mn = 50;
N = 1;
[x,y,z]=meshgrid(linspace(-10,10,mn));
val = x + y ;
isosurface(x,y,z,val,N)
xlabel( 'x' );
ylabel( 'y' );
zlabel( 'z' );
axis equal
grid on
mn = 50;
N = 1;
[x,y,z]=meshgrid(linspace(-1,1,mn));
val = x + y ;
isosurface(x,y,z,val,N)
xlabel( 'x' );
ylabel( 'y' );
zlabel( 'z' );
axis equal
grid on