Lines, Curves and Surfaces in 3D

Polygons (Cont.)
P 3 (x 3 ,y 3 )
P 2 (x 2 ,y 2 )
P 6 (x 6 ,y 6 )
P 4 (x 4 ,y 4 )
e 2
e 3
e 1
e 6
e 7
P 1 (x 1 ,y 1 ) P 7 (x 7 ,y 7 )
e 5 e 4
P 5 (x 5 ,y 5 )
• Each line is defined by two vertices — the start and end points.
• We can define a data structure which stores a list of points
(coordinate positions) and the edges define by indexes to two
points:
Points : {P 1 (x 1 , y 1 ), P 2 (x 2 , y 2 ), P 3 (x 3 , y 3 ), . . .}
Points define the geometry of the polygon.
Edges : Edges : {e 1 = (P 1 , P 2 ), e 2 = (P 2 , P 3 ), . . .
Edges define the topology of the polygon.
• If you traverse the polygon points in an ordered direction
(clockwise) then the lines define a closed shape with the inside
on the right of each line.
CM0268
MATLAB
DSP
GRAPHICS
542
1
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