Geometric modeling is the basic element of the all computer based design / engineering / manufacturing systems. There is many algorithms developed specially at the last two decades for the mathematical representation of the computer generated geometric models. Today, it seems the NURBS (Non-Uniform Rational B-Splines) is the winner. NURBS based representations of 3-D geometry can accurately describe any shape from a simple 2-D line, circle, arc, or curve to the most complex 3-D organic freeform surface or solid. Because of their flexibility and accuracy, NURBS models can be used in any process from illustration and animation to manufacturing but has also some limitations. Many times you can hear a designer say, "No, I can't do that. The system won't allow it".

You can also find some modelers which are using different technologies than NURBS. On the other hand marine based modelers also presents some specialized tools which are very valuable for the ship/yacht designers. In this point of view general purpose surface-solid modelers have some disadvantages for ship/yacht design as well as advantages. So the capabilities and price range of the free form surface modeling systems are significantly variable. There is always a suitable tool for any kind of design work between kayaks and nuclear attack submarines and you don't need a sledgehammer to break a nut! In general they are easy to use and learn for anyone familiar with mouse and 3D coordinate system. 

Solid modeling has some more advantages over surface modeling. A solid model represents the geometry with full access to it's all physical properties unlike a surface model. So the designer can also control all model parameters such as weight, centers of gravity and inertia moments etc. in real time. I think, they are specially useful for propeller, keel and hull structure design for the marine based works. They have also advantages on FEA side, indeed all solid modelers have easy access to leading analysis software.

The rules of the game are changing quickly for design professionals. Architects and engineers face rapidly escalating time-to-market issues, increasing the pressure to nimbly and inexpensively prototype and revise designs. Increasing global competition adds even more pressure to reduce costs. Preview your concepts to your clients in such a software and explore design alternatives in real-time. Confirm your designs by experimenting with alternative materials, lighting and arrangement of components. In the marine point of view specially valuable tools for yacht design market where aesthetics rule the game for the many clients.

1. Integrated ship design & production systems
2. Surface modeling software for marine based design
3. High-End integrated modeling systems
4. General purpose surface modeling software
5. Solid modeling software; mostly for mechanical applications
6. Software for virtual reality; rendering and animating
7. Check the technical papers section for related issue