Advanced design software for mastering ship geometry

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Menu Bar/File/Open (IGES file)

 

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 Purpose:

 When an IGES file has been selected to be directly opened in MAAT Hydro, a complementary dialog box appears, allowing to create and initialize a new MAAT Hydro project from the imported geomety:

        Open IGES Dialog Box

        

Options :

 In order to complete the imported data, useful complementary lines can be automatically added if necessary: 

 -          Reduce Huge Surfaces alows re-approximating the imported surfaces in order to reduce model's size and speedup the calculations accordingly. This option may alter slightly the imported geometry and must, therefore, only be checked when the initial model is too big. Nevertheless, importing compact data must be preferred whenever possible and a special attention must be paid  before, during and after the modelling stage tto avoid unnecessarily heavy models (see Rhino's best precision settings for example).. 

 -          Reduce Huge Lines alows re-approximating the imported lines in order to reduce model's size and speedup the calculations accordingly. Like the previous one, this option may alter slightly the imported geometry and must, therefore, only be checked when the initial model is too big. Nevertheless, importing compact data without any re-approximation must be preferred whenever possible and a special attention must be paid before, during and after the modelling stage to avoid unnecessarily heavy models (see Rhino's best precision settings for example)..

 -          Reduce Huge Surfaces alows re-approximating the imported surfaces in order to reduce model's size and speedup the calculations accordingly. This option may alter slightly the imported geometry and must, therefore, only be checked when the initial model is too big. Nevertheless, importing compact data must be preferred whenever possible and a special attention must be paid at the modelling stage to avoid unnecessarily heavy models (see Rhino's best precision settings for example).. 

 -          Include Stas LBP /  alows specifying how many stations must be included in the imported model (these stations allow calculating Bwl and associated data more accurately). The default '0' value allows ignoring this option, while 10 or 20 stations may commonly be requested. Notice that station's spacing and origin depend on the AP and FP Longitudinal positions specified in the corresponding fields (see below).

 -          Include Automatic Silhouette allows including a default silhouette automatically when no silhouette outline(s) is included in the IGES file. When this option is checked (unchecked by default), faces outlines are simply planished in ship's lateral plane and forced to the 'Silhouette' layer (when symetric data are imported, only the portside faces are planished).

 Inputs :

 -          Name allows naming projects root node.

 -          Water Density allows setting water's density for sea water (default is 1.0 for fresh water).

 -          Tolerance allows controlling the final face optimization process. The default 1 mm value is usually satisfactory but, depending on imported ship's size, parametrization quality, amount of data, etc..., a user defined value may allow reducing project's final data size significantly without noticeable incidence on its hydrostatic properties. Except in very special circumstances, you can ignore this setting.   

-          AP Longit. Position allows setting Aft Perpendicular's position in current units. This data is used by the Include Stas LBP  option (see above). AP and FP must be correlated to hull's reference waterplane (Dwl)  to make ship's balances faster to calculate.  

-          FP Longit. Position allows setting Fore Perpendicular's position in current units. This data is used by the Include Stas LBP  option (see above).  AP and FP must be correlated to hull's reference waterplane (Dwl)  to make ship's balances faster to calculate.  

 -         Height of Keel Pt allows locating the K point / vertical origin vertically. K point must necessarily be located below Dwl (i.e K point's height must be smaller than Dwl's height - see below).  

 -         Height of Dwl allows locating the reference floatation (Dwl)  vertically. Dwl must necessarily be located above the K point (i.e K point's height must be smaller than Dwl's height - see below).  

-          Weight allows defining ship's reference diplacement to use for creating a default mass in the project.  

-          LCG allows locating ship's reference LCG to use for creating a default mass in the project (the default TCG is set to 0 but can be modified in the [Data] page as soon as necessary).  

-          VCG allows locating ship's reference VCG to use for creating a default mass in the project (the default TCG is set to 0 but can be modified in the [Data] page as soon as necessary).

 Results :

 The IGES file translation starts when the project initialization data are validated.

 Depending on file's size and parametrization's quality, importation / optimization time may be long (may exceptionally exceed 30 minutes).hanged,) .

 The MAAT Hydro project is displayed on the 3D page as soon as it is created. You can, then, start checking the imported data and complete ship's model if necessary.  

Limitations:

The IGES file must comply with IGES 5.2 specifications and the following IGES entities are the only accepted ones (Rev. 7.3):

100: Circular Arc

102: Composite Curve

110: Line (segment)

120: Surface of Revolution

122: Tabulated Cylinder

124: Transformation Matrix

126: "Rational B-Spline" Curve

128: "Rational B-Spline" Surface

141: Boundary / Outline

142: Curve on Parametric Surface

144: Trimmed (Parametric) Surface

186: Manifold Solid B-Rep Object

504: Edge

508: Loop

510: Face

514: Shell

 Moreover:

- Lines must be exported as NURBS (avoid Splines).

-Faces must unconditionally be exported as trimmed NURBS.

- If possible, convert rational NURBS to non-rational ones.

Please refer to the FAQ for best Rhino settings and/or to "Part II: MAAT Hydro’s Quick Hydrostatic Modelling Guide Rev. 6.4" / Chapter 2 (http://www.sistre-marinesoftware.com/MH%20Quick%20Hydrostatic%20Modelling%20Guide.pdf)  for further details.  

  Typical Use:

Loading an IGES file directly is usually the fastest way to start analyzing a ship model in MAAT Hydro.

Right clicking in the 3D browser also allows importing an IGES file in the current project, but no project initialization is proposed in this case, as the geometry is simply imported in the current MAAT Hydro project.