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Chapter 22 Using Advanced 3D Features

The Autodesk® AutoCAD® 2014 software has an extended set of tools for working with 3D drawings that lets you create 3D objects with few limitations on shape and orientation. This chapter focuses on the use of these tools, which help you easily generate 3D forms and view them in both perspective and orthogonal modes.

The AutoCAD LT® software doesn’t support any of the features described in this chapter.

In this chapter, you will learn to:

Master the User Coordinate System
Understand the UCS options
Use viewports to aid in 3D drawing
Use the array tools
Create complex 3D surfaces
Create spiral forms
Create surface models
Move objects in 3D space

Setting Up AutoCAD for This Chapter

Before you start, we’d like you to set up AutoCAD in a way that will make your work a little easier. You’ll use the 3D Modeling workspace to which you were introduced in Chapter 21, “Creating 3D Drawings.” To do so, start AutoCAD, and then click the Workspace drop-down in the Quick Access toolbar and select 3D Modeling, as shown in Figure 22-1. You’ll see a new set of panels appear, as shown in Figure 22-2.

Figure 22-1 Select 3D Modeling from the Workspace drop-down.

In Chapter 21, you started a new 3D model using a template set up for 3D modeling. Here you’ll start to work with the default 2D drawing, acad.dwt. Now you’re ready to get to work.

Figure 22-2 The AutoCAD window set up for this chapter

Mastering the User Coordinate System

The User Coordinate System (UCS) enables you to define a custom coordinate system in 2D and 3D space. You’ve been using the default coordinate system called the World Coordinate System (WCS) all along. By now, you’re familiar with the L-shaped icon in the lower-left corner of the AutoCAD screen, containing a small square and the letters X and Y. The square indicates that you’re currently in the WCS; the X and Y indicate the positive directions of the x- and y-axes. The WCS is a global system of reference from which you can define other UCSs.

It may help to think of these AutoCAD UCSs as different drawing surfaces or two-dimensional planes. You can have several UCSs at any given time. By setting up these different UCSs, you can draw as you would in the WCS in 2D and still create a 3D image.

Suppose you want to draw a house in 3D with doors and windows on each of its sides. You can set up a UCS for each of the sides, and then you can move from UCS to UCS to add your doors and windows (see Figure 22-3). In each UCS, you draw your doors and windows as you would in a typical 2D drawing. You can even insert elevation views of doors and windows that you created in other drawings.

Figure 22-3 Different UCSs in a 3D drawing

In this chapter, you’ll experiment with several views and UCSs. All the commands you’ll use are available both at the command line and via the View tab’s Coordinates panel.

Defining a UCS

In the first set of exercises, you’ll draw a chair that you can later add to your 3D unit drawing. In drawing this chair, you’ll be exposed to the UCS as well as to some of the other 3D capabilities available in AutoCAD:

1. Open the barcelona1.dwg file. Metric users should open barcelona1_metric.dwg. This file contains two rectangles that you’ll use to create a chair.

2. Select SW Isometric from the 3D Navigation drop-down list on the Home tab’s View panel. You can also type -V↵SWISO↵. This gives you a 3D view from the lower-left corner of the rectangles, as shown in Figure 22-4. Zoom out a bit to give yourself some room to work.

Figure 22-4 The chair seat and back in the Plan (top) and Isometric (bottom) views

3. Select the two rectangles, and then right-click and select Properties.

4. In the Properties palette, enter 3 in the Thickness setting and press ↵. This gives the seat and back a thickness of 3″. Metric users should make the thickness 7.6 cm.

5. Press the Esc key, and close the Properties palette. Click the Convert To Solid tool in the Home tab’s expanded Solid Editing panel.

6. Select the two rectangles, and then press ↵.

Notice that the UCS icon appears in the same plane as the current coordinate system. The icon will help you keep track of which coordinate system you’re in. Now you can see the chair components as 3D objects.

Next you’ll define a UCS that is aligned with one side of the seat:

1. Click UCS ⇒ Named UCS in the View tab’s Coordinates panel or type Ucsman↵ to open the UCS dialog box.

2. Select the Orthographic UCSs tab to view a set of predefined UCSs.

3. Select Front in the list box, as shown in Figure 22-5. Figure 22-6 shows the orientation of the Front UCS.

Figure 22-5 The UCS dialog box

Figure 22-6 The six predefined UCS orientations

4. Click the Set Current button to make the Front UCS current.

5. Click OK to close the dialog box.

The Orthographic UCSs tab offers a set of predefined UCSs for each of the six standard orthographic projection planes. Figure 22-6 shows these UCSs in relation to the WCS.

Because a good part of 3D work involves drawing in these orthographic planes, AutoCAD supplies the ready-made UCS orientations for quick access. But you aren’t limited to these six orientations. If you’re familiar with mechanical drafting, you’ll see that the orthographic UCSs correspond to the typical orthographic projections used in mechanical drafting. If you’re an architect, the Front, Left, Back, and Right UCSs correspond to the south, west, north, and east elevations of a building.

Before you continue building the chair model, you’ll move the UCS to the surface on which you’ll be working. Right now, the UCS has its origin located in the same place as the WCS origin.

You can move a UCS so that its origin is anywhere in the drawing:

1. Click the Origin tool in the View tab’s Coordinates panel, or type UCS↵O↵.

2. Use the Endpoint osnap and click the bottom-front corner of the chair seat, as shown in Figure 22-7. The UCS icon moves to indicate its new origin’s location. If you typed in the command, press Enter to accept the other default values.

Figure 22-7 Setting up a UCS

You just created a new UCS based on the Front UCS you selected from the UCS dialog box. Now, as you move your cursor, the origin of the UCS icon corresponds to a 0,0 coordinate. Although you have a new UCS, the WCS still exists; you can always return to it when you need to.

Saving a UCS

After you’ve gone through the work of creating a UCS, you may want to save it—especially if you think you’ll come back to it later. Here’s how to save a UCS:

1. Choose Named from the Coordinates panel or type Ucsman↵ to open the UCS dialog box.

2. Make sure the Named UCSs tab is selected, and then highlight the Unnamed option in the Current UCS list box.

3. Click on the word Unnamed. The item changes to allow editing.

4. Type 3DSW↵ for the name of your new UCS.

5. Click OK to exit the dialog box.

Your UCS is now saved with the name 3DSW. You can recall it from the UCS dialog box or by using other methods that you’ll learn about later in this chapter.

Working in a UCS

Next, you’ll arrange the seat and back and draw the legs of the chair. Your UCS is oriented so that you can easily adjust the orientation of the chair components. As you work through the next exercise, notice that, although you’re manipulating 3D objects, you’re really using the same tools you’ve used to edit 2D objects.

Follow these steps to adjust the seat and back and to draw legs:

1. Click the seat back to expose its grips. The seat back is the box to the right.

2. Click the bottom grip, as shown in the first image in Figure 22-8.

Figure 22-8 Moving the components of the chair into place

3. Right-click the mouse to open the Grip Edit context menu.

4. Choose Rotate from the menu. The seat back now rotates with the movement of the cursor. It rotates in the plane of the new UCS you created earlier.

5. Type 80↵ to rotate the seat back 80°. Your view looks like the second image in Figure 22-8.

6. Click the bottom grip, as shown in the second image in Figure 22-8.

7. Right-click the mouse again and choose Move.

8. Using the Endpoint osnap, click the top corner of the chair seat to join the chair back to the seat, as shown in the second image in Figure 22-8.

9. Click the chair seat, making sure that the chair back is also selected; then click the bottom-corner grip of the seat, as shown in the third image in Figure 22-8.

10. Right-click and choose Rotate from the Grip Edit context menu.

11. Enter -10↵ to rotate both the seat and back negative 10°. Press the Esc key to clear the grips. Your chair looks like Figure 22-9.

Figure 22-9 The chair after rotating and moving the components

The new UCS orientation enabled you to use the grips to adjust the chair seat and back. All the grip rotation in the previous exercise was confined to the plane of the new UCS. Mirroring and scaling will also occur in relation to the current UCS.

Building 3D Parts in Separate Files

As you work in 3D, your models will become fairly complex. When your model becomes too crowded for you to see things clearly, it helps to build parts of the model and then import them instead of building everything in one file. In the next set of exercises, you’ll draw the legs of the chair and then import them to the main chair file to give you some practice in the procedure.

We’ve prepared a drawing called legs.dwg, which consists of two polylines that describe the shape of the legs. We did this to save you some tedious work that isn’t related to 3D modeling. You’ll use this file as a starting point for the legs, and then you’ll import the legs into the barcelona1.dwg file:

1. Open the legs.dwg file. Metric users should open the legs_metric.dwg file. The file consists of two polyline splines that are in the shape of one set of legs. You’ll turn these simple lines into 3D solids.

2. Click the Edit Polyline tool in the Home tab’s expanded Modify panel.

3. At the Select polyline or [Multiple]: prompt, enter M↵ to select multiple polylines. Then select the two polylines and press ↵.

