Howdi.

I promised to get back to the ship hull making issue, which is the only real problem area when modelling ships with NURBS. All the rest is fairly straightforward n-gonal shapes that can be made 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.

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 voilà!


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.

I include the model. Feel free to experiment. I have a slight concern about the accuracy of the shapes and even the symmetry, but all in all it does not look too bad, I’d say.

Hi Jean-Paul,

Sorry I haven't had a chance to respond to your mini tutorial. I have just done a test network of your hull and it worked very, very well.

I won't have a chance to try this on my current model until I get home but I'm looking forward to trying this out. I really didn't think network would work like that and have been lofting or using network individually by sections.

Very interesting.

Hi Mark,

Indeed, for years I was struggling with lofting and sweeping, with less than perfect results, to say the least. Then I started working on submarine hulls and on airplanes. I discovered rather by accident than design that network curves worked like a charm!

One thing I failed to include in my earlier post is the following: 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 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.

Feel free to ask should you have specific needs. I might have gone through the same difficult points before.

More great info. Thanks Jean-Paul.

>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.

My Sydney model has a razor edged stem, a definite mistake. Because the model is to be animated, I have a 90k poly limit and at the time I didn't think it was worth modeling in a less sharp stem. In retrospect, I've wasted so many poly's in other areas that this would have been a minor extravagance. The sharp edge is visually *very* unappealing.