Automatically generate NAPA patch model

Hello every one,

Good day!
This article is about NAPA, and the generation of NAPA patch model.

NAPA is popular in ship design industry, however, we spend most of our time to describe the ship as stated in the software's user manual:

Now we have developed a software and an interface to automatically generate NAPA Macro which can be directly executed and run in NAPA to generate NAPA patch hull. It takes only several seconds to generate a NAPA hull even if you are not familiar with NAPA at all.

The following are two ships I have tested :

01: KCS ship:

Hull (IGES file) displayed in Rhino:


Software and interface to generate NAPA Hull


Hull Surface displayed in NAPA:


Hull Surface displayed in NAPA with control points and patch:


02: Boat

a auto-generated boat hull


Now I am still testing our software, if you have any requirements please feel free to let me know.
Maybe we can further cooperate and do something interesting together.

The IGS file and NAPA macro file for KCS ship please see the attachment.

 

Hi I checked your hull, but has some errors and is impossible join the surfaces into one, here in the attached image is visible the overlapping of the igs model.

 

Dear Sir,

Thanks for your feedback.

The igs file is from the website：T2015 Workshop https://t2015.nmri.go.jp/

It is not a perfect hull indeed and actually have some errors as you mentioned.

For my software I only need those hull lines, I do not directly use the igs file as an input, and I have written some codes to cut the surface so as to get hull lines.

 

thanks, I thought also the IGS file was generated by your software, anyway it generates an excellent surface from what I see in the orange shaded image.

 

Never seen any Napa Iges files without problems an only few of them was accepted as production lines fairing. Actually there is a lot of not so expensive software can import Iges and make lines drawing without any macro.

 

yes, I aggree.

Some ship models in IGES format are not fairing enough for use and need further modifications.

And some ship models in IGES format may not well prepared for use in NAPA.

That is the reason I developed those functions to get cross sections from IGES file and furthermore to generate NAPA macros automatically.

Best Regards.

 

If you interested, I can check your Napa IGES file in my software. Moreover I can send you my IGES file for import into NAPA. This file had no any problems like gaps or overlapping. Contact me on aalexanov@lyse.net

 

Dear Alexanov，

Good day!
Thanks for your kind comment.

Our ship design software can easily export NAPA file but is based on spline.

So I studied the theories and functions for nurbs and write some codes to handle IGES file.

 

Can recommended to you read “The NURBS book” it is like a bible for NURBS for more deep understanding of it.

 

Dear Alexanov,

Yes, I read this book together with IGES Specifications, it really helps a lot.

Thanks for you kind recommendation.

But if one wants to cut or get the cross sections from an existing file, one needs to learn more and in some depth.

I am the kind of person who have idea and try to realize it.

 

Unfortunately there is nothing in "The NURBS Book" about making sections of surface and Surface-surface intersection. This is computational mathematics.

 

Yes，it took me some time and hard work to do that.

BSpline is the base of BSurface, if you want to handle BSurface, you have to make clean of BSpline.

The nurbs book covered those above topics.

But the hardest part must be the intersection algorithm both for curve and surface.

 

Some how you can generate precise mesh in UV space and make an intersection line with plane. But you also have to take into account that some of surface patches can be trimmed (inner and outer contours). So it can be full scale 3D CAD development in the end.))

 

Just one more comment. Contours of trimmed surfaces in IGES can be presented by two type of lines: set of polylines and set of B-Splines/NURBS curves.

 

Thank you very much for you kind reminder, Alexanov.