On 6/9/07, Chuck Hast <wchast@gmail.com> wrote:
> On 6/9/07, Ken Elliott <kelliott11@cfl.rr.com> wrote:
> > Ken Elliott wrote:
> > > Compare the Stealth Figher vs. the B2 Stealth Bommer.
> >
> > Chuck Hast wrote:
> > > The flat surfaces on the stealth fighter are set in such a way
> > > as to scatter radar and reduce the reflectivity of the fighter,
> > > that is why it is like that not due to the design limitations.
> >
> > I suggested this example because BOTH are designed to scatter radar. But
> > the flat surfaces tend to create a more focused reflection than the
> > non-uniform curved surfaces of the B2 Bommer. The figher has flat surfaces
> > because of the limitations of the CSG modeler and lack of processor power.
> > This is well known among CAD developers.
> >
> > CSG modelers usually describe non-uniform curved surfaces as a series of
> > connected triangles. The smoother the surface, the more triangles. Trying
> > to model a water hose can take millions (or more) of triangles, while a
> > NURBS modeler only needs 2 entities: a cross section curve (like a circle)
> > and a path curve. NURBS curves are very lightweight in data, but it takes
> > lots of number crunching to process it.
> >
> > In the past, NURBS were not practical for simple geometry (tables, houses,
> > tanks) because of the overhead of caluculations. CSG is super fast, and as
> > long as the geometry didn't get too complex, it was the tool of choice.
> > Most CAD systems today started off as CSG modelers. But once the CPUs got
> > fast, NURBS became possible, then practical, and now there is little reason
> > not to use them. This development occurred in the late 90's, and the first
> > affordable modeler (under $30,000) appeared on the market (Rhino in 98, I
> > think).
> >
> > So here's the big deal about Rhino. All other CAD packages started off as
> > CSG, and added some NURBS entities. So your model is a mixture of CSG and
> > NURBS. Rhino is 100% NURBS, except for text and dimensions. It can simply
> > do things that no other modeler can do. Just having this package on Linux
> > would be a wonderful thing. But McNeel has opened the source code and specs
> > of the file format. No other CAD company does this - they all hold your
> > design data hostage. McNeel is by far the most open minded of all the CAD
> > vendors. The tool is fantastic and he thinks like open source people think.
> >
> > OpenNURBS greatly lowers the difficulty of bring high-end design tools to
> > Linux, and we badly need this sort of thing for Linux to be taken serious in
> > engineering circles. Here's a thermal analysis program that supports Linux.
> > http://www2.rhino3d.com/resources/display.asp?language=en&listing=107
> >
> > This is all good for Linux. Engineering and design tools were one of the
> > early target markets Microsoft went after with Windows NT. The field was
> > dominated by Unix workstations, and MS went after them with a lower cost
> > platform. If anyone in a large company will be pro-Linux, it would be IT
> > people first, then engineers. I watched MS work hard to woo the CAD
> > developers in the early 90's and it paid off big time.
> >
> > Vote here:
> > http://offbroadway.blogspot.com/
> >
> > OpenNURBS
> > http://opennurbs.org/
> >
> > CSG
> > http://en.wikipedia.org/wiki/Constructive_solid_geometry
> >
> > NURBS
> > http://en.wikipedia.org/wiki/NURBS
> >
> > I'll shut up about this for now. As you can tell, I'm passionate about
> > getting good engineering tools ported to Linux.
> >
>
> I too, my biggest issue still remains with mapping. I do a lot of mapping
> and end up going to windows stuff because I just can not get what I need
> out of the stuff I find for Linux unless I am willing to shell out the big bux
> and get something I can not afford.
>
> It is a real shame, most all of this art started out on some form of Unix
> work stations as you pointed out, but the providers forgot their roots. That
> is sad.
>
> --
> Chuck Hast -- KP4DJT --
> To paraphrase my flight instructor;
> "the only dumb question is the one you DID NOT ask resulting in my going
> out and having to identify your bits and pieces in the midst of torn
> and twisted metal."
> -----------------------------------------------------------------------
Yep, I believe ProEngineer started on UNIX.
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