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The System Variables section of the online help’s Command Reference tells you which kind of system variable each one is. There are several hundred system variables, but understanding those listed in this chapter will help make you a happy CADster.

APERTURE

APERTURE controls how close the crosshairs must get to an object before an object snap marker appears. (We discuss object snaps in Chapter 7.) You can set APERTURE at the command line anywhere from 0 to 50 pixels, or you can set it in the Options dialog box by adjusting a slider to a maximum of 20 pixels. The default value is 10.

DIMASSOC

DIMASSOC controls how AutoCAD’s dimension objects are created (see Chapter 14 for the lowdown on dimensioning). When DIMASSOC is 0, AutoCAD creates exploded dimensions of separate lines, 2D solids, and text. You really don’t want to work on DIMASSOC=0 drawings. When DIMASSOC=1, dimensions are referred to as non-associative — that means that they’re single objects, but they usually don’t update if you change an object’s size. When DIMASSOC=2 (the default), AutoCAD creates fully associative dimensions. You can set this value at the command line or select the Make New Dimensions Associative check box after choosing Options User Preferences. If you work with older drawings, you’ll likely find that the DIMASSOC value is 1, which is the best that releases prior to AutoCAD 2002 could manage. The DIMASSOC setting is stored in the drawing.

MENUBAR

When MENUBAR is 1, AutoCAD displays its traditional classic menu bar below the application title bar. If MENUBAR is set to 0 (the default), the menu bar doesn’t appear. MENUBAR is set automatically when you switch between the AutoCAD Classic and Drafting & Annotation workspaces.

If you’ve been away from AutoCAD for a few years and feel in need of training wheels while you get used to the Ribbon, displaying the classic menu bar is a good approach. (We describe the differences between the traditional AutoCAD Classic and the newer Ribbon-based workspaces in Chapter 2.)

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MIRRTEXT

You’ve got to love it when a system variable’s name gives you a clear indication of what it does (ROLLOVERTIPS, anyone?). You’ll frequently want to build up a drawing by mirroring already-drawn components of it. That’s what the MIRROR command does. Luckily, AutoCAD is smart enough to realize that most of the time you don’t want to produce a mirror image of any text that may be included among the set of objects you are mirroring. Having to use a mirror to read the text on your drawing is counterproductive.

On the other hand, suppose you want to draw the mold for a cast part and the finished part has some text molded in it, such as a company name or a part number. The text features in the mold need to be mirror images so the final cast text will read correctly. No problem. Simply set the MIRRTEXT system variable to 1 and now the MIRROR command will mirror the text. When MIRRTEXT is 0 (the default), text is not mirrored and the text still reads the right way around. MIRRTEXT is stored in the drawing.

OSNAPZ

Sometimes drawing in 3D can be a little puzzling, especially if you’re looking at 3D objects in orthographic views. Say you have a wireframe cube that you’re looking at in Plan view, and you want to draw a line between two diagonal corners on the top of the cube. Using object snaps to pick the corners, as often as not you’ll find that you have a line that’s not on the plane of the top of the box, but starts at a top corner and ends at a bottom corner. One way around this problem is to set the OSNAPZ variable appropriately.

By default, OSNAPZ is set to 0, which means AutoCAD will find the X, Y, and Z coordinate of the snapped-to point. But often you don’t want that to happen. Set OSNAPZ to 1, and AutoCAD replaces the Z value of the picked point with the current elevation — or the Z value of the first point picked.

Because OSNAPZ affects drawing in three dimensions, it’s not available in

AutoCAD LT.

PICKBOX

The pickbox is the little square box that the crosshairs turn into when AutoCAD prompts you to select something. You control pickbox size by setting a value in pixels for the PICKBOX variable. The initial setting of PICKBOX is 3, which is fine for a lower screen resolution like 1024 x 768. But when you start running at higher resolutions — or when your hair is grayer, your face

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more wrinkled, and your vision not quite as acute as it once was — a higher setting might be more useful.

REMEMBERFOLDERS

Sometimes, you don’t want AutoCAD to start in the same Documents folder where every other program stores its files. Maybe you work on a number of projects and would like a separate desktop icon for each to start in a particular folder. REMEMBERFOLDERS is your ticket to Nirvana. By default, it’s set to 1, which means it defaults to storing files in My Documents (just plain Documents in Windows Vista and Windows 7). Set it to 0, and it will open from and save to the folder you specify in your desktop icon when you start, and the last folder you visit as you work. REMEMBERFOLDERS is stored in the Windows Registry.

ROLLOVERTIPS

You were waiting for this one, weren’t you? ROLLOVERTIPS controls the tooltiplike message boxes you see when you hover the mouse pointer over objects in the drawing editor. If ROLLOVERTIPS is 1, mousing over your drawing displays a temporary panel showing the object type with its layer, color, and linetype. If, like us, you find this a little intrusive, set its value to 0.

You can get double duty from this command. Not only can you key it into AutoCAD, but if you have a dog named Tips, you can also use it to teach him a neat pet trick! ROLLOVERTIPS is stored in the Windows Registry. (And believe it or not — and we bet you won’t — there’s another system variable called NOMUTT! Could that be AutoCAD-ese for BAD DOG TIPS!?)

TOOLTIPS

Tooltips themselves are the little text boxes that appear (by default, anyway) when you hover your mouse pointer over a toolbar or Ribbon button, or just about anywhere in a dialog box. Tooltips are really useful when you’re getting to know your way around a program, but when you have a sense of where things are, they can get in the way. By default, TOOLTIPS is set to 1,

which means that they appear when you hover the mouse pointer over something. Set TOOLTIPS to 0 if you don’t want to see them again. The TOOLTIPS setting is stored in the Windows Registry.

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VISRETAIN

If you work with xrefs (refer to Chapter 18), you know the potential for competing layer properties. Sometimes, you want your xref to look different from your current drawing so you can tell which is which. You can change layer colors of xrefs in the Layer Property Manager, but whether you have to do that every time you open a drawing with an attached xref depends on the setting of the VISRETAIN system variable. When VISRETAIN is set to 0, the layer properties in the xref take precedence, which means that you would have to make those changes every time you opened the host drawing. When VISRETAIN is set to 1 (the default value), changes you make to layer properties in the host drawing remain intact every time you open that host drawing; however, those changes have no effect on the external file itself. The VISRETAIN value is stored in the current drawing.

And the Bonus Round

Here are two system variables that may not help your productivity, but are a bit of fun.

MTJIGSTRING allows you to substitute up to ten characters of your choice to replace the usual abc prompt when you start the MTEXT command. For example, I’m great! just fits.

The final one is invoked slightly differently. Enter (setvar “screenmenu” 1) to turn on the officially dead screen menu from years ago. It is fast, having no icons or tooltips, and is fully context-sensitive. No more right-click to get command options because it was created before three-button mice existed. No matter how you start a command, its options appear automatically. The bad news is that it hasn’t been updated in years because it’s officially dead.

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552 Part VI: The Part of Tens

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