AutoCAD Platform Customization. Ambrosius Lee

Figure 2.5 Managing linetypes and scales

      Lineweights

      By default, all linework in a drawing is displayed as a single pixel in width onscreen unless the object is a polyline with a specified width or you use lineweights. Both layers and objects have a Lineweight property, which can be used to control the width or thickness of the linework for the objects in a drawing. Controlling the width of the linework allows you to emphasize the walls of a building or the edges of the main elements in a design while putting less emphasis on dimensions and other annotation objects. The correct balance of lineweight widths used in a drawing can improve how objects within the design are communicated to a client or contractor.

      Lineweights are commonly used to control the width in which an object should appear when plotted or printed, but they can also be used to affect how objects are displayed onscreen. If you want to display lineweights onscreen, you can use the Show/Hide Lineweight option on the application's status bar or change the value of the lwdisplay system variable.

      The display of lineweights is different based on whether you are working on the model or in a named layout. The following explains the differences in the way lineweights are displayed.

      Model Layout Independent of the current zoom scale, lineweights are measured in pixels. No matter the current zoom scale of the current view, the width of the linework never increases or decreases when zooming in or out.

      Named Layout Lineweights are displayed based on the current zoom scale. Just like placing a magnifying glass over a sheet of paper, the magnification of the drawing makes the linework appear thicker; the same happens when zooming in or out on a layout.

You can modify the settings that affect the display of lineweights in a drawing by using the Lineweight Settings dialog box. See Figure 2.6; the Windows version is displayed on the left, and the Mac OS version is on the right. The Default (Windows) or New Layer Default (Mac OS) drop-down list controls the lineweight used by the Default value of the Lineweight property for layers and objects, which can also be set with the lwdefault system variable. Use the Adjust Display Scale (Windows) or Preview Scaling (Mac OS) slider to control the lineweight scale of all lineweights on the Model layout. The other area that may have some significance is the Units For Listing (Windows) or Units (Mac OS) section, which controls the values in which lineweights are expressed in the AutoCAD user interface: millimeters (mm) or inches (in). Units for listing lineweights can also be controlled with the lwunits system variable.

Figure 2.6 Controlling the display of lineweights

      Transparency

      Transparency gives you the ability to see through to what is below or beyond an object. Objects can have a transparency value of 0 (fully opaque/solid) to 90 (nearly fully transparent). Unlike lineweights, the display of transparency is much more useful onscreen in a complex drawing, but it can have an impact on the display of your drawing based on your workstation's hardware. You can use the Show/Hide Transparency option on the application's status bar or change the value of the transparencydisplay system variable.

      Controlling Output with Plot Styles

      While layers and object properties control much of the way objects are displayed onscreen, you can use plot styles to override those values to alter the way objects are plotted or printed. Plot styles can also be used to affect the way objects appear onscreen if the Display Plot Styles option is enabled in the Page Setup dialog box.

      Plot styles are available in two styles: color-dependent and named. When you are using color-dependent plot styles, the name of the plot style is fixed based on the color value assigned to an object or the layer in which an object is placed. Assigning a named plot style to a layer or object is similar to assigning a linetype: first you specify which named plot style file you want to use, and then you specify the plot style you want to assign to the layer or object. For more information on plot styles and how to create them, see Chapter 1, “Establishing the Foundation for Drawing Standards.”

      Accessing Layer Settings

Besides the properties for a layer that are accessible from the Layer Properties Manager (Windows) or Layers palette (Mac OS), several other settings affect the way layers look or behave in the drawing window. In AutoCAD for Windows, you can use the Layer Settings dialog box (see Figure 2.7) to change the current layer settings, but you can also use a few system variables to change some of these settings. In the dialog box, the settings with a small drawing file icon next to them (the blue-and-yellow sheet of paper) indicate that the setting is stored with the drawing.

Figure 2.7 Changing layer settings affects the way you work with layers in the drawing window and user interface.

      In AutoCAD for Mac, there is no equivalent to the Layer settings dialog box (many of the same features in the Windows product are not available on Mac OS), but there are a few settings that you can access using system variables and commands to change your experience.

      The Layer Settings dialog box in AutoCAD on Windows can be displayed by doing the following:

      1. On the ribbon, click Home tab ➢ Layers panel ➢ Layer Properties.

      2. In the Layer Properties Manager, click Settings, located near the upper-right corner.

      Fading Objects on Locked Layers

      Locking a layer ensures that the objects on that layer are not accidentally selected when editing other objects in a drawing, but they still can be used as reference geometry. To help make it easy to identify when a layer is locked, AutoCAD fades the objects on a locked layer so they are less prominent in the foreground. You can toggle this feature on and off, as well as control the amount objects are faded. By default, objects on locked layers are faded by 50 percent.

      To change the amount a layer is faded, you can do one of the following:

      • In the Layer Settings dialog box (see Figure 2.7), in the Isolate Layer Settings section, choose Lock And Fade, and then drag the Locked Layer Fading slider. If the slider is not enabled, click the Locked Layer Fading toggle (the stack of three papers with a lock icon) and then drag the slider. Click OK (Windows).

      • On the ribbon, select Home tab ➢ Layers panel, click the panel's title to expand the panel, and drag the Locked Layer Fading slider. If the slider is not enabled, click the Locked Layer Fading toggle (the stack of three papers with a lock icon) and then drag the slider (Windows).

      • At the command prompt, enter laylockfadectl and press Enter. Enter a new fade value and press Enter. Entering a negative value disables the fading of objects on a locked layer (Windows and Mac OS).

      Isolating Objects; Turning Off or Locking

      Isolating layers allows you to quickly turn off or lock layers, work with objects on other layers in the drawing, and then quickly restore the previous state of the layers in the drawing. Layers can be isolated with the layiso command, and isolation can be reversed (unisolated) with the layuniso command. You can control the default isolation mode that the layiso command uses.

      To change the isolation mode of the layiso command, you can do one of the following:

      • In the Layer Settings dialog box (see Figure 2.7), in the Isolate Layer Settings section, choose Lock And Fade to lock the layers when using layiso or click Off to turn them off instead. When you