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Viewing an object in three dimensions lets you have a sense of its true shape and form. It also helps you conceptualize the design, which results in better design decisions. Finally, using three-dimensional objects helps you communicate your ideas to those who may not be familiar with the plans, sections, and side views of your design.

A further advantage to in three dimensions is that you can derive 20 drawings from your model, which might otherwise take considerably more’time with standard 20 drawing methods. For example, you could model a mechanical part in 3D and then quickly derive its top, front, and right-side views using the techniques discussed in this chapter.

AutoCAD offers two methods for creating 3D models: surface modeling and solid modeling. This chapter will introduce you to surface modeling. You’ll get a chance to explore solid modeling in Chapter 18

With surface modeling, you use two types of objects. One is called a 3D Face, which you will learn about later in this chapter. The other is the standard AutoCAO set of objects you’ve been using all along, but with a slight twist. By changing the thickness property of objects, you can create 3D surfaces. These surfaces, along with some 3D editing tools, let you create virtually any 3D form you may need.

In this chapter, you will use AutoCAD’s 3D capabilities to see what your studio apartment looks like from various angles.

Creating a 3D Drawing

By now, you are aware that objects have properties that can be manipulated to set color, line type, line weight, and layer assignments. Another property called thickness lets you turn two-dimensional objects into 3D forms. For example, to draw a cube, you first draw a square, and then change the thickness property of the square to some value greater than 0 (see Figure 15.1). This thickness property i~a value given as a z-coordinate. Imagine that your screen’s drawing area is he drawing surface. A z-coordinate of 0 is on that surface. A z-coordinate greater than 0 is a position closer to you and above that surface. Figure 15.2 illustrates this concept.





When you draw an object with thickness, you don’t see the thickness until you view the drawing from a different angle. This is because normally your view is perpendicular to the imagined drawing surface. At that angle, you cannot see the thickness of an object because it projects toward you just as a sheet of paper looks like a line when viewed from one end. Thus, to view an object’s thickness, you must change the angle at which you view your drawing.

Another object property related to 3D is elevation. You can set AutoCAD so that everything you draw has an elevation. By default, objects have a zero elevation. ‘This means that objects are drawn on the imagined 2D plane of Model Space, but you can set the z-coordinate for your objects so that whatever you draw is above . or below that surface. An object with an elevation value other than 0 rests not on the imagined drawing surface but above it (or below it if the z-coordinate is a negative value). Figure 15.3 illustrates this concept.



Changing a 2D Plan into a 3D Model

In this exercise, you will turn the 2D Unit drawing into a 3D drawing by changing the properties of the wall lines. You will also learn how to view the 3D image.

  1. Start AutoCAD and open the Unit file or use 15 a-unit.dwg from the corn panion CD-ROM.
  2. Set the current layer to Wall, and freeze all the other layers except Jamb. Remember that Freeze is the option just to the right of the light bulb in the Layer Properties Manager dialog box.
  3. Turn.on the grid (if it isn’t on already). Your screen should look like figure 15.4.
  4. Click View > 3D Views > SW Isometric. Your view now looks as if you are standing above and to the left of your drawing, rather than directly above it see Figure 15.5). The UCS icon helps you get a sense of your new orientation. The grid also shows you the angle of the drawing surface.
    FIGURE 15.4

    FIGURE 15.4

    FIGURE 15.6

    FIGURE 15.6


  5. Select all the objects in the drawing .
  6. Click the Properties tool on the Standard toolbar, or right-click and select Properties from the popup menu.
  7. In the Properties dialog box, locate the Thickness option, then double-click the 0 value in the right-hand column.
  8. Enter 8 (metric users should enter 244). The walls and jambs now appear to be 8 (244cm) high.
  9. Close the Properties dialog box.

Figure 15.6 shows the extruded wall lines. You can see through the walls because this is a Wireframe view. A Wireframe view shows the volumes of a 3D object by showing the lines representing the intersections of surfaces. Later, this chapter will discuss how to make an object’s surfaces opaque in order to facilitate a particular point of view for a drawing.

In step 4, you were able to quickly obtain a 3D view from a set of 3D View options. You’ll learn more about these options as you progress through this chapter.



Next you will change the elevation of the door headers by moving them in the z-axis using grips.

  1. First,zoom out a bit to get all of the drawing in view, as shown in Figure 15.7. You can use the Pan and Zoom tools in this 3D view as you would in a 2D view.
  2. Turn on the Ceiling layer. The door headers appear as lines on the floor where the door openings are located.
  3. Click the two magenta lines representing the header over the balcony door. As you do so, notice that your cursor’s shape conforms to the 3D view.
  4. Click the two magenta lines representing the header over the balcony door. As you do so, notice that your cursor’s shape conforms to the 3D view.
  5. Click again one of the hot grips.
  6. At the ** STRETCH ** prompt, enter @000 (metric users should enter @0,0,214).Don’t forget to indicate feet for the 7. The lines move to a new position 7 (214cm) above the floor (see Figure 15.7).
    FIGURE 15.7

    FIGURE 15.7


  7. Click the Properties button on the Object Properties toolbar and change the thickness of the header to 1 (30cm) using the Thickness input box. Click OK.
  8. Click the four lines representing the door header for the closet and entry.
  9. Repeat steps 3 through 7. Your drawing will look like Figure 15.8.
  10. Use the View Control dialog box (choose View > Named Views) to create a new view under the name of 3D. See Saving Views in Chapter 6 if you need help saving views.
    FIGURE 15.8

    FIGURE 15.8


You could have used the Move command to move the lines to their new elevation, entering the same @0,0,7 at the Specify second point of displacement or <use first point as displacement prompt for Move. Because you must select objects to edit them using grips, with the Move command, you save a step by not having to select the lines a second time for the Properties tool.

Creating a 3D Object

Though you may visualize a design in 3D, you will often start sketching it in 20 and later generate the 3D views you know from the start what the thickness and height of an object will be, you can set these values so that you don’t have to extrude the object later. The following exercise shows you how to set elevation and thickness before you start drawing.

  1. Choose Format > Thickness.
  2. Enter 12 at the Enter new val u.e for THICKNESS 0000 prompt. Metric users should enter 30. Now as you draw objects, they will appear 12 (30cm).
  3. Draw a circle representing a planter at one side of the balcony (see Figure 15.9). Make it 18″ (45cm for metric users) in diameter. The planter appears as a 3D object with the current thickness and elevation settings.
    FIGURE 15.8

    FIGURE 15.8


Having set the thickness setting to 12 (30cm), everything you draw will have a thickness of 12 inches (30cm) until you change it back to 0 or some other setting.

Giving objects thickness and modifying their elevation is a very simple process, as you have seen. With these two properties, you can create nearly any three dimensional form you need. Next, you will discover how to control your view of your drawing.

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