Thanks SO much!  I will get back to you once I've had time to repeat
your steps!

On 7/26/2016 8:18 PM, Neon22 wrote:

Please keep us updated!
It would be interesting to learn what specific subset of STEP they support.
If you know anything about which software they use on their end to import these files, we could take note of that in future documentation.

-Marius

On 7/27/2016 2:24 AM, jon wrote:

freecad is under development so best way to help, if your file is not
loading properly when you open it in freecad is to report a bug :)

as for why that company want "real" solid model (when you convert mesh
to solid it often stays mesh only in solid file format, but it is not a
solid) is that when you give them a mesh (irrelevant in what file
format) their software can't extract properly volume, problematic areas
(too small to "work", impossible to remove from mold etc..), as all
functions expect a proper solid and not a mesh. Some apps do work with
mesh too but most require proper solid (just like old cam sw's didn't
want to accept mesh and required solids)

What is the definition of a "real" solid here? Does OpenScad even have them
to export? It works with polyhedra and when they are manifold the STL files
doesn't lose anything anyway.

On 19 September 2016 at 05:00, Bogdan Kecman arhi.smece@gmail.com wrote:

On 2016-09-19 08:52, nop head wrote:

FreeCAD uses OpenCasCade I think. I am guessing a "real" solid would
mean a native CAD geometry/topology model with separate geometry
(point,curve,surface and more) and topology (vertex,edge,face,body and
more), like you have in OpenCasCade or ACIS. I have used both in the
past, but I am more familiar with ACIS. I guess in practical terms a
"real" solid could be exported like a STEP (AP214?) or an ACIS .sat
file. The difference from OpenSCAD is that these model representations
are not polyhedron based. In ACIS a solid would correspond to a BODY or
a LUMP.

Not a chance, except if you go the indirect route via .csg as previously
discussed and export primitives only. Then the receiving end can build
the geometry/topology from those. The problem is that you are limited to
a few primitives only, and things like hull or minkowski would
definitely break it. In ACIS you have

http://p.blog.csdn.net/images/p_blog_csdn_net/feijj2002_/153762/o_solid17.bmp

or rather, in more realistic detail

http://images.cppblog.com/cppblog_com/eryar/Windows-Live-Writer/Topology-and-Geometry-in-OpenCascade-Top_D29F/wps_clip_image-8073_thumb.png?_=1993008393

It will not work in general to convert from any mesh based
representation into OpenCasCade or ACIS, as the model representations
are very different.

Carsten Arnholm

what is meant (generally) by solid model is that it is made from
primitives which are mathematical entities. A collection of polygons
does not fall into this def. Here's why they do this:

From a pragmatic point of view its because of this:

• the solids and surfaces that a CAD system uses need to be able to have
  a number of operators performed on them which are continuous and give
  'clean' results. (Yes I'm using all sorts of uselessly vague words. Try
  to grasp what I'm getting at.)
  E.g.  Calculating a tangent so the forces on a tool path can be
  calculated. A collection of polygons does not have a "smooth" (yes I
  know) result so interpolation algorithms and other aspects give ill
  defined results in some circumstances.

So the CAD systems have defined a number of primitives which have well
exercised and resolved solutions to all of the manipulations they want
to do. OpenCASCADE, Solidworks, ProE, ACIS have what they refer to as
solids kernels which resolve all questions for interesctions etc.

Polygons make poor long path trajectories for entities like an Arc
because they approximate an Arc, whereas one of the Arc representations
will produce a smooth curve at CAM toolpath time, or Forces at
simulation time.

so forget words like "real" solids etc etc. Its a pragmatic reduced set
of well exercised parametric, math based, solid curve and surface
representations that they need.

On 9/19/2016 7:42 PM, arnholm@arnholm.org wrote:

Well you are never going to get that out of OpenScad because it converts to
polyhedra before doing any operations and a lot of designs generate their
own polyhedra programmatically.

On 19 September 2016 at 09:20, Mark Schafer mschafer@wireframe.biz wrote: