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ch03oddslns

# ch03oddslns - transformed back into object coordinates may...

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Angel: Interactive Computer Graphics, Fifth Edition Chapter 3 Solutions 3.1 The general problem is how to describe a set of characters that might have thickness, curvature, and holes (such as in the letters a and q). Suppose that we consider a simple example where each character can be approximated by a sequence of line segments. One possibility is to use a move/line system where 0 is a move and 1 a line. Then a character can be described by a sequence of the form ( x 0 ,y 0 ,b 0 ) , ( x 1 ,y 1 ,b 1 ) , ( x 2 ,y 2 ,b 2 ) , ..... where b i is a 0 or 1. This approach is used in the example in the OpenGL Programming Guide. A more elaborate font can be developed by using polygons instead of line segments. 3.11 There are a couple of potential problems. One is that the application program can map different points in object coordinates to the same point in screen coordinates. Second, a given position on the screen when
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Unformatted text preview: transformed back into object coordinates may lie outside the user’s window. 3.19 Each scan is allocated 1/60 second. ±or a given scan we have to take 10% of the time for the vertical retrace which means that we start to draw scan line n at .9n/(60*1024) seconds from the beginning of the refresh. But allocating 10% of this time for the horizontal retrace we are at pixel m on this line at time .81nm/(60*1024). 3.25 When the display is changing, primitives that move or are removed from the display will leave a trace or motion blur on the display as the phosphors persist. Long persistence phosphors have been used in text only displays where motion blur is less of a problem and the long persistence gives a very stable ²icker-free image. 1...
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