4. At the Enter an option [Close/Open/Join/Width/Fit/Spline/Decurve/Ltype gen/Reverse/Undo]: prompt, enter W↵.

5. At the Specify new width for all segments: prompt, enter 0.5↵ to give the polylines a width of 0.5″. Metric users should enter 1.27↵.

6. Press ↵ to exit the Pedit command.

Next you need to change the Thickness property of the two polylines to make them 2″, or 5 cm, wide:

1. With the two polylines selected, open the Properties palette and set their thickness to 2. Metric users should set their thickness to 5.

2. Close the Properties palette, or you can leave it open for the next exercise.

3. Click the Convert To Solid tool in the Home tab’s expanded Solid Editing panel, or enter convtosolid↵ at the Command prompt.

4. Select the two polylines if they’re not already selected, and then press ↵. The lines become 3D solids.

5. Click the Solid, Union tool in the Home tab’s Solid Editing panel, select the two legs, and press ↵. The two legs are now a single 3D solid, as shown in Figure 22-10.

Figure 22-10 The polylines converted to 3D solids

As you’ve just seen, you can convert polylines that have both a width and a thickness into 3D solids. Now you’re ready to add the legs to the rest of the chair:

1. Click the Tile Vertically tool in the View tab’s User Interface panel. You see the legs drawing on the left and the rest of the chair on the right.

2. Adjust the views so that your screen looks similar to Figure 22-11. If you see a third Drawing1.dwg panel, close it and click the Tile Vertically tool again.

Figure 22-11 Click and drag the leg from the left window to the right window, and align the leg with the chair seat and back.

3. Click in the barcelona1 drawing, and select Extents from the Zoom flyout Navigation bar to get an overall view of the chair so far.

4. Click in the legs drawing, and then click the legs 3D solid to select it.

5. Click and hold the cursor on the legs until you see the arrow cursor with a small rectangle (see Figure 22-11).

6. When you see the rectangle, drag the mouse into the barcelona1 drawing. The legs appear in the proper orientation.

7. Release the mouse button to place the legs in the barcelona1 drawing. You don’t need to be precise about placing the legs; you can move them into position next.

8. Use the Move tool to move the legs so that the endpoint of the horizontal leg joins the chair seat, as shown in the image in the right panel of Figure 22-11.

9. Save and close the legs.dwg file, and expand the barcelona1.dwg file to fill the AutoCAD window.

Use Copy and Paste

You can also use Copy and Paste to copy the legs to the barcelona1 drawing. In step 4, right-click and select Copy from the context menu. Skip steps 5 through 7 and instead click in the barcelona1 drawing, right-click, and select Paste.

In these last few exercises, you worked on the legs of the chair in a separate file and then imported them into the main chair file with a click-and-drag motion. By working on parts in separate files, you can keep your model organized and more manageable. You may have also noticed that, although the legs were drawn in the WCS, they were inserted in the 3DSW UCS that you created earlier. This shows you that imported objects are placed in the current UCS. The same would have happened if you inserted an Xref or another file.

Understanding the UCS Options

You’ve seen how to select a UCS from a set of predefined UCSs. You can frequently use these preset UCSs and make minor adjustments to them to get the exact UCS you want.

You can define a UCS in other ways. You can, for example, use the surface of your chair seat to define the orientation of a UCS. In the following sections, you’ll be shown the various ways you can set up a UCS. Learning how to move effortlessly between UCSs is crucial to mastering the creation of 3D models, so you’ll want to pay special attention to the command options shown in these examples.

Note that these examples are for your reference. You can try them out on your own model. These options are accessible from the View tab’s Coordinates panel.

Controlling the UCS Icon

If the UCS icon isn’t behaving as described in this chapter’s exercises, chances are that its settings have been altered. You can control the behavior of the UCS icon through the UCS dialog box. To open the UCS dialog box, click Named in the View tab’s Coordinates panel or type Ucsman↵; then click the Settings tab.

The settings in the UCS Icon Settings group affect the way the UCS icon behaves. Normally, the On and Display At UCS Origin Point check boxes are selected. If On isn’t selected, you won’t see the UCS icon. If the Display At UCS Origin Point check box isn’t selected, the UCS icon remains in the lower-left corner of the drawing window no matter where its origin is placed in the drawing.

If you have multiple viewports set up in a drawing, you can set these two options independently for each viewport. The third option, Apply To All Active Viewports, forces the first two settings to apply in all viewports.

Two more options appear in the UCS Settings group. If you have multiple viewports open, the Save UCS With Viewport option enables AutoCAD to maintain a separate UCS for each viewport. The Update View To Plan When UCS Is Changed option forces the display to show a plan view of the current UCS. This means that if you change a UCS orientation, AutoCAD automatically shows a plan view of the new UCS orientation. This option also forces viewport views to show the extents of plan views. If you find that your views are automatically zooming to extents when you don’t want them to, turn off this setting.

Another tool for controlling the UCS icon is the UCS Icon dialog box. To open it, click the UCS Icon Properties tool in the View tab’s Coordinates panel or enter Ucsicon↵P↵.

Using this dialog box, you can fine-tune the appearance of the UCS icon, including its size and color. The 2D radio button in the UCS Icon Style group changes the UCS icon to the old-style UCS icon used in earlier versions of AutoCAD.

UCS Based on Object Orientation

You can define a UCS based on the orientation of an object. This is helpful when you want to work on a predefined object to fill in details on its surface plane. The following steps are for information only and aren’t part of the tutorial. You can try this at another time when you aren’t working through an exercise.

Follow these steps to define a UCS this way:

1. Type UCS↵OB↵.

2. At the Select object to align UCS: prompt, pick the object that you want to use to define the UCS. For example, you could click a 3D solid that you want to edit. The UCS icon shifts to reflect the new coordinate system’s orientation. Figure 22-12 shows an example of using the OB option to select the edge of the chair back.

Figure 22-12 Using the Object option of the UCS command to locate a UCS

When you create a UCS using the Object option, the location of the UCS origin and its orientation depend on how the selected object was created. Table 22-1 describes how an object can determine the orientation of a UCS.

Table 22-1: Effects of objects on the orientation of a UCS

Object type	UCS orientation
Arc	The center of the arc establishes the UCS origin. The x-axis of the UCS passes through the pick point on the arc.
Circle	The center of the circle establishes the UCS origin. The x-axis of the UCS passes through the pick point on the circle.
Dimension	The midpoint of the dimension text establishes the UCS origin. The x-axis of the UCS is parallel to the x-axis that was active when the dimension was drawn.
Face (of a 3D solid)	The origin of the UCS is placed on a quadrant of a circular surface or on the corner of a polygonal surface.
Line	The endpoint nearest the pick point establishes the origin of the UCS, and the XZ plane of the UCS contains the line.
Point	The point location establishes the UCS origin. The UCS orientation is arbitrary.
2D polyline	The starting point of the polyline establishes the UCS origin. The x-axis is determined by the direction from the first point to the next vertex.
3D polyline	Returns the message This object does not define a coordinate system.
Spline	The UCS is created with its XY plane parallel to the XY plane of the UCS that was current when the spline was created.
Solid	The first point of the solid establishes the origin of the UCS. The second point of the solid establishes the x-axis.
Trace	The direction of the trace establishes the x-axis of the UCS, and the beginning point sets the origin.
3D Face	The first point of the 3D face establishes the origin. The first and second points establish the x-axis. The plane defined by the 3D face determines the orientation of the UCS.
Shapes, text, blocks, attributes, and attribute definitions	The insertion point establishes the origin of the UCS. The object’s rotation angle establishes the x-axis.

UCS Based on Offset Orientation

At times, you may want to work in a UCS that has the same orientation as the current UCS but is offset. For example, you might be drawing a building that has several parallel walls offset with a sawtooth effect (see Figure 22-13).

Figure 22-13 Using the Origin option to shift the UCS

You can easily hop from one UCS to a new, parallel UCS by using the Origin option. Click the Origin tool in the Coordinates panel, or type UCS↵O↵. At the Specify new origin point <0,0,0>: prompt, pick the new origin for your UCS.

Another UCS option, called Move, will move an existing, named UCS to a new location and keep its original orientation. You won’t find the UCS Move option on any panel or toolbar, but you can use it by entering UCS↵M↵ at the Command prompt.

The steps in the following section are for information only and aren’t part of the tutorial. You can try this at another time when you aren’t working through an exercise.

UCS Rotated Around an Axis

Suppose you want to change the orientation of the x-, y-, or z-axis of a UCS. You can do so by using the X, Y, or Z flyout on the View tab’s Coordinates panel. These are perhaps among the most frequently used UCS options:

1. Click the X tool flyout arrowhead in the View tab’s Coordinates panel, and select Z from the flyout. You can also type UCS↵Z↵. This enables you to rotate the current UCS around the z-axis.

2. At the Specify rotation angle about Z axis <90>: prompt, press ↵ to accept the default of 90°. The UCS icon rotates about the z-axis to reflect the new orientation of the current UCS (see Figure 22-14).

