plane intersection

It computes the intersection of two planes in space.

% Inputs:
% N1: normal vector to Plane 1
% A1: any point that belongs to Plane 1
% N2: normal vector to Plane 2
% A2: any point that belongs to Plane 2

%Outputs:
% P is a point that lies on the interection straight line.
% N is the direction vector of the straight line
% check is an integer (0:Plane 1 and Plane 2 are parallel'
% 1:Plane 1 and Plane 2 coincide
% 2:Plane 1 and Plane 2 intersect)

% Example:
% Determine the intersection of these two planes:
% 2x - 5y + 3z = 12 and 3x + 4y - 3z = 6
% The first plane is represented by the normal vector N1=[2 -5 3]
% and any arbitrary point that lies on the plane, ex: A1=[0 0 4]
% The second plane is represented by the normal vector N2=[3 4 -3]
% and any arbitrary point that lies on the plane, ex: A2=[0 0 -2]
% [P,N,check]=plane_intersect([2 -5 3],[0 0 4],[3 4 -3],[0 0 -2]);