In AutoCAD® there’s a hidden treasure trove of options that many users do not realize exist. System variables are values that control command settings, interface behavior, and user options. Some system variables are stored with the DWG file, while others are stored to your computer’s registry.
Most system variables can be controlled through a user-friendly front-end, such as the Options dialog box. Others can be found in drawing-specific areas such as the Units dialog or the status bar. A few system variables are key-in only. No matter where the front end is, they can be controlled through command-line input.
The following is an alphabetical list of some that I consider to be the most useful.
Most users who have worked with AutoCAD for any amount of time have needed to reset this registry-stored variable. When this variable is set to 0, or “off,” the dialog box display is suppressed for the Open and Save As commands. A script or LISP routine will frequently set this variable to the off position while it runs its course, but will reset it back to on at the end of the process. If AutoCAD happens to close unexpectedly during the running of the script, the variable does not get reset to the proper position.
Many people like to work with the AutoCAD grid on, but find the new engineering paper look makes the polar tracking guidelines difficult to see. The default value is 0, but changing the GRIDSTYLE to 1 will take the modelspace grid back to the pre-2011 dotted appearance. GRIDSTYLE can also be set to 2 through 7, which affects in which drawing environments the classic grid will appear. GRIDSTYLE set to 7 means that you will see dotted grid in model space, the block editor, and layout tabs. Whether the grid is on or not is saved with the drawing, but whether you are seeing the classic or new type of grid is saved in your computer’s registry.
AutoCAD 2012 has raised the bar for drafting productivity with multifunctional grips on everything from polylines to dimensions. However, if you are working with a large-scale drawing, the pop-up menus that appear as you move your cursor over grips can be distracting. GRIPMULTIFUNCTIONAL can be set to values between 0 and 3, defined below.
0 – will turn off multi-functional grips altogether.
1 – will allow you to access the grip-goodies by holding down the control key as you click.
2 – gives you hover-only grip menus.
3 – the default setting; gives you grip menus with or without using the CTRL key.
In AutoCAD 2012, joining arcs and lines into a polyline is easier than ever. The JOIN command on the Modify panel now works on lines even if they are not co-linear. However, if you need to specify a fuzz distance between objects you will still need the PEDIT command. By default, PEDITACCEPT is set to 0, but most users prefer to set this to 1. Setting this to 1 will skip over the prompt where AutoCAD asks you if you wish to convert lines, arcs, and splines to polylines. The objects will automatically convert to a polyline and save you the confirmation step.
In most cases, the PICKADD variable is changed accidentally either by a crash or when a user inadvertently changes it by clicking on its icon in the Properties dialog. By default, PICKADD is set to 2, which means that as you click items the selection set continues to grow. To release items from a selection set, users can hold down shift while they click. The only difference between PICKADD set to 2 and PICKADD set to 1 is how the command behaves during the SELECT command. When PICKADD is set to 1, items are released from selection after the command is completed, which seems to defeat the purpose. If PICKADD is set to 0, AutoCAD will release the last picked object from your selection set. In other words, for every new item you select, AutoCAD “lets go” of the previous item or items. An example of a situation where I deliberately set my PICKADD to 0 was when I was manually manipulating a group of polylines and using AutoCAD properties to set individual elevations. With PICKADD off, it saved me the step of hitting ESC after each edit.
Annotative objects are a time saver and can facilitate clean-looking drawings. However, when you select an annotative object, such as annotative text, you will see a “shadow” view of the text at its different sizes and positions. Many users find this distracting and wish to turn off the display. Set your SELECTIONANNODISPLAY to 0 and only the current scale will be displayed, much like a non-annotative object.
Most new workstation-grade computers come with more than one processor. More than one processor is great for multi-taskers who are drafting, listening to music and jumping in and out of email or word processors all day. AutoCAD can utilize multiple processors through setting the WHIPTHREAD variable. By default this is set to 1, where only REGEN tasks are sent to a secondary processor. I recommend setting this to 3 to maximize AutoCAD’s performance on panning and zooming tasks. WHIPTHREAD set to 3 will offload regen and redraw tasks to a secondary processor. If you are on an older computer with only one processor, this setting will not affect anything.
Hopefully, you are using your middle mouse wheel to do the majority of your panning and zooming. It does not take long for this to become second nature for most users. The ZOOMFACTOR system variable determines the amount of change to the zoom level that takes place with every notch of rotation. The lowest possible value for this is 3, which results in very small increments of zoom. The largest ZOOMFACTOR value is 100, which results in dramatic zooming with each roll. If you ever find the zoom getting “stuck” and AutoCAD reporting that you are already zoomed in or as far out as possible, use the REGEN command to refresh your screen.
AutoCAD users and Google map users tend to agree that rolling forward is an intuitive motion for zooming in. Autodesk Inventor® users might disagree. The default setting for this variable is 0. Setting it to 1 will make the middle mouse wheel zoom out as you roll forward and zoom in as you roll toward yourself.
This list is just the tip of the iceberg in terms of the options available to customize AutoCAD’s behavior. I encourage you to explore the options available by perusing the system variable list from the Express Tools tab. You may accidentally discover the solution to a years-old AutoCAD behavior mystery.
Louisa "Lou" Holland is a civil engineer and application engineer for MasterGraphics Inc., located in Milwaukee, WI. She has been teaching and counseling on AutoCAD and related products for more than 10 years. Check out her most recent book, Mastering Civil 3D 2012, by Sybex publishing. You can find Lou on Twitter @LouisaHolland ro by emailing firstname.lastname@example.org