AutoCAD & AutoCAD LT All-In-One Desk Reference For Dummies (2006)

32 Reaching for AutoCAD Help

AutoCAD system variables

Not everyone uses AutoCAD the same way. Despite its hundreds of commands, there are still specific ways that users want those commands to operate. AutoCAD accommodates with an array of system settings — called system variables — that cover nearly all the bases. Many system variables are toggles — they have a value of either 0 or 1, meaning they are either enabled or disabled. For example, the system variable MIRRTEXT controls what happens to text when a group of drawing objects is mirrored. If MIRRTEXT is enabled (that is, set to

1), then any text in the group is also mirrored — it reads backward on the screen. If MIRRTEXT is set to 0, the objects, including the text object, are all mirrored, but the text itself is not mirrored, so it reads right-way around.

Other system variables can have different settings (more than simply off and on), and still others can store values that remain intact until they’re replaced with new values.

For a blow-by-blow of most of AutoCAD’s system variables, go to the online help.

Reaching for AutoCAD Help

We hope that the AutoCAD & AutoCAD LT All-in-One Desk Reference For Dummies will answer most of your questions about using AutoCAD. Nevertheless, there are going to be times when you want to go to the horse’s mouth. Here are some ways of accessing the AutoCAD Help System:

Enter a ? at a blank Command: prompt to display the AutoCAD Help System.

From the Help menu, choose Help.

Press the F1 function key at any time.

From the command line type HELP

Using built-in Help

Most of the time, AutoCAD’s Help system is context-sensitive. If you’re in the LINE command and press F1 (or choose Help Help), the Help system will launch and take you to information about the LINE command.

You can get context-sensitive help at the command line, too, by entering an apostrophe and then a question mark (that is ’?).

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33

Using the Info Palette

This one is for newbies. If you turn on the Info Palette (click Info Palette on the Standard toolbar, choose Info Palette from the Tools menu, or use the Ctrl+5 key combination), you can see persistent help for whatever command you’re working with. If it’s a complicated sequence, you can click the padlock icon at the top of the palette. When it’s “locked,” the contents stay visible on-screen.

Finding online resources

Much as we’d like to think this book is all you’ll ever need, we recognize that there are millions of one-off requirements that no book can possibly cover comprehensively. One of the best resources available is Autodesk’s own discussion groups. Go to www.autodesk.com and click Discussion Groups to find your way to a shopping list of discussion groups based on AutoCAD (or AutoCAD LT version).

Book I

Chapter 2

the NavigatingInterface AutoCAD

34 Book I: AutoCAD Basics

Chapter 3: All about Files

In This Chapter

Reviewing AutoCAD’s file types

Starting a new drawing

Saving your drawing

Saving to different file types

Opening existing drawings

Closing windows

Passing File Management 101

Backing up

AutoCAD not only needs hundreds of files to keep itself going, it also generates more files than you can shake a stick at. All of these files are

important, but none is more important than DWG — the drawing file itself.

In this chapter we cover all of the important files that you’re likely to run into — and one or two that you’re not very likely at all to run into, but just in case, you should know what they are.

It’s also important that both AutoCAD and you be able to find the files you both need to work together. AutoCAD can usually take care of itself; after it’s initially installed, all the files the program needs are in appropriate places. But you need to be able to find your drawing files too, and AutoCAD by itself isn’t much help there. Left alone, it will save all your drawings in the Windows My Documents folder. It’s up to you to organize your storage space, and we give you some ideas at the end of the chapter.

File Types in AutoCAD

AutoCAD’s drawing (DWG) files contain everything that you draw, and a bit more besides. In addition to all those lines, arcs, circles, text, and dimensions, your DWG files also contain:

36 File Types in AutoCAD

Style definitions for things like your dimensions and text

Properties associated with your drawing objects, such as color, layer, and linetype

Layer definitions, each and every one of which includes such things as default color, linetype, plot style, whether the objects on the layer print or not, and so on

Not contained within the DWG file itself, but necessary for it to display properly, are associated files that define the fonts used by the text and dimension styles, hatch and linetype patterns, plot styles, and more. We cover those associated files in more detail a few paragraphs from now.

