You can find the Mirror command button in the Modify panel on the Home tab in both the 3D Basics and the 3D Modeling workspaces, as shown in the following diagram:

The mirror command will work normally with 3D objects, but with limitations. You select the objects, and then you specify the mirror line as usual, regardless of the object position. The mirror line will be created in the UCS XY plane, and the mirror plane will be created by passing through that line and perpendicular to the XY plane.

It is impractical to use the mirror command in the 3D perspective view. If you are going to use it, set the view to top or bottom standard views.

The 3D version of the mirror command is called 3D mirror. The 3D mirror command performs the same function as the standard mirror command, but it overcomes the limitations of using the latter with 3D objects. You can find the 3D Mirror command button in the Modify panel on the Home tab in both the 3D Basics and the 3D Modeling workspaces, as shown in the following screenshot:

The 3D mirror command used is shown by means of the following step-by-step example:

1. After you start the command, select the object(s) to be mirrored and then press Enter to end the selection phase.
2. Specify the mirror plane. The default method involves determining three points. Click to specify the three point locations, as shown in the diagram.
3. As with the regular mirror command, you have the option to either keep or erase the original object.
4. The mirror object will be created and the command terminates.

The following diagram is an illustration of the previous steps:

As shown in the previous example, you can set the mirror plane to be co-planar with any general 3D plane, thereby eliminating the limitation of the regular mirror command.

There are alternative methods/options to specify the mirror plane. In the example, the default 3point method was used. The other methods will appear in the command bar, as shown here:

These options are explained as follows:

• Object: The first option is called Object. To select it, click on the option name in the command bar, or you can just type O and press Enter. This option allows you to select a planar object, such as a circle, a polyline, or a rectangle, as the mirror plane, as shown in the following diagram:

• Last: The second option is called Last. To select it, click on the option name in the command bar, or you can just type L and press Enter. This option will use the mirror plane used the last time the command was activated.
• Z-axis: The third option is called Z-axis. To select it, click on the option name in the command bar, or you can just type Z and press Enter. The mirror plane is created by determining a point on the mirror plane, and then another point is specified. The first and the second points will form a vector, which is the Z-axis of the mirror plane, as shown in the following diagram:

• View: The fourth option is called View. To select it, click on the option name in the command bar, or you can type V and press Enter. This option will use the viewport viewing angle as the direction of the mirror plane, and then you specify a point to determine the location.

The next options are called XY, YZ, and ZX planes. These three options will set the mirror plane to be parallel to the three main UCS planes.

The last option is the default 3points method, which was demonstrated in the previous example.