Polygon Scan Conversion: Pseudo-Code

This section will present pseudo-code for the Polygon Scan Conversion algorithm to the user. The writing of the actual code for the algorithm will be left as an exercice for the reader.

Pseudo-Code

This pseudo-code is described in English with certain elements of a Pascal-like language. Some of the functions called in the pseudo-code are left intentionally blank, in order to motivate readers to write them on their own.

Procedure MAIN
Begin
  initialize ET
  initialize AET
  build ET
  y = <smallest non-empty bucket in ET>
  AET = NIL
  While ET and AET are not empty
  Begin
    Move all edges from ET[y] whose Y-min = y to the AET, sorting on x
    Using the odd-parity rule on the x coordinates in the AET, fill in appropriate pixel values.
    Remove from the AET all edges for which y = Y-max
    Increment y by 1
    For each nonvertical edge remaining in the AET, update x for the new y
    resort AET
  End
End

From Graphica -- see details 26.11.1996