matlab画三维图像

x = -5:0.01:15;
y = 4:0.01:6;
[x1, y1] = meshgrid(x, y);
z = 21.5 + x1.*sin(4*pi*x1) + y1.*sin(20*pi*y1);
plot3(x1, y1, z)

x = 11:0.001:12;
y = 5.5:0.001:5.8;
[x1, y1] = meshgrid(x, y);
z = 21.5 + x1.*sin(4*pi*x1) + y1.*sin(20*pi*y1);
mesh(x1, y1, z)