MC converts geometry data to the GHS Geometry File format from various other formats and vice versa. Currently it does the following conversions:
Note: IGES, STEP, DWG, and many other CAD file formats can be converted to GF format using Rhinoceros 3-D NURBS Modeler
- SHCP (SHC) hull and tank definitions to GHS Geometry
- HEC (HUL, CMP, CMA & SHP) hull and tank definitions to GHS Geometry
- Drawing eXchange format (DXF) to and from GHS Geometry
- Offset (OFE) files to and from GHS Geometry - File Spec
- IMSA Data Files (IDF) to and from GHS Geometry
- PIAS (EAG) offsets to and from GHS Geometry
- SEASAFE (IN) hull definitions to GHS Geometry
- ShipmoPC (SW7) files from GHS Geometry
- WAMIT (GDF) files from GHS Geometry
- Tank Property tables (TPF) to GHS
For a list of file conversions, please look here: Rhino File Conversions.
Since there is a significant difference in the way in which SHCP and GHS interpret offsets, MC reads and processes the SHCP data in the same manner in which SHCP does. However, MC does a much more thorough job of checking the SHCP offsets for errors than SHCP does itself. Many of these errors, if undetected, can lead to serious errors in SHCP calculations. So we would say that even if you are using SHCP you need MC to check for errors!
Compared to the SHCP method of representing hull geometry, GHS uses a simpler representation which is more reliable and more suitable for automatic computation. (SHCP bases its representation on the requirements of Simpson's first rule for area integration.) However, the GHS representation (based on the requirements of trapezoidal integration) requires roughly twice as many points and stations to achieve a comparable level of precision. MC adds these points and stations automatically.
One interesting feature of the SHCP-to-GHS conversion is that longitudinal and transverse aberrations (due to incorrect station spacing in the SHCP model) become visible after the conversion. Even when the SHCP model is considered "clean" because no transverse "blips" are present, there may be "longitudinal blips" which would appear in the area curve only at certain waterplane orientations and would therefore be difficult to detect. The GHS form of representation avoids this problem, since all area curves are closely related to the model as it appears by inspection.
HEC Conversions (HUL, CMP, CMA & SHP)
Ship hull and tank geometry are carried in separate files. Model Converter will read these files, convert the geometry data to the GHS format, and write the result to a GHS Geometry File. Conversion from GHS format to HEC format is not available.
MC will convert individual HEC files of the .HUL, .CMP, .CMA and .SHP types. Either single- or multiple-file conversions can be carried out with one MC execution. In this latter case, the relevant files in the indicated directory are converted and combined in one output Geometry File.
MC will read and write DXF files (2D or 3D). This allows a shape to be created in a CAD program (including digitizing from an existing body plan) and then converted into a Geometry File for use within GHS. It also allows components or individual stations from a Geometry File to be copied into a CAD drawing.
MC recognizes only LINE, POLYLINE, LWPOLYLINE, ARC and TEXT entities. Each MC execution can read only one GHS component from a DXF from a specified range of layers. Multiple executions can used to convert several shapes from the same DXF file and add them as individual components to a Geometry File. Since MC cannot merge its output with an existing DXF, each export execution creates a new DXF file with a single component or station.
Rhino can import a broad range of CAD file types including: IGES, STEP, DWG, Micro Station, SolidWorks, etc. Once the desired geometry is imported into Rhino, the built in AttachGHSData wizard can be used to establish part, component and shape data which can then be saved directly as a GF file.
OFE and PIAS Conversions
The OFE file format is used by some hull design systems as a means of exchanging shape data between programs. MC will both read and write OFE files. The PIAS EAG format is a simple offset list.
The IDF file format is described as "a neutral file format for exchange of hull description data between marine programs". MC converts the "SECTION" entity which describes the hull in terms of sectional curves. MC will both read and write IDF files.
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