Clipping - Computer Graphics and Geometric Modeling - page 93

procedure M_Clip ( ref pnt2ds inpts; integer numin);
ref pnt2ds outpts; ref integer numout)
{ inpts[0..numin-1] defines the input polygon with inpts[numin-1] = inpts[0] .
The clipped polygon is returned in outpts[0..numout-1]. It is assumed that
the array outpts is big enough. }
begin
integer i;
numout := 0;
{ Compute status of first point. If it is visible, it is stored in outpts array. }
if CS_StartClip () > 0 then
begin
outpts[numout] := startPt;
Inc (numout);
end ;
{ Now the rest of the points }
for i:=1 to numin-1 do
begin
cflag := CS_EndClip (i);
startC0 := endC; { endC may get changed }
if SegMetWindow (cflag)
then
begin
if Clipped (cflag) then
begin
outpts[numout] := startPt;
Inc (numout);
end ;
outpts[numout] := endPt;
Inc (numout);
end
else if TwoBitCase (endC)
then TwoBitEndPoint ()
else OneBitEndPoint ();
{ The basic turning point test }
if TwoBitCase (endC) then
begin
outpts[numout] := clipRegion[Cra[endC and not (TWOBITS)]];
Inc (numout);
end ;
startPt := inpts[i];
end ;
Algorithm 3.3.4.2. Continued