Navigation:  Quick Start Tutorials > Hull Modeling

This tutorial shows you the basics of modifying a hull surface in Orca3D using the Orca3D control points. For more detailed instructions and background information see the Hull Design section.

Hull modeling in Orca3D is accomplished using Rhino's NURBS surfaces, and the surfaces are modified by moving the control points. While you can do this using Rhino's control points, Orca3D has custom control points that provide more functionality: as they are moved, the sections are updated in real-time, and if you've checked the "Real-Time Hydrostatics" box in Define Design Condition, the hydrostatics will update in real-time as well.

Orca3D hull modeling tools include:

 

Starting from a "flat plate" NURBS Surface

Often a hull design is begun using an existing model, importing a hull from another program, or one of the Hull Assistants. But sometimes it is easiest to begin with a "flat plate" of NURBS surface, and then "sculpt" that flat surface into the desired shape. While Rhino has a function for creating a rectangular surface, it does not give you control over the degree and number of rows and columns. The OrcaCreatePlate command (in the Hull Design menu) provides this control, as shown in the dialog:

The plate will be created in the plane of the active viewport, and it may be moved or rotated. The Length and Height may be entered numerically, or graphically by clicking on the icon to the right of the values.

 

Orca Control Points

1. Start the command from the toolbar, menu, or command line.

2. Select the surface(s) you wish to edit, and hit Enter.

3. The control points for the surface(s) will be shown. Orca control points, and the lines that connect them, are drawn differently than the standard Rhino control points. You may control the color of the lines in the control polygon in the Orca Properties dialog (). By default, control lines in the U direction (longitudinal, in general) are drawn in cyan, and the V direction (transverse, in general) are drawn in green.

4. Move the control points just as you would the Rhino control points. If you have defined Orca Sections, they will update in real-time (remember that the smoothness of the real-time curves is controlled by the smoothness of the Orca Mesh, which can be adjusted in Orca Properties). If you have checked the Real-Time Hydrostatics box in the Define Design Condition dialog, you will also see a window showing the hydrostatics data updating.

5. To simplify the process of moving control points in the Perspective viewports, Orca3D implements Edit Planes. These are constraint planes, so that as you move a control point in the Perspective viewport, it will move parallel to the Edit Plane. For example, if the Edit Plane is chosen to be Station, the control points will move transversely and vertically, but not longitudinally. The Edit Planes are available from the toolbar (), or with the command OrcaEditPlane.

 

Orca3D Move Control

When hulls are modeled by the direct manipulation of control points, it's important to be able to easily and quickly drag the control points to "sculpt" the shape of the hull. But it is also important to be able to very precisely place the control points, or make "fine-tuning" adjustments to tweak the hull shape. The Orca3D Move Control allows you to easily enter the coordinates of an Orca Control Point (it will not work on standard Rhino control points) or other objects in your model. Multiple Orca Control points and/or objects can be moved together, and the coordinates may either be Absolute (World) or Relative. To make it easier to precisely set angles (such as a deadrise angle), you may also use a Polar coordinate system.

 

Real-Time Hydrostatics

As Orca control points are moved, the program can compute and display various hydrostatic properties of your hull . To enable this function, open the Design Hydrostatics dialog (Orca3D > Stability > Define Design Condition), and check the Real-Time Hydrostatics box. A window showing various values will be displayed.

The values to be shown (up to 4) may be chosen by clicking on the Values button.

As the hull is modified and the values change, the slider bar will move up and down to show the trend, and colored "LED's" are displayed to show how far the value is from the original value. The LED's will change from green to yellow when the value moves 2.5% from the original, and red at 5%. The sliders can be reset at any time to the current value by clicking on the "Reset Ranges" button.

 

Corner Continuity

One of the characteristics of NURBS surfaces is that they fundamentally have four corners and four edges. As they are applied to hull design, these four edges usually correspond to the sheer line, the stem, the bottom profile, and the transom corner. The corners are the intersections of these four edges. Generally, the corners are discontinuities, with the exception of the stem-bottom profile corner (forefoot). Here, it's usually the case that a smooth transition is desired, with at least slope continuity, but preferably with curvature continuity (which requires a surface that is cubic in both the U and V directions).

Orca3D provides a function to precisely place the corner control point to create this smooth transition.To create the smooth transition, select the Corner Continuity command from the Orca3D > Hull Design menu. The first prompt asks which surface the corner wrap should be applied to, and the second prompt allows you to select which of the four corners should be smoothly wrapped:

By clicking on any corner of the surface, its corresponding Corner will toggle between "No" and "Yes." Once you have selected the desired corner(s), hit Enter to complete the command. The corner control point will now be precisely located to create continuity at that corner.

 

Lines Plans

Using Rhino's Page Layout capability, a traditional three-view lines plan can be created instantly. All Orca sections are displayed on the lines plan. To create the lines plan, click on the Lines Plan toolbar icon, or select Lines Plan from the Orca3D > Hull Design menu.

 

Exporting Curves

Orca3d can export curves to either IDF or PIAS format, for use in other programs. To export in either format, select the curves to be exported, and then select Export Curves from the Orca3D > Hull Design menu. In the Export Filename dialog, select the file type, enter a file name, and click on Save. A dialog will be shown that allows for controlling the smoothness of the curves:

 

 

 

 

 

 

See also:

Hull Design