DWG/DXF support in FOSS

This discussion was created from comments split from: (FSF) Help us set high priorities for 2021: Send input by Jan. 8.


  • I spoke to Reini from LibreDWG and updated our DWG page with some more info on support in different software: https://wiki.osarch.org/index.php?title=Drawing_(DWG)
    He says it must have been removed from the list at some stage. Here's our discussion: https://lists.gnu.org/archive/html/libredwg/2020-12/msg00000.html
    Now that DWG is default supported in FreeCAD I think it really makes sense to test the hell out of it and start pushing development forward. Especially finding out what it takes to get 3D DWG support.

    To support and encourage better DWG support in LibreCAD see this issue I have commented on: https://github.com/LibreCAD/LibreCAD_3/issues/207

  • Thanks @duncan for the update. Now that OSArch.org exists and projects like FreeCAD and BlenderBIM are solid alternatives for AEC industry, the proposal for LibreDWG to be included in the list of priority projects of FSF, makes a lot of sense. Also, OSArch could suggest Blender.org to adopt LibreDWG, so it can be used by BlenderBIM users...
    (GauchoCAD??? first time I hear about... are they Argentinian? :) )

  • @bitacovir @Moult @aothms of course! Blender support for LibreDWG, especially 3D would be a great match. Who agrees and could make contact? If Blender supports the call and FSF gets behind it again even just for a year or two the publicity should bring a lot of improvements. Can Blender at GPLv2-or-later use a GPLv3 library?

  • edited December 2020

    @duncan said: Who agrees and could make contact?

    It would be better a official letter supported by open source projects from Blender ecosystem:
    CAD Transform

    You could publish it in some of the Blender channels of developers. This way the idea could be taken by the Blender Community.

  • @bitacovir you don't think the blender project itself would see use in being able to import high quality 3D DWGs?

  • @duncan said:
    @bitacovir you don't think the blender project itself would see use in being able to import high quality 3D DWGs?

    It is like Reini Urban says: current Blender DXF/DWG system is very primitive, instead using the available LibreDWG. This is probably because improving DXF/DWG is not a priority for them, right now. But, the good thing is Blender is a FLOSS project and independent developers do a lot of contribution to the code. Maybe it is a good idea to approach both parties at the same time: official Blender and community, about the need of LibreDWG implementation in Blender. Well, I am just saying. I don't know if other addon projects will see LibreDWG as a useful feature in Blender's export/import system... just saying.

  • I haven't recently looked into the current state of things, but naively from memory 3D DWG is going to be a incredibly hard nut to crack. Essentially you're just reading binary ACIS (their geometry kernel) blobs. I think you can expect very little interoperability from that (but again, things might have improved). Then there is the difficulty with the constantly renewed obfuscation of the DWG file format and the fearmongering in adsk products when opening 3rd party dwg, plus the legal grayzone of reverse engineering in certain territories.

    I get it, it's hard when you get dwg from clients, I'm just not optimistic on the kind of interoperability we will get (lagging a couple versions behind, missing some features). Is there also an alternative or additional path we can take? Can we ride the wave of negative adsk publicity to educate users and establish other ways to get data out of adsk products using open standards? Is that incredibly naive?

  • edited December 2020

    I agree with @aothms - no matter how much LibreDWG continues to reverse engineer it, ADSK will just move the target and renew the obfuscation. From what I hear in 3D DWG, it's kinda like a sub-format which is another binary, proprietary, undocumented nut to crack. It's seems like a huge timesink for developer time, when in the meantime the world is moving on. I'm optimistic that since lots of people are requesting IFCs already contractually, it isn't a stretch to say "hey, you're asking for open BIM, why not open 2D drawings? Ask for DXF, not DWG." Especially as increasingly more drawings now are generated from BIM models and don't use a lot of "magic" elements, like 3D DWGs. As a stopgap, the ODA converter is available. Certainly in my personal usecases, DXFs serve equally as well as DWGs. Governments should be easy to persuade.

    Maybe we should also call people out who make the claim that "DWG is a defacto interoperable / open / standard / whatever".

