Solid Polygon Clipping Techniques

Sutherland-Hodgeman Algorithm:

Compute each of the vertices against window edges. The inside vertices are saved for clipping against next boundary; outside vertices are discarded. There are four possible cases as we process line segments.

Processing line segments

Let S = previous point and P = new point

Look at three examplesof solid polygon clipping

• Example 1
• Example 2
• Example 3

So have procedure:

procedure SOLID_POLY (N: integer; X, Y: Points; FILL_COLOR: integer); 

var
   I : integer
   X_OUT, Y_OUT : Points; array [1..2] of real
   X_PDC, Y_PDC : PDC_Points; array [1..2] of integer
   M : integer;

begin
  POLYGON_CLIP (N, X, Y, M, X_OUT, Y_OUT);
  for I := 1 to M do 
     PointViewingTransform(X_OUT[I], Y_OUT[I], X_PDC[I], Y_PDC[I]);
  FILL_AREA_SOLID (N, FILL_COLOR, X_PDC, Y_PDC);
end;

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