AutoCAD Platform Customization. Ambrosius Lee

following explains what to do after you click on a column in the Layers palette or control in the Properties Inspector palette:

      • On (Visibility): Toggles the layer on or off. When set to Off, objects on the layer can still be selected using the All keyword at the Select objects: prompt, and the objects are regenerated when the drawing's display is updated.

      • Freeze: Toggles the freeze and thaw states of the layer. When set to Freeze, objects on the layer can't be selected using the All keyword at the Select objects: prompt, and the objects aren't regenerated when the display of the drawing is updated.

      • Lock: Toggles the lock state of the layer. The Lock setting restricts objects on the layer from being selected at the Select objects: prompt.

      • Color: Choose a color from the drop-down list or choose Select Color to display the Color Palette dialog box. Select a color value and click OK. For more information, see “Significance of Colors” later in this chapter.

      • Linetype: Choose a linetype from the drop-down list or choose Manage to display the Select Linetype dialog box. Select a loaded linetype and click OK. If the linetype you want to use is not loaded, click Load and load the layer first. For more information, see “Defining Appearance with Linetypes, Lineweights, and Transparency” later in this chapter.

      • Lineweight: Choose a lineweight from the drop-down-list. For more information, see “Defining Appearance with Linetypes, Lineweights, and Transparency.”

      • Transparency: Click and drag the slide to specify a new transparency value. For more information, see “Defining Appearance with Linetypes, Lineweights, and Transparency.”

      • Plot Style: Choose a plot style from the drop-down list.

      • Plot: Toggles the plottable state of the layer. Objects on the layer that is not plottable are displayed in the drawing window, but the objects are not part of the output when the drawing is plotted or printed.

      • New VP Freeze/Freeze In New Viewports: Toggles the freeze and thaw states of the layer when a new floating viewport is created on a named layout.

      • VP Freeze/Viewport Freeze: Toggles the freeze and thaw states of the layer in the current viewport.

      • VP Color, VP Linetype, VP Lineweight, VP Transparency, and VP Plot Style: These properties can be changed just like the properties without the VP prefix previously described.

      • Description: Edit the description of the layer. Adding a description can be helpful to those new to or unfamiliar with your CAD standards.

      TIP

      Right-click the column headings in the Layers palette to control the display of which columns you want to display. If there are properties that you commonly do not use, you can turn them off.

      5. Repeat steps 2–4 for each layer you want to create.

      6. Double-click one of the layers in the Layers list or choose one from the Layers drop-down list at the top of the palette to set it current.

      Significance of Colors

      The use of color in a drawing serves two distinct purposes. The first is to make objects easy to distinguish from each other, and the second is to control the way the objects in your drawing are output. A majority of drawings use color-dependent plot styles. However, that does not mean they are plotted or printed in color, just that each unique color in a drawing can be used to control not only the color of an object when it is output, but also several other object properties. In addition to color, plot styles can override the linetype, lineweight, and transparency (or screening) values that are assigned to an object directly or that it inherits from the layer. Object and layer colors do not affect the output of objects when you are using named plot styles, the other type of plot styles that AutoCAD supports.

From the Layer Properties Manager (Windows) or Layers palette (Mac OS), clicking the Color column of a layer allows you to display the Select Color dialog box or Color Palette (see Figure 2.4), respectively. This interface allows you to select from one of the AutoCAD index colors (255 unique colors), a true color value, or a color from one of the installed color books. The AutoCAD index colors are the most commonly used for both layers and objects because these values directly map to values in a color-dependent plot style (CTB) file. If you need to set an object's color directly, select the object and use the Color property on the Properties palette (Windows) or Properties Inspector (Mac OS).

Figure 2.4 Setting the color of a layer

      Defining Appearance with Linetypes, Lineweights, and Transparency

      Color is just one property of an object that affects how it appears onscreen and when it is output; the linetype, lineweight, and transparency properties also impact the way objects appear. These properties can be set by object using the Linetype, Lineweight, and Transparency properties on the Properties palette (Windows) or Properties Inspector (Mac OS). However, as I mentioned earlier, it is much more effective to let objects inherit property values from the layer they are placed on.

      Linetypes

      Linetypes help distinguish objects that make up your design from those that are used to annotate it by using gaps, dashes, and text in your linework. Common uses for linetypes are to indicate center lines that pass through the center of a circle or an arc, to show features that are behind or beyond an object with hidden or dashed lines, or even to designate where a utility line runs through a property by displaying text within the linework.

      The size of the dashes, gaps, and text in a linetype is determined by the linetype definition and two scale factors:

      • The global scale factor, which is set by the ltscale system variable

      • The linetype scale assigned directly to an object

      The global scale factor is often equal to or half the drawing scale that will be used to output the drawing. If your viewports are set to a scale of 1/4″ = 1′-0″, your drawing scale would be a factor of 48, which is calculated by the math statement of (1/4) × 12. Once you know the drawing scale, divide it by 2, and that will give you the range in which your global linetype scale should be – in this example, that range would be 24 to 48.

The predefined linetypes that come with AutoCAD are stored in the acad.lin and acadiso.lin files. You can create your own linetype definitions and store them in the LIN files that come with AutoCAD, or you can create your own LIN files. Creating custom linetype definitions is covered in Chapter 9, “Defining Shapes, Linetypes, and Hatch Patterns.” Linetypes must be loaded into a drawing with the Linetype Manager before they can be used. See Figure 2.5; the Windows version is displayed on top, and the Mac OS version is on the bottom. Once loaded, a copy of the linetype definition is stored in the drawing. When defining the layers in your drawing template files, only load the linetypes that are needed.