So obviously, there’s a lot of file interaction going on when you work in AutoCAD. A very important aspect of drafting in AutoCAD — or any CAD system — is having a good version of your drawing to fall back on, just in case bad things happen to it. Luckily for us, AutoCAD by default creates backup versions of our drawing file every time we save the drawing. When you click the Save tool button (or whatever your preferred method of interacting with the program), AutoCAD makes a copy of your drawing (let’s call it FOO.DWG) and renames the copy as FOO.BAK. After it’s done that, it takes all the changes that you’ve made and stored in memory, and spoons them into the drawing file. When it’s finished remembering everything, it saves a new version of FOO.DWG.

Not all programs will do this for you, but AutoCAD does, as long as you don’t tell it not to. We cover that a bit more later on in the chapter.

One of the things that puzzles new users to AutoCAD is the fact that not all the data needed to generate a drawing is included in the drawing file. Problems don’t arise if you only ever open your drawings on your own computer, but they can crop up if you ever have to send your drawings to someone else. If that someone else — a client, a contractor, your teacher, or boss — doesn’t have all the same files on her computer that you did on your computer when you made the drawing, then the drawing is not going to look the same as it did for you when you drew it.

Here are some of the files that are external to your DWG file that must be available on every computer on which the drawing will be opened:

Fonts (SHX and/or TTF files). AutoCAD comes with over 70 “vector” font files (SHX extension). These fonts are installed in AutoCAD’s own subfolders within the Program Files folder (usually) on your C: drive. AutoCAD can also use TrueType (TTF) fonts, which are part of Windows itself, and which live in the Fonts folder of your operating system. We tell you lots more about fonts in Book III.

File Types in AutoCAD 37

Be very careful about using non-standard fonts — either SHX fonts that didn’t come with AutoCAD, or TTF fonts that didn’t come with the Windows operating system. If you have to send your drawings to someone whose computer doesn’t have the fonts you used, they won’t see your drawing accurately.

Hatch patterns (PAT files). Hatch pattern files (by default, AutoCAD uses a file named acad.pat; AutoCAD LT’s version is named acadlt.pat, or aclt.pat in pre-2007 versions) are used to generate the cross-hatching that indicates objects cut in sections or specific areas on maps or plans. Hatching is also covered in depth in Book III.

Linetype patterns (LIN files). AutoCAD’s default linetype patterns are defined in a file named acad.lin (acadlt.lin or aclt.lin in AutoCAD LT). This file defines non-continuous linetypes such as center, dashed, and hidden used in standard drafting. We talk about linetypes in Chapter 5.

The acad and acadlt hatch pattern and linetype definition files are for use with imperial units. If you’re working in metric, use the acadiso.pat (acadltiso.pat) and acadiso.lin (acadltiso.lin) files. If you start your drawings correctly, these files are available automatically.

Plot style tables (CTB or STB files). Plot styles are collections of settings that tell your output device (a highfalutin way of saying printer) what color of drawing object corresponds to what thickness of printed line, or what printed properties are to be assigned to what drawing objects. (Don’t worry about printing for now — we cover it in much greater depth in Book VII. You can worry about it then!) Plot style tables are the files where all the plot styles live, and AutoCAD needs to find them or your drawing won’t print properly.

Image files. AutoCAD can display and print raster images that are placed in drawing files, but the files do not become part of the drawing file itself. If AutoCAD can’t find them (say, you forget to send them with the drawing file), then you get a rectangle showing the name of the missing file instead. We cover image files in Book VI.

Other DWG files. You can attach drawings to other drawings so you don’t have to keep redrawing the same things over and over again. Those attached drawings are called external references (or xrefs for short). The idea is that if you change something in a referenced drawing, it automatically changes in all drawings to which it’s attached. It’s a really useful feature, but it’s complicated (don’t worry — we tell all in Book VI!). The point here is that if AutoCAD can’t find the referenced drawing file, you get another one of those missing file messages.

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38 Starting a New Drawing

To sum up, if you’re sharing drawings with others outside your office:

You usually don’t have to worry about the font, hatch pattern, or linetype files if you’re using the standard fonts and patterns that come with AutoCAD.

You may have to worry about plot style tables if you’re using custom ones.

You usually do have to worry about images and external references, since those are files that you create yourself, and are not part of AutoCAD.

Starting a New Drawing

If all that information seems a little daunting at this point, don’t worry — all will be revealed within these pages. In the meantime, it’s just possible that you want to actually get down and dirty and draw something. So let’s look at a trio of ways to start a new drawing in AutoCAD.

If you’re using AutoCAD 2005, 2006, or 2007 out of the box (AutoCAD veterans call this the “out-of-the-box experience”), when you click the QNew button on the Standard toolbar, you get a Select Template dialog box (see Figure 3-1).

