The recent hull modeling tutorial gave me the incentive to share my own attempts, that have followed a somewhat different path. My attempts at virtual modeling (for ships and other things) have been concentrating on using Rhino3D and more recently MoI, that are both outstanding NURBS engines.
The only real problem area when modeling ships with NURBS is to generate fair and smooth hulls. All the rest is fairly straightforward n-gonal shapes (boxes and cylinders mostly) that can be made easily from basic NURBS techniques, but ship hulls are semi-organic and can be rather hard to get right. Of particular concern (at least to me) is continuity. One does not want kinks, sags or any other imperfection. Hulls need to be smooth and fair, and accurate too, according to plans and blueprints of the real thing.
Here is one way I found to generate near-perfect smooth hulls from simple curves. This is a generic, somewhat WW2 Italian looking, cruiser hull, but the principle can apply to many other shapes. The model is made of three ovals that are waterlines: the keel, about flotation level and top. The sheer can be made by trimming later. All the rest are half stations, including stem and stern, at reasonably regular intervals. It is important to keep the curves as simple and clean as possible. With this setup, one can generate a lovely hull in one go of the Network command. Et voil�!
Then, one can trim the top above the sheer line, rebuild the keel around the rudder and propellers, as the hull here is not smooth and continuous but displays hard angles etc.
You do not need to have an oval shape for the bottom closed curve. It can be square, which is more appropriate for a warship if the hull has a keel that is integral to it (many WW2 ships have that). In that case, the network method I recommend generates a troubled area at the stern because the flat portion under the hull and along the keel goes on across the stern, which is definitely undesirable.
The remedy is simple enough: the Network command generates two edges that materialize the sharp edges of the keel, all the way across the stern. This makes it easy to remove that portion and then blend the edges, which produces a smooth stern. Alternatively, one can model a pointier stern if so is desired. There are refinements too in the other delicate area on the other end of the ship: the stem. One should not want to make it pointy. Even the sharpest prows are not razor-edged. They are blunt to a point if seen from up close. Other possibilities include a bulge etc., for which specific techniques can be used.
We're going to build a plugin in Rhino so that we can use all tools and the GUI plus specific hull fairing tricks. Oh, we have a vacancy to help with this plugin...
find it fascinating how much is already so old. I think people in the 19th century experienced much larger changes in daily live than people claim we do now because they have a new iPhone. Anyway, although those 3D files seem great, we really spend a lot of money on our geometry files. Individual settings between CAD programs can result in forms that fair well in one program and not at all in the other. When clients are not careful, the surfaces that look continuous actually have gaps between them that are invisible to the eye. We create calculation meshes for analysis that look like this
Modern algorithms often work the same using a few tricks in between. I think we have some planimeters lying around as well... Nowaways I think people track a line with the camera of their smartphones and use GPS to calculate the path length and enclosed area