function [nx,ny,nz,xc,yc,zc] = plnorm(x,y,z)

%PLNORM Computes the normal and centroid of a 3-D triangle.

% [Nx,Ny,Nz,Xc,Yc,Zc] = PLNORM(X,Y,Z) returns the normal and

% centroid of a triangle defined by three (3) points with

% coordinates X,Y and Z. X, Y and Z must be vectors of length

% three (3). The coordinates should be listed in clockwise

% direction when seen from above.

%

% 28-Mar-96

%#######################################################################

%

% Check for Inputs

%

if (nargin<3)

error('PLNORM requires three input arguments.');

end

%

% Check that Inputs are Vectors

%

x = x(:);

y = y(:);

z = z(:);

%

[n l] = size(x);

[n2 l2] = size(y);

[n3 l3] = size(z);

%

if ((l~=1)|(l2~=1)|(l3~=1))

error('PLNORM only works with vectors.')

end

%

% Check that the Inputs have Three Rows

%

if ((n~=3)|(n2~=3)|(n3~=3))

error('X, Y and Z must be of length three (3).')

end

%

% Normal of Triangle

%

a = [(x(1)-x(2)); (y(1)-y(2)); (z(1)-z(2))];

b = [(x(3)-x(2)); (y(3)-y(2)); (z(3)-z(2))];

n = cross(a,b);

n = n/norm(n);

%

nx = n(1);

ny = n(2);

nz = n(3);

%

% Centroid of Triangle

%

xc = mean(x);

yc = mean(y);

zc = mean(z);

%

return