Terminology Resolution - this is a measure for the clarity of an image. The higher the resolution, the more clarity there will be in the image. In printers the normal measurement is in dots per inch (dpi). A good quality printer should be able to print in excess of 300 dpi. In monitors the normal measurement is in the total number of pixels that can be displayed horizontally & vertically.

Vector - vector graphics is a way of representing graphics in the memory as a mathematical formula. The formula, or primitives, contain information such as the beginning & end points of lines, their thickness, type of curve & colour of line. Vector graphics is one of the two ways that an image can be stored in the memory, the other being bit - mapped. Vector graphics has the advantage of using much less memory than bit - mapped graphics. Not all images are suitable for vector graphics. Images that require photographic quality are best represented as bit - mapped files.

Raster - is the process building up an image from a series of dots by sweeping over the image in a regular pattern. Monitors are often described as having “raster scan”. The electron beam that creates the image on a monitor starts in the top left - hand corner of the screen, moves across one line, turns off & moves back to the beginning of the next line. This process is repeated until the beam reaches the bottom right - hand corner of the screen where it turns off again & flies back to the top left - hand corner, where the process is repeated all over again.

Pixel - the word pixel is a contraction of 2 words - “picture element”. A pixel refers to the smallest part of a screen that a computer can control. To control 1 pixel on a screen will require more than 1 byte in the computer’s memory.

Bit - mapped - an output device is bit - mapped when there is a 1 to 1 correspondence between memory locations in the computer & elements of the output pattern.

Digitisers - a digitiser is any device that turns analogue data into digital data. Digitising devices include: - scanners - flat - bed scanners - digital cameras - video capture cards - fax machines

Interlacing - is related to the raster scan of a TV monitor. When interlacing is employed the scan only draws every even - numbered line on the screen on the first pass & then every odd numbered line on the next pass.

Presentation Graphics - is a term that is used to describe graphics that are used for communicating ideas by using: - colour - pictures & digitised images - a variety of fonts - drawings - charts - frames The images & graphics are created with a variety of different software & hardware & then brought together through software that is capable of linking pages, displaying graphics & video & playing sound.

Graphical Processing The graphic screen currently being displayed, is stored in memory called a frame buffer that is closely associated with the video controller circuitry. The frame buffer stores details regarding the current screen display. Other “screens” or frames may be stored elsewhere within primary storage or additional memory on the video controller circuitry. For other frames to be displayed they must firstly be transferred into the frame buffer. Therefore with a changing display the CPU is constantly delivering data to the frame buffer. The most common display types are raster based. Therefore regardless of wether we are working with a vector graphics package or a bit - mapped package, the frame buffer must be bit - mapped to display a raster pattern on the display device. Therefore, when working with a bit - mapped graphics package, the software needs to only instruct the CPU to transfer the bit - map to the frame buffer. In the case of a vector graphics package, the primitives are stored in primary storage (RAM). The vector graphics software instructs the CPU to process the list of primitives to form a bit - map which in turn is then transferred to the frame buffer. The size of the frame buffer (or even a buffer for a printer) will determine the resolution, number of colours or shadings available for a graphical image. Simply stated, the higher the resolution and/or the more colours/tones used, the larger the memory required for the frame buffer. In simple terms, as the complexity of the image increases, the amount of data in the frame will increase resulting in longer processing times. To achieve acceptable (to the user) display update speed, such as, scrolling quickly or animation requires a computer with greater processing power & associated video controller circuitry that includes processing capabilities. Each bit in a bit - mapped frame buffer can be 0 or 1. Therefore a single bit can control two colours/tones, 2 bits can control 4 colours/tones, 3 bits can control 8 colours/ones; and so on. Mathematicians will realise that the number of colours/tones controlled is 2 raised to the power of the number of bits. With colour displays each pixel is made up of 3 smaller elements (red, green, & blue).

