products.