Differentiate between Random Scan and Raster Scan.
Random Scan Display
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Raster Scan Display
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In vector scan display the beam is moved between the end points of the graphics primitives.
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In raster scan display the beam is moved all over the screen one scan at a time, from top to bottom and then back to top.
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Vector display flickers when the number of primitives in the buffer becomes too large.
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In raster display, the refresh process is independent of the complexity of the image.
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Scan conversion is not required.
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Graphics primitives are specified in terms of their endpoints and must be scan converted into their corresponding pixels in the frame buffer.
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Scan conversion hardware is not required.
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Because each primitive must be scan converted real time dynamics is far more computational and requires separate scan conversion hardware.
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Vector display draws continuous and smooth lines.
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Raster display can display mathematically smooth lines, polygons and boundaries of curves primitives only by approximating them with pixels on the raster grid.
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Mathematical functions are used to draw an image.
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Screen points/pixels are used to draw an image.
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It does not user interlacing.
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It uses interlacing.
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Editing is easy.
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Editing is difficult.
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Cost is more
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Cost is low
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Vector display only draws lines and characters.
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Raster display has ability to display areas filled with solid colors or patterns.
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Resolution is good because this system produces smooth lines drawings because CRT beam directly follows the line path.
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Resolution is poor because raster system in contrast produces zigzag lines that are plotted as discrete point sets.
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Picture definition is stored as a set of line drawing instructions in a display file.
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Picture definition is stored as a set of intensity values for all screen points, called pixels in a refresh buffer area.
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They are more suited to line drawing application e.g. CRO and pen plotter.
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They are more suited to geometric area drawing applications e.g. monitors, TV
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It uses beam-penetration method.
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It uses shadow-mask method
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