While digital RGB displays can only display 8 possible colours, analog RGB displays can vary the intensity for each red, green & blue element of a pixel & hence produce the required colour. While analog RGB CRTs are capable of producing an infinite range of colours the electronic circuitry in the computer is limited by the number of bits used to define each colour - more bits per pixel = more possible colours. Two main methods are use to represent different colours in the frame buffer: 1. bits are stored for each red, green & blue element. Therefore a single pixel with 5 bits for each red, green & blue element, provides 25 = 32 tones for each red, green & blue element. The actual pixel would therefore require a total of 15 bits. The data from the frame buffer can be directly sent by the video controller to the monitor & displayed. 2. bits are stored that represent the overall colour or tone of the pixel & other bits are stored in a look up table that determines the intensity of each red, green & blue element. Therefore a single pixel may contain 8 bits which allows 28 =256 possible colours/tones. However the frame buffer must be processed prior to sending to the monitor : the look up table must be accessed to determine the intensity of each red , green & blue elements. The second of the above 2 methods is more commonly used - primarily because it requires less memory , & thereby less expensive. it also has the advantage that the look up table can be easily changed be easily changed to provide a large choice of colours. The term palette is used to describe the range of currently available colours. The actual number of colours possible will also be dependant on the actual display device. In general the number of bits per pixel stored in the frame buffer (and a buffer for printing a full page) will depend on: - the number of possible colours. - the intensity of each colour (or shading with a single colour). Therefore the larger the number the number of colours or tones, the more bits needed for each pixel. The number of possible colours is sometimes referred to as pixel depth or colour depth. The downside of more colours & higher resolution is the vastly increased amount of data that must be processed. Obviously graphics of such colour depth & resolution will take time to process. To calculate the memory required for a frame buffer (or a printed page) perform the following steps: - multiply pixels across by pixels down, then multiply this by the number of bits needed for each pixel. This gives the total number of bits required for each frame buffer. - to obtain the frame buffer size in kilobytes divide by 8 (8 bits in a byte), & divide by 1024 to get the answer in kilobytes (1024 bytes in a kilobyte). Resolution (across & down) Colours Bits/Pixel Frame buffer (bytes) 320 x 200 16 4 32000 640 x 480 16 4 153600 640 x 480 256 8 307200 640 x 480 65356 16 614400 800 x 600 16 4 240000 800 x 600 256 8 480000 800 x 600 16356 16 960000 1024 x 768 16 4 393216 1024 x 768 256 8 786432 1280 x 1024 16 4 655360

Increasing the resolution (number of pixels) and/or colours will increase the time taken to process & display a graphic image.

Graphic Input Devices Mouse - a mouse is a little “box” with button/s on top, about 5 cm wide & 10 cm long, connected to the computer by a cable & moved by the user around the desk. A mouse is a pointing device, it is used to point the cursor to the desired position on the display. The cursor or pointer on the screen matches the movement of the mouse on the desk. The mouse is used to move the cursor/pointer within the document and/or select a command, EG: to save text to a file. - a mouse is made to execute an action by pressing a button on the mouse, called ‘clicking’. To select items click once. To perform a different command you can also double click. Some software is now configured to recognise triple or even quad clicks. The action of a click may also be affected by the use of modifier keys on the keyboard. - a mouse is more suitable than a keyboard for selections & graphical operations like drawing or manipulating graphic images.

