x=rand(50,1)*4-2;
y=rand(50,1)*4-2;
z=exp(-x.^2-y.^2);

[xi,yi]=meshgrid(-2:0.25:2,-2:0.25:2);
zi=griddata(x,y,z,xi,yi);

mesh(xi,yi,zi);
hold on;
plot3(x,y,z,'o');
hold off;