Grip Editing

The usage of grips at first can be confusing because the grips appear so often, but after grips are understood and utilized, they can be extremely helpful and efficient at editing existing geometry.

Grip editing is a facility that integrates object snap points with the most commonly used editing commands and then places the combined capabilities literally at your fingertips. With grips, it is possible to edit objects and select specific object snap points without ever having to pick a tool, use a menu command, or type a command. In the following sections, you will learn how to enable the grips function, activate grips, and make use of the various options available with grips.

Enabling Grips

Grips are an optional facility. By default, grips are enabled. You can disable grips with the Enable Grips toggle in the Selection tab of the Options dialog box (see Figure 11.3), which is displayed by choosing Options from the Tools pull-down menu.

With grips enabled, you start the process of using the grip editing modes by selecting the objects you want to edit at the Command: prompt. In other words, you do not initiate any commands. Instead, you simply select the objects by picking them or by using implied windowing. After you have selected the objects, the object’s grips are displayed as blue squares. The color and size of these unselected grips are set with the Unselected button in the Grips dialog box. The displayed grips correspond to the control points of the objects, and for the most part, the grip locations are the same as the object snap points for the various types of objects. The major exceptions to this rule are presented in Table 11.1.

Table 11.1. Specific Grip and Object Snap Discrepancies

Object	Description
Arc	Only three grips exist for an arc: its two endpoints and its midpoint. In contrast, object snap points include the center point and any valid quadrant points. Grip editing on an arc can be used to shorten to an intersection. Note: When moving a grip on an arc, it will change the geometry unless the new point placement results in the same radius and center coordinate.
Block Insertion	By default, only one grip is displayed at the insertion point of each block insertion. However, if you enable the Enable Grips Within Blocks setting from the Selection tab in the Options dialog box, then the grips of all the component objects are also displayed. Grip editing a block will relocate the insertion point.
Elliptical arc	Grips correspond to the arc’s endpoints, midpoint, and center points but not to its visible quadrant points. Grip editing an ellipse will relocate it or resize it about its center.
Mline	Grips exist at the points used to locate the mline object. In contrast, endpoint and midpoint object snap points can exist on each visible segment. Grip editing an mline will change the vertex points.
Mtext	Four grips exist on an mtext object—one at each corner of the imaginary box that surrounds an mtext object. In contrast, only one insertion object snap point can be shown on an mtext object. Grip editing an mtext object can be used to relocate or resize the bounding box affecting the paragraph appearance.
Spline	A grip exists at every point used to define the spline, known as the spline’s control points. Object snap points include only the endpoints. Grip editing can be used to redefine the curves as well as the start and endpoints of the spline.

As with object snap, grips enable you to easily choose a very specific point on an object. After the grips are displayed, you can choose one grip to activate the grip editing modes.

Activating the Grip Editing Modes

When you select one or more objects, grips are displayed. You may then pick any grip location and initiate the grip edit mode for the selection set. Selecting a grip affects the cursor much like osnaps do: The grip acts as a magnet and pulls the cursor to the grip. By default, the unselected grip box color is blue.

After a grip is selected, by default it is displayed as a red box and is referred to as a hot or selected grip. The color used to fill in the grip box is set from the Selection tab of the Options dialog box. The selected grip subsequently is used as the base point for the various grip editing modes: Stretch, Move, Rotate, Scale, and Mirror. Initially, the Stretch grip mode is activated, but you can press Enter or the spacebar to cycle through the other grip commands. Alternatively, right-click and pick the desired grip mode from the shortcut menu that appears (see Figure 11.4). The various editing mode options are discussed in the following sections.

Deactivating the Grips

When you select objects at the Command: prompt, the grips of the objects are displayed and the objects are highlighted. The highlighting indicates the objects that have been selected. In AutoCAD 2000, if you then press the Esc key, the objects would be deselected (no longer highlighted) but the grips would still be displayed. You then had to press the Esc key again to cancel the display of the grips. With AutoCAD 2000i this was streamlined to allow a single Esc key press to both unhighlighted and ungripped the gripped objects.

You can also selectively deselect highlighted objects by pressing the Shift key and selecting the highlighted objects, thereby leaving the grips displayed. This procedure is useful, but the Autosnap feature makes them irrelevant because Autosnap automatically displays the snap points on nearby objects.

Another common problem that users experience using grips is that they accidentally select objects and activate a grip editing mode by selecting one of the grips. To exit a grip editing mode, just press the Esc key. Remember that in AutoCAD 2002, pressing the Esc key always cancels the current operation. To deselect the objects and clear the display of the grips, press the Esc key one more time.

The first grip edit mode to discuss is the Stretch mode. The next section covers this valuable grip editing feature.

Using the Stretch Mode

The default edit mode when working with grips is Stretch, which enables you to relocate the selected grip. This in turn affects only the object or objects defined by the selected grip. For example, if the selected grip is the endpoint of a line (as shown in Figure 11.5), then that endpoint of the line can be stretched to the new position.

If the selected grip is the endpoint at which two lines meet, then both lines are stretched to the new endpoint location. As you decide on the new location of the selected grip, notice that the rubberband line is anchored at the selected grip. Thus, the selected grip is referred to as the base point of the stretch.

Stretching Multiple Points at the Same Time

If you want to stretch more than one point on the selected object(s) at a time, you must initiate a modified procedure to activate grips. First, you must hold down the Shift key while selecting all the grips you want to edit during the stretching procedure. Then, after releasing Shift, pick the grip that you want to use as the base point (the hot grip) of the stretch. This activates the grip edit modes on the prompt line.

Using the Move Mode

Use the Move grip mode simply to move the selected objects to the new location. Unlike the Stretch grip editing mode—in which only the selected objects controlled by the selected grip are affected—all selected objects are moved with the grip’s Move editing mode (see Figure 11.6).

Using the Rotate Mode

The Rotate grip editing mode enables you to rotate the selected objects about the selected grip (see Figure 11.7).

You can specify the amount of rotation to apply to the selected objects graphically with the “rubberband” line or by typing the specific value. The angle entered is relative to the drawing’s 0 degree angle set in Units. Alternatively, you can specify the Reference option.

To use the Reference option, you first specify a reference angle by picking two points that define that angle or typing an angular value. Then, you specify the desired angle the reference line is to be rotated by dragging or typing the angle.

Using the Scale Mode

The Scale grip mode enables you to scale the selected objects about the selected grip. You can either type the scale factor or pick a point using the rubberband line. Picking a point is subsequently used as the graphic specification of the scale factor. The grip point is the static point about which the objects expand or contract. Similar to the Rotate grip mode, the Scale grip mode has a Reference option.

To use the Reference option, you specify a reference length by picking two points to define that length or typing a known length value. Then, you specify the desired length to which you want the reference line to be scaled. The second length can be defined by entering the desired length or picking two points to define that length.

Using the Mirror Mode

The Mirror grip edit mode enables you to mirror the selected objects about the mirror line that is anchored at the selected grip (see Figure 11.8).

The mirror line is the imaginary line about which all the selected objects are flipped. Text and mtext objects also are flipped so that they appear backward. By default, the MIRRTEXT system variable is set to On, which produces backward text objects during mirroring. If you want the text and mtext objects to remain readable, type MIRRTEXT at the Command: prompt, and type 0 to turn off the mirroring of text objects.

Invoking the Grip Editing Base Point Option

The base point option of the grip edit modes enables you to relocate the anchor point of the rubberband line. In the Stretch grip edit mode, relocating the base point does not affect the grip that is stretched. A base point option exists in each grip edit mode. This option is very useful in the mirror grip edit mode when either of the mirror line points do not coincide with a grip location.