XX=min(X):(max(X)-min(X))/100:max(X);
YY=min(Y):(max(Y)-min(Y))/100:max(Y);

[XI,YI] = meshgrid(XX,YY);
ZI=griddata(X,Y,Z,'cubic');

surf(XI,YI,ZI);

xlabel('X')
ylabel('Y')
zlabel('Z')