Figure 22-14 Rotating the UCS about the z-axis

Similarly, the X and Y options enable you to rotate the UCS about the current x- and y-axis, respectively, just as you did for the z-axis earlier. The X and Y tools are helpful in orienting a UCS to an inclined plane. For example, if you want to work on the plane of a sloped roof of a building, you can first use the Origin UCS tool to align the UCS to the edge of a roof and then use the X tool to rotate the UCS to the angle of the roof slope, as shown in Figure 22-15. Note that the default is 90°, so you only have to press ↵ to rotate the UCS 90°, but you can also enter a rotation angle.

Figure 22-15 Moving a UCS to the plane of a sloping roof

Finally, you align the z-axis between two points using the Z-Axis Vector option. This is useful when you have objects in the drawing that you can use to align the z-axis. Here are the steps:

1. Click the Z-Axis Vector tool in the Coordinates panel, or type UCS↵ZA↵.

2. At the Specify new origin point or [Object]<0,0,0>: prompt, press ↵ to accept the default, which is the current UCS origin, or you can select a new origin.

3. At the prompt

Specify point on positive portion of Z-axis
<0′-0″, 0′-0″, 0′-1″>:

select another point to indicate the z-axis orientation. Figure 22-16 shows the resulting UCS if you use the bottom of the barcelona1 chair leg to define the z-axis.

Figure 22-16 Picking points for the Z-Axis Vector tool

Because your cursor location is in the plane of the current UCS, it’s best to pick a point on an object by using either the Osnap overrides or the coordinate filters.

Orienting a UCS in the View Plane

Finally, you can define a UCS in the current view plane. This points the z-axis toward the user. This approach is useful if you want to switch quickly to the current view plane for editing or for adding text to a 3D view.

Click the View tool in the Coordinates panel, or type UCS↵V↵. Note that the View tool also has a flyout arrowhead that contains the Object and Face tools. If you accidentally click the flyout arrowhead, make sure to click the View tool in the flyout. The UCS icon changes to show that the UCS is aligned with the current view.

AutoCAD uses the current UCS origin point for the origin of the new UCS. By defining a view as a UCS, you can enter text to label your drawing, just as you would in a technical illustration. Text entered in a plane created this way appears normal.

You’ve finished your tour of the UCS command. Set the UCS back to the WCS by clicking the UCS, World tool in the View tab’s Coordinates panel, and save the barcelona1.dwg file.

You’ve explored nearly every option in creating a UCS except one. Later in this chapter, you’ll learn about the 3-Point option for creating a UCS. This is the most versatile method for creating a UCS, but it’s more involved than some of the other UCS options.

Manipulating the UCS Icon

The UCS icon displays the direction of the axes in your drawing file. It can also be directly manipulated by selecting and right-clicking it or by using its multifunction grips. If your UCS icon is not selectable, or to turn off this selectable feature, open the UCS dialog box (click Named in the View tab’s Coordinates panel), click the Settings tab, and see if the Allow Selecting UCS Icon option is checked (see Figure 22-17).

Figure 22-17 Making the UCS icon selectable

There are essentially two selection options on the icon: the origin and the end of an axis. In either case, select the UCS icon, and then place your cursor over the appropriate grip and click the origin or endpoint (see Figure 22-18). Select how you want to change the UCS (move and align) and move the cursor. The UCS icon will relocate, showing you where your new coordinate system will be. The origin can be moved to a new location or it can be aligned to another object or surface using this method. This makes working in a 3D environment a bit easier. Selecting the origin also allows you to return the current UCS to the World Coordinate System (it resets the UCS). The x-, y-, and z-axes all work the same way. Pick the endpoint of the axis (the grip) to rotate the selected axis about the other axis (for example, if the x-axis is selected, it can rotate about either the y- or z-axis).

Figure 22-18 Selecting and moving the UCS Icon will alter your UCS.

When you right-click the UCS icon, you will see a context menu containing a list of the UCS commands you can choose without having to leave the drawing area. Pick the UCS command you want to access.

Saving a UCS with a View

AutoCAD has the ability to save a UCS with a view. Either click the View Manager option in the In-Canvas View Controls (top-left corner of the drawing area) or click the View Manager option, found at the bottom of the 3D Navigation drop-down list in the Home tab’s View panel (see Figure 22-19). In the View Manager dialog box, click the New button. This opens the New View/Shot Properties dialog box. Enter a name for your new view in the View Name box, and then choose a UCS to save with a new view by using the UCS drop-down list in the Settings group of the dialog box. Click OK to complete.

Figure 22-19 Select the View Manager option in either the in-canvas View Controls or the 3D Navigation drop-down list.

Using Viewports to Aid in 3D Drawing

In Chapter 16, “Laying Out Your Printer Output,” you worked extensively with floating viewports in Paper Space. In this section, you’ll use tiled viewports to see your 3D model from several sides at the same time. This is helpful in both creating and editing 3D drawings because it enables you to refer to different portions of the drawing without having to change views.

Tiled viewports are created directly in Model Space, as you’ll see in the following exercise:

1. Click the Named tool in the View tab’s Model Viewports panel to open the Viewports dialog box (see Figure 22-20).

Figure 22-20 The Viewports dialog box

2. Make sure the New Viewports tab is selected, and then select Three: Right from the Standard Viewports list on the left.

The window on the right changes to display a sample of the viewport configuration. It shows three rectangles, which represent the viewports, arranged with two on the left and one larger one to the right. Each rectangle is labeled as Current; this tells you that the current view will be placed in each viewport.

3. Open the Setup drop-down list at the bottom of the dialog box and select 3D.

The labels in the viewport sample change to indicate Top, Front, and SE Isometric. This is close to the arrangement you want, but you need to make one more adjustment. The viewport to the right, SE Isometric, will show the back side of the chair. You want an SW Isometric view in this window.

4. Click the SE Isometric viewport sample. The sample viewport border changes to a double border to indicate that it’s selected.

5. Open the Change View To drop-down list just below the sample viewports, and select SW Isometric. The label in the selected viewport changes to let you know that the view will now contain the SW Isometric view.

The Change View To list contains the standard four isometric views and the six orthogonal views. By clicking a sample viewport and selecting an option from the Change View To drop-down list, you can arrange your viewport views nearly any way you want.

6. To name this viewport arrangement, enter My Viewport Setup in the New Name box.

7. Click OK. Your display changes to show three viewports arranged as they were indicated in the Viewports dialog box (see Figure 22-21).

Figure 22-21 Three viewports, each displaying a different view

You’ve set up your viewports. Let’s check to see that your viewport arrangement was saved:

1. Click the Named tool in the View tab’s Model Viewports panel to open the Viewports dialog box again.

2. Click the Named Viewports tab. My Viewport Setup is listed in the Named Viewports list box. If you click it, a sample view of your viewport arrangement appears on the right.

3. After you’ve reviewed the addition to the Named Viewports list, close the dialog box.

Now, take a close look at your viewport setup. The UCS icon in the orthogonal views in the two left viewports is oriented to the plane of the view. AutoCAD enables you to set up a different UCS for each viewport. The top view uses the WCS because it’s in the same plane as the WCS. The side view has its own UCS, which is parallel to its view. The isometric view to the right retains the current UCS.

A Viewports dialog box option you haven’t tried yet is the Apply To drop-down list in the New Viewports tab (see Figure 22-22).

Figure 22-22 The Apply To drop-down list

This list shows two options: Display and Current Viewport. When Display is selected, the option you choose from the Standard Viewports list applies to the overall display. When Current Viewport is selected, the option you select applies to the selected viewport in the sample view in the right side of the dialog box. You can use the Current Viewport option to build multiple viewports in custom arrangements.

You have the legs for one side. The next step is to mirror those legs for the other side:

1. Click the top view of the chair in the upper-left viewport.

2. Turn on Polar Tracking in the status bar, and then click the Mirror tool in the Home tab’s expanded Modify panel.

3. In the upper-left viewport, click the 3D solid representing the chair legs and then press ↵.

4. At the Specify first point of mirror line: prompt, use the Midpoint osnap and select the midpoint of the chair seat, as shown in Figure 22-23.

Figure 22-23 Mirroring the legs from one side to another

5. At the Specify second point of mirror line: prompt, pick any location to the right of the point you selected so that the rubber-banding line is exactly horizontal.

6. Press ↵ at the Erase source objects? [Yes/No] <N>: prompt. The legs are mirrored to the opposite side of the chair. Your screen should look similar to Figure 22-23.

Your chair is complete. Let’s finish by getting a better look at it:

1. Click the viewport to the right showing the isometric view.

2. Click Single from the Viewport Configurations List drop-down list in the View tab’s Model Viewports panel (see Figure 22-24), or enter -Vports↵Si↵.

Figure 22-24 Click Single in the Viewport Configurations List drop-down list.

