Scanline algorithm for polygons                     /| (2,4)
                                             |  y = 2x  / |
                                             |         /  |       y = -2x+8
                     fig. 1                  |  (0,0) /__ | (3,2)
     __________________                      |        y = 2/3x
     __________________     Keep             |                   fig. 2
     ____________/|____     It               |
     ___________/x|____     Simple           |
     __________/xx|____     Stupid           |
     _________/xxx|____                      |
     ________/xxxx|____     K.I.S.S.         |
     _______/xxxxx|____                      |
     __________________                      |
 ------------------------------------------------------------------------------------------------------------
     Edge Table       ref. fig. 2                   |    Active Edge Table      ref. fig. 2
                                                    |
     Delta X / Delta Y, X, Ymax                     |(y=0)   |1/2| 0 | 4 | ---> | 3/2| 0 | 2 | Draw (0,0)
     Y = 2 ---> |-1/2| 0 | 4 |                      |(y=1)   |1/2|1/2| 4 | ---> | 3/2|3/2| 2 | Draw (1,1) & Draw (2,1)
     Y = 0 ---> | 1/2| 0 | 4 | ---> |3/2| 0 | 2 |   |(y=2)   |1/2| 1 | 4 | ---> |-1/2| 3 | 4 | Draw (1,2) & Draw (2,2) & Draw (3,2)
                                                    |(y=3)   |1/2|3/2| 4 | ---> |-1/2|5/2| 4 | Draw (2,3) & Draw (3,3)
                                                    |(y=4)
------------------------------------------------------------------------------------------------------------------------------------

     Star Example
                                         (7,15)
           |   |   |   |   |   |   |   | . |   |   |   |   |   |   |         Edge Table
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |         y = 0 |1/3| 2 | 15| ---> |6/5| 2 | 10| ---> |-6/5| 12| 10| ---> |-1/3| 12| 15|
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |-----------------------------------------------------------------------------------
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |         Active Edge Table
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |         (y=0) |1/3| 2 | 15| ---> | 6/5| 2 | 10| ---> |-6/5| 12| 10| ---> |-1/3| 12| 15|
     (0,10)| . |   |   |   |   |   |   |   |   |   |   |   |   | . |(14,10)        Draw (2,0)               |              Draw (12,0)              |
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |                    |                   |                  |                    |
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |         (y=1) |  2+(1/3)  | ---> |   3+(1/5)  | ---> |  10+(4/5)  | ---> |  11+(2/3)  |
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |         (y=2) |  2+(2/3)  | ---> |   4+(2/5)  | ---> |  9+(3/5)   | ---> |  11+(1/3)  |
           |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
           |   |   |   |(.)|(.)|(.)|(.)|(.)|(.)|(.)|(.)|   |   |   |         (y=3) |     3     | ---> |   5+(3/5)  | ---> |  8+(2/5)   | ---> |     11     |
           |   |   |   |(.)|(.)|(.)|   |   |(.)|(.)|(.)|   |   |   |
           |   |   |   |(.)|(.)|   |   |   |   |(.)|(.)|   |   |   |         (y=4) |  3+(1/3)  | ---> |   6+(4/5)  | ---> |  7+(1/5)   | ---> |  10+(2/3)  |
           |   |   |(.)|(.)|   |   |   |   |   |   |(.)|(.)|   |   |                                              <--SWAP-->
           | . |   |(.)|   |   |   |   |   |   |   |   |(.)|   |   |         (y=5) |  3+(2/3)  | ---> |-6/5| 6 | 10| ---> | 6/5| 8 | 10| ---> |  10+(1/3)  |
      (0,0)         (2,0)                               (12,0)