Modify

Perform operations such as select, erase, move, and trim on the objects in a drawing.

The most common of these tools are located on the Modify tab in the Command palette.

Select Multiple Objects

You can select individual objects by simply clicking them. However, instead of selecting each object individually, you can click in an area to create a selection box.

If your selection box is created from right to left, it will make a crossing selection, and if your selection box is created from left to right it will make a window selection.

• With a crossing selection, any objects within or touching the green area are selected.
• With a window selection, only the objects completely contained within the blue area are selected. The result is called the selection set, which is the set of objects that will be processed by a command.

Erase

To erase an object, use the ERASE command. You can enter E in the Command window, or click the Erase tool. When you see the cursor change to a square pickbox, click each object that you want to erase, and then press Enter or the Spacebar.

Move and Copy

Here's how you would use the COPY command to lay out a row of decorative tiles. Starting with a polyline that represents its shape, you need to make copies that are 1/8" apart.

You click the Copy tool or enter CP in the Command window to start the command. From here, you can choose between two methods, depending on what's more convenient. You will use both these methods frequently.

The Distance Method The second tile needs to be a total of 9-7/8" + 1/8" = 10" to the right of the original tile. So, you select the tile, press Enter or the Spacebar to end your selection, and click anywhere in the drawing area (1). This point does not have to be located on the tile.

Next, you move your cursor to the right, relying on the polar tracking angle to keep the direction horizontal, and then enter 10 for the distance. Press Enter or the Spacebar a second time to end the command.

The specified distance and a direction from the point (1) is applied to the tile that you selected.

The Two Points Method

Another method, one that you will often use when you don't want to add numbers together, requires two steps. You start the COPY command and select the tile as before, but this time you click the two endpoints as shown. These two points also define a distance and direction.

Next, to add the 1/8" space between the tiles, click the Move tool or enter M in the Command window. The MOVE command is similar to the COPY command. Select the newly copied tile, and press Enter or the Spacebar. As before, click anywhere in the drawing area and move your cursor to the right. Enter 1/8 or .125 for the distance.

For example, enter the MOVE command. Use a selection method to select the objects in the rectangle (1). Specify a base point (2) and a second point (3) to determine the distance and direction of the move. Press Spacebar or Enter to see the results.

The distance and direction determined by the endpoints at 2 and 3 in the illustration are applied to the rectangle at the right. This is a good way to specify existing distances for moving and copying objects.

Create Multiple Copies

Similarly, you can use the two-points method as a repeating sequence. Let's say that you want to make more copies of the circle at the same horizontal distance. You start the COPY command and select the circle as shown.

Then, using the Center object snap, click the center of circle 1, followed by the center of circle 2, and so on.

For larger numbers of copies, try experimenting with the Array option of the COPY command. For example, here's a linear arrangement of deep foundation piles. From a base point, you specify number of copies and the center-to-center distance.

Offset

Most models include a lot of parallel lines and curves. Creating them is easy and efficient with the OFFSET command.

1. Click the OFFSET tool or enter O in the Command line.
2. Select the object to offset.
3. Point the cursor in the direction you want to offset the object and specify the offset distance. Either enter a value using dynamic input, or click to specify the new location.

Trim and Extend

A popular technique is to use the OFFSET command in combination with the TRIM and EXTEND commands. Trimming and extending are some of the most commonly used operations. Click the TRIM or EXTEND tool or enter TR for TRIM or EX for EXTEND in the Command line.

In the following illustration, let's say you want to extend the lines that represent the steps for this deck. You start the Extend command and select the objects to be extended (near the ends to be extended) and then press Enter or the Spacebar to end the command.

As a result, the lines are extended to the first boundary that they encounter.

The TRIM command follows the same steps, except that when you select the objects to trim, you select the portions to trim away.

Mirror

The following illustration comes from a tile project. The walls in this residential bathroom are flattened out to be able to lay out the tile pattern and estimate the number of tiles needed.

You can save a lot of work by taking advantage of the symmetry between the left and right walls. All you need to do is create the tiles on one wall and then mirror the wall across the center of the room.

In the example below, you start the MIRROR command (or enter MI in the Command line), use window selection (1 and 2) to select the geometry on the right wall, press Enter or the Spacebar, and then specify a mirror line (3 and 4) corresponding to the centerline of the bathroom.

Finally, decline the option to "Erase source objects" by pressing Enter or the Spacebar.

Fillet

The FILLET command creates a rounded corner by creating an arc that is tangent to two selected objects. You can create a fillet between most types of geometric objects, including lines, arcs, and polyline segments. In this example, an arc is created tangent to the selected lines, which are trimmed to meet the endpoints of the arc.

To fillet objects:

1. Click FILLET or enter F in the Command line.
2. Choose Radius in the command options, enter a radius, and press Enter. This number will be the radius of the arc between the two objects you fillet.
3. Select the first object.
4. Select the second object.

If the objects intersect, the objects are trimmed based on their intersection point. If the objects do not intersect, the objects are extended until they intersect.

Explode

The EXPLODE command (enter X in the Command line) disassociates a compound object into its component parts. For instance, if you want to turn a polyline from one object into a series of individual lines, you can explode them.

After you explode a compound object, you can modify each resulting individual object.

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