3. Use the Zoom tool to adjust your view so that it looks similar to Figure 22-25.

Figure 22-25 The chair in 3D with hidden lines removed

4. Click the Visual Styles drop-down list, and select Shades Of Gray. Note that your background may appear much darker.

5. Exit the file. You can save if you like or close without saving in case you want to do the exercise again.

Using the Array Tools

In Chapter 6, “Editing and Reusing Data to Work Efficiently,” you were introduced to the Array command. Let’s take a look at how this works in the 3D world. In AutoCAD 2014, you can create a 3D array from any type of array, whether it is rectangular, polar, or path. Let’s do an example using the path array:

1. Open the file called 3Dseating.dwg.

2. Click the Path Array tool in the Array flyout on the Modify panel of the Home tab, or type ARRAYPATH↵.

3. At the Select object: prompt, click the chair at the left end of the arc in the drawing and then press ↵.

4. At the Select path curve: prompt, select the magenta arc toward the left end.

5. At the Enter number of items along path or [Orientation/Expression] <Orientation>: prompt, use the Endpoint osnap and select the right endpoint of the magenta arc.

6. At the Specify the distance between items along path or [Divide/Total/Expression] <24.8518>: prompt, press ↵. You could enter a value here, but you’ll see how you can make adjustments later.

7. At the Press Enter to accept or [Associate/Base point/Items/Rows/Levels/Align items/Z direction/eXit] <eXit>: prompt, type R↵ to select the number of rows.

8. At the Enter the number of rows or [Expression] <1>: prompt, type 3↵.

9. At the Specify the distance between rows or [Total/Expression]: prompt, type 48↵.

10. At the Specify the incrementing elevation between rows or [Expression]: prompt, type 12↵.

11. Press ↵ to end the command.

In this exercise, you made an array of a chair that follows the path of an arc. The distance between chairs is 48″ (1219.2 mm), and the vertical riser between each section is 12″ (304.8 mm).

Now suppose you want to adjust the curvature of your array. This is a simple matter of adjusting the shape of the arc, as described in the following exercise:

1. Click the arc to expose its grips.

2. Click the middle grip, and then drag it upward. Notice that all of the chairs adjust as you drag the arc.

Here you see how the associative feature of the Arraypath command enables you to control the array by adjusting the object you used for the path. Arrays can be edited through a variety of methods, as you’ll see in the next section.

Making Changes to an Associative Array

Now let’s take a look at how you can make changes to an array. You may have noticed the Associative option in the Array command’s prompt. By default, the Associative option is turned on, which enables you to edit array objects as a group. You’ll see how this works in the following exercises.

You’ll start by editing the array you created using the Path Array tool. You’ll see that the chairs are now skewed and are no longer pointing to the center of the arc. You can realign them by making a simple change to the original chair.

The following steps show you how this is done:

1. Click the array of chairs. Notice that the contextual Array tab appears (see Figure 22-26).

Figure 22-26 The Array tab appears and a new set of panels and options is displayed.

We’ll change the number of chairs to allow for more seating.

2. In the Array Creation tab in the Items panel, change the item count from 5 to 10 and press the Tab key.

3. The number of chairs dynamically changes to the new value.

4. Save the file.

Experiment with other values in the Array tab to see what effects they have.

As you can see from these exercises, you can easily make changes to an array through the Array tab options in the Ribbon. Many of these options are also available through the multifunction grip menus when you have Dynamic Input turned on.

Creating Complex 3D Surfaces

In one of the previous exercises, you drew a chair composed of objects that were mostly straight lines or curves with a thickness. All the forms in that chair were defined in planes perpendicular to one another. For a 3D model such as this, you can get by using the orthographic UCSs. At times, however, you’ll want to draw objects that don’t fit so easily into perpendicular or parallel planes. In the following sections, you’ll create more complex forms by using some of the other 3D commands in AutoCAD.

Laying Out a 3D Form

In this next group of exercises, you’ll draw a butterfly chair. This chair has no perpendicular or parallel planes with which to work, so you’ll start by setting up some points that you’ll use for reference only. This is similar in concept to laying out a 2D drawing. As you progress through the drawing construction, notice how the reference points are established to help create the chair. You’ll also construct some temporary 3D lines to use for reference. These temporary lines will be your layout. These points will define the major UCSs needed to construct the drawing. The main point is to show you some of the options for creating and saving UCSs.

To save time, we’ve created the 2D drawing that you’ll use to build your 3D layout. This drawing consists of two rectangles that are offset by 4″ (10 mm). To make it more interesting, they’re also off-center from each other (see Figure 22-27).

Figure 22-27 Setting up a layout for a butterfly chair

The first thing you’ll need to do is set up the drawing for the layout:

1. Open the butterfly1.dwg file.

2. Click SW Isometric in the 3D Navigation drop-down list, or type –V↵SWISO↵. This gives you a view from the lower-left side of the rectangles.

3. Zoom out so that the rectangles occupy about a third of the drawing area window.

Now you need to move the outer rectangle in the z-axis so its elevation is 30″ (76 cm):

1. Click the outer rectangle, and then click one of its grips.

2. Right-click to open the Grip Edit context menu.

3. Choose Move, and then enter@0,0,30↵; metric users should enter @0,0,76↵. This tells AutoCAD to move the rectangle a 0 distance in both the x- and y-axes and 30″ (or 76 cm) in the z-axis.

4. Pan your view downward so that it looks similar to Figure 22-28.

Figure 22-28 The finished chair layout

5. Use the Line tool to draw lines from the corners of the outer square to the corners of the inner square. Use the Endpoint osnap to select the exact corners of the squares. This is the layout for your chair—not the finished product.

As an alternate method in step 3, after choosing Move from the Grip Edit context menu, you can turn on Ortho mode and point the cursor vertically so that it shows –Z in the coordinate readout. Then enter 30↵ (76↵ for metric users).

Spherical and Cylindrical Coordinate Formats

In the previous exercise, you used relative Cartesian coordinates to locate the second point for the Move command. For commands that accept 3D input, you can also specify displacements by using the Spherical and Cylindrical Coordinateformats.

The Spherical Coordinate format lets you specify a distance in 3D space while specifying the angle in terms of degrees from the x-axis of the current UCS and degrees from the XY plane of the current UCS (see the top image in Figure 22-29). For example, to specify a distance of 4.5″ (11.43 cm) at a 30° angle from the x-axis and 45° from the XY plane, enter @4.5<30<45 (or @11.43<30<45 for metric users). This refers to the direct distance followed by a < symbol, then the angle from the x-axis of the current UCS followed by another < symbol, and then the angle from the XY plane of the current UCS. To use the Spherical Coordinate format to move the rectangle in the exercise, enter @30<0<90 (or @76<0<90 for metric users) at the Second point: prompt.

The Cylindrical Coordinate format, on the other hand, lets you specify a location in terms of a distance in the plane of the current UCS and a distance in the z-axis. You also specify an angle from the x-axis of the current UCS (see the bottom image in Figure 22-29). For example, to locate a point that is a distance of 4.5″ (11.43 cm) in the plane of the current UCS at an angle of 30° from the x-axis and a distance of 3.3″ (8.38 cm) in the z-axis, enter @4.5<30,3.3 (or @11.43<30,8.38 for metric users). This refers to the distance of the displacement from the plane of the current UCS followed by the < symbol, then the angle from the x-axis followed by a comma, and then the distance in the z-axis. Using the Cylindrical Coordinate format to move the rectangle, you enter @0<0,30 (or @0<0,76 for metric users) at the Second point: prompt.

Figure 22-29 The Spherical and Cylindrical Coordinate formats

Using a 3D Polyline

Now you’ll draw the legs for the butterfly chair by using a 3D polyline. This is a polyline that can be drawn in 3D space. Here are the steps:

1. Click 3D Polyline in the Home tab’s Draw panel, or type 3P↵.

2. At the Specify start point of polyline: prompt, pick a series of points as shown in Figure 22-30 (top), by using the Endpoint and Midpoint osnaps. Use the Close option to close the series of lines.

Figure 22-30 Using 3D polylines to draw the legs of the butterfly chair

3. Draw another 3D polyline in the mirror image of the first (see the lower image in Figure 22-30).

4. Erase the connecting vertical lines that make up the frame, but keep the rectangles. You’ll use them later.

All objects, with the exception of lines and 3D polylines, are restricted to the plane of your current UCS. Two other legacy 3D objects, 3D faces and 3D meshes, are also restricted. You can use the Pline command to draw polylines in only one plane, but you can use the 3DPoly command to create a polyline in three dimensions. 3DPoly objects cannot, however, be given thickness or width.

Creating a Curved 3D Surface

Next, you’ll draw the seat of the chair. The seat of a butterfly chair is usually made of canvas, and it drapes from the four corners of the chair legs. You’ll first define the perimeter of the seat by using arcs, and then you’ll use the Edge Surface tool in the Home tab’s Modeling panel to form the shape of the draped canvas. The Edge Surface tool creates a surface based on four objects defining the edges of that surface. In this example, you’ll use arcs to define the edges of the seat.

To draw the arcs defining the seat edges, you must first establish the UCSs in the planes of those edges. In the previous example, you created a UCS for the side of the chair before you could draw the legs. In the same way, you must create a UCS defining the planes that contain the edges of the seat.

