GENERATE

Purpose

To generate patch data for interfacing with the BMT HULLSURF system and Plate data for input to the BMT BRITSHELL system.

Syntax

Description

A PATCH or PLATE is defined by a grid of data points which lie on the surface of the ship. The data points are calculated by girthing the mesh of defining curves of the Patch/Plate. Each Patch/Plate is GENERATED by specifying two, three or four stored curves as the boundaries. There are three types of patches available, Scatter, Boundary and Regular. Scatter patches are generated by the boundary curves and any other curves which cross the patch (that means,, FOB, FOS, knuckles, ). This generally gives the most accurate method of representing the curves. Boundary patches only use data from the boundary curves, and as such, are ideal for representing flat areas. Regular patches are fitted using data from one set of orthogonal curves, usually Sections, Waterlines or Buttocks but in the case of Patches other curves may be used, see ADD command.

The boundary curves are selected by specifying their name or, by using the IDENTIFY option, can be selected from any currently DISPLAYed curves using the cursor.

If FOUR curves are specified, then they are intersected to form the corner points of the Patch/Plate. Patches can also be generated using only 2 or 3 boundary curves by the NULL option. When PATCHES are generated they automatically use continuity between the boundaries with tangency continuity being the default. To change this use the /NOCONTINUITY option. (see CONTINUITY command)

The internal curve type for the Patch/Plate is automatically assigned. This is set by the DEFINE HULLSURF and DEFINE BRITSHELL commands. The internal curve type may be modified at any time without re-defining the boundaries by using the appropriate DEFINE command. In the case of Patches other non-orthogonal curves may be assigned as the internal curves by using the ADD command.

As an alternative to generating PATCHES from stored curves, a PATCH can be generated from a patch data file as output by LINES (see the OUTPUT command) or by the BMT PATCHGEN system. In this case the /FILE= option is used to specify the input patch data file name. The patch points contained within the file are fitted to generate a set of defining PLINES with the names:

The patch is then generated and stored as for other patches. Patch data files must be in CREATE format and names of patches generated in this way must not exceed six characters. Please refer to the PATCHGEN User Manual for further information.

The definition is stored in the appropriate directory and can be examined using the DIRECTORY PATCH / PLATE command. Definitions can be SWITCHed ON or OFF, DELETED and DISPLAYED. Note that only the definition is stored, data points for the Patch/Plate are not calculated until the OUTPUT command is used.

When defining PLATES the user must specify the Strake name as well as the Plate name and may also assign Plate attributes for DENSITY, GRADE, NUMBER_OFF and THICKNESS. If the plate attributes are not specified then the current default values, as set by the DEFINE BRITSHELL command, will be assigned.

Examples