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

162 AutoCAD’s Editing Commands

Rotating and resizing

The next set of commands modifies objects by changing their size or orientation in the drawing.

ROTATE

ROTATE spins objects around a base point, either rotating the original or making a copy and leaving the original in place. You specify the amount of rotation by entering an angle or using reference geometry. A typical ROTATE command sequence looks like this:

Command: ROTATE

Current positive angle in UCS: ANGDIR=counterclockwise ANGBASE=0

Select objects: 3 found Select objects: Specify base point: 0,0

Specify rotation angle or [Copy/Reference] <0>: 32

After pressing Enter at the last prompt, the selected objects are rotated.

SCALE

SCALE proportionately resizes selected objects about a base point. You specify a numeric scale factor, or use reference geometry to specify the new size. The procedure is very similar to that for ROTATE: Select your objects, specify a base point, and then specify a scale factor.

Use the SCALE command if you need to convert a drawing done in millimeters so that you can work on it in inches, or vice versa. If you scale a drawing based in inches by a factor of 25.4, the distance values (including the dimensions) will be equivalent to true distances in millimeters. If you have to go the other way, scale the drawing by a factor of 0.03937.

STRETCH

STRETCH stretches but also compresses. Perhaps it should be called STRETCHANDSHRINK? STRETCH is one of the trickier commands to get a handle on because there’s only one way you can select objects for stretching. It’s also one of those commands that works only in verb-noun mode.

LENGTHEN

LENGTHEN changes the length of lines, splines, arcs, and open polylines. Start the command by choosing Modify Lengthen or typing LEN. Lengthen

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(which can shorten, too) changes object length by the option you specify at the command line.

Breaking, mending, and blowing up real good

AutoCAD has let you break objects for years and years. And what’s really great is that you never have to pay for the stuff you break. Recent versions have also let you fix things (well, a few things, under very particular conditions). But sometimes, there’s just no alternative to blowing things up.

BREAK

BREAK is a tricky command to master because you really, really have to keep a watch on the command line. The normal function of BREAK is to remove a chunk of object — say a piece of a line to make two lines with a gap between, or a piece of a circle to turn it into an arc. The following steps describe how to use BREAK to create a gap in an object:

1.Select Break (not Break at point) from the Modify toolbar, or choose Modify Break, or type BR to start the BREAK command.

You can use this command only in verb-noun mode. AutoCAD prompts you to select an object; once you’ve done so, the prompt reads:

Specify second break point or [First point]: F

BREAK’s default behavior is to take the point where you selected the object as the first point of the break. The second point would be the other end of the break; after the second pick, AutoCAD would go ahead and break the object and then return to the command line. This is usually not a very precise way of working, so most of the time you should use the First point option.

2.Type F to specify the First point option.

AutoCAD prompts:

Specify first break point:

Use your favorite precision technique to pick the exact point where the break should start. AutoCAD then prompts:

Specify second break point:

Pick again to specify the second break point. AutoCAD removes the portion of the object between the first and second points.

Use the Break at Point button on the Modify toolbar to break an object into separate pieces without creating a gap between them — the objects would meet endpoint-to-endpoint. Break at Point is a command macro; you can

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achieve the same result by starting the BREAK command in other ways, but this way is the easiest.

JOIN

JOIN enables you to combine separate objects into single ones, as long as some fairly stringent criteria are met. For starters, all objects must lie on the same plane. Separated lines to be joined must be collinear. Arcs must be concentric. JOIN is another command that can be used only in verb-noun mode.

EXPLODE

That stick of dynamite down at the bottom of the Modify toolbar runs the EXPLODE command. EXPLODE breaks up complex objects into their primitive elements. You can explode polylines, as well as dimensions and blocks. (We discuss dimensions in Book III and blocks in Book VI.) If you use EXPLODE on a polyline, the separate entities (that is, lines and arcs) end up on the same layer as the original polyline.

A related command called XPLODE explodes complex entities and gives you a range of options you can set for the exploded objects.

Double-barrel commands

Love and Marriage. Horse and Carriage. Trim and Extend . . . Even though they don’t rhyme, TRIM and EXTEND do work in similar fashion, so we’re going to discuss them together here. And while we’re at it, we’ll talk about CHAMFER and FILLET, as well.

TRIM and EXTEND

TRIM and EXTEND use existing geometry to modify other geometry. The TRIM command lets you cut objects by selecting other objects that cross them. The EXTEND command lets you lengthen objects by selecting other objects that you want them to reach.

The following steps and Figure 2-9 describe how to use TRIM to shorten and extend objects:

AutoCAD’s Editing Commands 165

Figure 2-9:

The long and short of TRIM.

1.Select the Trim button from the Modify toolbar, or choose Modify Trim, or type TR to start the TRIM command.

In this two-part command, you first select the objects you want to trim with — your temporary pair of scissors. AutoCAD prompts:

Current settings: Projection=UCS, Edge=None

Select cutting edges ...

Select objects or <select all>:

The first prompt line displays the current command settings. To change the Projection or Edge settings, use the command options that display after you’ve finished selecting your cutting edges. The second line tells you that the objects you’re going to select will be used as the cutting edges.

2.At the Select objects: prompt, use any object selection method to select linework or other drawing objects as the cutting edges, or press Enter to select everything visible as a cutting edge.

After you finish selecting, AutoCAD prompts:

Select object to trim or shift-select to extend or [Fence/Crossing/Project/Edge/eRase/Undo]:

3.On the object that you want to trim, pick a point on the part you want to get rid of, or choose one of the command options.

TRIM and EXTEND are such close relatives that you can actually run EXTEND from within Trim, and vice versa. To do so, simply hold down the Shift key and select objects.