Because the UCS you want to define isn’t orthogonal, you’ll need to use the 3-point method. This lets you define the plane of the UCS based on three points:

1. Click the 3-Point tool on the View tab’s Coordinates panel, or type UCS↵3↵. This option enables you to define a UCS based on three points that you select. Remember, it helps to think of a UCS as a drawing surface situated on the surface of the object you want to draw or edit.

2. At the Specify new origin point <0,0,0>: prompt, use the Endpoint osnap to pick the bottom of the chair leg to the far left, as shown in the left image of Figure 22-31. This is the origin point of your new UCS.

Figure 22-31 Defining and saving three UCSs

3. At the Specify point on positive portion of X-axis: prompt, use the Endpoint osnap to pick the bottom of the next leg to the right of the first one, as shown in the left image in Figure 22-31.

4. At the Specify point on positive-Y portion of the UCS XY plane: prompt, pick the top corner of the butterfly chair seat, as shown in the left image in Figure 22-31. The UCS icon changes to indicate your new UCS.

5. Now that you’ve defined a UCS, you need to save it so that you can return to it later. Click UCS ⇒ Named UCS in the View tab’s Coordinates panel, or typeUC↵ to open the UCS dialog box.

6. With the Named UCSs tab selected, right-click the Unnamed item in the list box, and choose Rename from the context menu.

7. Enter Front↵.

8. Click OK to exit the UCS dialog box.

You’ve defined and saved a UCS for the front side of the chair. As you can see from the UCS icon, this UCS is at a nonorthogonal angle to the WCS. Continue by creating UCSs for two more sides of the butterfly chair:

1. Define a UCS for the side of the chair, as shown in the middle image in Figure 22-31. Use the UCS dialog box to rename this UCS Side, just as you did for Front in steps 5 through 8 in the previous exercise. Remember that you renamed the unnamed UCS.

2. Repeat these steps for a UCS for the back of the chair, named Back. Use the right image in Figure 22-31 for reference.

3. Open the UCS dialog box again. In the Named UCSs tab, highlight Front.

4. Click the Set Current button, and then click OK. This activates Front as the current UCS.

5. Click the Start, End, Direction tool from the Arc flyout in the Home tab’s Draw panel.

6. Draw the arc defining the front edge of the chair (see Figure 22-32). Use the Endpoint osnap override to pick the top endpoints of the chair legs as the endpoints of the arc.

Figure 22-32 Drawing the front and back seat edge using arcs and a polyline spline

7. Repeat steps 3 through 6 for the UCS named Back, each time using the top endpoints of the legs for the endpoints of the arc.

8. Restore the UCS for the side, but instead of drawing an arc, use the Polyline tool and draw a polyline spline similar to the one in Figure 22-32. If you need help with polyline splines, see Chapter 19, “Drawing Curves.”

Next you’ll mirror the side-edge spline to the opposite side. This will save you from having to define a UCS for that side:

1. Click the World UCS tool on the View tab’s Coordinates panel to restore the WCS. You do this because you want to mirror the arc along an axis that is parallel to the plane of the WCS. Remember that you must use the coordinate system that defines the plane in which you want to work.

2. Click the polyline you drew for the side of the chair (the one drawn on the Side UCS).

3. Click the midpoint grip of the arc in the Side UCS; then right-click and choose Mirror from the context menu.

4. Enter C↵ to select the Copy option.

5. Enter B↵ to select a new base point for the mirror axis.

6. At the Specify base point: prompt, use the Midpoint override to pick the midpoints of the rectangle at the bottom of the model. Refer to Figure 22-33 for help. The polyline should mirror to the opposite side, and your chair should look like Figure 22-34.

Figure 22-33 Set your UCS to World, and then mirror the arc that defines the side of the chair seat.

Figure 22-34 Your butterfly chair so far.

7. Press the Esc key twice to clear the grips.

Finally, let’s finish this chair by adding the mesh representing the chair seat:

1. Click the Loft tool from the Extrude flyout in the Home tab’s Modeling panel, or enter Loft↵ at the command line.

2. At the Select cross-sections in lofting order or [POint/Join multiple edges/MOde]: prompt, click the arc at the front of the layout.

3. At the Select cross-sections in lofting order or [POint/Join multiple edges/MOde]: prompt, click the arc at the back of the layout, and then press ↵ to finish your selection of cross sections.

4. At the Enter an option [Guides/Path/Cross sections only/settings] <Cross sections only>: prompt, enter G↵ for the Guides option. You’ll use the two polylines as guides.

Quick Hops to Your UCSs

If you find you’re jumping from one saved UCS to another, you’ll want to know about the Named UCS Combo Control drop-down list. This list is located in the View tab’s Coordinates panel, and it contains the World and other standard UCS options as well as all the saved UCSs in a drawing. You can use this list as a quick way to move between UCSs that you’ve set up or between the predefined orthogonal UCSs.

Another great way to jump quickly between UCSs is to use the UCS Face option. The Face option requires a 3D solid, but once you have one in place, you can choose Face from the View flyout on the View tab’s Coordinates panel and then click on the face of the solid to which you want to align your UCS. For example, you can use the Loft command (see the section “Shaping the Solid” later in this chapter) to create a solid similar to the solid shown later in Figure 22-37 that connects the top and bottom rectangles of the butterfly chair. You can then use the UCS Face option to align to the sides of that solid to draw the arcs and polylines for the seat outline. This way, you’re using the 3D solid as a layout tool.

5. At the Select guide profiles or [Join multiple edges]: prompt, select the two polylines on the sides of the layout, and then press ↵ to complete your selection. Your chair begins to take form, as shown in Figure 22-35.

6. Click Save from the Quick Access toolbar to save the chair so far.

Figure 22-35 The butterfly chair with a mesh seat

You’ve got the beginnings of a butterfly chair with the legs drawn in schematically and the seat as a 3D surface. You can add some detail by using a few other tools, as you’ll see in the next set of exercises.

Converting the Surface into a Solid

In the previous example, you used the Loft tool to create a 3D surface. Once you have a surface, you can convert it to a solid to perform other modifications.

You’ll want to round the corners of the seat surface to simulate the way a butterfly chair hangs off its frame. You’ll also round the corners of the frame and turn the frame into a tubular form. Start by rounding the seat surface. This will involve turning the surface into a solid so that you can use solid-editing tools to get the shape you want:

1. Click the Thicken tool in the Home tab’s Solid Editing panel.

You can also enter Thicken↵ at the Command prompt.

2. Select the seat surface, and press ↵ to finish your selection.

3. At the Specify thickness <0′-0″>: prompt, enter 0.01↵ (0.025↵ for metric users).

The seat surface appears to lose its webbing, but it has just been converted to a very thin 3D solid.

Shaping the Solid

The butterfly chair is in a fairly schematic state. The corners of the chair are sharply pointed, whereas a real butterfly chair would have rounded corners. In this section, you’ll round the corners of the seat with a little help from the original rectangles you used to form the layout frame.

First you’ll use the Fillet command to round the corners of the rectangles. Then you’ll use the rounded rectangles to create a solid from which you’ll form a new seat:

1. Choose the Fillet tool from the Home tab’s Modify panel, or enter F↵ at the command line.

2. At the Select first object or [Undo/Polyline/Radius/Trim/Multiple]: prompt, enter R↵.

3. At the Specify fillet radius <0′-0″>: prompt, enter 3↵. Metric users enter 7.5↵.

4. At the Select first object or [Undo/Polyline/Radius/Trim/Multiple]: prompt, enter P↵ for the Polyline option.

5. At the Select 2D polyline or [Radius]: prompt, select the top rectangle, as shown at the top of Figure 22-36. The polyline corners become rounded.

Figure 22-36 Round the corners of the rectangles with the Fillet command.

6. Press ↵ to repeat the Fillet command.

7. Enter P↵ to use the Polyline option, and then click the bottom rectangle, as shown at the bottom of Figure 22-36. Now both polylines have rounded corners.

Next create a 3D solid from the two rectangles using the Loft tool:

1. Click the Loft tool in the Home tab’s Modeling panel, or enter Loft↵.

2. At the Select cross-sections in lofting order or [POint/Join multiple edges/MOde]: prompt, select the two rectangles and press ↵ to finish your selection.

3. At the Enter an option [Guides/Path/Cross sections only/Settings] <Cross sections only>: prompt, press ↵. The rectangles join to form a 3D solid (see Figure 22-37).

Figure 22-37 The lofted rectangles form a 3D solid.

Finding the Interference Between Two Solids

In this next exercise, you’ll use a tool that is intended to find the interference between two solids. This is useful if you’re working with crowded 3D models and you need to check whether objects may be interfering with each other. For example, a mechanical designer might want to check to make sure duct locations aren’t passing through a structural beam.

You’ll use Interfere as a modeling tool to obtain a shape that is a combination of two solids: the seat and the rectangular solid you just created. Here are the steps:

1. Click the Interfere tool in the Home tab’s Solid Editing panel.

You can also enter Interfere↵ at the Command prompt.

2. At the Select first set of objects or [Nested selection/Settings]: prompt, select the chair seat solid and then press ↵.

