Re: Autocad to Acrobat

Subject: Re: Autocad to Acrobat
From: Dan Azlin <dazlin -at- SHORE -dot- NET>
Date: Mon, 5 May 1997 00:53:49 -0400


This is a new twist on an old problem. AutoCAD (like other CAD packages)
defines lines differently from how it is done in the rest of the graphics
world. In CAD a line is a simple vector with unit width. Width
characteristics assigned to the lines displayed from within the CAD program
depends on selecting a plotter pen of a specific width and color to
determine the thickness and color of a line. Thus, an .eps export of the
line will only define the vector with a minimum default width.

The .DXF file format also suffers from this problem. (It also suffers from
font definition/substitution problems, although that issue has improved in
recent years.) The plot file (i.e. .plt file) is actually an HPGL file that
gives the most accurate representation of the drawing, but still suffers
from the fundamental presumption that the plotter pens will supply
appropriate line widths.

I have translated many CAD files for use in many kind of documents and I
have yet to find an acceptably formatted file directly from the CAD
software. They don't seem to find the problem important enough to develop
an intelligent .eps filter to fix fonts, colors and line widths. My usual
approach is to import a .dxf file or .plt/.hpg file into a drawing program
like Corel Draw or Illustrator. If the drawing program's import filter can
handle the dialect of the file, I then ungroup it and clean up the image
with some simple line width/color assignments, font fixes, and the removal
of extranious details. Sometimes the drawing works best as an illustration
if it is simplified...YMWV. Then the drawing is exported as an .eps or .tif
graphic file. The Acrobat Distiller likes .eps best.

Another method that can work on simple drawings is to use a file conversion
utility like Debablizer or Hijaak to convert the file and make some simple
adjustments (like changing a mulitcolor drawing to a simple B&W line
drawing). The converted file usually looks better than the original.

Keep in mind also that drafters don't create their drawings to be document
illustrations. Theirs is a diffferent agenda. I once had a drawing that
took an unusually long time to import as an AutoCAD .dxf file. I discovered
that the drawing was originally created to be plotted with inexpensive
ballpoint plotter pens which only come in one width. To get heavier lines,
the drafter duplicated some datum lines one on top of another more than 30
times! This inflated the file size by about 33% and made editing the file
an exercise in extreme frustration.

You should also experiment with Distillers settings for image reproduction.
By default Distiller is designed to reduce the resolution of the converted
image to reduce file size and loading time. For a screen viewable only
application 144 - 200 dpi is usually ok. If you expect to have hard copy
commonly made, you may need to increase the resolution. The down-sampling
methods can also give mixed results depending on the nature of the source.
Experimentation is the only way to find the best combination.

One positive note: A few months ago I was asked to develop a method to
capture images from ProEngineer's 3D rendering view. This is a fully
rotatable 3D rendering far beyond AutoCAD's capability. And, although
ProEngineer listed several standard graphic formats as being available for
export purposes, they were not installed and were unavailable from the 3D
view in any case. I solved the problem by doing a screen capture of the
active window. While this only gave me a bitmap that needed cropping to
remove the framing, the image was very usable. The point being, the most
obvious approach is not always the best approach.

Good luck,
Dan Azlin
At 11:59 4-25-97 MDT, Dave Quebbeman wrote:
>We have recently been able to create monochrome AutoCad
>PostScript files for use with Acrobat Distiller, but when
>we print the resulting .pdf files all the lines are extremely
>thin. Does anyone know how to get the lines thicker? I have
>checked the Adobe and AutoDesk sites but can't find an
>Dave Quebbeman

Dan Azlin ** WORD ENGINEERS, Technical Writing & Publishing **
dazlin -at- shore -dot- net 7 Myrtle Street
ph/fax 508-921-8908 Beverly, MA 01915-3315

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