Hull Design Software Based on NURBS

Discussion in 'Software' started by ancient kayaker, Jan 12, 2014.

  1. DCockey
    Joined: Oct 2009
    Posts: 4,726
    Likes: 319, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    FreeShip and DelftShip do not use NURBS (Non-Uniform Rational B-Splines. Rather they use a subdivision methodology which has significant and fundamental differences from NURBS based methodologies.

    It is completely possible with NURBS based software such as Rhino to create curves which pass through a set of points in the same manner that curve can be drawn through a set of points using a physical spline. Using a set of these curves a surface can be created which goes through the points.
     
  2. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Thank you for the correction. I was not aware of that.


    FreeShip can import offsets effectively doing the same; it creates markers from that and presumably solves for the necessary control points, but it's obviously not in Rhino's class. I'm not familiar with Rhino. How easy is it to define a mathematically precise surface?
     
  3. DCockey
    Joined: Oct 2009
    Posts: 4,726
    Likes: 319, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Is that capability a recent addition to FreeShip? When I looked at FreeShip several years ago it appeared not to be possible to import a set of points into FreeShip and directly create a curve which passes directly through the points. FreeShip would create a curve which would be close to the points, but not one which passes directly through the points.

    Rhino has a simple command, CurveThroughPt, which creates a NURBS curve which passes through a set of points. After creating a network of curves a NURBS surface can be created which passes though the curves. There are some limitations on the arrangement of the curves in the network.

    The mathematical formulations of NURBS curves and surfaces are parameterized, precise and explicit.
     
  4. DCockey
    Joined: Oct 2009
    Posts: 4,726
    Likes: 319, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    I use Rhino software as a set of tools when creating a hull shape, very similar to how someone working at a drafting board uses splines, ducks, ships curves, triangles, etc as a set of tools. I provide the fundamental knowledge and decisions about the hull shape, not the software.
     
  5. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    - good point, I have never checked. I checked one file and the markers are exactly on the line for the sheer and keel but off a small amount for the plank lines - up to 1/64" or 0.4mm for that one example. That assumes the markers represent the original offset file of course. There are other import files for FreeShip but I don't have the capability to create them.
     
  6. DCockey
    Joined: Oct 2009
    Posts: 4,726
    Likes: 319, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Using Rhino I have gone from sets published of offsets through faired surfaces to curves for CNC cutting station molds for several Saint Lawrence River Skiffs. Along the way curves were created on the surface which represented the planking lines for constant width strip planks. Hulls were built using the CNC cut molds without any hand fairing of the molds.

    The offsets were imported into Rhino, a network of curves (stations, waterlines, buttocks, rabbet, sheer, etc) created using the offsets, and then a surface was developed which passes through the curves. Along the way mistakes in the offsets were created and the curves and surfaces faired, much like what would be done when lofting by hand. Curves representing the plank lines of equal width strips were created in several different arrangements to guide the builder in planking the hull. The corresponding inner surface was developed, and the shapes of station molds derived. The shapes of the curves were exported to a CNC system which cut physical station molds. The physical station molds were then assembled onto strongbacks and fair hulls built using strip planking.

    The CAD work was done using Rhino (which is NURBS based) and was very straightforward. I used Rhino as a tool set in much the same manner someone working at a drafting board would use splines, ducks, curves, etc as a set of tools.

    Based on my knowledge and limited experience with DelftShip and FreeShip (which are based on a subdivision formulation, not NURBS) this would be much more difficult to do in either DelfShip or FreeShip.
     
  7. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    The only thing I use in FreeShip that approaches that would be the plank developments. Mostly I use those as a check of my calculations and FreeShip's hydrostatic outputs are usually what I am really after, although I have it do the planking weight calculations for me. Definitely not a Rhino class tool - but priced right for the amateur :)

    I don't often have to deal with offset mistakes since I calculate those in a spreadsheet based on a mathematical definition of the curve required. I use mathematically-defined curves to ensure fairness. If I am working from published offsets I can calculate fairness within the spreadsheet using a rolling 2nd derivative and "largest step" detection. No doubt the spreadsheet has a function for that but I don't know what it's called and there's hundreds to search in.

    Interestingly I find that the optimum number of control points for use in creating a FreeShip design "freehand" within FreeShip seems to be the number of spline weights needed to define the shape with a batten, and the location of the weights in X is a good place to place each control point: Y and Z are much easier to determine.
     
  8. SukiSolo
    Joined: Dec 2012
    Posts: 1,270
    Likes: 25, Points: 0, Legacy Rep: 271
    Location: Hampshire UK

    SukiSolo Senior Member

    I use Rhino as an all round 3D package. It has the right tools to do the job and true NURB based (engine from Integrity Ware). The curves may be defined correctly by Degree - Deg 1 = straight line, Deg 2 = Arc, Deg 3 = Spline with 3 or more control points. You have the ability to edit the curves by control points to very fine tolerances. Similar to lofting with battens and weights. This software is capable of serious professional work. The curves are the key. Editing and refairing input files are also capabilities inside it, as well as some of the best and widest classes of file formats. Years ago Autodesk wanted £1000 for an IGES translator and Rhino V 1.0 (full commercial version) cost £300....

    I'll second David's comments above about the ability of the program. It lacks some features for full on Naval Architecture but quite a few can be obtained in an add on package. However as long as you are aware of the basics and when a few calculations are needed it will do the job.

