The first type of surface in AutoCAD is a planar surface, which has no curvature. To start the planar surface command, you can type PLANESURF, or just use the short version and type PLA, and then press Enter. Alternatively, the Planar surface tool button is located in the Create panel on the Home tab in the 3D Basics workspace. If you are using the 3D Modeling workspace, you can find it in the Create panel on the Surface tab, as shown in the following screenshot:
The planar surface command can be used to quickly create planar surfaces using one of two available methods. The first method is limited to creating rectangular-shaped surfaces, where the surface is created by specifying two opposite corners for the rectangle. The second method allows you to create general planar surface shapes by using a closed 2D object. The following is an example of using the first (default) method:
- Start the planar surface command.
- Using your mouse, specify the first corner of the rectangular surface. Alternatively, you can type the coordinates using the keyboard and then press Enter.
- Specify the opposite corner, again, either by using the mouse or the keyboard.
- Once the second point is specified, the surface will be created and the command terminates.
The following diagram is an illustration of the previous steps:
If you select the rectangular planar surface created by the default method, you find four grab points on the corners. These points act just like base points, from which you can grab and move the planar object, as shown in the following diagram:
The second method available in the planar surface command can be accessed by choosing the Object option that appears in the command bar right after you initiate the command. To select it, click on the option name in the command bar, or you can just type O and then press Enter, as shown here:
This option allows you to create a planar surface, but you are not limited to rectangular shapes. You can select any closed 2D planar shape, such as a closed polyline, a circle, or a set of lines that create a closed shape. The following is an example of using the Object option:
- After starting the planar surface command, type O and then press Enter to select the Object option.
- Click on a closed shape, like the closed polyline shown in the example.
- Press Enter to confirm the selection. The surface will be created and the command terminates.
The following diagram is an illustration of the previous steps:
When using the Object option, you will have access to the surface associativity option. This option will be activated by default, and it behaves in a similar way to the associative option found in the hatch command. If you have selected the objects that are used to create the surface (the polyline in the previous example), and the surface associativity option is activated, you can use the associated object grab points (the polyline in the previous example) to modify both the polyline and the surface, as shown in the following diagram:
As mentioned earlier, the surface associativity option is turned on by default. To turn it off, you can click on the Surface Associativity tool button located in the Create panel on the Surface tab in the 3D Modeling workspace. If you turn it off before creating the surface, the created surface will have grab points just like the default rectangular surface option, but they will only act as base points, as shown here:
By default, the objects used to create the surface will be deleted once the planar surface command terminates. You can control weather to delete these objects using the DELOBJ system variable. To access this, just type DELOBJ and then press Enter. The current value of the DELOBJ system variable will be displayed. Then, you can type the new value and press Enter. For more details on the DELOBJ system variable, please refer to the extrude command section in Chapter 12, Conversion between 2D and 3D.
Now that we have learned about the first surface type, which is the planar surface, let's have a look at the second type, which is network surfaces.