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 ...test if 2 lines cross and find the intersection? Autor: FastGEO library [ Print tip ]

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procedure IntersectionPoint(const x1,y1,x2,y2,x3,y3,x4,y4:Double; out Nx,Ny:Double);
var R : Double;
dx1,dx2,dx3 : Double;
dy1,dy2,dy3 : Double;
begin

dx1 := x2 - x1;
dx2 := x4 - x3;
dx3 := x1 - x3;
dy1 := y2 - y1;
dy2 := y1 - y3;
dy3 := y4 - y3;
R:= dx1 * dy3 - dy1 * dx2;

if R <> 0 then
begin

R := (dy2 * (x4 - x3) - dx3 * dy3) / R;
Nx := x1 + R * dx1;
Ny := y1 + R * dy1;
end else
begin
if
Collinear(x1,y1,x2,y2,x3,y3) then
begin

Nx := x3;
Ny := y3;
end
else
begin

Nx := x4;
Ny := y4;
end;
end;
end;
(* End Of IntersectionPoint *)

function Collinear(const x1,y1,x2,y2,x3,y3:Double):Boolean;
begin

Result := IsEqual((x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1),0);
end;
(* End Of Collinear *)

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