This document is loosely organized into a task based structure. In order to be able to translate a DXF file you need to be able to perform certain tasks.
To export a DXF file, you should be able to perform the following tasks;Understand what will and won't be translated from your drawing.
Be able to prepare your drawing to make a clean translation.
Be familiar with the various options you have available.
Be able to physically transfer the resulting DXF file to the receiving party.
Be able to instruct the other person in how to import the DXF file.
In order to import a DXF file it helps to know these tasks;Understand what will and won't be transferred via DXF.
Know what will and won't be read by the MiniCad import routines.
Know what to ask the other person in order to ease the translation process.
Be able to instruct the other person in transferring the file to you.
Understand how to get the file onto your Macintosh.
Understand what needs to be preset in MiniCad for best results.
Additionally, you should be able to do some troubleshooting of DXF files. This might be as simple as recognizing a problem, to as complex as editing the DXF file in a word processor.
THE BASIC CONCEPTS
The majority of the problems translating files are caused by people, not software. There are a few things which will reduce these problems considerably. Communicate! In most cases, the entire drawing is neither needed nor wanted. Tell each other what you need and export your drawings accordingly. If you know a few things about the drawing which you are trying to exchange, it is far easier to translate it. You should know...
- the scale,
- the units,
- the sheet size,
- and which program originated the drawing.
ABOUT DXF
DXF stands for Drawing eXchange Format, and was created solely by Autodesk to provide for a method of exchanging drawing file information in a generic language which they could control without having to give out their own proprietary format. It was NOT designed as a universal language by multiple software companies. To quote AutoDesk "Since the AutoCAD drawing database (.dwg file) is written in a compact format that changes significantly as new features are added to AutoCAD, we do not document its format and do not recommend that you attempt to write programs to read it directly. To assist in interchanging drawings between AutoCAD and other programs, a Drawing Interchange file format (DXF) has been defined. All implementations of AutoCAD accept this format and are able to convert it to and from their internal drawing file representation."
Like any other interpretation process, it is close, but still inexact. Programmers must make assumptions about what some items in a DXF file mean. Features written into CAD programs which are not written into AutoCAD do not have direct support in DXF and must be worked around. There is no standard code used in programming DXF import and export routines available to software developers, therefore every software company writes their program to handle things in slightly different ways, depending on how they interpret the DXF item. Knowing the nuances of your particular program will make the translation task easier.
One important point to note about DXF files is that they are plain text files which can be read or modified in most word processors or text editors. In many cases it may be easier to solve DXF problems by editing the text file, rather than by re-creating the DXF file in a CAD program.
One of the leading causes of problems with DXF files is that they are not actually DXF files. In many cases they are;a) AutoCad drawing files (.DWG)DOS files have a (maximum) 8 character name with a (maximum) 3 character extension which describes the type of file. The .DXF extension is used to indicate a DXF file. While t his is a good indicator of it being a DXF file, it is by no means certain, as you cannot control what some fool types in as an extension.
b) binary DXF files (.DXF & .DXB)
c) compressed ZIP files (.ZIP & .EXE)
Since DXF files are plain text files, the easiest way to ensure you have a real DXF file is to open it with a text editor. The first part of the file will look like this...
0
SECTION
2
HEADER ....
and so on it will read. Don't be alarmed if you have funny looking characters at the start of each line, they are line feeds caused by the difference in the way that PC and Macs write text files, and will not affect the translation. If the file is all on a single line like...
0SECTION2HEADER
you probably have a DXF file created on a UNIX machine which was not filtered for a non-UNIX computer. Send it back, it won't do you much good.
MY FAVORITE TEXT EDITOR FOR DXF
I highly recommend MacSink, which is available on-line. It is the shareware version of a commercial product called Vantage, by Baseline Publishing. MacSink has one feature in particular which lends itself to working with DXF files - the ability to add line numbers to a file. This allows you to pinpoint problems when you get a "error on line xxx" message. Since it is a desk accessory, it is easily accessed while still in your other programs.
WHY NOT .DWG SUPPORT
Many people ask why MiniCad can't just read and write a drawing file to AutoCad without DXF. Aside from being a nice sales feature to put into advertisements, I don't believe this will work! AutoDesk does not give out or license their binary drawing code format, therefore any support for the DWG format would have to either come from reverse engineering or from 3rd parties who reverse engineer the format. Since there would be minimal, if any, documentation on this format, it would be nearly impossible to support over the long run. The time lag between a change in the AutoCad drawing format and the reverse engineering would be huge.
Additionally, there is the all or nothing psychological factor. If you tell someone that you can exchange a .DWG file, they will not fix or modify it to suit any shortcomings in the program you are using. Therefore, unless you can support a 100% compatible format, you will still get an inexact translation. I have not yet seen a third party .DWG reader which can correctly read or write everything in a drawing.
