Why is some part of the surface not being rendered?

Question

MATLAB

Answer 1

You have a segment more than will fit up to 360 degrees. You can either lengthen the rotation (the ends will kind of add up)

[u,t] = meshgrid(0.01:0.1:4,0:0.01:2.1*pi);
disp(t)
x = u.*sin(t);
y = u.*cos(t);
z = u;
surf(x,y,z)
xlabel x, ylabel y

or increase the sample

[u,t] = meshgrid(0.01:0.1:4,0:0.025:2*pi);
disp(t)
x = u.*sin(t);
y = u.*cos(t);
z = u;
surf(x,y,z)
xlabel x, ylabel y