Trackball - a trackball is a pointing & provides features like a mouse - some people prefer a trackball to a mouse. A trackball is a small box with a ball one third protruding from the top. Rolling the ball moves the cursor or pointer on the screen, the overall operation is similar to the mouse where actions are executed by pressing a button on the trackball. Trackballs use less space than a mouse & are therefore more useful where space is limited. Some keyboards & notebook size computers have a trackball built in, however trackballs are not as good as a mouse for freehand drawing. Scanner - a scanner is a digitising device. that is, it converts an image into binary form which can be further processed or saved on secondary storage. - until recently most scanners available were only monochrome (black & white), however colour printers are quickly becoming standard. Many of the monochrome scanners produce up to 256 grey scales & hence can provide a representation of colours and/or shadings. Current colour scanners can interpret a range of millions of possible colours to create a binary representation, of these colours, that can be used to produce very realistic images. Most scanners usually offer a scan resolution of 300 dpi. However, flatbed scanners are available that offer 1200 dpi scan resolution. - scanners work by moving the image or by moving the scanner. As the image is moved past a strip of light (in the scanner) the reflected light is measured with light sensors producing binary data with a one to one rel’ship. The scanned image, now in binary form, may then be manipulated using a graphics software package. - there are 2 types of scanners, hand held & flat bed. Flat-bed or desk top scanners, typically scan a complete A4 page in one pass. The scanner moves the strip of light across the page, which is similar to a photocopier. These are more expensive than hand scanners, but are more suitable for larger amounts of accurate graphic scanning. - hand held scanners are relatively inexpensive. With a hand scanner, the user moves the scanner over the text. Several passes are usually necessary to scan a complete A4 page, hence they are really only useful for small areas of graphic scanning. Users of hand scanners must have a steady & accurate hand action, otherwise the scanned image may be blurred. This problem does not occur with flat bed scanners as the scanning mechanism precisely moves the light & the light sensors over the scanned image. - in the professional world a third type of scanner called a Drum Scanner is used. Drum scanners are very expensive but achieve excellent results. The image to be scanned is placed in a drum, which is spun, thereby moving the image past a light source. The resolution achieved is 1200 dpi or better. While many high quality flat bed scanners the difference is in the light sensor. The drum scanner uses a photomultiplier tube which gives better tonal quality. Graphics Tablet - also called a digitising tablet. The tablet is a pad with a fine grid of electronic sensors underneath. a pen (stylus) or mouse like pad (puck) is connected with a cable (usually but not always) to the tablet. The fine grid of sensors detects the position of the stylus or puck & sends the position in binary form to the computer. Touching the tablet with the stylus/puck & moving the stylus/puck (like drawing with a pen on paper) causes equivalent drawing on the screen. Some graphics tablets are pressure sensitive allowing certain operations to be performed by pressuring, EG: when freehand drawing, heavier pressure produces a thicker graphic line. Typically pressure sensitive stylus provide 256 levels of pressure. A graphics tablet can be used for graphics applications & even typing. They require extra desk space & also for the user to continually look up to the screen, & back down at the tablet, which may cause muscle strain. Graphics tablets are used mainly for graphics based applications, such as Computer Aided Design (CAD), general graphics work, technical illustration & cartography (map making). A graphics tablet is much better than a mouse for free hand drawing. A further development of graphics digitising tablets is the concept of “pen computing”. Underneath a visual display is a transparent digitising tablet that determines the movement of a “pen”. The actual display acts like a piece of paper where the user can directly write onto the screen. This means that computers can be smaller, more portable, & do not require a keyboard. The pen is great for drawing, taking notes, & making “pen written” notes on existing documents downloaded from a conventional computer system. To interact with a pen based digitising visual display involves a combination of pointing & gestures. A gesture is a special movement that issues a command such as cut, copy, paste & delete. Video/Digital Camera Interface - this interface is used to directly capture “real world” images. The term capture refers to digitising the real world image. Digital cameras are available that directly capture an image in digital form, which can be transferred to a computer at a later time. Another alternative is to capture & digitise a single image from video tape deck or directly from a video camera. The electronic signals representing the single image is digitised & converted into the necessary bit patterns. Computers with large memory, high processing power & a video capture card (interface), can ‘capture’ an electronic signal that represents a video image. Graphics Output Devices Display Devices Cathode Ray Tube (CRT) - the traditional computer is a bit mapped screen using a CRT to produce the image. A CRT monitor works on the same principle as a TV. The inside of the glass screen is coated with phosphor. When phosphor is hit by an electron it glows for a short period of time, thus if a particular dot of phosphor is continually hit it will be visible to the human eye. The electron gun in the back of the CRT continually scans the screen refreshing the screen on each pass. Typical screen refresh rates are about 72 times per second. In a colour monitor there are 3 electron guns, each one for red, blue & green. The coating on the inside of the screen is composed of 3 different phosphors which glow red, blue or green. By placing them very close together & exciting them in combination many different colours can be produced. The 3 dots at each screen location combine to be one pixel. Liquid Crystal Displays (LCDs) - LCDs are very popular in laptop computers as they are lightweight, reasonably robust, flat & consume very little electricity. An LCD is composed of a number of cells of liquid crystal, with electrical contacts attached to each cell which allows the video circuitry to turn the pixels on & off. Monochrome LCDs are difficult to read unless you are sitting directly in front of them & hard to read in poor light. A backlit LCD has its own light source, usually arranged as a number of miniature fluorescent tubes around the edge of the screen. A backlit screen can be read in any light conditions. Current technology has seen the use of colour LCDs in laptops & portables. The colour screens are far superior to the monochrome in terms of resolution & viewing angle. As colour LCDs improve they may well replace the traditional CRT monitor for general computer use. This would allow for more working space on a desktop, no radiation, & less power consumption. Hard Copy Devices A wide variety of graphic printer technologies are available, but can be classified into 2 main groups: - impact - dot matrix - non-impact - inkjet, thermal wax, laser & plotters. Impact printing involves a key/hammer or series of tiny hammers (pins) hitting an inked ribbon, which causes ink to be pressed onto the paper, leaving a printed image on the paper. In contrast non-impact printing involves printing the hard copy by squirting ink, in minuscule amounts, or by use of heat or laser beams where the print mechanism does not touch the paper. Currently the most common method of printing is by bit mapped printing. Dot Matrix Printers - these types of printers create an image by converting it to a close - packed series of dots. The closer & the smaller the dots will be the better the resulting image. Impact dot matrix printers create their image by striking the ribbon with small metal pins. The bit data is sent to the printer by the computer that controls the movement of the head containing the pins when the pins should fire. Current models of printers have up to 32 pins arranged so that the dots overlap. As the number of pins increases the size of the pins becomes smaller so that the quality of the image improves