Sweep is very similar to the Extrude command—a 2D-cross section shape is extruded (or swept) along a specified path, but the difference here is that if the 2D base shape and the path are separated, the Extrude command will create the object at the 2D location, while the Sweep command will create it at the path location. In addition to that, the Sweep command has more options for the behavior of the base shape along the path such as the Alignment and the Twist angle options, which are not present in the Extrude command. To start the Sweep command you can type the command name SWEEP, or just type SW then press Enter. Alternatively, you can click on the Sweep button found in the Create panel in the 3D Basics workspace, and if you are using the 3D modeling workspace, you will find the Sweep button in the Modeling panel under the Home tab, or in the Solid panel under the Solid tab, as shown in the following screenshots:

Depending on the selected object, the Sweep command will create a 3D solid or a surface. Generally, if you select a surface or a 2D closed shape (such as a circle, a polygon or a closed polyline), the Sweep command will create a 3D solid, else if the selected object is an open 2D shape (such as a line or an open curve), the extruded object will be a surface, as shown in the following steps:

1. After starting the Sweep command, select the object that will be swept, then press Enter to end the selection stage.
2. Click to select a sweeping path; the sweep path can be a line, a polyline, or a curve.
3. Once you click, the swept volume will be created.

The following figure shows an illustration for the previous steps:

There are a number of options associated with the Sweep command. These options allow for alternative methods and settings.

The first set of options appear in the command bar right after you start the Sweep command, as shown in the following figure:

This set contains only one option called Mode. To select this option, you can just type MO and press Enter or you can click on the option name in the command bar. This option is used to determine the type of the Swept object, either to be a solid or a surface. By default when you select a closed shape or a surface, the Sweep command will produce a solid. This option allows you to create a surface even if the Swept object is a closed shape or a surface.

The second set of options appear after you select the objects to be swept. This set contains four different options as shown here:

The first one is called Alignment. To select it, you can just type A and press Enter, or you can click on the option name in the command bar, then you choose whether to set it to Yes or No. Yes is the default and by choosing that, the swept object is automatically aligned to be perpendicular to the sweep path.

If you select No, the sweep object keeps its relative angle with the sweep path as shown in the following figure:

The next option in the second set is called Base point. To select this option, type B then press Enter, or you can click on the option name in the command bar. This option allows you to set the sweeping base point. By default, the swept shape is automatically moved so that its center point is on the sweep path, or in other words the center point of the selected shape is used as the sweep base point. When you activate the base point option, you can click to specify or type the coordinates of a new sweep base point.

The third option is called Scale. To select this option, type S then press Enter, or you can click on the option name in the command bar. This option allows you to apply a scaling factor for the swept shape along the sweep path as follows:

1. Start the Sweep command, select the object to be swept, and press Enter to end the selection stage.
2. Type S to activate the Scale option.
3. Type the scaling factor and press Enter.
4. Click to select the sweep path, and the swept volume will be created. Notice that the scaling factor is applied at the side where the object was.

The following figure is an illustration of the previous steps:

The fourth option is called Twist. To select this option, you just type T and then press Enter, or you can click on the option name in the command bar. This option allows you to apply a gradual twist angle along the sweep path as follows:

1. Start the Sweep command, select the objects to be swept, and then press Enter.
2. Type T and press Enter to activate the Twist option.
3. Type the required twist angle and press Enter.
4. Select the twist path, and the swept volume will be created with the specified twist angle.

The following figure shows an illustration of the previous steps:

By default, the swept objects and the paths will be deleted after the Sweep command ends. You can control whether to delete these objects or not using the DELOBJ system variable. To access that, just type DELOBJ and press Enter, and the current value of the DELOBJ system variable will be displayed, then you can type the new value and press Enter. For more details about the DELOBJ system variable please refer to the Using the Extrude command section of this chapter.

We have learned about three commands in the 2D-to-3D conversion group, so let's now take a look at the fourth one, which is the Loft command.