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Vector graphics or '''geometric modeling''' is the use of geometrical Primitive s such as Point s, Lines , Curve s, and Polygon s to represent Image s in Computer Graphics . It is used by contrast to the term Raster Graphics , which is the representation of images as a collection of Pixel s (dots). The human eye works as a bitmap picture: it catches the image in a mosaic raster of photon recipient nerves, a pixel image. But the brain—according to recent studies—handles it as a vector image. Perhaps because—like in our computers—this is easier to store. It explains why we can recognize simple drawings like cartoons with just outlines because this is so close to what our brain makes of the visual world anyway. It also serves as an explanation for the fact that logos and signs with easy and geometric shapes are more easily remembered and recognized. OVERVIEW Virtually all modern current computer video displays translate vector representations of an image to a Raster Format . The raster image, containing a value for every pixel on the screen, is stored in memory and the entire screen is repainted 30 or more times per second. 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 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 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. These vector-based monitors were also known as '''X-Y displays'''. Raster image. ]] as a vector-based image, originally Windows Metafile (converted to GIF for display here).]] Two 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 specialized systems. Vector graphics were also used on the TX-2 at the MIT Lincoln Laboratory by computer graphics pioneer Ivan Sutherland to run his revolutionary 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 '' and Space Wars . The Tektronix 4014 also deserves a mention even though the display was static. The term ''vector graphics'' is mainly used today in the context of two-dimensional computer graphics. It is one of several modes a programmer can use to create an image on a raster display. Other modes include text, Multimedia and 3-d Rendering . Virtually all modern 3-d rendering is done using extensions of 2-d vector graphics techniques. Plotter s used in Technical Drawing still draw vectors directly to Paper . MOTIVATION For example, consider a Circle of Radius ''r''. The main pieces of Information a Program needs in order to draw this circle are # the radius ''r'' # 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 to rotate, move, mirror, stretch, skew, generally perform Affine Transformation s of objects, change Z-order and combine the primitives into more complex objects. More sophisticated Transformation s include set Operation s 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. 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 bumpmapping). At the low-end, simple Meshes of Polygons 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 . SEE ALSO
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