from having smaller dots. Inkjet Printers - inkjet printers work by spraying ink onto the paper through tiny nozzles. In some printers there are up to 64 nozzles, thus the resolution of these printers is very good. When using an inkjet it is important to use good quality paper that has been stored correctly. If the paper is of poor quality then the ink will ‘bleed’ along the fibres in the paper reducing the resolution in the paper. Paper that has been stores in damp conditions will also cause the inkjet to produce unclear images. The ink is forced out of each nozzle by a heating process. Each nozzle consists of a chamber of ink with a tiny resistor at the back. To make the nozzle spray ink the resistor is heated very rapidly causing the ink in front to vaporise & spray out of the nozzle. Laser Printers - a laser printer is very similar to a photocopier in action. The function of the laser is to draw the required image on a rotating drum that has a coating that can either be positively or negatively charged. The laser beam has the effect of reversing the charge on the drum. The drum then spins around & comes into contact with the toner, which has the original electrical charge, & the toner is attracted to the areas that have been hit by the laser printer. as paper is fed into the printer it passes across a corona wire that gives the paper the opposite electrical charge to the toner, & as the paper continues through the printer it is brought into contact with the drum. Finally the paper passes out of the printer through the fusing rollers that heat the paper to over 200 degrees C for a fraction of a second to melt the toner onto the paper. the very high temp. inside a laser means that care must be taken when choosing paper or transparencies on which to print. A wrong selection may see the paper catch fire or the transparency melt inside the printer. Thermal Wax Printer - this printer is used to provide high quality colour graphic printing. The printing process uses wax based inks laid out in page sizes onto a long ribbon. The ribbon has page sized sections of yellow, cyan, magenta & some also have black. at the start of the print job the printer pulls a piece of paper in between a set of rollers. Tiny heating elements melt the wax ink from the ribbon (in small dots) onto the paper. After the first colour has been placed on the paper, the paper movement is reversed & the next colour is laid (melted in tiny dots) down. The paper is moved back & forth until 3 or 4 colours have been laid down. The thermal wax process is slow & if the paper slips out of alignment in the middle of the print job then the image is ruined. Also the wax inks are easily scratched off the paper. However despite disadvantages thermal wax printers provide quality colour graphic output, While thermal wax doesn’t quite provide the resolution or range of colours of colour laser printers thermal wax printers are much more reasonably priced. Plotters - a plotter is a device that uses pens to draw the output. The pens are under the control of the computer & different colours can be used. Plotters are ideal for drawing plans, maps & diagrams requiring very fine detail. By using a plotter the computer is capable of producing a genuine line rather than a series of closely spaced dots. A flat-bed plotter has the paper placed into the bottom of a tray. The pens are held by an arm that can move in 2 directions. The computer controls the movement on the arm & thus the drawing. Good flat-bed plotters have a range of coloured pens available. When plotting in different colours the computer will draw all the lines in the one colour at the same time, so the partial drawing may not look correct. A drum plotter has the pens held in one arm that moves in one direction only. The paper to be plotted on is attached to a drum that revolves underneath the pen. They can also do colour. A drum plotter takes up a lot less room than the equivalent sized flat-bed plotter. Graphical Techniques The 2 main types of software packages used to produce graphic images are typically either vector based or bit mapped based, although there are packages that can simultaneously work with vectors & bit maps. In general terms, graphic images produced are either: Static Images - drawing programs are vector or object based, whereas paint programs use bit maps. A vector package, for example, is basically useless in touching up individual pixels in a scanned colour photograph. On the other hand, a paint package is useless if you wish to overlay & manipulate objects. Painting (Bit mapped) - painting on a computer is similar to painting on a piece of paper or canvas. Once you have applied paint you cannot easily alter the canvas. Either you paint over it or “scrape the paint off” (erase). the computer paint program does offer many enhancements over conventional painting, EG: undo. Sophisticated bit mapped programs contain a comprehensive set of tools & really require training to make full use of the application. From the simple to the sophisticated bit map graphics application, the image is composed of individual pixels. Each pixel can be edited independently or groups of pixels can be edited. Bit map programs are best for producing or editing scanned images. Drawing (Vector) - instead of working with a single surface of pixels you are working with objects that can be layered one on top of the other. The big advantage is that any object can be edited at ant time. Once the concept of working with objects is mastered, vector drawing packages are a more accurate & faster way to produce technical illustrations & design work. Vector based packages offer potentially higher print quality, because the drawings (defined mathematically) will print to the maximum resolution of the printer. Whereas, with a bit map graphic the quality is determined by the number of pixels in the graphic (more pixels = better quality). Likewise the drawing can be scaled up & down without jagged edges appearing - as would be the case with a bit map graphic. File Formats - apart from the wide range of graphic input & output devices there are a wide range of graphic file formats for both vector & bit mapped applications. Some of the more commonly used graphic file formats are: - Computer Graphics Metafile (CGM) - a vector format with technical illustrations. -Windows Metafile (WMF) - a vector format supported by most windows applications. - Encapsulated Postscript (EPS) - uses both bit mapped & vector formats. What is displayed on the screen is bit map stored in a TIFF format (stored in the EPS file), but what is sent to the computer is vector instruction. You require a postscript printer to print EPS graphics images. - PICT - proprietary Apple graphics format that cab be either bit mapped or vector. - Tagged Image File Format (TIFF) - a bit mapped format. Usually the standard choice for string scanned images - which is what it was developed for. Typically TIFF files are the easiest graphic to swap between Macintosh & Windows/DOS systems. - Graphics Interchange Format (GIF) - bit mapped format that stores & compresses the graphic image. Most useful for transferring graphics images via telecommunications & swapping between different computer systems. - Bit-map (BMP) - a bit-mapped file format. Animation - is the joining together of a number of still graphics & displaying them quickly enough to give the impression of movement. Cel-based Animation - is similar to the original cartoonists had to draw every individual frame of a cartoon & then run them together to give the illusion of movement. In this type of animation, many still images are produced. The individual frames are then displayed in rapid succession to give the impression of movement. Path-based Animation - the designer simply has to create beginning & end positions & the computer will produce all the in between images. This process is called ‘tweening’. A large number of frames still need to be generated & displayed at a suitable rate. Ray Tracing - used to generate the shadows for each cell. This is a complex task & will take a long time on anything except the fastest processors. Morphing - takes two distinctly different images & transforms one into the other. To enable this to happen the animator has to define which points on the original image are going to be linked to which points on the transformed image. This is called defining a net. The net is made up of all points on each image that are going to be connected, & the more points in the net the smoother will be the morphing. However, as more points are added to the net more memory & processing power is required to carry out the morph.

