AutoCAD Platform Customization. Ambrosius Lee

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      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.

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 СКАЧАТЬ