Transformations and the Graphics Pipeline - Computer Graphics and Geometric Modeling - page 127

Procedure Clip (( move , draw ) flag)
begin
label moveit, nontriv, finish;

Calculate BC1, CODE1;

if flag = move then goto moveit;
if (CODE0 and CODE1) π 0 then goto finish;
if (CODE0 or CODE1) π 0 then goto nontriv;
ViewPt( p1 , draw );

finish:
[ p0 ,BC0,CODE0] := [ p1 ,BC1,CODE1];
return ;

moveit:
if CODE1 π 0 then goto finish;
ViewPt( p1 , move );
goto finish;

nontriv:
DoNontrivialStuff ();
goto finish;
end ;

Algorithm 4.6.2. More efficient clipping using homogeneous coordinates.

Figure 4.12. Single- and double-clip pyramid.