Orca3D Hull Assistants

[lleibman]

Orca3D currently has 3 hull assistants (sailboat, planing hull, ship hull) for creating preliminary hull shapes that conform to user-specified input parameters (our expectation is that the user will want/need to modify the preliminary shape with other Rhino/Orca functionality). The input parameters for these assistants correspond to the principal controls on the surfaces we create. For example in the planing hull assistant an input parameter is Length on Deck because this corresponds directly to the length of the deck surface as well as the length of the hull surface sheer line. This may or may not be the same as the Overall Length depending on the transom rake angle. For a case with transom raked forward as you move up the transom, the Overall Length will be longer than the Length on Deck. (Note that the length overall is reported in the hydrostatics output.)

We plan to add figures to the Orca3D documentation illustrating the meaning of the current input parameters. We are open to suggestions on changing some of these if it makes sense. For example we could use Length Overall instead of Length on Deck. The implication of this is that for a given Length Overall, the deck length could change as you change the transom rake angle which might be non-intuitive.

We are also soliciting suggestions on additional features in the existing Hull Assistants as well as suggestions for entirely new Hull Assistant types.

LL

[wallygator]

It would really be helpful to have the ability to input sections from an existing set of hull lines.
A lot of our work is derivative, our smaller hulls serve as real world tank test models for the larger hulls.  A "Fit to Sections" wizard would be terrific.

[Admin]

Fitting to sections is something that can already be done with Rhino's "loft" command. Loft has a fair number of options that makes it quite powerful. However, the process can easily result in a surfac that, while matching your input sections, is difficult to use in a design and fairing process. It's best to use the "Loose" option, which will create a surface with a reasonable number of control points, but may not exactly match the curves. Detailed fairing can then be done using Orca's "OrcaMove" control.

To best condition the curves for a loft process, you should be sure that each curve has the same degree, and the same number of intervals. The FitCrv command is useful for this.

[miro]

I really like the interface with hull graphics in Rhino Marine 4. This avoids any confusing with the dimensions. Can you add something like that in Orca3d interface of Hull Assistant?

[imbehind]

Admin is right, automatically fitting hull form, or 3D surface to sections, set of 2d curves in 3d space is really the holy grail of the whole industry, and it may be never achieved.

The sections in Orca3d as well as in almost any naval CAD software are only representations of existing and described 3d surface not the building blocks for such a surface.

So you have to fit the surface manually. Great advantage of Orca3d however, is to assist you with such fitting process.

Start with the wizard to obtain hull similar to target hull regarding general particulars of the ship, and then start fitting.

First, define sections as are in your lines plan. Then import your sections from the lines plan as overlay bitmap and calibrate the image.

Then modify the hull using Orca3d control mesh. Since Orca3d sections are interactive (they reflect your changes to the 3d surface) you should be able to fit Orca3d sections to your own, thus recreating the hull.

But it can be very difficult sometimes for more complex hulls.

[ndar]

The key to matching / copying a (hull) shape is understanding the 3D evolution of curvature of the shape in question.

The direct control net editing technique will give the greater benefits when the initial control net is built accordingly.

As a hull shape generally evolves primarily in a longitudinal direction, stations do not help much as a starting reference, while waterlines / buttocks / diagonals will provide a more relevant guide.  On the other hand, due to their "local" nature and limited extent, stations may be an easier "template" to check against.

The above constitutes the fundamental topic in all our hull modelling classes.

I'll be happy, time allowing, to look at "difficult" shapes to be modelled in Orca3D.