Mega Code Archive
Determine if two 2D segments intersect each other
<![CDATA[
Title: Determine if two 2D segments intersect each other
function Intersect(const x1,y1,x2,y2,x3,y3,x4,y4:Double):Boolean;
var UpperX,UpperY : Double;
LowerX,LowerY : Double;
Ax,Bx,Cx : Double;
Ay,By,Cy : Double;
D,F,E : Double;
begin
Result := false;
Ax := x2 - x1;
Bx := x3 - x4;
if Ax
begin
LowerX := x2;
UpperX := x1;
end
else
begin
UpperX := x2;
LowerX := x1;
end;
if Bx 0.0 then
begin
if (UpperX
Exit;
end
else if (Upperx
Exit;
Ay := y2 - y1;
By := y3 - y4;
if Ay
begin
LowerY := y2;
UpperY := y1;
end
else
begin
UpperY := y2;
LowerY := y1;
end;
if By 0.0 then
begin
if (UpperY
Exit;
end
else if (UpperY
Exit;
Cx := x1 - x3;
Cy := y1 - y3;
d := (By * Cx) - (Bx * Cy);
f := (Ay * Bx) - (Ax * By);
if f 0.0 then
begin
if (d f) then
Exit;
end
else if (d 0.0) or (d
Exit;
e := (Ax * Cy) - (Ay * Cx);
if f 0.0 then
begin
if (e f) then
Exit;
end
else if(e 0.0) or (e
Exit;
Result := true;
(*
//Simple method, yet not so accurate for certain situations:
Result := (Orientation(x1,y1,x2,y2,x3,y3) Orientation(x1,y1,x2,y2,x4,y4))
and
(Orientation(x3,y3,x4,y4,x1,y1)
Orientation(x3,y3,x4,y4,x2,y2));
*)
end;
(* End Of SegmentIntersect *)
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