    I've documented what I know about making the switch here: https://wiki.osarch.org/index.php?title=Getting_started_with_2D_CAD_drafting

  • edited December 2020

    Reini, LibreDWG developer wrote, "Creating 3dsolids from scratch, writing acis data is also not yet good enough. Wonder what FreeCAD did there. They got rid of OpenCASCADE recently. I'm writing and converting acis manually currently." So it sounds like 3D is on the way.

    I'm sorry @Moult but I also say that .dwg is a de facto standard. Surely it's the definition of 'de facto' for 2D CAD? "in fact, whether by right or not." "existing or holding a specified position in fact but not necessarily by legal right."

    I'm not sure Autodesk is all that interested in DWG any more. It may be that they use is but it seems that all innovation is coming from outside Autodesk. There is revision control and multi user, but that's not come to AutoCAD so what's that about?

    I just don't see the neighbourhood housing coop with 100-300 tenants using free software to open the plans they got 15 years ago. Is more transparent handling of DWGs the solution? None of us would consider switching file formats from the original authoring format without a fair amount of manual checking.

    I'll say that I'm not at all concerned with .dwg writing, indeed there are ethical reasons to avoid it. But robust and trustworthy import is crucial.

  • Sorry, I shouldn't have used the word de facto. You are absolutely right. I still hold my views about a better approach being to switch contracts to accept DXF instead of DWG. I consider reading DWGs mostly solved as most simple plans are 2D without funky 3D solids, and ODA freeware already exists to somewhat reliably convert to DXF.

  • @duncan said:
    Wonder what FreeCAD did there. They got rid of OpenCASCADE recently. I'm writing and converting acis manually currently." So it sounds like 3D is on the way.

    Did FreeCAD get rid of OpenCASCADE ?

  • @CadGiru said:

    @duncan said:
    Wonder what FreeCAD did there. They got rid of OpenCASCADE recently. I'm writing and converting acis manually currently." So it sounds like 3D is on the way.

    Did FreeCAD get rid of OpenCASCADE ?

    Looking at the FreeCAD wiki that does not seem to be the case. https://wiki.freecadweb.org/OpenCASCADE
    It is possible that there is some confusion between the use of the community edition which it does look like they have stopped using.

  • Excuse my ignorance, why is not possible to have a FOSS format for 2D and 3D?,something like ODF for documents.

    I was searching for years an open alternative for DWG and I found that DXF is not completely support in all open source software, for example there is not support in blender out of the box, FreeCAD support DWG and DXF but just 2D and some objects are not exactly how was exported, I mean their support is incomplete.

    Why not simply was not created a global FOSS for construction software since zero? I mean, all software are creating more and more formats, I think someone could call others others forums for voting and create a universal format for construction ... Maybe CSV?

    A sample ...

    ... The SAF look awesome and is very similar to CSV...

    Well is just an idea

  • We should stick to w3c formats like svg and 3d counterpart (still in evaluation phase) as it enable native viewer in browser.

  • Check out this new app! I could have post it to my question about CityJSON support, but this is about the need and excistance of DXF also. Go Netherlands ! :P To add to the discussion. I do believe that DXF is a very good way to adrress the need for 2D/3D 'traditional' CAD. I doubt there is any need to "real" (more open) dwg. DWG was born as efficient DXF..
    Try this : https://pdok.mapconverter.app/

    2.jpg 51.4K
  • edited January 2021

    According to internet, Autodesk is dxf owner, is very probable than dxf never will evolutionate.

  • edited January 2021

    Sorry about my unknowing. Is it developed or owned? How can anybody 'own' a open standard that was meant to be a fileformat for open exchange? And if it is was the case.. i really don't think a group like Buildingsmart has ever even thought about the future and possibilities of DXF? Or 2d openCAD as concept. I have never ever seen anything else then 'IFC 4 this and that and Everrything'. :P

    Somebody ever talked to Autodesk about DXF lately? Put some pressure there? For their support on open community word..

  • Still curious about STEP 2d implementation, related to post

  • ... @magicalcloud_75 sorry if i did offen

    IMHO the dxf and DWG support is already good, similar is for me STEP and IFC, I don't see nothing more to add.

