function [x,y,z] = sPlotSurf(sM, x1,y1,z1)
% sPlotSurf -  plots a surface in cartesian coordinate system 
%	       from spline matrix in spherical coordinates
%	   [x,y,z] = sPlotSurf(sM, x1,y1,z1)
%	       sM - spline coeffitients matrix, can be obtained from 
%		    the function sFitCart
%	       x1,y1,z1 - optional cartesian coordinates displayed in the 
%		       figure(2) by surf(x1,y1,z1)
%	   x,y,z - mesh matrices that can be used with 'surf'
%	       [x,y,z] = sPlotSurf(sM);
%	       surf(x,y,z);
%	   Without output parameters, sPlotSurf plots the surface
%
%  see also:  sFitCart, sFit, sMBA

sM = sExtend(sValueM(sM),[0 1],[0 0]);

[m,n] = size(sM);
fi = (((1:m)-1)/(m-1)*2*pi-pi)' * ones(1,n);
teta= ones(m,1) * (((1:n)-1)/(n-1)*pi-pi/2);

x = sM.*cos(teta).*cos(fi); 
y = sM.*cos(teta).*sin(fi); 
z = sM.*sin(teta);

fig = gcf;
if nargout == 0,
   figure(fig); surf(x,y,z);
   if nargin == 4,  
       hold on;
       plot3(x1,y1,z1,'o'); 
       hold off;
   end;
end;

return;