help me about drawing 3D in matlab ?

Let D is the region limit by: y = x^2 + 1, y = 0, x = 0, x = 3. Now I can draw the region D by fill command. Could you please help me how to draw the round cubic created by rotating D around x axis. thanks (like the picture below)

Answer 1

[Walter Roberson]

xvals = linspace(0, 3, 1025);
yvals = x.^2 + 1;
zvals = zeros(size(xvals));

xyz = [xvals(:), yvals(:), zvals(:)];

now you put xyz through standard rotation matrices, using a variety of angles, getting a series of output xyz for each input xyz. Put all of the resulting coordinates into arrays as vertices. Then construct edge lists, linking in a rectangular mesh -- the xyz for the N'th point on the K'th angle connecting to the (N-1)'st point and the (N+1)'th point at the K'th angle, and linking to the N'th point on the (K-1)'st and (K+1)'th angle. Toss everything into appropriate arguments for patch(). Adjust the face color parameters as you prefer: if you want everything to be the same nominal color then you will probably want to set up a lighting object (your sample diagram is lit from the right-and-back somewhere.)