home - about - advertise     

AutoCAD Feature

AutoCAD As an Illustration Tool

by Ron Adee, CADdigest.com

Electronic media is being shared and exchanged by a wide variety of clients, contractors, architects and engineers. Microsoft has made much of this collaboration possible through its operating systems and software. It is no problem to exchange files generated from a Microsoft Office Suite program (i.e. Word, Excel, Access, PowerPoint). But what happens when you want to share an AutoCAD drawing with a non-AutoCAD user?

AutoCAD has tried to address this need by providing free drawing viewers such as Volo View and Whip! But even these programs are too cumbersome and confusing for the average office worker. A need exists to be able to translate an AutoCAD drawing that is immediately viewable and understandable to the least computer literate recipient.

In this article I will try to address AutoCAD’s limitations and some solutions I have found using two of the most widely used graphic viewers in use today, PowerPoint and Adobe. But first some background.

CAD vs. Image Editors

AutoCAD is a powerful CAD drafting program that has been around since 1982. It is the world's most popular CAD program, accounting for 70% of CAD sales since its inception. It is a good generic CAD program. By generic I mean that the program can draw all of the basic geometric shapes such as lines, text, arcs, circles, etc. By generic I also mean that it can be adapted to a wide variety of uses. For instance, it can and has been used for machine design, and for countless architectural, structural, civil, electrical and mechanical projects. It does what all CAD programs do: draw objects with extreme precision and accuracy.

What AutoCAD does not do very well is image editing -- that is, tasks such as freehand artwork, or shading, rendering and annotating. Programs designed for image editing and as publishing aids have been available for years; there are distinct differences between these image editor programs and CAD systems.

AutoCAD, for example, was designed with the ultimate goal of sending the finished result (a drawing) to a plotter. Great care was taken in programming AutoCAD to enable a user to plot a drawing with various line weights and at different scales and sizes. You might say that, in a sense, AutoCAD is plotter driven.

Image editor programs, on the other hand, were designed with the goal of sending the finished result to a lithographer. In other words, the finished product has to look good when printed. Therefore, image editor programs could be considered printer driven.

An AutoCAD drawing does not look so good on a screen. This is because the lines are vector lines, which have no width. This goes back to the days of pen plotters when vector lines were used to give distance and direction information to a plotter pen.

Image editor lines look good on a screen because they are raster lines. Raster lines are composed of a series of “dots.” Raster images are not meant to be sent to a plotter, but to a camera. A camera in the hands of a lithographer will take a picture of the image and transfer that image to a plate. This image will contain hundreds of dots.

With the advent of the Internet, AutoCAD and other CAD programs have made great strides in incorporating raster images into their software. Image editor programs have likewise made great strides in incorporating vector images into their products. However, neither one can totally replace the other.

In general, CAD programs are best for doing straight, rectilinear lines and for crisp clean angles and corners. Image editor programs are best suited for images with gradual changes in texture, color, shape and shade. To put it in other terms, CAD drawings are cartoon-like while image editor drawings are more like photographs.

PDF or PowerPoint

PDF, which stands for Portable Document Format, is the file format produced by programs such as Adobe Illustrator and Photoshop. I installed Photoshop on my computer when I was testing out a scanner. Even after I uninstalled the software, I was left with a plug-in program called PDF Writer. This program installs a "virtual" printer and also installs a new command line in all Microsoft products called Create Adobe PDF, which directs output to the PDF Writer. This in turn translates all Microsoft information into a PDF file that is readable by Acrobat.

Since PDF Writer also installs a virtual printer, it is possible to use it to convert other types of documents, inlcuding AutoCAD drawings. First, you have to configure a Windows System Printer in AutoCAD. To do this, go to Settings, Printers and make the PDF Writer the Default printer, then (in AutoCAD) go to Tools, Preferences (Options) and add a New Printer. Pick the System Printer option and answer all defaults.

A word of caution: in AutoCAD 2000 there is a bug when doing a full preview to the PDF Writer. This is documented in the AutoCAD “known limitations” file. Doing a full preview will cause AutoCAD 2000 to fatal error.

Sending an AutoCAD drawing to PDF Writer has several advantages:

  • You can use the AutoCAD pen assignments and widths

  • You don’t have to change the background color to white

  • You can plot paperspace viewports as well as modelspace

PowerPoint is installed on many office computers that come with the Microsoft Office Suite. I have used PowerPoint many times for distributing AutoCAD drawing information to non-AutoCAD users. It has proven effective, but has several drawbacks. You must:

  • widen the lines of the AutoCAD drawing

  • change all fonts to a bold Truetype font

  • change the background color of the drawing to white

  • minimize the drawing window to be the approximate size of the graphic

  • export a .wmf file from AutoCAD and paste this into a blank PowerPoint slide

There are also advantages to using PowerPoint. You can:

  • crop or enlarge the graphic and other add other elements such as arrows, bullets, and text

  • project the graphic onto an overhead screen

  • build a slide show

The advantages of PDF include its ability to:

  • distribute drawings to contractors or others who don’t have PowerPoint

  • easily and quickly create a multiple pen width drawing in paperspace

  • create a drawing that is not editable and therefore “secure”

For those without access to PDF Writer, there are other free alternatives. One is a program called PDF995, available as a download. I have used it and it is very versatile. The free version has banner ads that pop up each time the program is launched, but these can be disabled for the cost of $9.95 (hence the 995 in PDF995). Here is a link to their site: <http://www.pdf995.com>.

And here is a link to another PDF site: <http://www.jwwalker.com/pages/pdf.html>.

Some things to consider when preparing AutoCAD for graphic illustration

Before I export a .wmf file, I always make the background of my drawing white. To do this, go to Tools, Preferences (Options), and Display. Choose Colors and the “Graphic windows background.” Then select white from the basic colors palette. Then click OK and Apply. This is not necessary for .pdf files, because the drawing is sent to the PDF Writer as a Postscript file. Postscript ignores background color.

But the color of the vector lines and text is important. Most AutoCAD users are accustomed to working with a black background. Foreground colors like yellow, magenta and cyan contrast well with a black background but not with a white one.

Another consideration is the printed color. Most modern monochrome printers apply a grayscale equivalent to certain colors. For instance, red will be printed as a dark gray color and blue will be printed pure black. Yellow, on the other hand, will be printed as a light gray.

When preparing for a presentation I make a separate drawing. I then revise my colors on that drawing to a more practical palette. How do I determine what colors go on this palette? First, I choose what looks good on the screen. Colors that offers the best contrast on a white background are red, blue, green and white (which converts to black when the background color is changed). I sometimes use colors such as cyan and magenta for hatch patterns and fills.

Next, I find the best contrast between these colors on a monochrome print. To do this, take the AutoCAD “chroma” or “colorwh” drawing (found in the Support folder) and make a print of it. This will give you an idea of the grayscale shading that occurs in every AutoCAD color. Below is an example (click image to enlarge)

It can be a challenge sometimes to find a color that looks good on both a screen and a print. After some practice, you will develop an “eye” for the saturation of a particular color and how dark it will print.

For more information, see my article, “Raster Images,” which can be found in my Adee’s AutoCAD Answers website archive. See my home page for details.

About the Author

Ron Adee is a senior engineering technician who works for the Kansas Air National Guard in Topeka, Kansas. He began drafting in 1975, started using CAD full time in 1983 and has been using AutoCAD since 1991.

CADdigest Weekly
Email (required) *

A week's worth of articles will be emailed to you. See latest issue .