Background Layers
A DXF file can be imported as a background layer and used for the graphical input of objects. In contrast to the DXF import (see Chapter 12.5.2) where the complete model is converted into nodes and lines and loaded, background layers represent a sort of transparent sheet for specific modeling.
It is possible to use several background layers in a model.
To open the dialog box for creating a new background layer, use the menu option
- Insert → Background Layer
or the shortcut menu in the Data navigator.
The Open dialog box from Windows appears. Enter the directory and the name of the DXF file.
Click the [Open] button to access the Background Layer dialog box.
The No. of the layer is automatically allocated by the program. In the Background Layer Description dialog section, you can enter any name, making later assignment easier.
Use the 
button to access more settings for the DXF import.
This dialog box is depicted and explained in Figure 12.50.
After clicking [OK], RFEM imports the layer, which appears gray in the background of the work window. In this line model, you can now define nodes, lines, and members.
Make sure that the object snap for background layers is activated so that you can arrange objects on the points available in the layer. To activate the object snap for DXF points, use the [DXF] button in the middle of the status bar. Alternatively, select Tools → Work Plane, Grid/Snap, Object Snap, Guidelines in the menu or use the corresponding toolbar button.
In the Background Layers dialog tab of the Work Plane and Grid/Snap dialog box, you can not only activate the snap but also create new layers, as well as edit, hide, or display them.
To open the edit dialog box, double-click the background layer or the relevant entry in the Data navigator (see Figure 11.67). You can also use the Background Layers dialog tab available in the dialog box for work plane settings (see Figure 11.71): After selecting the layer in the list, you can [Edit] it.
You can also delete a background layer with the Data navigator.
To move, rotate, or mirror a background layer, select it first. Then you can apply the function described in Chapter 11.4.1.
The Display navigator controls the display of background layers in detail.