3. At the Select second set of objects or [Nested selection/checK first set] <checK>: prompt, click the rectangular solid you created in the previous exercise and press ↵. The Interference Checking dialog box appears (see Figure 22-38), and the drawing temporarily changes to a view similar to the Realistic visual style.

Figure 22-38 Checking for interference

The view shows the interference of the two solids in red. Notice that the corners are rounded on the red interference.

4. In the Interference Checking dialog box, turn off the Delete Interference Objects Created On Close check box and click Close. The display returns to the Wireframe view. If you look carefully at the seat corners, you see a new solid overlaid on the seat (see Figure 22-39).

5. Delete the rectangular solid and the original seat, as shown in Figure 22-39.

Figure 22-39 The interference solid appears on top of the original seat.

As mentioned earlier, the Interference Checking tool is intended to help you find out whether objects are colliding in a 3D model; as you’ve just seen, though, it can be an excellent modeling tool that can help you derive a form that you may not otherwise have the ability to create.

A number of other options are available when you’re using the Interference Checking tool. Table 22-2 lists the options in the Interference Checking dialog box.

Table 22-2: Interference Checking dialog box options

Option	What it does
First Set	Specifies the number of objects in the first set of selected objects
Second Set	Specifies the number of objects in the second set of selected objects
Interfering Pairs Found	Indicates the number of interferences found
Previous	Highlights the previous interference object
Next	Highlights the next interference object if multiple objects are present
Zoom To Pair	Zooms to the interference object while you’re using the Previous and Next options
Zoom Realtime	Closes the dialog box to allow you to use Zoom Realtime
Pan Realtime	Closes the dialog box to allow you to use Pan
3D Orbit	Closes the dialog box to allow you to use 3D Orbit
Delete Interference Objects Created On Close	Deletes the interference object after the dialog box is closed

The prompt for the Interference Checking command also showed some options. The prompt in step 2 shows Nested selection/Settings. The Nested selection option lets you select objects that are nested in a block or an Xref. The Settings option opens the Interference Settings dialog box (see Figure 22-40).

Figure 22-40 Settings for interference

This dialog box offers settings for the temporary display of interference objects while you’re using the Interference command. Table 22-3 lists the options for this dialog box.

Table 22-3: Interference Settings dialog box options

Option	What it does
Visual Style	Controls the visual style for interference objects
Color	Controls the color for interference objects
Highlight Interfering Pair	Highlights the interfering objects
Highlight Interference	Highlights the resulting interference objects
Visual Style	Controls the visual style for the drawing while displaying the interference objects

Creating Tubes with the Sweep Tool

You need to take care of one more element before your chair is complete. The legs are currently simple lines with sharp corners. In this section, you’ll learn how you can convert lines into 3D tubes. To make it more interesting, you’ll add rounded corners to the legs.

Start by rounding the corners on the lines you’ve created for the legs:

1. Use the Explode tool to explode the 3D polyline legs into simple lines.

2. Choose the Fillet tool from the Home tab’s Modify panel, or enter F↵ at the command line.

3. At the Selectfirst object or [Undo/Polyline/Radius/Trim/Multiple]: prompt, enter R↵.

4. At the Specify fillet radius <0′-0″>: prompt, enter 2↵. Metric users should enter 5↵.

5. At the Select first object or [Undo/Polyline/Radius/Trim/Multiple]: prompt, enter M↵ and then select pairs of lines to fillet their corners.

6. When all the corners are rounded, press ↵ to exit the Fillet command.

7. Delete the two polyline splines you used to form the sides of the seat. Your drawing should look like Figure 22-41.

Figure 22-41 Drawing the circles for the tubes

The chair is almost complete, but the legs are just wireframes. Next you’ll give them some thickness by turning them into tubes. Start by creating a set of circles. You’ll use the circles to define the diameter of the tubes:

1. Draw a 3⁄8″ (19 mm) radius circle in the location shown in Figure 22-41. Don’t worry if your location is a little off; the placement of the circle isn’t important.

2. Use the Rectangular Array command to make 15 copies of the circle. In Figure 22-41, a 4 × 4 array is used with the default 1″ spacing. Metric users should use a spacing of about 30 mm.

Now you’re ready to form the tubes:

1. Click the Sweep tool from the Extrude flyout in the Home tab’s Modeling panel. You can also enter sweep↵ at the command line.

2. At the Select objects to sweep or [MOde]: prompt, click one of the circles you just created. It doesn’t matter which circle you use because they’re identical. Press ↵ when you’re finished.

3. At the Select sweep path or [Alignment/Base point/Scale/Twist]: prompt, select one of the lines or fillet arcs that make up the legs.

4. Press ↵ to repeat the Sweep command, and then repeat steps 2 and 3 for each part of the leg segments, including the fillet arcs.

5. Continue with step 4 until all the lines in the legs have been converted into tubes.

6. Change the color of the solid representing the seat to cyan, and then select the Realistic visual style from the Visual Style viewport control. Your drawing will look similar to the image on the left of Figure 22-42, which shows a perspective view. The image on the right is the chair with some materials assigned to its parts and a slight adjustment to the seat location.

Figure 22-42 A perspective view of the butterfly chair with tubes for legs

7. Close the file. You can save it or, if you intend to repeat the exercise, close and do not save.

Using Sweep to Create Complex Forms

Although you used circles with the Sweep command to create tubes, you can use any closed polyline shape. Figure 22-43 gives some examples of other shapes you can use with the Sweep command.

Figure 22-43 You can use any closed shape with the Sweep command.

In step 3 of the previous exercise, you may have noticed some command-line options. These options offer additional control over the way Sweep works. Here is a rundown on how they work:

Alignment This option lets you determine whether the object to sweep is automatically set perpendicular to the sweep path. By default, this option is set to Yes, which means the object to sweep is set perpendicular to the path. If set to No, Sweep assumes the current angle of the object, as shown in Figure 22-44.

Figure 22-44 Alignment lets you set the angle between the object to sweep and the sweep path.

Base Point By default, Sweep uses the center of the object to sweep as the location to align with the path, as shown in Figure 22-45. Base Point lets you set a specific location on the object.

Figure 22-45 Using the Base Point option

Scale You can have Sweep scale the sweep object from one end of the path to the other to create a tapered shape, as shown in Figure 22-46. This option requires a numeric scale value.

Figure 22-46 Scale lets you scale the object to sweep as it’s swept along the path.

Twist You can have the object sweep twist along the path to form a spiral shape, as shown in Figure 22-47. This option requires a numeric value in the form of degrees of rotation.

Figure 22-47 You can have the object sweep twist along the path to create a spiral effect.

These options are available as soon as you select the sweep object and before you select the path object. You can use any combination of options you need. For example, you can apply the Twist and Scale options together, as shown in Figure 22-48.

Figure 22-48 The Scale and Twist options applied together

Creating Spiral Forms

You can use the Sweep tool in conjunction with the Helix tool to create a spiral form, such as a spring or the threads of a screw. You’ve already seen how the Sweep tool works. Try the following to learn how the Helix tool works firsthand.

In this exercise, you’ll draw a helicoil thread insert. This is a device used to repair stripped threads; it’s basically a coiled steel strip that forms internal and external threads. Here are the steps:

1. Open the Helicoil.dwg file. This is a standard AutoCAD drawing containing a closed polyline in a stretched octagon shape. This is the cross section of the helicoil thread, and you’ll use it as an object to sweep after you’ve created a helix.

2. Click the Helix tool in the Home tab’s expanded Draw panel, or type Helix↵.

You see the following prompt:

Number of turns = 3.0000  Twist=CCW
Specify center point of base:

3. Pick a point roughly in the center of the view. A rubber-banding line appears along with a circle.

4. At the Specify base radius or [Diameter] <1.0000>: prompt, enter 0.375↵.

5. At the Specify top radius or [Diameter] <0.3750>: prompt, press ↵ to accept the default, which is the same as the value you entered in step 4.

6. At the Specify helix height or [Axis endpoint/Turns/turn Height/tWist] <1.0000>: prompt, enter T↵ to use the Turns option.

7. At the Enter number of turns <3.0000>: prompt, enter 15↵ to create a helix with 15 turns total.

8. At the Specify helix height or [Axis endpoint/Turns/turn Height/tWist] <1.0000>: prompt, press ↵ to accept the default height of 1. The helix appears as a spiral drawn to the dimensions you’ve just specified for diameter, turns, and height (see Figure 22-49).

Figure 22-49 The helix and the helicoil after using Sweep

In step 6, you used the Turns option to specify the total number of turns in the helix. You also have other options that give you control over the shape of the helix. Figure 22-50 shows you the effects of the Helix command options. You may want to experiment with them on your own to become familiar with Helix.

Figure 22-50 The Helix command options

Edit a Helix with the Properties Palette

If you find that you’ve created a helix with the wrong settings, you don’t have to erase and re-create it. You can use the Properties palette to make adjustments to any of the helix options presented in Figure 22-50, even after a helix has been created. Select the helix, right-click, and choose Properties. Look in the Geometry section of the Properties palette for the helix settings.