Simulations A simulation is the instance in which a computer model is used to imitate a real life situation, in which there is no risk or lasting effects on the user. Computer graphics can be used to create a realistic scene of the situation by providing a visual model which follows a set of defined rules. Flight simulators are commonly used by airlines and air forces around the world to train pilots and air crew. Realistic pictures and graphical images, coupled with full size models of the craft, sound and motion, are used to create realistic experiences for the people being trained. For flight simulators, air crew sit in a full size model of a cockpit of an aircraft. Large, high resolution monitors situated around the windows provide images similar to what crews would expect when flying in an actual aeroplane. The whole cockpit can e moved to provide the sensation of movement, while the instruments and displays provide realistic information to the crew. By using simulators, air crew can be trained to operate the aircraft without leaving the ground. Their reactions to emergencies can be assessed and developed, without placing lives and planes at risk. Air crews can be trained to react to normal flight operations and emergencies without risk and at less expense than in an actual plane. A recent development involving graphical simulations that of ‘virtual reality’. In a virtual reality system the user wears a helmet that blocks out the face, eyes and ears. All that they can see or hear is the simulation that is running on the screen in front of their eyes. People using these systems are submersed in a new world. The helmet contains two small visual displays that display slightly offset images to give a three dimensional effect. This, together with the use of special power gloves, participants interact to move through the simulated world by pointing, and to examine objects by grabbing them. An application of virtual reality would be to generate a computer graphical model of a building that is yet to be built. A potential customer could then ‘walk around and view the building’ just as if it had been really built. Before technology, simulations were non-existent. Over the years simulations have progressed from being non-existent to very very basic, to extremely high quality and realistic images. Simulations have helped people immensely, as training for equipment such as aeroplanes does not require the risk (of both the people and also the equipment) that used to be the concern.

