Connecting objects and Styles in autocad

The word object is usually considered pretty generic, but in the world of Civil 3D it means something very specific. A Civil 3D object is an intelligent piece of your design model that stores information about itself and has the ability to interact with other objects in the drawing. Another characteristic of a Civil 3D object is that it is affected by a Civil 3D style. A Civil 3D style is a collection of settings that con- trol the appearance and behavior of a Civil 3D object.

Recap of important Definitions

A Civil 3D object is an intelligent piece of your design model that stores informa- tion about itself and has the ability to interact with other objects in the drawing.

A Civil 3D style is a collection of settings that control the appearance and behavior of a Civil 3D object.

The relationship between objects and styles is one of several key relationships that you must understand and be able to take advantage of when using Civil 3D. Here are a few examples of Civil 3D objects that you’ll encounter in this book as well as in a production environment:

Surface  A 3D model typically used to represent the shape of the ground, either existing or proposed

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Alignment A series of 2D lines, arcs, and spirals typically used to represent a linear feature such as a road centerline

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Profile   A series of lines and curves that represent changes in elevation along  an alignment

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Parcel   A closed shape typically used to represent a legal property boundary

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What is Elevation?

Depending on where you are in your civil engineering or surveying learning experience, the term elevation may be foreign to you. One way to visualize this concept is to think of it in terms of a piece of grid paper laid out over an area of land with the horizontal lines running west to east and the vertical lines run- ning south to north. Elevation would be coming straight up out of the paper. So, the top of a hill would have a greater elevation than the bottom of a ravine. Another way of thinking about this is in terms of an XYZ coordinate system. X and Y would be the lines on the grid paper and Z (elevation) would be coming out of it. Because Civil 3D combines general AutoCAD® software and civil engineering commands, elevation and the z-axis are the same. One more thing—depending on where you live in the world, it may be appropri- ate to use the word level instead of elevation.

Each of the objects listed previously can be controlled by styles. For example, surface styles can be used to show a surface in many forms, including contour lines, a 3D grid, a series of arrows pointing downhill, shading representing differ- ent elevation ranges, and many more (see Figure 2.1). In addition to changing the overall appearance of an object, styles can control specific details that differ slightly between similar configurations. For example, in one case there may be surface con- tours that need to be shown on an existing layer, while in another case the same contours are shown on a proposed layer (see Figure 2.2). The configuration is the same (contours), but the way that configuration is displayed (which layer) is differ- ent between two different styles.

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Fi G u RE  2.1    The same surface is shown in four different configurations using four different styles (from left to right): using contours, elevation banding, TIN lines and contours, and slope arrows.

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Fi G u RE  2.2    The contours on the left are displayed using proposed layers that are typically darker and more prominent. The contours on the  right are displayed using existing layers that are typically lighter, so they  appear more as background information.
To use styles to change the appearance and behavior of Civil 3D objects, follow these steps:
1.  Open the drawing named Objects and Styles.dwg located in the Chapter 02 class data folder. The plan view of the surface in the left viewport should appear similar to the first image shown in Figure 2.1.
2.  Click one of the contour lines in the drawing to select the surface object.

3. Click Properties on the Home tab of the ribbon.

4. In the Properties window, change the Style property to Elevation Banding (2D). The surface will display as colored bands, representing different ranges of elevations, similar to the second image in Figure 2.1.

5. Change the Style property to Contours & Triangles. The surface should now appear similar to the third image in Figure 2.1. The triangles are the fundamental framework of the surface and give it the shape that it has.

What Are Contours?

Contours are lines that are used to represent topography or changes in elevation across the ground. Most people experience contours in things like trail maps that cover a large area (square miles or square kilometers) in comparison to what we typically see in Civil 3D. By definition, contours are lines that connect points of equal eleva- tion. If you took a giant horizontal blade and passed it through the ground at equal elevation intervals, you would get contour lines. In flat areas, the lines would be far apart, and in steep areas, the lines would be close together. With practice, you can look at a contour map and visualize the 3D shape of the land that the map represents.

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6. Change the Style property to Contours 1′ and 5′ (Design) (0.5m and 2.5m (Design)). The surface should now resemble the left image in Figure 2.2.

7. Change the Style property to Contours 1′ and 5′ (Background) (0.5m and 2.5m (Background)). This is the style that was assigned to the surface when you first opened the drawing. Note that both of the last two styles displayed contours but on different layers.

8. With the surface still selected, click the Tin Surface: Existing Ground ribbon tab and then click Surface Properties a Edit Surface Style.

9. Click the Display tab, and then click the color column next to Major Contour.

10. Choose a noticeable color and click OK. Click OK again to return to the drawing. Some of the contours will change to the new color as a result of this change.

As you worked through the previous exercise, did you notice that no extra steps were required to update or redraw the surface when a new style was assigned or the style was edited? The effect was immediate—as soon as you modified the assigned style or assigned a different style, the appearance of the surface changed. This is because of a dynamic relationship between the object and its style, a relationship that is honored throughout the software.

Editing a Style vs. Assigning a Different Style

In steps 5 through 7 of the previous exercise, you changed the appearance of the surface by assigning a different style to it. This is the way to do it 99 percent of the time. In steps 8 through 10, you edited the style that was already assigned to the surface. Editing styles is typically the responsibility of a CAD manager. In fact, in many companies, end users are not permitted to modify or create styles. However, it is still important to understand that when a style is modified, any object using that style will change its appearance or behavior to honor the new version of the style.

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