CompuServe Thread

I'd love to know the least little bit about the format of DWG files. Several companies have deciphered the format. Is anyone talking about it? Any clues would be appreciated… (I know, you're supposed to use DXF.)

J, Those that have deciphered it are charging for the information. Dennis

I'm well aware of that. But really, they're not charging for the information, they're charging for their implementation. It's not as if they've got the details of DWG printed in a little book that costs $1000.00. They've got link libraries you can use on the PC and maybe one or two other platforms… or less. Out of all the smart guys in the AutoCAD marketplace, you can't tell me that only one or two companies have deciphered DWG, and that in the several years since they've figured it out, that no one's talking. Didn't Microstation just announce that they read and write DWG now, too? Hey, I've got to ask around, or I'll never know. 🙂 My company makes InterChange Plus, a 3D file format translator program. Yes, having DWG would be quite a feather in our cap. Yes, we'd be glad to pay to find out.

There's a big difference between "deciphering" the DWG file for your own purpose and marketing a DWG access library. Most people who access DWG files are just trying to get at a small part of the file. BTW, Intergraph licensed the source from Marcomp.

>> It's not as if they've got the details of DWG printed in a little book that costs $1000.00. << If I'm not mistaken, there used to be a product (circa 2.62) called Auto I/O which was printed in a little book and cost a couple hundred. (Not much use now but I still wouldn't mind getting my hands on it) <g> I never saw it and don't recall who published it but remember that it was reviewed as a written explanation of the DWG format. I've heard it _rumored_ here that a new book is coming out but haven't seen anything yet. Well… I've got it and can't figure out what to do with it. 🙂 Any ideas? -Chuck

"Well… I've got it": what exactly have you "got"?

I didn't know that Integraph licensed Marcomp's code. How did you learn that?

J. I'm sure you'll be contacted by somebody now that you say you're willing to pay for it. Dennis

Intergraph sent a flier about a year or so ago. I also know MAtt Richards.

I believe the book was co-authored by Fred Jones, of the late Eclat. He is now with E-BOOK. If you can find him, he'll be able to say where to get the book.

Who is Matt Richards? Also, in a previous message I disparagingly said that Marcomp only supported a few platforms with link libraries. No one corrected me, but my sense of honesty requires me to state that thaey do support a half-dozen platforms.

I guess that means it's not such a secret, then? 🙂 Also, someone mentioned an old v2.6-era book that discussed the format of DWGs. Had anyone heard of that book, or do they have a copy they could lend?

>> I'd love to know the least little bit about the format of DWG files. Several companies have deciphered the format. Is anyone talking about it? Any clues would be appreciated… << Being from one of those companies, I'd be happy to talk about it. The DWG format mostly parallels the DXF, in that there is a header section, tables section, blocks, and entities. In general, you can take a dwg file, convert it to dxf, and convert it back to dwg without losing any information. That means that both formats contains the same information, just in vastly different formats. DWG is a binary compressed file. The specific implementation varies from one release of Autocad to the next, and can get quite hairy. There are CRC checksums throughout the file for error checking, and some information is stored twice for redundency. If you want to access DWG files directly, you would be better off using a 3rd party library. My company produces such a library, called the CAD++ ENGINE, which is available for DOS, Windows, and Unix platforms. Sirlin can be reached at 603-437-0727. –Jonathan.

Thank you for your comments. As I said in one of my other postings, my company makes a 3D translator. We're at the fringes of the CAD market, the bulk of our customers are shuttling data between what are more commonly called "3D" programs, used for video and animation. A lot of these people have clients who can supply data in DXF form, but DWGs would be nicer for file-size and convenience. I've hesitated to consider a third-party link library for this. First, we have a version of our program for the Amiga. The Windows version will be out this fall. We're also porting to the Mac. So for two out of three platforms that we *need* to be on, I can't get a DWG library. And I'm not even sure if (say) Marcomp's library is available in Metaware's 32-bit Windows form, as opposed to 32-bit DOS. Is your library in this form? Having dealt with third-party libraries in the past, I know what kinds of binds can occur. Without source, my company's reputation is at the mercy of another company.

What I've got is the source for my own library which reads DWG files using the familiar ADS function interface. I've used it to develop a standalone DXF translator and am working towards a windows viewer. My guess is that Autodesk will eventually provide an external API but will not document the DWG file itself. As Jonathan mentioned, it can get "quite hairy" and, IMHO, would be a nightmare to support. I would be quite interested in seeing my code put to good use and hope that I may be able to help you out in some way. -Chuck

Sorry, never heard of it 'til now. Dennis

Intergraph announced in their press release over DWG that Marcomp supplied the library. There was some discussion on the Forum whether Marcomp would loose its Registered Autodesk Developer status for that–they didn't. However, it took Bentley Systems a year to produce the DWG-write code to work between MicroStation and the Marcomp library.

Why would Marcomp lose developer status? For supporting an unsupported file format? If they released proprietary info, I would understand… but they deciphered the undocumented. Are you saying that Bentley had troubles with Marcomp's code?

Matt Richards wrote Autodirect and a few other utilities. Thus the name MARcomp as in MAtt Richards. (he's also from MARyland) Don't you ever get on CIS Matt???

Marcomp's library is available in Metaware's 32-bit Windows form>> 32-bit libraries are available, as well as 16-bit. They work for both DOS and Windows. (Although you never know when/if Windows will be a separate license) I expect things will get exciting when R13 hits, but I also expect Mcomp & Sirlin will do whatever it takes to make it work. I wouldn't worry about getting 'burned'.

I guess if you haven't been following the ebb and flow of the forum over the last couple of years you wouldn't understand the political implications of an Autodesk Registered developer selling access to the DWG code to AutoCAD's #1 competitor.

Sirlin's CAD++ ENGINE provides full DWG read/write support for DOS, Extended DOS, ADS, Windows, and Unix platforms, including Sun, HP700, SGI. RS600, Ultrix, NT, and Mac are on the way. Regarding cost, if you just want to access the DWG information, our read-only library only costs $495 and no royalties. This includes lots of good tech support. –Jonathan.

J.– 1. The Sirlin CAD++ ENGINE libraries definately support Metaware on DOS. We are working on a Mac port now. Your's is the first request I've seen for Amiga. 2. Perhaps you could just use a DWG2DXF utility to convert drawings before importing them into your program using DXF. Sirlin's DWGxDXF utilities go both ways for $99. 3. If source is an issue, we can arrange an escrow account. We've done this before. –Jonathan.