Intersection Algorithms - Computer Graphics and Geometric Modeling - page 553

for e in E do
begin
fc := PseudoFacetItDefines (e); { Delete e and possibly other edges from E }
if NotNull (fc) then Add fc to F;
end

end ;

pseudofacet function PseudoFacetItDefines ( edge e0)
begin
pseudofacet fc;
face

f, lastf;

edge e;

boolean more;

Delete e0 from E;
Initialize fc to z, the intersection of e0 with x-y plane;
for each face f adjacent to e0 do flag the e0 in Exs[f] as SEEN;
(lastf,e) := face lastf is adjacent to e0 and edge e in Exs[lastf] is not yet SEEN;

more := true ;
while more do
begin
Delete e from E;

Add intersection z of e with x-y plane to end of fc;
for each face f adjacent to e do flag the e in Exs[f] as SEEN;

if some face f (π lastf) adjacent to e has edge (π e) in Exs[f] marked SEEN
then more := false
else

begin
lastf := face adjacent to e;
e is edge in Exs[lastf];
end ;

end ;

Delete all references to edges in all Exs[] which were marked as SEEN;

return (fc);
end ;

Algorithm 13.4.3.1. Continued