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FILLET and CHAMFER

FILLET and CHAMFER offer methods of finishing off intersecting objects. CHAMFER creates a straight beveled edge between two non-parallel objects. FILLET creates a curved transition (actually an arc object) between two nonparallel objects. FILLET can also create a semicircular connection between parallel lines. Figure 2-10 shows a typical intersection after filleting and chamfering.

Setting the Fillet radius to 0 before you fillet lines or arcs creates a clean intersection, as shown at the right of Figure 2-10.

Figure 2-10:

Cornering your intersections.

		Specialized commands
		Most of the commands we’ve discussed so far can work on any type of
		object; for example, you can trim or extend lines, arcs, or polylines. Some
		object types are sufficiently complex that they require unique edit tools.
		You’ll find those tools on the Modify Object submenu and the Modify II
		toolbar (see Figure 2-11). (To display the Modify II toolbar, right-click over
		any tool button and choose Modify II.)
		Edit Hatch
				Edit Spline
	Figure 2-11:
	More
	modification		Edit Polyline
	methods.
		Draworder

AutoCAD’s Editing Commands 167

The four tool buttons on the right side of the Modify II toolbar are for working with block attributes (we discuss those in Book VI). The four buttons at the left are for modifying graphic objects as follows:

Draworder. Invokes the DRAWORDER command; move objects in front of or behind other objects.

Edit Hatch. Invokes HATCHEDIT command; modify pattern, scale, and other properties of existing hatch objects.

Edit Polyline. Invokes PEDIT command; modify width, linetype generation, curve type, and other properties of existing polyline objects.

Edit Spline. Invokes SPLINEDIT command; modify curve type, vertexes, and other properties of existing spline objects.

For additional information on these commands, refer to the online Help.

Changing properties

All of the edit commands we’ve looked at so far have involved modifying or duplicating object geometry in some form or other. But sometimes you may just want to change an object’s layer, or find out how long something is.

MATCH PROPERTIES

MATCHPROP is AutoCAD’s magic wand. To use it to copy the properties (linetype, color, layer, text or dimension style, and so on) of one object to one or more other objects, simply click the source object, and then the objects you want to change.

PROPERTIES

PROPERTIES displays a window (or, palette) of its own (see Figure 2-12) in which you see listed every property (editable or not) of the selected object.

The Properties palette is a dockable window. Unlike dialog boxes, dockable windows can stay open while you’re working in the drawing. And by doubleclicking their title bars, you can dock them — that is, anchor them — at the left or right edges of the display.

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Figure 2-12:

Checking out the Properties palette.

Changing your mind

We introduce you to UNDO in Book I and point out a little-known, but useful, AutoCAD command called OOPS. Remember: OOPS restores the last things you erased. UNDO undoes the last operation. Refer to Book I if you need a refresher on the difference.

Coming to Grips with Grips

When you select objects, not only do they highlight, they also sprout little blue boxes, called grips. You can perform a number of editing operations by clicking these grips and then following the command line (or the dynamic input tooltip if you’re using it — and if you’ve forgotten what dynamic input is, have a look at Book I, Chapter 2).

By default, grips appear as solid blue squares at specific points on selected objects. Grip locations often correspond with object snap points, but they’re not the same. To make a grip active, move the crosshairs over the grip and click. You’ll know it’s selected when its color changes from blue to red (see Figure 2-13).

Coming to Grips with Grips 169

Red grip

Blue grip

Figure 2-13:

A gripping way of editing.

Selecting a grip activates grip-editing mode. The grip turns red to show it is active. As soon as a grip becomes active, the command prompt is replaced by a series of five grip-edit commands. When a grip is active, you can choose the grip-edit commands and options in any of these ways:

Press Enter or the space bar to cycle through the five commands. If you go past the one you want, keep hitting Enter until it reappears. To select an option, type its capitalized letter.

Right-click and choose the command or option from the shortcut menu.

If dynamic input is enabled, you can use the down arrow on your keyboard to choose an option, although you must choose the grip-edit command by right-clicking or pressing Enter or the space bar.

If you’re using the keyboard, activating a grip replaces the command line with the grip-edit commands. They look like this:

**STRETCH ** <Stretch to point>/Base point/Copy/Undo/eXit:

**MOVE ** <Move to point>/Base point/Copy/Undo/eXit:

**ROTATE ** <Rotation angle>/Base point/Copy/Undo/Reference/eXit:

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**SCALE ** <Scale factor>/Base point/Copy/Undo/Reference/eXit:

**MIRROR ** <Second point>/Base point/Copy/Undo/eXit:

**STRETCH ** ... and round and round you go.

Each grip edit command has options to change the base point or make multiple copies. The **ROTATE** and **SCALE** options also let you use reference options.

Grips also have an automatic object snap; as soon as you move your cursor close to a grip, it jumps to the precise control point.

Chapter 3: Managing Views

In This Chapter

Zooming in and out of your drawings

Panning around your drawings

Going back to where you were with named views

When you draw things in AutoCAD, you draw them full size. If you’re drawing the cross section of a 2 x 4 (or a 38 x 89 for our metrically inclined friends), you can look at it full size, so that the screen width is the

same as the width of the actual piece of lumber. If your monitor is big enough, you could even view a 2 x 12 (38 x 286) on your screen at its real size. Sooner rather than later, though, it becomes uneconomical to keep getting a bigger monitor as you need to draw bigger things.

Luckily, the ZOOM command lets you increase or decrease the magnification of your drawing objects through a number of options, which we discuss in this chapter. In addition to zooming in and out of drawings, another couple of display commands will come in handy in your drawings: PAN and VIEW. PAN lets you move around in the drawing without changing the magnification. The VIEW command displays a dialog box in which you can save and restore named views.

Table 3-1 lists AutoCAD’s 2D display commands in alphabetical order, together with locations for finding them and general descriptions of what they do.