Drawings stored in AutoCAD's DWG format are so prevalent that Belgium-based CAD vendor Bricsys is pinning its success on using the aging format for every aspect of its CAD software. In the opinion of the company's officers, users shouldn't endure more than one file format just to use CAD systems specialized for MCAD or ECAD or BIM or GIS.
For Bricsys CEO Erik de Keyser, DWG is sufficiently flexible to handle all the extra data needed by 3D MCAD and BIM models. (See figure 1.) His BricsCAD software accomplishes this by storing the unique data sets in these areas of DWG files: • Extended entity data (a.k.a. xdata) • Xrecords (like xdata but not limited in size) • Extension dictionaries (for document-level definitions) • Named object dictionaries (for object-level definitions, a.k.a. tables) • Custom entities (for defining entities not available in plain AutoCAD)
Figure 1 BricsCAD modeling a tripod through an assembly of 3D parts
These parts of DWG are no secret; Autodesk provides APIs [application programming interfaces] so that third-party developers can write and read data with these locations. So it's a simple matter for Bricsys to combine the data locations with documented API calls to extend DWG to many disciplines of CAD.
Bricsys embraced and then extended AutoCAD's APIs, specifically the following ones: • ARx, the all-powerful API, which Bricsys calls Brx • Tx, an ARx workalike licensed from the Open Design Alliance • .Net, COM, and VBA from Microsoft • LISP for interactive programming • DCL for designing dialog boxes • Diesel for menu macros and the command line • ADS obsoleted by Autodesk but still supported by Bricsys as SDS
Mr de Keyser figures he has the solution to a problem Autodesk created for itself and for Autodesk’s MCAD and BIM customers. He thinks that instead of users being forced to deal with a half-dozen file formats would prefer a single one. The question is, why doesn't Autodesk do this? Autodesk at one time recognized the problem when it many years ago showed at Autodesk University a nascent universal format that held data from many of its CAD programs. It was based on Navisworks. Work stalled as Autodesk acquired and launched more products with their own file formats.
Autodesk's Move Away from DWG
It wasn't always this complex. Autodesk had releases of MCAD running on AutoCAD -- Mechanical Desktop (MDT) and AutoCAD Mechanical. They employed DWG files with custom objects, for which Autodesk provided "object enablers" so that non-MDT users could view and edit the specialized drawings.
But then Autodesk developed Inventor to replace MDT, and with it an entirely new file format -- well, four of them, actually: .ipt files to store 3D parts in Inventor, .iam for assemblies, .idw for 2D drawings, and .ipn for presentations.
The formats were designed to make a fundamental break from AutoCAD. At the time, this kind of thinking was okay, because in the late 1990s DWG was seen as yesteryear's file format, destined to fade away. Years later, however, Autodesk realized it had misread DWG's decline as a multiplicity of emerging AutoCAD clones made DWG more prominent than ever before. It took years for Autodesk just to give Inventor and AutoCAD an ability to read each other's drawings properly.
The same sequence of events befell Revit, another development of the late 1990s.
More recently, Autodesk decided on replacing the Windows-bound Inventor with a new MCAD program that could operate online: Fusion. Users again faced new file formats, this time designed for today's multi-user, multi-server world.
The same compatibility crisis affects Dassault Systems, whose mid-range Solidworks software is data-incompatible with its high-end 3DExperience line. The compatibility problem is sufficiently complex that after ten years of effort Dassault has not solved it to its satisfaction.
Mr de Keyser saw the contortions taking place among competitors, and wondered if the solution could the reverse: not abandoning DWG but extending it to meet the needs parts and assemblies, BIM, sheet metal, GIS, and more.
A single file format means no disruption due to translation between CAD systems. Modeling and editing techniques developed for one discipline (MCAD, say) are reused for others, such as BIM. No need for multiple teams of programmers working on silo'ed software.
Bricsys Did It; Autodesk Will Do It Differently
I think the reason Autodesk didn't stick with DWG is related to technology. On the technology side, it is easier to write a new file system from scratch than to adapt DWG, whose basic structure goes back 22 years (when it received its only serious make-over with 1994’s DWG R13).
For the future, Autodesk will also go with a single file format for its design software -- although to call it a “file format” is inaccurate, because it is an Envoia-like database. Autodesk is developing Quantum as a database that runs on multiple servers. Revit will be rewritten as a group of apps that perform specific functions. Each function is a multi-discipline module that works with the others, such as for room planning, structural steel, and heat analysis. The apps access the data they need from Quantum, while users have their own workspaces. Quantum is currently in pre-alpha. I expect Quantum to spread to Fusion and AutoCAD-on-the-cloud. This would solve the translation problem, as well as lock Autodesk customers tighter into the grip of the third-largest CAD vendor.
For Bricsys, it's also about technology, but for an opposite reason. The company is showing off that its programmers are quite clever by adapting DWG to modern needs. The company doesn't need to work out new file formats or solve the subsequent tedious translation issues. On the marketing side, it uses the sole-source DWG to lure the users of millions of DWG files, saying, "It doesn't matter what you do, we can edit it with one program and not worry about translation" -- albeit with extra-cost vertical add-ons in some cases.
For instance, the most important concept in MCAD and BIM is the assembly, and Bricsys has figured out how to do it with DWG: attach xrefs (parts) in 3D with a 3D constraint system, which the company wrote itself. To show what's possible with DWG, Bricsys built its own add-on app for doing sheet metal design ($300). Much of its MCAD technology is being applied to their BIM add-on module ($240).