Now use the Sweep tool to complete the helicoil:

1. Click the Sweep tool from the Extrude flyout in the Home tab’s Modeling panel, or enter Sweep at the command line.

2. At the Select objects to sweep or [MOde]: prompt, select the thread cross section in the lower-left corner of the drawing and then press ↵.

3. At the Select sweep path or [Alignment/Base point/Scale/Twist]: prompt, select the helix. After a moment, the helicoil appears.

4. To see the helicoil more clearly, choose the Realistic option from the Visual Styles drop-down list, and then change the helicoil to the Helicoil layer.

5. Close and save the file. If you intend to repeat this exercise, close but don’t save.

If the space between the coils is too small for the cross section, you may get an error message. If you get an error message at step 3, make sure you created the helix exactly as specified in the previous exercise. You may also try increasing the helix height.

In step 3, instead of selecting the sweep path, you can select an option to apply to the object to sweep. For example, by default, Sweep aligns the object to sweep at an angle that is perpendicular to the path and centers it. See “Using Sweep to Create Complex Forms” earlier in this chapter.

Creating Surface Models

In an earlier exercise, you used the Loft command to create the seat of a butterfly chair. In this section, you’ll return to the Loft command to explore some of its other uses. This time, you’ll use it to create a 3D model of a hillside based on a set of site-contour lines. You’ll also see how you can use a surface created from the Loft command to slice a solid into two pieces, imprinting the solid with the surface shape.

Start by creating a 3D surface using the Loft command:

1. Open the contour.dwg file.

2. Click the Loft tool from the Extrude flyout on the Home tab’s Modeling panel.

3. Select each brown contour in consecutive order from right to left or left to right. It doesn’t matter whether you start at the left end or the right end, but you must select the contours in order.

4. When you’re finished selecting all the contours, press ↵. You see the surface applied over the contour lines (see Figure 22-51).

Figure 22-51 Creating a 3D surface from contour lines

5. At the Enter an option [Guides/Path/Cross sections only/Settings] <Cross sections only>: prompt, press ↵ to exit the Loft command.

Once the loft surface has been placed, you can make adjustments to the way the loft is generated by using the arrow grip that appears when you select the surface:

1. Click the surface to select it.

2. Click the arrowhead that appears by the surface. This is known as a multifunction grip.

3. Select the Ruled option from the menu. The surface changes slightly to conform to the new Ruled surface option (see Figure 22-52).

Figure 22-52 The surface showing the multifunction grip menu with the Ruled option selected

In the butterfly chair exercise, you used the Guides option in the Loft Command prompt. This allowed you to use the polyline curves to guide the loft shape from the front arc to the back arc. In this exercise, you didn’t use the command options and went straight to the multifunction grip menu. The Ruled setting that you used in step 3 generates a surface that connects the cross sections in a straight line.

Slicing a Solid with a Surface

In the barcelona1.dwg chair example, you converted a surface into a solid using the Thicken command. Next, you’ll use a surface to create a solid in a slightly different way. This time, you’ll use the surface to slice a solid into two pieces. This will give you a form that is more easily read and understood as a terrain model:

1. Click the Extrude tool from the Extrude flyout in the Home tab’s Modeling panel.

2. At the Select objects to extrude or [MOde]: prompt, select the large rectangle below the contours and press ↵. The rectangle turns into a box whose height follows your cursor.

3. At the Specify height of extrusion or [Direction/Path/Taper angle/Expression]: prompt, move the cursor upward so that the box looks similar to the one shown in Figure 22-53. Then click the mouse to fix the box’s height.

Figure 22-53 The box extruded through the contours

You may have noticed that, as you raised the box height, you could see how it intersected the contour surface. Next you’ll slice the box into two pieces:

1. Click the Slice tool in the Home tab’s Solid Editing panel.

2. At the Select objects to slice: prompt, select the box and press ↵.

3. At the Specify start point of slicing plane or [planarObject/Surface/Zaxis/View/XY/YZ/ZX/3points] <3points>: prompt, enter S↵ to use the Surface option.

4. At the Select a surface: prompt, select the contour surface.

5. At the Select solid to keep or [keep Both sides] <Both>: prompt, click the part of the box that is below the surface. The top part of the box disappears, and you see the surface once again.

6. Delete the contour surface and the contour lines. The box remains with an imprint of the surface, as shown in Figure 22-54.

Figure 22-54 The box with the contour surface imprinted

In step 3, you saw a prompt that offered a variety of methods for slicing the box. The Surface option allowed you to slice the box using an irregular shape, but most of the other options let you slice a solid by defining a plane or a series of planar objects.

Finding the Volume of a Cut

Civil engineers frequently ask us how they can find the volume of earth from an excavated area. This is often referred to as a cut from a cut and fill operation. To do this, you first have to create the cut shape. Next you use the Interfere command to find the intersection between the cut shape and the contour surface. You can then find the volume of the cut shape using one of the inquiry commands in AutoCAD. The following exercise demonstrates how this is done.

Suppose that the contour model you’ve just created represents a site where you’ll excavate a rectangular area for a structure. You want to find the amount of earth involved in the excavation. A rectangle has been placed in the contour drawing representing such an area:

1. Select Wireframe from the Visual Styles flyout on the Home tab’s View panel (see Figure 22-55). This allows you to see the excavation rectangle more clearly.

Figure 22-55 Select Wireframe from the Visual Styles flyout.

2. Turn on the Selection Cycling tool in the status bar. This will help you select the rectangle in step 4.

3. Click the Extrude tool in the Home tab’s Modeling panel.

4. Select the rectangle shown in Figure 22-56.

Figure 22-56 Selecting the rectangle representing the excavation area

5. In the Selection dialog box, select Polyline and then press ↵.

6. Extrude the rectangle to the height of 10′ (3 meters).

Here you used the Selection Cycling tool to help you select the rectangle, which is overlapped by the contour solid. The Selection Cycling tool presents the Selection dialog box, which lets you determine the type of object you want to select, thereby filtering out other objects nearby that might be selected accidentally.

With the excavation rectangle in place, you can use the Interfere command to find the volume of the excavation:

1. Click the Interfere tool in the Home tab’s Solid Editing panel.

2. At the Select first set of objects or [Nested selection/Settings]: prompt, click the contour and press ↵.

3. At the Select second set of objects or [Nested selection/checK first set] <checK>: prompt, select the box and press ↵. The Interference Checking dialog box appears.

4. In the Interference Checking dialog box, deselect the Delete Interference Objects Created On Close check box and click Close.

5. Delete the box you used to represent the excavation area. The remaining shape contains the volume of the excavation.

6. Start the Region/Mass Properties tool by typing Massprop↵.

7. At the Select objects: prompt, select the excavation solid as shown in Figure 22-57 and then press ↵. The properties of the excavation area display in the command-line interface. At the top, you see the volume of the selected solid (see Figure 22-58).

Figure 22-57 The 3D solid representing the excavation

8. Press ↵↵, and then at the Write analysis to a file? [Yes/No] <N>: prompt, press ↵ to exit the command or enter Y↵ to save the information to a text file.

Figure 22-58 The mass and volume information from the Region/Mass Properties tool

Understanding the Loft Command

As you’ve seen from the exercises in this chapter, the Loft command lets you create just about any shape you can imagine, from a simple sling to the complex curves of a contour map. If your loft cross sections are a set of closed objects like circles or closed polygons, the resulting object is a 3D solid instead of a surface.

The order in which you select the cross sections is important because Loft will follow your selection order to create the surface or solid. For example, Figure 22-59 shows a series of circles used for a lofted solid. The circles on each side are identical in size and placement, but the order of selection is different. The solid on the left was created by selecting the circles in consecutive order from bottom to top, creating an hourglass shape. The solid on the right was created by selecting the two larger circles first from bottom to top; the smaller, intermediate circle was selected last. This selection order created a hollowed-out shape with more vertical sides.

Figure 22-59 The order in which you select the cross sections affects the result of the Loft command.

In addition to the selection order, several other settings affect the shape of a solid created by the Loft command. In the contour-map example, you selected the Ruled setting from a multifunction grip after you had completed the Loft command. You can also set Loft command options through the Loft Settings dialog box (see Figure 22-60). This dialog box appears during the Loft command when you select the Settings option after you’ve selected a set of cross sections.

Figure 22-60 Loft Settings Smooth Fit

You can radically affect the way the Loft command forms a surface or a solid through the options in this dialog box, so it pays to understand what those settings do. Take a moment to study the following sections that describe the Loft Settings dialog box options.

Ruled and Smooth Fit

The Ruled option connects the cross sections with straight surfaces, as shown in the sample to the left in Figure 22-61.

Figure 22-61 Samples of a Ruled loft at left and a Smooth Fit loft on the right

The Smooth Fit option connects the cross sections with a smooth surface. It attempts to make the best smooth transitions between the cross sections, as shown in the right image in Figure 22-61.

