PIAS Manual  2021
Program for the Integral Approach of Shipdesign
Supporting functionality

Check Solid

check_solid.png
The Check Solid docking window with markers in the model.

There are several kinds of conditions that can exist in a Fairway model that may be unwanted, although they are allowed and thus no errors. With the menu option [Objects]→[Check Solid] active solids are scanned for the following three conditions:

warning_yellow_20x21.svg

Crossing deviations. Fairway allows crossing polycurves to deviate from their common intersection point to a configurable degree, which is a valuable functionality in the process of incremental hull fairing. However, larger deviations can cause deficiencies in surface generation, and a production-ready model should not contain deviations that exceed tight bounds. If the corresponding checkbox is ticked, points are indicated where the distance between intersecting curves exceed the given threshold. The actual distance is shown in the tree view of the docking window, and by expanding an item either of the two corresponding curves can be selected to resolve the deviation using [Change the shape of a curve].

warning_green_20x21.svg

Coinciding points. Points that have identical coordinates or that are unproportionally closely spaced can be confusing, and they can cause complications for fairing and degrade surface rendering. Where possible, one may want to eliminate such coinciding points. By ticking the corresponding checkbox all points that fall within the given threshold are marked. The tree view in the docking window shows the respective curve.

warning_pink_20x21.svg

Unconnected knuckle points. Usually, one will want corresponding knuckles in successive polycurves to be connected by another polycurve or chine, to express that surface feature across the shell surface. To easily detect any unconnected knuckles, the corresponding checkbox can be ticked.

Clipping

To prevent parts of the model from occluding an area of interest, the menu option [Display]→[Clipping]→[Clip to Box] can be used to hide the parts of the model that fall outside a resizable box.

clip_250.png
Clip to box.

The coloured facelets can be picked and dragged to resize the box (along the edges and in the corners) or to translate the box (in the middle of each face). The box can be resized to contain the whole model with the menu option [Display]→[Clipping]→[Clip Box Contain All]. The option [Display]→[Clipping]→[Hide Box] will hide the box and its facelets, but the clipping will remain active.

When a curve is being manipulated that partly falls outside the clipping box, it will not be clipped but drawn in its entirity.

Hydrostatic Data

The menu option [Hydrostatics]→[Hydrostatic Data] will bring up a window with hydrostatic information of the vessel. The window can either be floating separated from the main window, or be embedded in it somewhere around the modelling area. The hydrostatics are dependant on the frame shapes, so when a frame shape changes, the [Update] button in the hydrostatics window will be enabled, which allows the information to be recalculated.

Attention
Hydrostatics are computed on the basis of the areas of the submerged parts of the frames. This mechanism might as such yield an incorrect result in case the frame set contains a frame not extending over the full draft, as depicted in the figure below. For this reason a mechanism is included to detect and ignore such incomplete frames. However, in order to verify the correctness of the result it is advised to inspect the SAC (Sectional Area Curve) with [Hydrostatics]→[Sectional Area Curve (SAC) Window].
hydrostatics_450.png
Hydrostatics window and a defective sectional area curve due to a (not ignored) incomplete frame.

Attention
Note that the same information can also be obtained from the local cloud in real time, see Local cloud: simultaneous multi-module operation on the same project. Through the cloud not only the upright hydrostatics are available, but (potentially) all PIAS results, such as full intact stability — loading conditions, GZ-curve and verification against the stability criteria — resistance and propulsion, tanks capacities etc. Not only this wider range of computation options is a reason that the local cloud is advised above this Fairway ‘hydrostatics’ function, another advantage is the availability of tools for graphical inspection of frames as they are actually used in PIAS’ computation processes.