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Vector graphics (also called '''geometric modeling''' or '''object-oriented graphics''') is the use of geometrical Primitive s such as Point s, Lines , Curve s, and Polygon s, which are all based upon mathematical equations to represent Image s in Computer Graphics . It is used in contrast to the term Raster Graphics , which is the representation of images as a collection of Pixel s, and used as the sole graphic type for actual photographic images. OVERVIEW Most computer displays translate vector representations of an image to a raster format. The Drawing Software is used for creating and editing vector graphics. You can change the image by editing these objects. You can stretch them, twist them, colour them and so on with a series of tools. The raster image containing a value for every pixel on the screen, is stored in memory. Starting in the earliest days of computing in the 1950s and into the 1980s, a different type of display, the vector graphics system, was used. In these "calligraphic" systems the Electron Beam of the CRT display monitor was steered directly to trace out the shapes required, Line Segment by line segment, with the rest of the screen remaining black. This process was repeated many times a second ("stroke refresh") to achieve a flicker-free or near flicker-free picture. These systems allowed very high-resolution line art and moving images to be displayed without the (for that time) unthinkably huge amounts of memory that an equivalent-resolution raster system would have needed, and allowed entire subpictures to be moved, rotated, blinked, etc. by modifying only a few words of the graphic data "display file." These vector-based monitors were also known as X-Y displays. A special type of vector display is known as the Storage Tube , which has a video tube that operates very similar to an Etch A Sketch . As the electron beam moves across the screen, an array of small low-power electron flood guns keep the path of the beam continuously illuminated. This allows the video display itself to act as a memory storage for the computer. The detail and resolution of the image can be very high, and the vector computer could slowly paint out paragraphs of text and complex images over a period of a few minutes, while the storage display kept the previously written parts continuously visible. The image retention of a storage display can last for many hours with the vector storage display powered, but the screen can clear instantly with the push of a button or a signal from the driving vector computer. or Line Art . (Images were converted to JPEG for display on this page.)]] One of the first uses of vector graphic displays was the US SAGE Air Defense System . Vector graphics systems were only retired from U.S. en route Air Traffic Control in 1999, and are likely still in use in military and specialised systems. Vector graphics were also used on the TX-2 at the MIT Lincoln Laboratory by computer graphics pioneer Ivan Sutherland to run his program Sketchpad in 1963. Subsequent vector graphics systems include Digital 's GT40 {Link without Title} . There was a home gaming system that used vector graphics called Vectrex as well as various Arcade Game s like Asteroids and Space Wars . Storage scope displays, such as the Tektronix 4014 , could also create dynamic vector images by driving the display at a lower intensity. Modern vector graphics displays can sometimes be found at Laser Light Shows , using two fast-moving X-Y Mirror s to rapidly draw shapes and text on a large screen. The term vector graphics is mainly used today in the context of two-dimensional computer graphics. It is one of several modes an artist can use to create an image on a raster display. Other modes include text, Multimedia and 3D Rendering . Virtually all modern 3D rendering is done using extensions of 2D vector graphics techniques. Plotter s used in technical drawing still draw vectors directly to paper. MOTIVATION For example, consider Circle of Radius ''r''. The main pieces of Information a Program needs in order to draw this circle are # that the following data are describing a circle # the radius ''r'' and equation of a circle # the Location of the center point of the circle # stroke line style and colour (possibly transparent) # fill style and colour (possibly transparent) Advantages to this style of Drawing over Raster Graphics :
TYPICAL PRIMITIVE OBJECTS
This list is not complete. There are various types of curves ( Catmull-Rom Spline s, NURBS etc.), which are useful in certain applications. Often, a Bitmap image is considered as a primitive object. From the conceptual view, it behaves as a Rectangle . VECTOR OPERATIONS Vector Graphics Editor s typically allow rotation, movement, mirroring, stretching, skewing, Affine Transformation s, changing of Z-order and combination of primitives into more complex objects. More sophisticated Transformation s include set Operations on closed Shape s ( Union , Difference , Intersection , etc.). Vector graphics are ideal for simple or composite drawings that need to be device-independent, or do not need to achieve Photo-realism . For example, the PostScript and PDF Page Description Language s use a vector graphics model. Advanced vector artists are developing more photo-realistic vector art every day. With the use of Adobe Illustrator, the mesh tool has been extremely helpful in advancing the realism of vector graphics and pushing the technology to the edge. PRINTING Vector art is key for Printing . Since the art is made from a series of mathematical curves it will print very crisp even when resized. For instance one can take the same vector logo and print it on a Business Card , and then enlarge it to Billboard size and keep the same crisp quality. A low-resolution Raster Graphic would blur incredibly if it were enlarged from business card size to billboard size. 3D MODELING In 3D Computer Graphics , vectorized surface representations are most common (bitmaps can be used for special purposes such as surface texturing, height-field data and Bump Mapping ). At the low-end, simple Meshes of Polygon s are used to represent geometric detail in applications where interactive Frame Rate s or Simplicity are important. At the high-end, where one is willing to trade-off higher rendering times for increased image Quality and Precision , smooth Surface representations such as Bézier Patch es, NURBS or Subdivision Surface s are used. One can however achieve a smooth surface rendering from a polygonal mesh through the use of shading algorithms such as Phong and Gouraud . SEE ALSO
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