Entertainment Computer graphics have had a major impact in the area of entertainment. Graphics have found their way into many forms of entertainment, from video or computer games, to movies and cartoon making, to art and sport. Video Games - exciting, colourful animated graphics are central to the video game industry. Many advances that have occur in computer graphics have resulted from the fierce competition in arcade games to produce more exciting visual effects. These advances have filtered into the world of personal computing and many of the games that can be played in the arcade can also be played on a personal computer. Many of the computer games draw from more serious uses of computer graphics. Simulation software has been used to give enjoyment and adventure in many forms. Any one can use these games and a little imagination to become a racing car driver, a fighter pilot, tank commander, etc. Virtual reality has also been applied to computer games to provide more realistic experiences and multi-player games involving two or more players (such as a simulated battle game). In the case of video games, technology has changed from being basic arcade games, to becoming high-tech, relatively inexpensive home computer games. This has allowed society to experience more realistic games, and to play them in the comfort of their home, or even their car. Cartoons and Film Making - most, if not all, cartoons produced now, use computer graphics animation techniques. Initial development of the carton is to create a storyboard. The storyboard describes the events and sequencing that occurs during the cartoon. Stick figure animations are then composed and tested. Next the figures are coloured and appropriate background scenery is added. Much of the background is created from a library of pre-prepared graphics. The final cartoon is then recorded to video and/or film. Special effects in movies such as ‘Star Wars’ and ‘Jurassic Park’ as the result of computer technology. Using computer animation is one method of creating special effects, however computers are also used to control the movements of cameras and models. Typically, scenes involving special effects, are achieved by combining several films into one to achieve a final composite image. For the composite image to appear as one the camera movements for each separate film must be identical - this is achieved by the use of computer controlled cameras. Computer controlled cameras can also be used to give the illusion of movement. For example in Star Wars the spaceships in many scenes were stationary and the camera moved (computer controlled) to give the illusion of movement. More recent movies such as ‘Terminator 2’, ‘The Abyss’ and ‘Death Becomes Her’ used computer generated animation, superimposed onto video film, to create realistic special effects and sequences. even after the film has been completed the computer can be used to edit the film. The entire film can be saved to video tape or optical disk and then the computer can be used to edit out scenes and/or or change the sequences of the scenes. ‘Blue screening’ is an old technique used successfully to place a background behind an animation. A background screen made of true blue colour is placed behind the participants, then the graphics software is used to extract the colour blue from the system and replace it with a background graphic. As a result of increased technology in the area of cartoons and film making, cartoons and films are now easier to make and manipulate. Audiences can also experience realistic images and quality special effects. The technology itself has changed immensely in this area. Now, with the aid of computers high quality special effects can be achieved. Art - computer graphic drawing packages provide the artist with a powerful and flexible tool to provide visual images. Graphic applications allow production of realistic images and such images can be stored and easily modified. For example, it only requires a few keystrokes to change the colour/s of a graphic - such dramatic change are not possible using conventional means. Powerful computer graphics packages can simulate the appearance of oils, water colours, pastels, chalks and air brushes. The computer graphic artist can quickly choose different size brush strokes, draw curves accurately and draw free hand as well. Colours can be easily changed overall or within parts of the graphic drawing or even be painted over. When finished it can be stored on disk for later use. Sport - by using high speed cameras to record the body and limb movements, then digitising the frames into a computer system, the movements can e carefully analysed. Usually the digitising process removes extraneous information; hence the computer uses a stick figure - this makes it easier to see what the body and limbs are doing. By analysing the motion frame by frame it is possible to determine factors that will help athletes make more efficient use of their bodies and perfect their movements.