    As the libredwg wiki mentioned, the dwg support should be just for allow migration since closed source but not should be the standard.

    I just think than what really need a universal standard or at least a minimal integration between software, taking as example Revit and Robot Structural, both have a nice workflow.

    We are 2021 and still can not communicate between 3D and 2D software, we still need convert to multiple formats. IMHO this is the main problem in the open source software.

  • ... Or maybe a format than copy to dxf could be more easy to implemented.

  • @magicalcloud_75 a format is generally judged to be "open" based on two factors: documentation, and ownership. In terms of ownership, DXF is owned by Autodesk (a competitive private player) and copyrighted. Both of these factors shuffle it toward the "closed" side of the spectrum, as private ownership generally means lack of user freedom and anti-competitive changes which benefit one player more than others, and copyrighted generally means lack of third party innovation. The term DXF is trademarked by Autodesk, and the first sentence in the spec describes it as merely a representation of what's possible in DWG - hence the scope of DXF will always be tied back to an Autodesk proprietary format.

    This is the copyright statement in the DXF spec (note, in the online version, maybe they have relicensed it to be CC-BY-SA-NC):

    ©2011 Autodesk, Inc. All Rights Reserved. Except as otherwise permitted by Autodesk, Inc., this publication, or parts thereof, may not bereproduced in any form, by any method, for any purpose.

  • edited January 2021

    Ok. So i understand LibreCAD is opensource software using an entirely wrong format to save yours vector data. But it can read dwg. And only save (very limited) to DXF. I guess saving dwg would mean even more and bigger legal pitfalls.

  • @CadGiru
    Sound interesting , step format can be used now for 2D and 3D at same time?

  • @jtm2020hyo IFC supports 2D.

  • edited January 2021

    And STEP, probably has more 2d defined than IFC, sadly to my knowledge it is not much used.
    Maybe STEP / IFC 2d as translation format is a way forward. Have worked with DXF since early 80's, it is generally nothing more than a 'transport' format, mainly not used directly in Editing. Also it is proprietary.

    Spent some time looking at SVG. Initially looks good, but to me it looks to be very geared towards browser interface.
    Found this The Limits of Numbers in SVG
    "For reliable results cross-browser, use numbers with no more than 2 digits after the decimal and four digits before it."

    Also found, InkScape Dimensioning , has anybody tested?

    Will try to write some thoughts on need for 2d and integration with 3d on wiki.

  • Ifc and step should be the standard, but not many software support it, for example in blender is need install add-ons , and there is not way to export import with these formats in Sweet Home 3D.

    How can be promote STEP and IFC formats?

    Specially in simulation software, according to the link related to saf format, is necessary use solids instead mesh for FEM structural analysis, and related to animations, step and IFC are useful for that?

    For a good consensus I think osarch could invite others forums to vote or promote any standard.

  • The topic of this thread is "DWG/DXF support in FOSS" - please stay on topic and make new threads as needed. Perhaps by copying parts of this discussion.

    This is not the place for a discussion about STEP, IFC & SVG excpet as they relate to DWG/DXF

  • edited January 2021

    May we conclude that DXF is a dead end waist of time, until the time Autodesk changes its game? Will they?

    What do governments need to ask for as datatype for drawings meanwhile? Now only pdf is stored mostly (Civil works NL) so there is a huge loss of data and effort for the next guy who works on designs. As build data only in pdf without natives (cad or 'bim') . Its kind of painful. 2021. Doesn't have to done this way. Could be a lot smarter.

    To add to the discussion about 2D IFC,.. be aware the discussion about 'competing DXF' will stay long after. A smart little converter to make dwg /dxf geometry ifc would be nice. Just my cent.

  • And we still did not mentioned " object enabler" which is need for visualize custom objects created for all AutoCAD verticals (AutoCAD mechanical, AutoCAD architecture, AutoCAD MEP, AutoCAD electrical,AutoCAD AutoCAD map 3D, AutoCAD civil 3D, AutoCAD plan 3D, advanced steel , and custom objects created by users)...
    ...for visualize these objects maybe will be need others 10 years.

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