Figure 3-1:

Select a template to start a new drawing.

Starting a New Drawing

39

It may look like a “New” button, but it actually runs a command called QNEW. Who knew? Here’s what QNEW can do for you. If you don’t change any settings in AutoCAD, clicking QNEW will always display the Select Template dialog box. Now, if you always start a drawing using the acad.dwt template (not the best idea, but read on), you have to click Acad.dwt, and then click OK. That can get a bit tedious. But if you go into the Options dialog box and click Files, you can identify a specific template file (maybe even Acad.dwt). Doing so will tell AutoCAD to start a new drawing using the specified template every time.

A further wrinkle in starting a new drawing occurs if a system variable called STARTUP is enabled. By default, STARTUP is disabled or set to 0; for more on system variables, see the sidebar “AutoCAD System Variables” in Chapter 2 of this minibook.

If STARTUP is enabled (or set to 1), the first time you start AutoCAD you see a Startup dialog box (see Figure 3-2).

Figure 3-2:

The Startup dialog box you see

if STARTUP = 1.

From this dialog box, you can choose to open an existing drawing or start a new drawing in one of three different ways: starting from scratch, using a template, or employing a wizard. Once the first drawing in an AutoCAD session has been opened using any of these methods, subsequent clicks of the QNew button will display a Create New Drawing dialog box. This dialog box looks suspiciously like the Startup dialog box — it gives you the same three choices for starting a new drawing, but the icon for opening an existing drawing is grayed out.

The STARTUP system variable must be set to 1 in order for the Startup and Create New Drawing dialog boxes to appear when you start AutoCAD or when you click the QNew button. If you only ever see the Select Template dialog box on either starting AutoCAD or clicking QNew, then your STARTUP variable is disabled.

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40 Starting a New Drawing

We suggest you leave STARTUP set to 0, as the other options for starting a new drawing — that is, from scratch or using a wizard — are much less efficient, as we explain now.

Starting from scratch

When you start a new drawing from scratch, you’re starting AutoCAD with no preconfigured settings. There are no layers in the drawing other than Layer 0, nor are there any text styles, or dimension styles other than STANDARD. There are no table styles, and no predefined layouts. When you choose this option, you really do start from scratch, and you must spend a fair old whack of time making settings that you could easily make once and save in a template. For simple sketching, or working out design ideas, it’s okay to start from scratch, but once you’re into working drawing production, it’s a lot more efficient to use a template. But even starting from scratch is better than using a wizard.

Using a Wizard

Wizard, schmizard — what do they know? Not much, when it comes to setting up drawings in AutoCAD. We don’t mean to disparage all wizards — there are a few useful ones in AutoCAD — but the one that offers to start a new drawing for you is not one of them.

There are two kinds of wizard to choose from: You can run a Quick Wizard or an “Advanced” one (see Figure 3-3).

Figure 3-3:

Pick your wizard.

The problem with the wizards — both of them — is that the settings that they make for you are not very useful. Both wizards will set these values:

Starting a New Drawing

41

Units. Choose the format and precision for your linear drawing units (see Figure 3-4). Regardless of the format you choose, the units are based on inches if you live in the U.S.A, or millimeters if you live outside the U.S.A.

Figure 3-4:

Both wizards (this is the Quick one) ask you to select the units type.

Area. Specify the drawing area by its length and width. You arrive at the correct figures by multiplying the intended plot scale of the drawing by the dimensions of the paper on which it will be plotted.

In addition to units and area, the Advanced wizard also sets these values:

Angular Units. Choose the format and precision for angular measure. The default type of angular measure (and the easiest by far for most people to work with) is decimal degrees.

Angle Measure. Specify where in the circle 0 degrees lies. By default, 0 degrees lies due east. If you don’t have a compass handy, you can also think of this direction as 3 o’clock, or to the right, in a dead horizontal alignment.

Angle Direction. Specify whether angles are measured in a clockwise or counterclockwise direction. By default, angles are measured in a counterclockwise direction, so if 0 degrees lies on an east-pointing horizontal axis, then 90 degrees is straight up, 180 degrees is horizontal pointing west

(9 o’clock for you clock watchers), and 270 degrees is straight down.

Nearly all major industries go with the AutoCAD defaults for angular measure — that is, 0 degrees is on an easterly horizontal axis, and angles are measured in a counterclockwise direction. One exception to this rule is in surveying, where 0 degrees usually points north, and angles are measured

Book I

Chapter 3

about All

Files