The blame factor is also going to come into play. Right now, people blame all the translation problems on DXF for being a poor standard of exchanging info. It isn't all that bad really. If MiniCad reads and writes a DWG file, that blame will be shifted to MiniCad and its import/export routines.
This being said, Graphsoft has stated a commitment to implementing DWG support in version 7 of their program. Although they are working with the best intentions, and pressure from users, I am not convinced that it will actually be an improvement. Problems with translations are not because of DXF - rather they are because DXF does not support the rich variety of features found in all other CAD programs. Since the DWG format is nothing more than an encoded version of the same DXF file, anyone who is expecting a miracle cure is out of luck.
DISKS - THE 3 1/2" DOS FORMAT STANDARD
The Macintosh only has a 3 1/2" drive. It does not have a drive which reads 5 1/4" disks. Sending information on 5 1/4" disks will not accomplish anything except clean out a supply of ancient outdated disks.
By convention, most information is transferred on DOS formatted disks.
Remember that disks can often fail, and become unreadable. Depending on the situation, it may be prudent to ship duplicate sets of disks just in case one disk fails. You can increase your chances of the disk being reliable by reformatting it prior to copying your file onto it. The few minutes this takes are worth it, compared to how much time you will waste if the disk fails. Consider using a modem instead of disks. A high speed modem pays for itself quickly by savings in courier costs, and savings in time.
FILE SIZES & COMPRESSION
In some cases the file is larger than what one disk will hold. PKZIP is the standard format for compressing files on PC based machines. On average a zip compression of a DXF file will be only 10%-20% of the original file size. No information is lost due to Zip compression. A well translated DXF file could be as much as 3 times the size of the drawing. Using these rough guidelines, you should be able to fit the DXF file from a 3 meg drawing onto a single disk. There are several programs which support the ZIP standard for the Macintosh, the best one being Zipit. These are mostly available as public domain software. Since ZIP is the only method that is commonly available on both platforms, it is recommended as how you should compress files when interchanging data across platforms.
Do not use the DOS or Windows BACKUP command as there is no easy way of uncompressing these disks on the Macintosh. Likewise, using Macintosh specific compression utilities, such as Stuffit or Disk Doubler, will leave the PC user no way
of accessing the information with what they normally have available.
USING ZIP ON A PC
PKZIP is now on version 2.04G widely available as PK204G.EXE (a self extracting archive). PKWARE, Inc. 9025 N. Deerwood Drive, Brown Deer, WI 53223 USA Phone (414) 354-8699 Fax (414) 354-8559 BBS (414) 354-8670
The syntax for using it is: PKZIP [what you want to call the zip file] [what you want to include] for example; PKZIP ARCHIVE.ZIP 9001*.DWG
If your zip file is larger than a single floppy, you can use the -& modifier and you will be prompted to insert floppies. Floppies will be formatted as needed.
for example: PKZIP B:DXFFILES.ZIP *.DXF -&
Although the current version of Zipit will join these segments on a Mac, many other programs which decompress zipped files will not, so this should be avoided if at all possible. It is preferable to confine the zipped files to one disk or less per file. Since DXF files compress about 80%, you can fit roughly 10 megs worth of DXF onto a single floppy. If you have a drawing which creates a larger file than this, then I suggest you split the drawing into sections, or split it by layers.
Converting your ZIP files to EXE (self extracting ZIP archives) is a waste of time when giving them to a Mac user. An EXE file will not execute on the Macintosh (Although the Mac programs will still extract the information properly).
USING ZIPIT ON THE MACINTOSH
There is a shareware Macintosh program which will both create and extract ZIP files, namely Zipit. It is widely available on-line. The author, Tommy Brown, has an e-mail address of tbrown@dorsai.org if you wish to contact him. The interface is quite Mac-like and resembles Compact Pro in how it works. You start out with a window to which you add the files you wish to Zip. To compress the files, you do a Save... and the archive is created upon saving.
Two items to note here which are critical...
1) Give the archive a proper name, under 8 characters, and ending with .zip
2) In the preferences, make certain that "Use MacBinary - Never" is checked on.
Remember - ZIPIT is shareware, support it by registering.
TRANSFERRING FILES TO DOS MACHINES
You can either send your files by disk or by modem.
To transfer a file by disk, you must use a DOS disk, as there are few consultants in the DOS world who have the ability to read a Mac disk. Modern versions of system software have a control panel called PC Exchange which allows formatting, reading, and writing of DOS disks. Disks have a high failure rate. Reformatting (erasing) the disk prior to copying the files onto it will reduce the risk of that disk being unreadable on the other end. If the file on the DOS disk has an exclamation mark as the first character, you have named it wrong.
When sending files by modem, you must ensure that you do not send the file as MacBinary. In simple terms MacBinary is extra data that is attached to the file to tell your Mac what program to launch when the file is double clicked. Unfortunately, this MacBinary header will make a file unusable for a DOS based user.
©1996-2001
Dave Weber dave@wmw.ca
last modified December, 2001