IN THIS CHAPTER

APERTURE

DIMASSOC

MENUBAR

MIRRTEXT

OSNAPZ

PICKBOX

REMEMBERFOLDERS

ROLLOVERTIPS

TOOLTIPS

VISRETAIN

System variables are the settings that AutoCAD checks before it decides how to do something. For example, if you leave the system variable SAVETIME at its default value of 10, AutoCAD saves the drawing file automatically every ten minutes; if you change SAVETIME to 60, the time between automatic saves is 1 hour. Hundreds of system variables control AutoCAD’s operations.

Most system variables are controlled by the OPtions command, but you can also change the value of a system variable by simply typing its name at the AutoCAD command prompt and pressing Enter. AutoCAD displays the current value of the system variable setting and prompts you for a new value. Press Enter to confirm the existing setting, or type a value and press Enter to change it.

This list describes the three kinds of system variables in AutoCAD and what happens when you change them:

• Saved in the Windows Registry: Affects all drawings when you open them on your system, but not necessarily on other computers.
• Saved in the drawing: Affects only the current drawing, but on any computer. The Drawing icon in the Options dialog box indicates the variables that are saved in the drawing. If you change these and then save the drawing as a template, all subsequent drawings that you start from this template inherit these values. I cover templates in Chapter 4.
• Not saved anywhere: Lasts only for the current drawing session.

The System Variables section in the Resource area of the online Help system indicates the kind of system variable. Several hundred system variables exist, but understanding the ones described in this chapter can help make you a happy CADster.

APERTURE

APERTURE controls how closely the cursor must be to an object before an object snap marker appears. I discuss object snaps in Chapter 11. You can set APERTURE from the command line to any value between 1 and 50 pixels, or you can set it in the Options dialog box by adjusting the slider to a maximum of 20 pixels. The initial value is 10.

DIMASSOC

DIMASSOC controls how the AutoCAD 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 nonassociative — they’re single objects, but they usually don’t update if you change the size of an object.

When DIMASSOC=2 (the default setting), AutoCAD creates fully associative dimensions. You can set this value from 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 earlier than AutoCAD 2002 could manage. The DIMASSOC setting is stored in the drawing and carries forward from the template.

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. The menu bar can also be turned on and off by using the down arrow at the right end of the Quick Access toolbar.

If you’ve been away from AutoCAD for a few years and you feel that you could benefit from training wheels while you become accustomed to using the Ribbon, display the classic menu bar.

MIRRTEXT

You’ve got to love seeing a clear indication of a system variable’s purpose from its name. ROLLOVERTIPS, anyone? You’ll frequently build up a drawing by mirroring already-drawn components of it. That’s what the MIrror command does. Luckily, AutoCAD realizes that you rarely want to produce a mirror image of any text that may be included among the set of objects you’re mirroring. Having to use a mirror to read the text on your drawing is counterproductive.

On the other hand, suppose that 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 that the final cast text is read correctly. No problem: Simply set the MIRRTEXT system variable to 1, and the MIrror command mirrors the text. When MIRRTEXT is 0 (the default setting), text isn’t mirrored, and the text still reads the right way. MIRRTEXT is stored in the drawing and carries forward from the template.

OSNAPZ

Sometimes, drawing in 3D can be a little puzzling, especially if you’re looking at 3D objects in orthographic views. Say that you’re looking at a wireframe cube in Plan view and you want to draw a line between two diagonal corners on top of the cube. By using object snaps to pick the corners, you’ll find, as often as not, that the line isn’t on the plane of the top of the box, but that it starts at a top corner and ends at a bottom corner. One way around this problem is to set the OSNAPZ variable appropriately. Because OSNAPZ is set to 0 by default, AutoCAD finds the X,Y,Z coordinates 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 unavailable in AutoCAD LT.

PICKBOX

The pickbox is the little square box that the cursor turns into when AutoCAD prompts you to select an item. You control the 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, such as 1024 x 768. But when you start running at higher resolutions or when your hair is grayer, your face 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 you want a separate desktop icon for each one to start in a particular folder. If so, REMEMBERFOLDERS is your ticket to Nirvana. By default, it’s set to 1, so it defaults to storing files in Documents in Windows 7 and 10.

Set this variable to 0, and it opens from, and saves to, the folder you specify in the desktop icon when you start AutoCAD, and in the last folder you visit as you work. REMEMBERFOLDERS is stored in the Windows Registry.

If you regularly work on several different projects or for specific clients, simply create appropriate copies of the Windows desktop icon that launches AutoCAD. Now right-click each icon in turn, click Properties, and change the Start In window to display your desired default folder for each case. Now when you launch AutoCAD from a specific icon, it will default to finding and storing your drawings in the specified folder.

There are three signs of old age. The first is loss of memory. I forget the other two.

ROLLOVERTIPS

You were waiting for this one, weren’t you? ROLLOVERTIPS controls the tooltip-like message boxes you see when you hover the mouse pointer over objects in the drawing area. When ROLLOVERTIPS is set to 1, pausing the cursor on an object opens a temporary panel showing the object type with its layer, color, and linetype. If (like me) you find the panel intrusive, set its value to 0.

This command can serve double duty. You can not only enter it into AutoCAD but also (if you have a dog named Tips) use it to teach your pet a neat trick. ROLLOVERTIPS is stored in the Windows Registry. And believe it or not (and I would bet that you don’t), another system variable is named NOMUTT. Maybe it’s AutoCAD-ese for BAD DOG TIPS.

TOOLTIPS

A tooltip is the little text box that appears (by default, anyway) when you hover the mouse pointer over a toolbar or Ribbon button, or just about anywhere in a dialog box. Tooltips are truly 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, to appear whenever you hover the mouse pointer over a program element.

Set TOOLTIPS to 0 if you don’t want to see tooltips again. The TOOLTIPS setting is stored in the Windows Registry.

VISRETAIN

If you work with xrefs (see Chapter 18), you know the potential for competing layer properties. Sometimes, you want an xref to look different from the current drawing so that you can tell which is which. You can change the 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, so you would have to make those changes every time you open 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

This section describes two system variables that are fun to use, even if they don’t boost your productivity.

Using MTJIGSTRING, you can substitute as many as 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 last variable I want to tell you about is invoked slightly differently from MTJIGSTRING. Enter the following line to turn on the deprecated DOS screen menu (in use years ago):

(setvar "screenmenu" 1)

The DOS screen menu is fast, has no icons or tooltips, and is fully context-sensitive. No longer do you right-click to see command options because it was created before 3-button mice even existed. No matter how you start a command, its options appear automatically.

Clicking AutoCAD always returns you to the root menu, and clicking **** opens a list of the temporary object snap overrides. The bad news is that the DOS screen menu hasn’t been updated in years because it’s deprecated (officially dead but still lying around). The really bad news is that it cannot be customized by users.