From: Christopher Sean Morrison <brlcad@ma...> - 2011-10-04 04:16:15
Revisiting this old thread because things were a bit hectic to reply properly earlier.
On Apr 27, 2011, at 12:00 PM, Kathy Miller wrote:
> Thank you for your help. I am just tired of working with .stl conversions
> and all the bots they create. Looking for a better way. There is no
> solidworks to BRL-CAD converter. I know that there is a plug-in converter
> developed from PROE to .g, but it hasn't been tested much and is not
> supported. Haven't had much time to delve into that yet. Once again, thanks
> for your help. I will email you more soon with more info and news.
We're all tired! 
In short, the BRL-CAD export plugin for ProE should do what you need to get BoTs exported (and is pretty extensively tested and used for production work) but it's definitely still labor-intensive (but better than stl..). Even ProE has trouble turning their geometry into a polygonal mesh, so export failures that require manual investigation are not uncommon.
Our ProE export plugin does a fair bit to help alleviate the problem, but it's an uphill battle. The original geometry almost always has errors (which will fail to convert) and we ask Pro/E to change the geometry format (from BREP/NURBS to polygonal mesh). That is the underlying problem and weakness of the approach.
>>> iges, etc.). Please tell me which format is best to export to which would
>>> make these solids (NURBS?) that will contain an editable solid module
>>> that is not a BOT or facetized.
NURBS is the path forward we're pushing. We just finished an extensive validation and verification to make sure our ray tracing (i.e. analysis) is accurate since that's always top priority. Performance is next though we already beat BoT performance for most target descriptions (and more importantly are considerably more accurate).
>> 1. See what converters are available:
You'll need a very recent version of BRL-CAD, but our step-g and 3dm-g importers on a non-Windows platform are your best bet for importing NURBS geometry. We'll have both of them working on Windows in about two months if everything goes smoothly. Otherwise, the ProE plugin is going to be your best option for exporting a polygonal mesh.
>> 2. See what formats Solidworks can export to.
The Rhino 3dm format works well today but STEP is where we're putting all of our conversion effort.
>> 4. If possible try a later version of BRL-CAD on Linux. I believe
>> that there is a limited BOT editing capability now (as of the version
>> you have).
It's not at all ready for production use, but Bob Parker has been putting in some really nifty BoT editing capabilities into archer/mged that will hopefully be unveiled before the calendar year ends. Just a heads up.
>> Aside from the nurbs concern, some of the formats are not very
>> friendly for keeping your original object grouping--a big issue for
>> complex models.
That is the current limitation of the current STEP importer in particular but is an active development area that we should have implemented soon. Importing hierarchies is obviously pretty important. ;)
 Changing the underlying geometry representation in any CAD system invariably introduces new errors. The dev team has been working hard at implementing BREP/NURBS support to fix that problem. With BREP/NURBS support implemented, we don't change the geometry format so no new problems are introduced and we can perform analysis on the original data.