Digitizing an Existing Body Plan (ProSurf Only)

If you have a body plan (cross-sections) of a boat and you have a digitizing tablet with a cross-hair "puck", you can use the Digitizer module to trace in the sections of the boat and convert them to B-spline surfaces. To do so, please follow these general directions:

A. Since the Digitizer module is a DOS program, you have to start the Nautilus DOS Executive program and use the F9 Configuration function key to select the correct video/tablet combination. This configuration section also has a test function which displays the raw (button,X,Y) data that it reads from the tablet. If this tablet test function works correctly, then you know that the tablet will work in the Digitize module. (See the Introduction manual to the DOS Nautilus modules for configuration details.)

B. Use the Digitize module to trace in the shape of each station. Tape the body plan drawing to the tablet and select the F4 Set Tab function key. This step defines the coordinate system, scaling, and orientation of the drawing on the tablet. The Digitize manual gives a complete step-by-step procedure for digitizing your stations.

C. Once digitized, verify the station shapes using the Body Plan display or the Hull Draw module. You want to make sure that the station shapes looks good before you fit surfaces to them.

D. Correct any errors using the Offsets or Digitize modules. The Digitize module can also be used with a mouse for doing interactive editing of station shapes.

E. Convert this "Station Definition" to a "Surface Definition" using the Convert Hull module. This program fits or "skins" the stations with one or more B-spline surfaces. A "Station Definition" of a hull describes the hull shape using only a number of stations located along the length of the hull. The program fits B-spline curves through the offset points. The "station definition" is good for input and calculation, but not accurate enough for fairing and construction templates. A B-spline (NURB) surface definition is required to perform full surface fairing and lofting. See the Convert Hull manual for an example of this surface fitting process.

F. Read the new surfaces into ProSurf using the File-Get Old Surf command.

Conversion from an arbitrary table of offsets to a surface definition is a complex process, since the hull being defined might have many chines separating many surfaces. Before you begin this conversion process, you need to read up on the definition of the "Station Definition" and "Surface Definition" of a hull and read about the conversion example in the Convert Hull manual.