Normal To

Normal To is a set of four options presented in a drop-down list. To understand what this setting does, you need to know that normal is a mathematical term referring to a direction that is perpendicular to a plane, as shown in Figure 22-62. In these options, normal refers to the direction the surface takes as it emerges from a cross section.

Figure 22-62 A normal is a direction perpendicular to a plane.

If you use the All Cross Sections option, the surfaces emerge in a perpendicular direction from all the cross sections, as shown in the first image in Figure 22-63. If you use the End Cross Section option, the surface emerges in a direction that is perpendicular to just the end cross section, as shown in the second image in Figure 22-63. The Start Cross Section option causes the surface to emerge in a direction perpendicular to the start cross section. The Start And End Cross Sections option combines the effect of the Start Cross Section and End Cross Section options.

Figure 22-63 Samples of the Normal To options applied to the same set of cross sections

Draft Angles

The Draft Angles option affects only the first and last cross sections. This option generates a smooth surface with added control over the start and end angles. Unlike the Normal To option, which forces a perpendicular direction to the cross sections, Draft Angles allows you to set an angle for the surface direction. For example, if you set Start Angle to a value of 0, the surface will bulge outward from the start cross section, as shown in the first image of Figure 22-64.

Figure 22-64 The Draft Angles options

Likewise, an End Angle setting of 0 will cause the surface to bulge at the end cross section (see the second image in Figure 22-64).

The Start and End Magnitude settings let you determine a relative strength of the bulge. The right image in Figure 22-64 shows a draft angle of 0 and magnitude of 50 for the last cross section.

Close Surface or Solid

The Close Surface Or Solid option is available only when the Smooth Fit option is selected. It causes the first and last cross section objects to be connected, so the surface or solid loops back from the last to the first cross section. Figure 22-65 shows the cross sections at the left, a smooth version in the middle, and a smooth version with the Close Surface Or Solid option turned on. The Close Surface Or Solid option causes the solid to become a tube.

Figure 22-65 The Close Surface Or Solid option connects the end and the beginning cross sections.

Moving Objects in 3D Space

AutoCAD provides three tools specifically designed for moving objects in 3D space: 3D Align, 3D Move, and 3D Rotate. You can find all three commands in the Home tab’s Modify panel. These tools help you perform common moves associated with 3D editing.

Aligning Objects in 3D Space

In mechanical drawing, you often create the parts in 3D and then show an assembly of the parts. The 3D Align command can greatly simplify the assembly process. The following steps show how to use 3D Align to line up two objects at specific points:

1. Open the align.dwg file.

2. Click the 3D Align tool on the Home tab’s Modify panel, or type 3dalign↵.

3. At the Select objects: prompt, select the 3D wedge-shaped object and press ↵. (The source object is the object you want to move.)

4. At the Specify base point or [Copy]: prompt, pick a point on the source object that is the first point of an alignment axis, such as the center of a hole or the corner of a surface. For the align drawing, use the upper-left corner of the wedge.

5. At the Specify second point or [Continue] <C>: prompt, pick a point on the source object that is the second point of an alignment axis, such as another center point or other corner of a surface. For this example, select the other top corner of the wedge.

6. At the Specify third source point or [Continue] <C>: prompt, press ↵ if two points are adequate to describe the alignment. Otherwise, pick a third point on the source object that, along with the first two points, best describes the surface plane you want aligned with the destination object. Pick the lower-right corner of the wedge shown in Figure 22-66.

Figure 22-66 Aligning two 3D objects

7. At the Specify first destination point: prompt, pick a point on the destination object to which you want the first source point to move. (The destination object is the object with which you want the source object to align.) This is the top corner of the rectangular shape. (See the first destination point in Figure 22-66.)

8. At the Specify second destination point or [eXit] <X>: prompt, pick a point on the destination object indicating how the first and second source points are to align in relation to the destination object. (See the second destination point in Figure 22-66.)

9. You’re prompted for a third destination point. Pick a point on the destination object that, along with the previous two destination points, describes the plane with which you want the source object to be aligned. (See the third destination point in Figure 22-66.) The source object will move into alignment with the destination object.

Moving an Object in 3D

In Chapter 21, you saw how you can use the move gizmo tool to help restrain the motion of an object in the x-, y-, or z-axis. AutoCAD offers a Move command specifically designed for 3D editing that includes a move gizmo tool to restrain motion.

You don’t need to perform these steps as an exercise. You can try the command on your own when you need to use it.

Here’s how it works:

1. Click the 3D Move tool in the Home tab’s Modify panel. You can also enter 3dmove↵.

2. Select the object or set of objects you want to move and press ↵. The Move gizmo appears on the object (see Figure 22-67).

Figure 22-67 The Move gizmo

3. Point to the x-, y-, or z-axis of the Move gizmo but don’t click it. As you hover over an axis, an axis vector appears indicating the direction your object will move if you click the axis, as shown in Figure 22-68.

Figure 22-68 An axis vector appears when you hover over an axis of the gizmo.

4. Click an axis while the vector appears, and then enter a distance along the axis or click a point to complete the move.

Alternately, in step 3, you can hover over and click a plane indicator on the gizmo to restrain the motion along one of the planes defined by two of the axes (see Figure 22-69).

Figure 22-69 Hover over the plane indicator to restrain the motion along a plane.

Rotating an Object in 3D

The 3D Rotate command is another command that is like an extension of its 2D counterpart. With 3D Rotate, a Rotate gizmo appears that restrains the rotation about the x-, y-, or z-axis.

You don’t need to perform these steps as an exercise. You can try the command on your own when you need to use it.

Here’s how it works:

1. Click the 3D Rotate tool in the Home tab’s Modify panel. You can also enter 3drotate↵.

2. Select the object or objects you want to rotate and then press ↵. The Rotate gizmo appears on the object (see Figure 22-70).

Figure 22-70 The Rotate gizmo

3. At the Specify a base point: prompt, you can select a point about which the selected objects are to be rotated. The gizmo will move to the point you select.

4. Point to the colored circle that represents the axis of rotation for your objects. A vector appears, representing the axis of rotation. When you’re happy with the selected axis, click the mouse.

5. At the Specify angle start point or type an angle: prompt, you can enter an angle value or click a point. You can use the Shift key or Ortho mode to restrain the direction to 90°.

6. If you click a point in step 5, you will see the Specify angle end point: prompt. Enter an angle value or click another point for the rotation angle.

You can also just select one of the circles in step 3 instead of selecting a base point. If you do this, then the selected object begins to rotate. You don’t have to select a start and end angle.

Using 3D Mirror

Two other tools, 3D Mirror and 3D Array, are available in the Home tab’s Modify panel. They work in a way that’s similar to how the standard Mirror and Array tools work, with a slight difference.

3D Mirror begins by asking you to select objects. Then you’re asked to specify a mirror plane instead of a mirror axis. You can define a plane using the default three points, or you can use one of the seven other options: Object/Last/Zaxis/View/XY/YZ/ZX. By using a plane instead of an axis, you can mirror an object or set of objects anywhere in 3D space. One way to visualize this is to imagine holding a mirror up to your 3D model. The mirror is your 3D plane, and the reflected image is the mirrored version of the object. Imagine tilting the mirror to various angles to get a different mirror image. In the same way, you can tilt the plane in the 3D Mirror tool to mirror an object in any number of ways.

The Bottom Line

Master the User Coordinate System. The User Coordinate System (UCS) is a vital key to editing in 3D space. If you want to master 3D modeling, you should become familiar with this tool.

Master It Name some of the predefined UCS planes.

Understand the UCS options. You can set up the UCS orientation for any situation. It isn’t limited to the predefined settings.

Master It Give a brief description of some of the ways you can set up a UCS.

Use viewports to aid in 3D drawing. In some 3D modeling operations, it helps to have several different views of the model through the Viewports feature.

Master It Name some of the predefined standard viewports offered in the Viewports dialog box.

Use the array tools. The array tools—Rectangular, Path, and Polar Array—allow you to create 3D arrays dynamically.

Master It What prompt in the Array command will allow you to have a 3D array?

Create complex 3D surfaces. You aren’t limited to straight, flat surfaces in AutoCAD. You can create just about any shape you want, including curved surfaces.

Master It What tool did you use in this chapter’s butterfly chair exercise to convert a surface into a solid?

Create spiral forms. Spiral forms frequently occur in nature, so it’s no wonder that we often use spirals in our own designs. Spirals are seen in screws, stairs, and ramps as well as in other man-made forms.

Master It Name the commands used in the example in the section “Creating Spiral Forms,” and name two elements that are needed to create a spiral.

Create surface models. You can create a 3D surface by connecting a series of lines that define a surface contour. You can create anything from a 3D landscape to a car fender using this method.

Master It What is the tool used to convert a series of lines into a 3D surface?

Move objects in 3D space. You can move objects in 3D space using tools that are similar to those for 2D drafting. But when it comes to editing objects, 3D modeling is much more complex than 2D drafting.

Master It What does the Rotate gizmo do?

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Table of Contents for Chapter 22: Using Advanced 3D Features

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Chapter 22

Using Advanced 3D Features