AutoCAD 2005 for Dummies

AutoCAD prompts you to specify tangent lines for each end of the spline:

Specify start tangent:
Specify end tangent:

  The Specify start tangent and Specify end tangent prompts can control the curvature of the start and end points of the spline. In most cases, just pressing Enter at both prompts to accept the default tangents works fine.

6. Press Enter twice to accept the default tangent directions.

AutoCAD draws the spline.

Figure 5-9 shows some examples of splines.

Figure 5-9: A slew of splines.

  After you’ve drawn a spline, you can grip edit it to adjust its shape. See Chapter 6 for information about grip editing. If you need finer control over spline editing, look up the SPlinEdit command in the AutoCAD online help.

Donuts: The circles with a difference

Creating a donut is a simple way to define a single object that consists of two concentric circles with the space between them filled.

When you start the DOnut command, AutoCAD prompts you for the inside diameter and the outside diameter — the size of the hole and the size of the donut, as measured across their widest points. After you’ve entered these values, AutoCAD prompts you for the center point of the donut. But one donut is rarely enough, so AutoCAD keeps prompting you for additional center points until you press Enter (the AutoCAD equivalent of saying, “no, really, I’m full now!”).

The following example draws a regulation-size donut, with a 1.5-inch hole and 3.5-inch outside diameter. Figure 5-10 shows several kinds of donuts.

Command: DOnut Enter
Specify inside diameter of donut 0.5000: 1.5 Enter
Specify outside diameter of donut 1.0000: 3.5 Enter
Specify center of donut or exit:
 pick or type the center point of one or more donuts
Specify center of donut or exit: Enter

Figure 5-10: Donuts, plain and jelly-filled.

  You can use the DOnut command to create a filled circle — also known as a jelly-filled donut. Just specify an inside diameter of 0.

Revision clouds on the horizon

It’s customary in many industries to submit a set of drawings at a stage of completion and then submit them again later with revisions — corrections, clarifications, and requested changes. Often, the recipients like to locate changed stuff easily. A common drafting convention in many industries is to call attention to revised items by drawing free-form clouds around them. The REVCLOUD command makes quick work of drawing such clouds.

Drawing revision clouds is easy, after you understand that you click with the mouse only once in the drawing area. That one click defines the starting point for the cloud’s perimeter. After that, you simply move the cursor around, and the cloud takes shape. When you return to near the point that you clicked in the beginning, AutoCAD automatically closes the cloud.

The following example shows you how to draw a revision cloud. Figure 5-11 shows what revision clouds look like.

Command: REVCLOUD
Minimum arc length: 0.5000 Maximum arc length: 0.5000
Style: Normal
Specify start point or [Arc length/Object/Style] Object:
 pick a point along the perimeter of your future cloud
Guide crosshairs along cloud path...
 sweep the cursor around to define the cloud’s perimeter

Figure 5-11: Cloud cover.

You don’t need to click again. Simply move the cursor around without clicking. AutoCAD draws the next lobe of the cloud when your cursor reaches the Minimum arc length distance from the end of the previous lobe.

Continue moving the cursor around until you return to the point that you clicked at first.

Revision cloud finished.

  Here are a few tips for using revision clouds:

? It’s a good idea to put revision clouds on their own layer so that you can choose to plot with or without the clouds visible.

? You’ll probably find it easier to control the shape of revision clouds if you turn off ortho mode before you start the command.

? You may need to add a triangle and number, as shown in Figure 5-11, to indicate the revision number. A block with an attribute is a good way to handle this requirement: Chapter 13 covers blocks and attributes.

  If the revision cloud’s lobes are too small or too large, erase the cloud, restart the REVCLOUD command, and use the command’s Arc length option to change the minimum and maximum arc lengths. The default minimum and maximum lengths are 0.5 (or 15 in metric drawings) multiplied by the DIMSCALE (DIMension SCALE) system variable setting. If you make the minimum and maximum lengths equal (which is the default), the lobes will be approximately equal in size. If you make them unequal, there will be more variation in lobe size — you’ll get “fluffier” clouds. Fortunately, of these options are more than most nonmeteorologists will need. If you’ve set DIMSCALE properly during your drawing setup procedure (see Chapter 3), REVCLOUD should do a pretty good job of guessing reasonable default arc lengths.

Scoring Points

I thought about not covering points in this book, but I didn’t want you complaining that AutoCAD 2005 For Dummies is pointless.

  The word point describes two different things in AutoCAD:

? A location in the drawing that you specify (by typing coordinates or clicking with the mouse)

? An object that you draw with the POint command

Throughout this chapter and most of the book, I tell you to specify points —

that’s the location meaning. This section tells you how to draw point objects.

A point object in AutoCAD can serve two purposes.

? Points often identify specific locations in your drawing to other people who look at the drawing. A point can be something that displays on the screen, either as a tiny dot or as another symbol, such as a cross with a circle around it.

? You can use points as precise object snap locations. Think of them as construction points. For example, when you’re laying out a new building, you might draw point objects at some of the engineering survey points and then snap to those points as you sketch the building’s shape with the polyline