Duplicating Objects

Depending on the specific command you use, you can create exact duplicates using the COPY, OFFSET, MIRROR, and ARRAY commands—and even the Clipboard—to make copies of selected objects.

Copying Objects

With the COPY command, you can make exact duplicates of selected objects. After you select the objects to be copied, you are prompted to specify the base point of the displacement and a second point. The distance and direction from the first point to the second point are calculated and used to locate the new copied objects. To help you visualize the results, pick a base point on one of the objects to be copied (for example, the center of a circle). The second point then becomes the point on the copies that corresponds to the first point on the originals.

Just as you can use the displacement function with the MOVE command, if you know the exact displacement, you can enter it at the prompt for the base point when you’re using the COPY command. You force the COPY command to interpret your entry as a displacement by pressing Enter again at the prompt for the second point. (In other words, you do not define a second point.)

By default, the COPY command makes one copy of the selected objects. You can, however, use the Multiple option to make multiple copies of the selected objects. After you select the Multiple option and choose an initial base point, the COPY command repeatedly prompts you to select a second displacement point to locate the copies. Press Enter to end the multiple copy process.

The following exercise illustrates using the MOVE, COPY, and ROTATE commands.

Exercise 10.4 Editing the Floor Plan with Basic Editing Commands

When the objects you have are valid and all you need are more copies of them, using the COPY and OFFSET can certainly help you out.

Duplicating Objects with OFFSET

With the OFFSET command, you can create a copy of the selected object and have AutoCAD offset it a specified distance from the original object. At the initial prompt, you have the choice of entering the offset distance or using the Through option. To enter a specific offset distance, type the distance (or pick two points on the screen) at the Specify offset distance: prompt. Thereafter, you can select one object at a time to create an offset from the duplicate and choose the side of the original on which you want the duplicate made.

If you choose the Through option, you pick a point the offset object is to go through after you select the object you want to copy. The distance along a perpendicular from the point that you pick to the original object serves as the offset distance. The copy made by the OFFSET command might or might not be an exact duplicate of the original. Table 10.1 lists the various types of objects you can choose with the OFFSET command and the shape of the resulting copy. The differences between the sizes and lengths of the resulting copies can be attributed to the side of the original object specified for the offset copy.

Creating a Mirror Image

With the MIRROR command, you can create a mirror image copy of the selected objects. After you select the objects to be mirrored, you are prompted to pick two points to define the mirror line. The mirror line is the line, or axis, about which the mirror image is created. The mirror line itself does not have to be a physical line in the drawing.

The only option you have with the MIRROR command is whether the original objects should be deleted. The default is to not delete the original objects.

By default, the copy of text and mtext objects will appear backward, as if you were holding a page of text up to a mirror. To prevent text from being reversed in the mirrored objects, set the system variable MIRRTEXT to 0 before you begin the MIRROR command.

Creating Arrays of Objects

The ARRAY command is used to make multiple copies of selected objects so the copies are arranged in rows and columns (a rectangular array) or in a circular arrangement (a polar array).

Creating a Rectangular Array

If you choose to create a rectangular array (see Figure 10.17), you are prompted to enter the number of rows and columns, the distance between adjacent rows, and the distance between adjacent columns.

Generally, you type the row and column distances. You can, however, specify the distances with a window (referred to as a “unit cell”) by picking the two corner points of the window at the Unit cell or distance between rows (-): prompt. The height of the window is used as the distance between rows, and the width of the window is used as the distance between columns.

If you enter a negative distance for the distance between columns, the columns of the array are created in the negative direction along the X axis; otherwise, they are created in the positive X direction. Likewise, if you enter a negative distance for the distance between rows, the rows are created in the negative direction along the Y axis; otherwise, they are created in the positive Y direction. If you choose to use a unit cell to specify the distances, the direction in which the rows and columns are created is determined by the direction from the first window point to the second window point.

The ARRAY command has been enhanced to use a dialog box interface. It provides real-time feedback about your pending array procedure in its sample area and even a Preview option. The traditional ARRAY command has been renamed -ARRAY and is still a viable method. Fortunately, any AutoLISP and Script files used automatically utilize the command-line version and function like previously.

In the next exercise, you create a rectangular array. You then use the MIRROR and OFFSET commands to duplicate the objects to the drawing.

Exercise 10.5 Creating a Rectangular Array of Duplicates

1.	Start AutoCAD and open the drawing file CHAP10-1.DWG from the accompanying CD. This drawing may currently be open from a previous exercise.
2.	Choose Named Views from the View pull-down menu. Then select the view named OFFICE-C, click the Set Current button in the View Control dialog box, and click OK.
3.	Choose Array from the Modify toolbar or the Modify pull-down menu.
4.	Verify that Rectangular Array is selected and pick it if needed.
5.	Type 3 for the number of rows and 4 for the number of columns.
6.	Type 10' for the Row offset and -12' for the Column offset distance.
7.	Then click the Select Objects button. The dialog dismisses and allows you to select the desk and chair and press Enter. When done, the dialog will reappear.
8.	When complete, you can review your settings and preview for accuracy and then click OK (see Figure 10.18) to end the command. The rectangular array is created. Figure 10.18. The Array dialog offers various controls for creating object arrays.
9.	From the Modify pull-down menu, select the MIRROR command. Select the cabinets, as shown in Figure 10.19. Figure 10.19. The cabinets used in the MIRROR exercise.
10.	At the Specify first point of mirror line: prompt, use the Endpoint osnap and pick a point near .
11.	At the Specify second point of mirror line: prompt, type @1<0 to define the second point about which to mirror. AutoCAD duplicates the cabinets into the room adjacent to the current one.
12.	Choose Named Views from the View pull-down menu. Select the view named OFFICE-B, click the Set Current button in the View Control dialog box, and click OK.
13.	In this room, you need to increase the size of the conference table. From the Modify pull-down menu, choose Offset. At the Specify offset distance or [Through]: prompt, type 12 .
14.	At the Select object to offset or <exit>: prompt, choose anywhere on the circle edge. Then at the Specify point on side to offset: prompt, pick a point outside of the circle. This indicates which side of the object you want to offset toward. At this point, you can close this drawing without saving.

As you can see developing large quantities of objects is very simple using the ARRAY command.

Creating a Polar Array

If you choose to create a polar array, you are required to specify the center point about which the copies are made, the number of items (or copies) to be created (including the original), and the angle to fill, as shown in Figure 10.20.

For example, if you specify six items and enter 180 degrees as the fill angle, the angular separation between adjacent items is 180 divided by 6, or 30 degrees. If you specify a positive fill angle, the copies are made in a counterclockwise direction; otherwise, the copies are made in a clockwise direction by default (see Figure 10.21).

As with rectangular arrays, the Array dialog provides a visual guide to your Polar array sequences. Experiment with the various controls to see how they relate and can be used for all your polar arrays. You can also use the command-line version by typing -ARRAY and pressing Enter.

The final area of the Array dialog gives you the choice of rotating or not rotating the copies. If you check the option (the default), the copies are rotated about the specified center point of the array. If you uncheck the box, the copies are not rotated about the center point but are copied about a reference point in the selection set and determined from the last object selected. If a window of some type is used to select the objects, the last object in the selection set is picked arbitrarily: The reference point that is selected is based on the type of object (see Table 10.2).

As long as you use the default setting for rotating the copies, the resulting polar array will appear to be symmetrical regardless of the objects selected.