Each object in AutoCAD Civil 3D has a base layer on which the object physically resides, and component layers that control the display of object components, such as surface triangles or contours.
The base layer is defined in the Drawing Settings or at creation time. The component layers are defined in the object styles.
Object Base Layer
You specify the default base layers for objects on the Object Layers tab of the Drawing Settings dialog box.
When you create an object, you can accept the default or specify a new layer. The base layers are used only for the main object types, such as surfaces and alignments.
Because the object physically resides on the base layer, you can control object visibility by changing the layer state. For example, if you turn off the base layer for surfaces, all surfaces are turned off in the drawing.
To append an object name to the layer name for that object, add an asterisk (*) as a prefix or suffix to the base layer name.
For more information, see Object Layers Tab (Drawing Settings Dialog Box).
Object Component Layers
You specify component layers on the Display tab of the <object> Style dialog box. The following example shows layers used for alignment components:
The component layers, such as C-ROAD-LINE, allow you to work with objects as if parts of them are located on different layers. For example, to turn off only the alignment lines, you can turn off the C-ROAD-LINE layer in the drawing.
Objects are physically created on the base layer, but the display of components is governed by the associated component layers. Each object component uses the visibility settings for the component layer (such as on/off), as well as the color, linetype, lineweight, and plot style for the layer if the various Component Display settings are set to ByLayer.
Layer 0 has a special meaning in the Component Display settings. When the layer is set to 0, the object base layer is used for that component. For example, if the alignment base layer is C-ROAD, and the layer for the Line component is set to 0, then the alignment lines behave as if they are located on layer C-ROAD (not layer 0).
For more information, see Display Tab (Style Dialog Box).
Setting Up Styles Using the ByLayer Setting or Specific Settings
If you are accustomed to controlling objects by manipulating layers, you may want to set the various object style Component Display settings to ByLayer. Then you can simply change the layer settings using the AutoCAD Layer command rather than editing separate styles to change the color, linetype, lineweight, or plot style of an object component.
Using the ByLayer settings provides more control over object display to people viewing AutoCAD Civil 3D drawings in object-enabled AutoCAD.
However, if you want the object to always have the same settings regardless of component layer settings, you can set specific Component Display settings.
For more information, see Using ByLayer and ByBlock to Assign Display Values.