FreeShip to Rhino produces a zillion surfaces?

Discussion in 'Software' started by adt2, Aug 3, 2012.

  1. adt2
    Joined: Sep 2009
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    adt2 Senior Member

    Howdy, folks -

    I've got a model in FreeShip that I'd like to get into Rhino; the FS version was sent by somebody I'm working on a project with, and I'm just more comfortable working in Rhino.

    I read elsewhere on this forum that FS > Export as IGS > Rhino was the best way to accomplish this, but when I do that, although I get a decent representation of the hull, it's composed of about a zillion small surfaces instead of two sides, a transom, a deck, and a bottom.

    Is that normal, or am I doing something wrong?

    EDIT: So in further working with the Rhino version of the model, I've come across another problem. I've drawn a centerline and station lines under the model, and I'm trying to use Curve > Curve From Object > Project to create some sections. When I select the station lines and make the menu selection, I get the "Select surfaces..." command line, and I select the entire hull. When I press Enter, though, I get an error that "The projection missed the selected objects."

    What's that about?
     
  2. DCockey
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    DCockey Senior Member

    What view are you in when you use the Project command? Where are the centerline and station lines relative to the hull surface? Do the centerline and station lines overlay the hull surface in that view? The direction of the projection in Project depends on the direction of the active view.
     
  3. adt2
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    adt2 Senior Member

    Thanks, David. I actually ended up just using the table of offsets to re-create the hull surface in Rhino.
     
  4. CmbtntDzgnr
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    CmbtntDzgnr Senior Member

    Not sure if this will help, but the Freeship model you received might have the precision level set to Highest or to High. If you obtain a copy of Freeship/Hydronship, you may be able to test this. Comparfe file sizes to get a feel for how big that particular hull is in file size, then compare sizes based on the Precision being set to Low, Medium, High, and Highest.

    I have the same problem in Punch ViaCAD, wherein if I export a hull in Low precision, it *seems* nice and fine til I realize I really wanted High or Higest precision for the stations, WLs, and some of the meshes I hoped to convert to surfaces.

    HTH,

    Cheers,
     
  5. quequen
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    quequen Senior Member

    adt2, interesting, how did you do that?
     
  6. adt2
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    adt2 Senior Member

    Actually, the guy I'm helping sent me a corrected table of offsets that had been faired using the full-size lofting. The lofting was done using the offsets table produced by FreeShip, I believe.

    Or are you asking specifically how I use the table of offsets to draw the hull in Rhino?
     
  7. DCockey
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    DCockey Senior Member

    I exported two of the FreeShip+ examples, Motorboat4 and FREE!ship demo tug, as IGES files and imported the IGES files into Rhino 5. No problems. The data opened in Rhino as clean NURBS surfaces.

    Motorboat4 has 44 surfaces for the entire hull (22 per side). The majority of the surfaces are at near the bow and stern. The majority of the sides, bottom and chine flats have a single surface each per side. There was a gap at the stem which I needed to repair (simple to do in Rhino) before joining the surfaces and running the Hydrostatics command. I could model this hull in Rhino with 4 surfaces per side.

    The tug has 34 surfaces for the entire hull (17 per side). The smaller surfaces are in the forefoot and around the base of the transom. No repairs were needed. I could model this hull in Rhino with 7 surfaces per side.
     
  8. DCockey
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    DCockey Senior Member

    Tried some more FreeShip to Rhino moves with FreeShip demo files. FreeShip Demo 4 and FreeShip Demo 5 were fine. FreeShip Demo 3 has some problems with folded surfaces along the keel near the bow and stern. Not sure what causes the differences but it may be how the modeling is done in FreeShip.
     
  9. adt2
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    adt2 Senior Member

    I'm guessing number of surfaces has a lot to do with it. I don't remember exactly how many surfaces there were in the original file, but it was north of several hundred. This was for a 24' runabout.
     
  10. quequen
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    quequen Senior Member

    Yes, are you using some automation to turn a table of offsets into nurbs?
     
  11. adt2
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    adt2 Senior Member

    Nah, I just type in the values. Takes a little figuring out -specifically, which values on the table of offsets correspond to which axes in Rhino (i.e. X, Y, and Z) - but once you get that worked out, it doesn't take long at all to reproduce a hull.

    I generally enter all the sheer points on one layer (SHEER_PTS), then draw a curve through those points on a second layer (SHEER_ORIG). Finally, I'll copy the sheer curve to a new layer (SHEER_FAIRED) and use curvature analysis and the Fair command to smooth out the curve.

    I repeat that process as many times as necessary (i.e. chine, rabbet, keel, etc.) to get all the curves that define the hull. Then I draw a centerline and station lines underneath the hull and use Curve > Curve From Objects > Project to get sections. Nice thing about this is, if you draw station lines at the proper station spacing, and then offset the lines to one side by the thickness of your frames, then you get both the forward and the aft faces of the frames - giving you the exact bevel.

    See http://nauticallyobsessed.posterous.com/ for some tips; I started this site last year sometime, and I haven't updated it recently, but there's some information there that's likely relevant to this discussion.
     

  12. quequen
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    quequen Senior Member

    Thanks adt2!
    To export big files from freeship to rhino, just divide the freeship file in different layers, freeze all but one and export one by one. It's simple, I use this method to export to many other packages.
     
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