Now that you have learned how to generate a surface from a table of markers, you can start to create your own table of markers as you would for a new design.

Choose Close Marker Data from the File menu to close the table of yacht markers you have been working with.

Next, select New Marker Data from the File menu and you will be presented with a dialog box in which you may input the four corners of a new surface.

These corners are input as ‘Bow at deck edge’, ‘Bow at foot’, ‘Transom at deck edge’, and ‘Transom at keel’. You may also enter the number of points you intend using in the definition of the bow and in the definition of the stern, including the edge points.

The remaining stations may then be entered in the Markers window and the splining and surface fitting performed as in the preceding example. Choose Markers from the Window menu to bring the Markers window to the front.

All cells in the Markers table are editable except:

§   The column titles

§   The row numbers

§   The station column

Under most circumstances, it is desirable to have vertical stations (except for the Bow and Stern). However, it is possible to have non-vertical stations.

To change the number in a cell, simple click on the cell to select it and then type in the new number. You can use the tab key to move to the next cell to the right and the Return key to move to the cell below. You can also use the arrow keys to move around in the table.

In order to add and delete information from the table of markers, it is necessary to select cells and rows in the table.

Clicking in a cell selects that individual cell and highlights it. When an editable cell is selected new data may be entered from the keyboard. The data may be input in any units and Prefit converts to the current units as set in the Units option of the Display menu.

Append the appropriate unit’s symbol to enter data, which is not in the current units. See Data Menu | Units in the Reference section for further details.

Clicking on a row number selects that row. When a row is selected a marker may be inserted or removed from the marker definition of the surface.

Clicking in a column title selects that column. A selected column may be copied to the clipboard or may have the contents of the clipboard pasted into it.

Clicking in the Sheet Select box (top left cell of table) selects the entire Markers window. This is useful only to copy the entire Markers window.

Apart from the basic numerical editing of individual cells, operations may be performed on whole rows or individual stations in the Markers window.

Holding down the shift key while copying data from the table, will also copy the column titles.

On Windows, various other features relating to the table may be selected from the context menu, which is activated by ‘right clicking’ in the table window.

To insert an marker at a given station:

§   Select a row in the table. The marker will be inserted immediately below this row.

§   Select Add Marker from the Edit Menu.

To delete an marker from the table:

§   Select the row of the marker to be deleted.

§   Select Delete Marker from the Edit Menu.

To add a new station to the table:

§   Choose Add Station from the Edit menu.

§   A dialog box will appear allowing you to enter the position of the station and the number of markers you require at this station.

§   Enter the longitudinal position of the station and the number of markers you require at this station.

§   Click OK.

The new station will be inserted in the table at the correct location.

To delete a station from the table:

§   Choose Delete Station from the Edit menu.

§   A dialog box will appear:

§   Enter the numbers of the first and last stations to be deleted. To delete a single station enter the same number in the From and To boxes.

§   Click OK.

All of the markers for these stations (inclusive) will be removed from the table.

From time to time during the creation of your markers table, it is a good idea to save your table to disk. Choose Save Marker Data from the File menu to save your table. If you have not yet saved the data, Prefit will ask you to name your file.

Markers may be imported from a standard, tab delimited text file. The text file should have the following format:

There are 4 columns: the first contains the station number; the second the station longitudinal position; the third the transverse offset and the fourth column contains the vertical height of the markers.

A text file may be imported by selecting Open Text from the File menu.