Business Perhaps the area where computer graphics is now having the biggest impact is the business sector. In recent years, with the reduction in the costs of computer hardware, the increasing sophistication of computer software, and the already common use of computers for data processing within the business sector, the use of computer graphics has increased considerably. Computer graphics systems have become easier to use and more affordable, allowing any business to access and use computer graphics without expensive hardware, professional graphic artists or complex methods. Businesses can use graphics to produce graphs and charts, logos and letterheads, and in advertising. These graphics are used for two basic functions - to analyse numerical data and for presentation. Graphs and Charts - in any business, numerical and financial data are important. The best way to quickly visualise trends and differences is through the use of charts and graphs. Graphs and charts are used to summarise, analyse and present numerical data in a pictorial, easily understood form. Data can be extracted from a spreadsheet or a database. The data can then be used in a graphics program which can create various types of graphs including a line graphs, bar graphs and pie charts. Specialist forms and Logos - letters and forms are important for a business for correspondence, advertising, and promotion of products. In the past, companies had to use graphic artists or agencies to create and produce company logos, letterheads, business cards, invoice or billing forms or any data forms required. With readily available software, such as desk-top publishing or painting software, anyone can create letterheads, business cards and other specialist forms as required. Most painting packages accept a scanned image of as a graphic source to allow editing and enhancing of company logos. These images can then be combined with letterheads and business cards. Graphics could be printed onto blank paper for later usage, or alternatively, the graphic could be automatically printed during the normal printing of reports and/or documents. Packages that are designed to specifically produce business forms are also available. Advertising - with the integration of text, presentation graphics, sound, video and computer animation, it is possible to produce sophisticated advertising. Such multimedia sequences posses a high degree of realism and thereby it is possible to produce complete advertisements. Computer graphics now make available to anyone techniques and methods which were previously only used by large companies or were not available. Painting, drawing, presentation and desk-top publishing software enables even small companies to produce high-quality brochures and promotional material. Graphic designers are able to quickly produce advertising graphics in a variety of forms, such as animation, video clips, brochures, and magazine advertisements, using the computer. The computer system can also be used to create graphics or to manipulate digitised still photography or video images which can then be incorporated in the promotional material being produced. Computer artists can also use drawing and painting programs to create static images that are intended for billboards, magazines, and posters. Once the basic layout has been created it is easy to experiment with different colour shadings, move objects, enlarge or reduce, and in general experiment until the desired result is achieved. A wide range of graphical techniques are being used by organisations to add to and replace some of their advertising campaigns. There have been a number of advertisements on television that have taken advantage of the process of morphing. It is common to see inanimate objects become animated through the use of computer graphics.

