The Revolve command is conceptually the same as the Extrude command: you have a 2D base shape but instead of extruding it, it is revolved around a specified axis and with a given angle. The same results can be created using Extrude but you will have to draw the exact path, and it is much easier to just specify the axis of rotation and the angle, as will be shown in this section. To start the Revolve command you can type the command name REVOLVE, or just type REV then press Enter. Alternatively, you can click on the Revolve button found in the Create panel in the 3D Basics workspace, and if you are using the 3D modeling workspace, you will find the Revolve 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 Revolve command will create a 3D solid or a surface. Generally, if you select a surface or a 2D closed shape (like a circle, a polygon, or a closed polyline), the Revolve 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 revolved object will be a surface, as shown in the following step-by-step example:

1. After starting the Revolve command, select the object or the objects that will be revolved, then press Enter to end the selection stage.
2. Specify the revolving axis by specifying two points. You can use the mouse or type the coordinates of the two points using the keyboard.

3. Move the mouse specify the revolve angle. Alternatively, you can enter the angle value using the keyboard.
4. When you arrive at the required revolve angle, click or press Enter to finish.

The following figure shows an illustration for the previous steps:

There is a number of options associated with the Revolve command. These options allow for alternative methods and settings. The first set of options appears in the command bar right after you start the Revolve 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 Revolved object, either to be a solid or a surface. By default, when you select a closed shape or a surface, the Revolve command will produce a solid. This option allows you to create a surface even if the revolved object is a closed shape or a surface.

The second set of options appear after you select the objects to be revolved. This set contains four different options as shown in the following figure:

The first one is called Object. To select it, you can just type O and press Enter, or you can click on the option name in the command bar. This option allows you to select an object to be the revolve axis as shown in the following step-by-step example:

1. Start the Revolve command, select the object to be revolved, and press Enter to end the selection stage.
2. Type O then press Enter to activate the Object option.
3. Select an object to be the revolve axis (for example, the small line).
4. Move to determine the revolve angle, then click to finish.

The following figure is an illustration of the previous steps:

The next options in the second set are called X, Y, and Z. To select any of them, just type the option name then press Enter, or you can click on the option name in the command bar. These options allow you to use the user coordinate system (UCS) axis as the revolve axis.

The third option set appears after you specify the revolve axis. This set contains three options as shown here:

The first one is called Start angle. To select it you can just type ST and press Enter, or you can click on the option name in the command bar. By default the Revolve command will start the revolution from the selected object. This option allows you to set an angle between the object you selected and the start of the revolved objects as shown in the following step-by-step example:

1. Start the Revolve command, select an object to be revolved, then specify the revolve axis.
2. After you specify the revolve axis, type ST and press Enter to activate the STart angle option.
3. Move the mouse cursor to set the required start angle then click. Alternatively, you can type the desired start angle using the keyboard then press Enter.
4. Specify the revolve angle using the mouse movement or the keyboard. Notice that the angle will start from the specified start angle.
5. After you arrive at the required angle, click again or press Enter to finish.

The following figure shows an illustration for the previous steps:

The next option is called Reverse. To select this option, you can type R and press Enter, or you can click on the option name in the command bar. During the specification of the revolve angle, activate this option to reverse rotation angle direction as shown in the following figure:

The last option is called Expression. To select this option you just type E then press Enter, or you can click on the option name in the command bar. This option allows you to enter a formula or an expression that will be calculated and the result will be used as the revolve angle.

By default, the revolved objects will be deleted after the Revolve command ends. You can control whether to delete these objects or not using the DELOBJ system variable, which you can access just by typing DELOBJ and pressing Enter, and the current value of the DELOBJ system variable will be displayed for you to type the new value and press Enter again. For more details about the DELOBJ system variable, please refer to the Using the Extrude command section of this chapter.

Now that we have learned how to use two commands of the 2D-to-3D conversion group, let's take a look at the third one, which is the Sweep command.