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Re: [PSUBS-MAILIST] Reverse engineering in CAD
David,
Thanks for the credit, but that was Ian. My email screwed up.
Re: [ > I agree with Steve, and you are following the right
> steps: ] No big deal I suppose.
However, I agree with you. Better to stick with a program you are
familiar with.
Peter did mention the boat hull being in "jpg". It will have to be
converted
to vector and layered accordingly, I would think, before it can be scaled
and manipulated? Simply cutting and pasting parts of it won't do?
Am I understanding what you're trying to do, Peter?
--Steve
On Thu, 17 Jun 2004 22:06:46 -0700 (PDT) david cutajar
<davecutajar@djcengineering.com> writes:
> Good old NURBS- Non Uniform Rational B-splines?? It's
> been so long.....
>
> I don't believe AutoCad uses the nurbs command for
> splines anymore (at the user interface level, I mean)
> You don't have the option of what power you would like
> your spline to be. Catia still has the functions,
> albeit in another format.
>
> I have been on CAD since the 7th grade (Applecon @ the
> General Motors tech center - When drawing lines, you
> had a million color choices - all of them green!!)I
> was on MES which evolved into solution 3000, which
> ACAD purchased and integrated for Mech Desktop and
> Autocad. I've been on alot of systems, Catia, UG, etc.
>
> The System you are using doesn't matter to much. How
> well you know the system may be the issue.
>
> I agree with Steve, and you are following the right
> steps:
>
> Create accurate point data-
> Convert to splines, curves or known line geometry
> (i.e. circle).
> Extrude or revolve to a solid.
> Stay away from surfaces and volumes for now.
>
> If you have ACAD, I don't believe a free, or
> inexpensive CAD system will have more to offer, as
> ACAD is actually pretty decent (esp. for the price).
>
> If you are familiar with ACAD, and the solids choices
> are crude, you could try Mechanical Desktop. I suggest
> this because it is a "sister" product and you will
> have an easier transition.
>
> It provides for sketching and more powerfull Solids
> modeling.
>
> Again, I am sure there are a ton of CAD systems that
> would work for you, and everybody has a system they
> are comfortable with.
>
>
> My $.02
>
> David Cutajar
> DJC Engineering
>
>
>
> --- Steven Mills <cirtemoeg@juno.com> wrote:
> >
> >
> > On Thu, 17 Jun 2004 18:59:17 -0700 Ian Roxborough
> > <irox@ix.netcom.com>
> > writes:
> > >
> > > Hi Peter,
> > >
> > > I don't really know anything about autocad2004,
> > but if it's worth
> > > it's
> > > salt then it I'll probably have the following
> > features.
> > >
> > > NURBS!
> > >
> > > See if your cad/modeling software has Nurbs
> > support (Nurbs are just
> > > fancy curves or a fancy word for curves). You
> > should be able to use
> > > the Nurbs tool to create some boat like curves,
> > similar to the ribs
> > > of a woodern boat (you may want search drawning
> > Nurbs or curves on
> > > the internet or in the library, but if mess around
> > long enough
> > > you'll
> > > probably get the hang of it).
> > >
> > > Once you have enough curves (draw them a foot a
> > part, or whatever
> > > you
> > > think it takes) to get it to start looking
> > boat-ish, then save your
> > > work and look for a "skinning" tool. A "skinning"
> > tool (I've no
> > > idea
> > > what it will be called in autocad) should allow
> > you to select all
> > > your
> > > curves, then create a skin that fits prefectly
> > over the curves.
> > > You'll
> > > probably find that you have to edit the curves a
> > few times before it
> > > starts looking correct.
> > >
> > > But that's pretty much it. Not too different from
> > the join the
> > > dots,
> > > only with curves.... ;-)
> > >
> > > If your doing solid modelling, then hopefully
> > there is tool for
> > > giving
> > > the skin 'thickness' or volume. Otherwise you
> > might have to create
> > > a
> > > copy of the hull and shrink it down by a very very
> > small amount and
> > > put
> > > it inside the bigger hull skin, then joint the two
> > object together.
> > > The
> > > distance between the inner and outer skin
> > determines how thick the
> > > hull
> > > will be.
> > >
> > > This is how I would tackle the problem, but it's
> > probably worth
> > > noting
> > > that the software I use to do this type of thing
> > isn't a true solid
> > > modeller.
> > >
> > > Hope this helps.
> > >
> > > Ian.
> > >
> > >
> > >
> > > On Fri, 18 Jun 2004 08:36:12 +1000 (GMT+10:00)
> > > Peter McKellar <submckellar@earthlink.net> wrote:
> > >
> > > > Hi All,
> > > >
> > > > I am trying to reverse engineer a boat hull for
> > my pressure hull's
> > > exo-skeleton.
> > > >
> > > > I am using autocad 2004 and solid modelling, but
> > i just can't
> > > split the shape into the primitives i need to draw
> > it (in my head
> > > anyway). I am also trying to scale it down (and
> > this has its own
> > > pitfalls as it may not scale and retain its
> > properties).
> > > >
> > > > I have a jpg of it, including cross sections
> > both horizontally and
> > > vertically at a number of points. I am
> > considering pasting these
> > > planar jpgs into the drawing and then doing a 3d
> > join-the-dots.
> > > >
> > > > can anyone think of a better solution?
> > > >
> > > > cheers
> > > > peter
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> >
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