point_n = 31;
x1 = 0; x2 = 1;
y1 = 0; y2 = 1;
x = linspace(x1, x2, point_n);
y = linspace(y1, y2, point_n);
zy1 = sin(10*x).*exp(-2*x);	% when y = y1
zy2 = cos(2*x);			% when y = y2
z11 = zy1(1);
z21 = zy1(point_n);
z12 = zy2(1);
z22 = zy2(point_n);
zx1 = sin(4*2*pi*y)/4+(z12-z11)*y+z11;	% when x = x1
zx2 = -y.*(1-y)*4+(z22-z21)*y+z21;	% when x = x1


[xx, yy] = meshgrid(x, y);
p1 = (xx-x1)/(x2-x1);
p2 = 1-p1;
q1 = (yy-y1)/(y2-y1);
q2 = 1-q1;
zzy = (ones(point_n,1)*zy1).*q2 + (ones(point_n,1)*zy2).*q1;
zzx = (zx1'*ones(1, point_n)).*p2 + (zx2'*ones(1, point_n)).*p1;

figure;
%subplot(2,2,1);
h = mesh(xx, yy, zzy);
set(h, 'facecolor', 'none');
line(x, y1*ones(size(x)), zy1, 'linewidth', 3, 'color', 'y');
line(x, y2*ones(size(x)), zy2, 'linewidth', 3, 'color', 'y');
xlabel('X'); ylabel('Y'); zlabel('Z');
set(gca, 'box', 'on');
frot3d on

figure;
%subplot(2,2,2);
h = mesh(xx, yy, zzx);
set(h, 'facecolor', 'none');
line(x1*ones(size(y)), y, zx1, 'linewidth', 3, 'color', 'c');
line(x2*ones(size(y)), y, zx2, 'linewidth', 3, 'color', 'c');
xlabel('X'); ylabel('Y'); zlabel('Z');
set(gca, 'box', 'on');
frot3d on

figure;
%subplot(2,2,3);
h = mesh(xx, yy, zzx+zzy);
set(h, 'facecolor', 'none');
line(x, y1*ones(size(x)), zy1, 'linewidth', 3, 'color', 'y');
line(x, y2*ones(size(x)), zy2, 'linewidth', 3, 'color', 'y');
line(x1*ones(size(y)), y, zx1, 'linewidth', 3, 'color', 'c');
line(x2*ones(size(y)), y, zx2, 'linewidth', 3, 'color', 'c');
xlabel('X'); ylabel('Y'); zlabel('Z');
set(gca, 'box', 'on');
frot3d on

figure;
%subplot(2,2,4);
p1 = (xx-x1)/(x2-x1);
p2 = 1-p1;
q1 = (yy-y1)/(y2-y1);
q2 = 1-q1;
zz = z11*(p2.*q2) + z12*(p2.*q1) + z21*(p1.*q2) + z22*(p1.*q1);
mesh(xx, yy, zz);
line(x1, y1, z11, 'linestyle', '.', 'markersize', 25);
line(x1, y2, z12, 'linestyle', '.', 'markersize', 25);
line(x2, y1, z21, 'linestyle', '.', 'markersize', 25);
line(x2, y2, z22, 'linestyle', '.', 'markersize', 25);
xlabel('X');
ylabel('Y');
zlabel('Z');
set(gca, 'box', 'on');
frot3d on

figure;
%subplot(2,2,3);
h = mesh(xx, yy, zzx+zzy-zz);
set(h, 'facecolor', 'none');
line(x, y1*ones(size(x)), zy1, 'linewidth', 3, 'color', 'y');
line(x, y2*ones(size(x)), zy2, 'linewidth', 3, 'color', 'y');
line(x1*ones(size(y)), y, zx1, 'linewidth', 3, 'color', 'c');
line(x2*ones(size(y)), y, zx2, 'linewidth', 3, 'color', 'c');
xlabel('X'); ylabel('Y'); zlabel('Z');
set(gca, 'box', 'on');
frot3d on