Bricsys DWG Files Not Necessarily AutoCAD-compatible
Being compatible with AutoCAD is not a concern of de Keyser. Customers ought to be bringing their AutoCAD drawings to BricsCAD, and not the other way around. This approach is no different than most other CAD vendors. All the stuff that BricsCAD adds to DWG files is incompatible with AutoCAD. While both CAD systems use the ACIS solid modeling kernel (well, Autodesk uses a variant that it modifies on its own), the two have incompatible constraint management systems.
I found that AutoCAD has no problems opening and displaying complex 3D models constructed in Bricsys. I tested a BIM model of a house, a sheet metal part, and an assembly of 3D parts. The imported 3D parts look accurate in AutoCAD. (See figure 2.) But editing is limited as AutoCAD lacks the ability to define BIM slabs, bends of sheet metal, or constraint parts in 3D.
Figure 2 BricsCAD-made 3D model opened in AutoCAD
For accessing files from other CAD systems, Bricsys licensed translators to handle all the usual neutral formats (STEP, IGES, and so on) and many MCAD systems, like Creo, Inventor, and Catia. To analyze incoming 3D models, Bricsys added intelligence to BricsCAD using design intent and direct editing -- similar to what SpaceClaim is famous for. The Bricsys Communicator translation add-on is US$610; Autodesk translates models in the cloud and does not charge for the service.
For BIM models, BricsCAD is IFC-certified for exports; its IFC importer is due to be certified at some point in the future. The company is working with the ODA to add Revit compatibility to read (and eventually write) RVT model and RFA family files.
Any thing can be stored in DWG, but it is not necessarily the best place for every thing. On the AutoCAD side, shared data like hatch patterns, line types, and block libraries are stored externally. Support files are typically written in ASCII or XML format, and so easily parsed. The same happens in BricsCAD, where it stores shared data like bending tables for sheet metal and material definitions for BIM slabs in their own files.
The ODA is doing its part in modernizing DWG by adapting the file format to multi-user streaming environments, along with change management and project archiving. This will let several people work on a single DWG file online. The organization credits Onshape for some of its inspiration.
Bricsys executives are betting the company on a file format they do not control. Whatever Autodesk does to DWG in the years to come, however, is immaterial to the millions of CAD users who don't follow Autodesk. The security of these users rests instead on the one or two billion DWG files that are already in place. Firms will always need to access them, update them, and even start anew.
Unified file systems are becoming important to the future of the CAD industry, as we see electrical diagrams become part of MCAD models housed in BIM buildings situated on GIS/DTM terrains being viewed in VR and AR. History shows that a more convenient product often overcomes a superior one, and DWG is sufficiently a common denominator that it could become the one pervasive file format for all types of CAD.
== Professional 3D File Conversion/Viewing/Rendering Software ==
For over 2 decades Okino (Toronto) has provided mission-critical 3D conversion software used extensively by tens of thousands of professionals. We develop, support and convert between all major CAD, DCC & VisSim formats. Robert Lansdale (CTO, firstname.lastname@example.org) tailors each package to the specific conversion requirements of each customer.
Popular formats include 3ds Max, Maya, C4D, LW, ProE, SolidWorks, Inventor, SketchUp, DWF/DWG, DGN, CATIA, IGES/STEP/Parasolid, 3D PDF/U3D, JT, FBX, Collada & more. We know data translation, and provide immaculate developer-to-customer relations. http://www.okino.com
And One More Thing...
IntelliCAD Technology Consortium released IntelliCAD 8.3 just after Christmas to its members. New functions include eTransmit, gradient fills, filters for selecting entities, file search through Tools > Find, and updated APIs.
While IntelliCAD is best known as the first AutoCAD work-alike, it also supports marking up Microstation DGN files. http://www.intellicad.org
Even More News
There is more at our WorldCAD Accessblog about the CAD industry, tips on using hardware and software, and our popular travelogues. You can keep up with the blog through its RSS feed and email alert service. These are some of the articles that appeared on WorldCAD Access during the last week:
Why did you not mention a single word about Solidworks - instead choosing to talk about a much smaller player like Solid Edge? Considering Solidworks has an installed base that's 5x larger (at a bare minimum) than Solid Edge, it seems quite obvious this was very deliberate on your part. - C. M. Australia
The editor replies: There is also no mention of PTC. The opinion piece, written by Dave Ault, mentions Inventor/Fusion and Solid Edge, because those are the two programs he works with.
Mr M responds: Oops, I stand corrected. You did mention the name Solidworks once.
- - -
Thanx for the good read on the future of the Autodesk extortion racket. This pretty much sums up the subject for me:
"Lots of Fusion 360 adopters are small startups and with their millennial mindsets they don't get the value of intellectual property -- yet. They will, when they start acquiring wealth and realize they have things to protect. ... objections from people like me have no value until the inevitable online hack makes them see differently ..."
Stupid people doing stupid things until it's too late to make the change they should have had from the beginning. Too bad we're talking about intelligent tech people! - Chris
The editor replies: Mr Ault's article has hit a nerve with the CAD world -- possibly because he is a serious, long-term MCAD user who understands the market better than some CAD software vendors seem to.
Thank You, Readers!
Thank you to readers who donate towards the operation of upFront.eZine.
Samuel Wilson of Inland Architects
Should you wish to support upFront.eZine through PayPal, then the suggested amounts are like these: