[freearchitecture] Open 3D CAD file format

[Terry Hancock]

Eric Wilhelm wrote:
> How does STEP deal with something like CSG?  From my reading, it seems 
> to focus more on BREP.

STEP is divided into a bunch of "Application Protocols" ("APs"), each of
which deals with domain-specific CAD needs. As such, it's designed to be
multi-paradigm. I suspect that you've been reading about just one of the
APs (and indeed, I think most STEP implementations only read and write a
few of them).

I did this research over two years ago, so I don't recall more detail
than that. But I suspect that there is a CSG AP for STEP. Even if they
somehow overlooked this, of course, STEP is intended to be extended by
adding APs.

> With X3D, is there anything in this standard which significantly 
> deviates from VRML?  If not, it seems that it wouldn't be expressive 
> enough for any sort of mechanical or architectural CAD.

No, I agree. X3D is presently intended for artistic 3D graphics. I would
expect it would need extension to do real CAD work. But building on an
XML base does make sense.

> My plan with the VectorSection CAD hub is to initially implement all of 
> the 2D primitives and 3D coordinate systems

"All"? :-)

There's a plethora of ways to represent 3D models, as I'm sure you
already know. What are you using as a guide to decide what to implement?

> The upshot of this in format terms (particularly with regard to avaCADo) 
> will be a plaintext data structure which is capable of representing any 
> non-associative 2D/3D CAD data.  The bonus is then that you don't have 
> to write all of your own import/export routines.

Sounds like a cool thing to do, but also a HUGE project. Do you have the
resources to complete it?

You're going to market this better if you want to see it get adopted. At
the very least, you need an easy-to-remember name and a resources
website for the _format_ (not just your program).

Also, it must absolutely be included on these Wikipedia pages:

http://en.wikipedia.org/wiki/CAD_data_exchange
http://en.wikipedia.org/wiki/List_of_file_formats#Computer-aided_design_.28CAD.29
http://en.wikipedia.org/wiki/List_of_vector_graphics_markup_languages

I just want to point out that I didn't find your project when I started
researching this problem. So either it's less than 2 yrs old, or it
wasn't visible enough then.

This is an important problem that has been standing unsolved for several
years now: there is no really definitive open source CAD system, format,
or community, and certainly nothing to challenge proprietary systems
like AutoCAD.

I think you are right to focus on the storage and modeling format. The
disorganized nature of existing free software CAD efforts wouldn't be so
much of a problem if they were interoperable.

Cheers,
Terry

-- 
Terry Hancock (hancock at AnansiSpaceworks.com)
Anansi Spaceworks http://www.AnansiSpaceworks.com