    Developing that equal plank spaced canoe would be a simple job for it. It can take in curves through defined points, if you create the file (pretty simple) from say a spread sheet output.

    I have looked at and played with a couple of the freeware programmes but they always so far seem to lack something. Things like MaxSurf work OK but I just don't do enough naval architecture design to justify it. It might be because I'm more used to stuff like Pro-E or SolidWorks. Might be I just need to use it longer, I'm still finding stuff in a 2D program I've used for 20 years!, and I am very familiar with, customising it quite a bit. I have spent many hours learning the nuances of some programmes in my own time not company time. But by understanding the tools better this has often resulted in shorter and more successful (and accurate) modelling and drafting.

    The tools to get the shape you want rather than be controlled by software is the main issue. Aim for the best shape and solution, even if you have to hand draw it.

    There is no real shortcut to learning software in depth. However I would say that the interface design and help files are usually a good guide as to how much thought is in the programme. Rhino is pretty good and it is easy to get the basics but will take a while to fully master. I've been using it since before commercial release and would not claim to be a master of it. Like Ad Hoc says once the true design work is done, it is doing the do to get to the resulting output.

    Designing for real production is different and the more complex or higher the volume, the more important to get it right. I've done stuff produced in 1 million items+ in less than 3 months, right through to one offs and prototypes.
    As Ad Hoc says the restrictions of real world issues intrude in the production process but are just part of the armoury of the designer.
     
  9. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    So returning to the purpose of the original post which started the thread, it would appear that Rhino provides the designer with the ability to exactly specify the curves needed to define a hull design, in a manner at comparable with the spine weights and batten, French curves, and compass of the paper-and-pen based designers. Good to know. Of course at $700 and up it is beyond the range of mere dabblers. Thank you all for the information!
     
  10. Baltic Bandit

    Baltic Bandit Previous Member

    Dunno what happened to my post - but I posted a link to http://oneshape.com

    the founders are the same guys who did a lot of the work on the early versions of PRoE - then left and started Solidworks.

    Now they are essentially starting a new company to build a brand new 3D modeling kernel that is seeking to integrate solids modeling with NURBS without it being a patchwork of code special cases. That's the problem with NURBS - the equations don't work well when trying to do intersections of solids

    Anyhow - its a bunch of very smart guys. something you might want to pay attention to
     
  11. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    I get nothing at that link.
     
  12. SukiSolo
    Joined: Dec 2012
    Posts: 1,270
    Likes: 25, Points: 0, Legacy Rep: 271
    Location: Hampshire UK

    SukiSolo Senior Member

    Those Pro-e guys might be the same as the ones who founded Revit a Parametric architectural program which Autodesk bought.

    Up until Pro-E 2001/2 ie including Version 20, SolidWorks would read in a Pro-E file almost faultlessly. So PTC changed the text file format to fully binary which was harder to decipher.....and about half the file size.

    Actually Ancient Kayaker, I consider Rhino to be within the finances of the serious amateur/professional even though it may seem expensive. It is not a 2D drafting tool though compared with many out there which are good at that but cannot handle true NURBS 3D modelling. If you need to get stuff CNC'd or develop surfaces/panels/planks or otherwise modelled full size or scale it will pay back in time though. Compared to the annual license for a seat of Pro-E or SolidWorks, it is cheaper and you get free fixes and support between releases. It was 6 years between Rel 4 and 5, and McNeel have done a very good job IMHO.
     
  13. Baltic Bandit

    Baltic Bandit Previous Member

    Nope - different guys. PtC had to change its formats because Solidworks was cheaper, easier to use and was eating their lunch.

    this link works for me http://www.onshape.com/ But there's not much there.... yet. All I can tell you is that Scott Harris, John McEleny, Jon Hirshtick are three of the smartest and most innovative guys I've had the pleasure to work with in the CAD industry
     
  14. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Thanks SujuSolo but I confessed to being a dabbler earlier in the thread! I invest moderate amounts of cash in boat books and study plans as part of my self-imposed hull design course of study 101 (I may be up to 102 by now) but so far I've managed to get my designed into anaytical form without spending money on design software. I find FreeShip and Carenne a nice pair, I know them fairly well and each covers the deficits of the other, and with an occasional forey into spreadsheet territory - where I still retain some skills acquired in a half-lifetime of preparing and engineering proposals & estimates - I manage quite well.

    As examples of recent work I adapted Joel Wight's lovely Haven 12-1/2 to a smaller lighter format for car-topping and beach launching, and closer to home (I live an hour's drive from Toronto) Walter Dean's famous Sunnyside Cruiser (for which no plans are available AFAIK) as an investigation into a transverse planking method of construction.

    I've started work on adapting other classic hull designs to modern construction, and found I needed another tool to get to where I wanted to be. Developing a fresh spreadsheet for each design is time-consuming which is what prompted my question in the first post. I did start designing a general purpose spreadsheet for creating accurate offsets for old (not yet digitalized) designs; perhaps I will take another look at that in the light of what I have learned here.

    From what I have heard Rhino would be my choice if I intended to get serious or planned to sell my work, I'm sure I can recall the tricks and techniques of working with splines again if I needed to. Thanks for the advice and information.
     

  15. Ad Hoc
    Joined: Oct 2008
    Posts: 6,634
    Likes: 646, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Given the prices quoted for Rhino, I would tend to agree. Since the amount of time wasted using other software for the job you have at hand, if not up to the job to begin with, compared to Rhino; which on the face of what comments from yourself and DC note; would be worth the investment.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.