Required Defns Anti-aliasing - the process of removing faults such as ‘jaggies’ in computer images caused by the physical size & shape of the pixel. Done by software changing the colour of adjacent pixels to an average of the two colours or tones. Bit-mapped - a correspondence between memory allocations & elements of the output pattern on whatever output device available. Composite Video - a video system in which the synchronisation signals are transmitted to the monitor via the same cable as the green signal. Used in RGB systems. Coordinates - location of a pixel on a screen in raster or bit-mapped images OR location of a point in space in a vector graphics image 2D images use x & y coords 3D images use x, y & z coords. Coords can be global (relating to a base point) or relative (relating to another point). Dithering - the representation of a grey shade or colour not available in the existing palette by the use of a pattern of varying black dots (for grey shades) or colours where the eye performs the averaging to produce the required shade or colour. GIF file - acronym & file extension for a document saved in the Graphics Interchange File Format. This is the most common standard format for graphic file transfer across the internet. HLS - a representation of the colour appearing in an image by stating the levels of the measures Hue, Luminance & Saturation. Leading - a term used to describe the amount of space separating one line of type from the line above & below. Also known as vertical spacing. Paint - generally refers to a graphic package that is bit-mapped in nature. Palette - the set of colours available for selection to display at a pixel. Paste - the process of inserting a selection of data from the “clipboard”. A copy of the selection of the screen that was cut or copied is inserted in a document at the current screen location. Pixel - picture element. Display is made up of tiny dots. The size & number of pixels determines the quality of the image and the amount of memory required to store the image. Pixel averaging - the method of anti-aliasing where each pixel represents the average of a number of colours which would be present in the physical area covered by the pixel. Resolution - monitors all have a set number of pixels per inch that they can display. The size of a monitor is measured diagonally across the screen. The resolution is measured in the number of pixels per width & height. Frame Buffer - a selection of memory used to store data for the current image being displayed. RGB - a method of colour representation using the levels of the three primary colours red, green & blue, required to produce that colour. Usually associated with colour television where the three colours are represented by individual spots of phosphor on the face of the picture tube. Frame - also known as a cel in cel-based animation. An entity displayed on screen. Field - the two passes in interlacing are known as fields. Aspect Ratio - a way of describing the shape of an image by reporting the ratio of picture width to height. EG: the usual ratio for a television is 4:3 or 1:33:10. Non-reproducible Blue - a shade of blue that will not normally reproduce in black & white photography. Buffer - a temporary storage for data, normally used to accommodate the difference in the rate at which two devices can handle data during a transfer. Colour Register - a table that translates the colour of the pixel selected from the available palette into the correct combination of RGB. Colour Value - the numerical value of the bit pattern stored in the frame buffer to be matched to the colour look up table & assigned to a pixel or set of pixels on the screen. Rendering - the process of completing a computer image usually by adding surface colours or textures to shapes in 2D or wire frames in 3D. Polygon - a many sided object or shape in a drawing (vector graphic). Any closed plain figure with 3 or more sides. Interlace - the method used by television to display an image by generating alternate lines of the picture in two passes, aimed at improving the image. The two passes are called fields. The method was designed to reduce the flicker caused by the refresh rate of broadcast television; however, interlacing can actually cause flicker if adjacent lines contain distinctly different information. Most computer display screens are non-interlaced. Raster Display - the means by which an image is built up on the screen of a cathode ray tube. The image is formed from a pattern of horizontal scanning lines (the raster scan) traced by the electron beam. Time Code - a numbering system for identifying individual frames in a video sequence or film. Spline - a smooth mathematical curve or which passes through a number of given points. Used in CAD drawings. Bezier Curve - a smooth curve controlled by a number of individual points . Used in drawing programs. Gradient Fill - the process of filling an area of a computer image by a smooth variation of colours along a particular direction using the colour defined at each end of the pattern. Wire Frame - an image of a 3D object formed by drawing only the edges of polygons representing the faces of solid objects.

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