AutoCAD 2005 For Dummies (2004)

70 Part I: AutoCAD 101

If you want to avoid this nonsense, create a folder where you can find it easily (for example, C:\Acad-templates or F:\Acad-custom\templates on a network drive). Put the templates that you actually use there and change the Drawing Template File Location so that it points to your new template folder.

As this chapter demonstrates, there’s quite a bit to drawing setup in AutoCAD. As with any other initially forbidding task, take it step by step and soon the sequence will seem natural. The Drawing Setup Roadmap on the Cheat Sheet will help you stay on track and avoid missing a step.

Part II

Let There Be Lines

In this part . . .

Lines, circles, and other elements of geometry make up the heart of your drawing. AutoCAD offers many different drawing commands, many ways to use them to draw objects precisely, and many properties for controlling the objects’ display and plot appearance. After you

draw your geometry, you’ll probably spend at least as much time editing it as your design and drawings evolve. And in the process, you need to zoom in and out and pan all around to see how the entire drawing is coming together. Drawing geometry, editing it, and changing the displayed view are the foundation of the drawing process; this part shows you how to make that foundation solid. And for those who want to build a little higher, this section ends with an introduction to 3D modeling and presentation.

Chapter 4

Get Ready to Draw

In This Chapter

Managing layers

Managing other object properties: color, linetype, and lineweight

Copying layers and other named objects with DesignCenter

Typing coordinates at the keyboard

Snapping to object features

Using other precision drawing and editing techniques

CAD programs are different from other drawing programs. You need to pay attention to little details like object properties and the precision of

the points that you specify when you draw and edit objects. If you just start drawing objects without taking heed of these details, you’ll end up with an unruly mess of imprecise geometry that’s hard to edit, view, and plot.

This chapter introduces you to the AutoCAD tools and techniques that help you prevent making CAD messes. This information is essential before you start drawing objects and editing them, which I describe in Chapters 5 and 6.

Drawing and Editing with AutoCAD

When you first start using AutoCAD, its most daunting requirement is the number of property settings and precision controls that you need to pay attention to — even when you draw a simple line. Unlike in many other programs, it’s not enough to draw a line in a more-or-less adequate location and then slap some color on it. All those settings and controls can inspire the feeling that you have to find out how to pilot an airliner to make a trip down the street. (The advantage is that, after you are comfortable in the cockpit, AutoCAD will take you on the long-haul trips and get you there faster.)

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These are the three keys to good CAD drawing practice:

Pay attention to and manage the properties of every object that you draw — especially the layer that each object is on.

Pay attention to and manage the named objects in every drawing — the layers, text styles, block definitions, and other nongraphical objects that serve to define the look of all the graphical objects in the drawing.

Pay attention to and control the precision of every point and distance that you use to draw and edit each object.

These can seem like daunting tasks at first, but the following three sections help you cut them down to size.

Managing Your Properties

All the objects that you draw in AutoCAD are like good Monopoly players: They own properties. In AutoCAD, these properties aren’t physical things; they’re an object’s characteristics such as layer, color, linetype, and lineweight. You use properties to communicate information about the characteristics of the objects you draw, such as the kinds of real-world objects they represent, their materials, their relative location in space, or their relative importance. In CAD, you also use the properties to organize objects for editing and plotting purposes.

You can view — and change — all of an object’s properties in the Properties palette. In Figure 4-1, the Properties palette shows properties for a line object.

Figure 4-1:

A line rich in properties.

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To toggle the Properties palette on and off, click the Properties button on the Standard toolbar. Before you select an object, the Properties palette displays the current properties — properties that AutoCAD applies to new objects when you draw them. After you select an object, AutoCAD displays the properties for that object. If you select more than one object, AutoCAD displays the properties that they have in common.

Putting it on a layer

Every object has a layer as one of its properties. You may be familiar with layers — independent drawing spaces that stack on top of each other to create an overall image — from using drawing programs. AutoCAD, like most CAD programs, uses layers as the primary organizing principle for all the objects that you draw. Layers organize objects into logical groups of things that belong together; for example, walls, furniture, and text notes usually belong on three separate layers, for a couple of reasons:

They give you a way to turn groups of objects on and off — both on the screen and on the plot.

They provide the best way of controlling object color, linetype, and lineweight.

Looking at layers

If you spent any time “on the boards,” as grizzled old-timers like to call paper-and-pencil drafting, you may be familiar with the manual drafting equivalent of layers. In pin-bar drafting, you stack a series of transparent Mylar sheets, each of which contains a part of the overall drawing — walls on one sheet, the plumbing system on another, the electrical system on another, and so on. You can get different views of the drawing set by including or excluding various sheets.

If you’re too young to remember pin-bar drafting — or old enough to prefer not to — you may remember something similar from a textbook about human anatomy. There’s the

skeleton on one sheet, the muscles on the next sheet that you laid over the skeleton, and so on until you built up a complete picture of the human body — that is, if your parents didn’t remove some of the more grown-up sections.

CAD layers serve a similar purpose; they enable you to turn on or off groups of related objects. But layers do a lot more. You use them in AutoCAD to control other object display and plot properties, such as color, linetype, and lineweight. You also can use them to make some editing tasks more efficient and reduce the time that it takes AutoCAD to load some drawings. Take the time to give each of your drawings a suitably layered look.

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You create layers, assign them names, assign them properties such as color and linetype, and then put objects on them. When you draw an object, AutoCAD automatically puts it on the current layer, which appears in the drop-down list on the Layers toolbar.

Before you draw any object in AutoCAD, you should set an appropriate layer current — creating it first, if necessary, using the procedure described later in this section. If the layer already exists in your drawing, you can make it the current layer by choosing it in the Layers toolbar, as shown in Figure 4-2.

Make sure that no objects are selected before you use the Layer drop-down list to change the current layer. (Press the Esc key twice to be sure.) If objects are selected, the Layer drop-down list displays — and lets you change — those objects’ layer. When no objects are selected, the Layer drop-down list displays — and lets you change — the current layer.

If you forget to set an appropriate layer before you draw an object, you can select the object and then change its layer by using either the Properties palette or the Layer drop-down list.

Figure 4-2:

Set a current layer before you draw.

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Stacking up your layers

How do you decide what to call your layers and which objects to put on them? Some industries have developed layer guidelines, and many offices have created documented layer standards. Some projects even impose specific layer requirements. (But be careful; if someone says, “You need a brick layer for this project,” that can mean a couple of different things.) Ask

experienced CAD drafters in your office or industry how they use layers in AutoCAD. If you can’t find any definitive answer, create a chart of layers for yourself. Each row in the chart should list the layer name, default color, default linetype, default lineweight, and what kinds of objects belong on that layer. Chapter 15 includes an example.

Accumulating properties

Besides layers, the remaining object properties that you’re likely to want to use often are color, linetype, lineweight, and possibly plot style. Table 4-1 summarizes these four properties.

Table 4-1	Useful Object Properties
Property	Controls
Color	Displayed color and plotted color or lineweight
Linetype	Displayed and plotted dash-dot line pattern
Lineweight	Displayed and plotted line width
Plot style	Plotted characteristics (see Chapter 12)

In Release 14 and older versions of AutoCAD, color also controlled the plotted lineweight of each object — strange, but now very common in the AutoCAD world. You may find yourself working this way even in AutoCAD 2005, for compatibility with drawings (and co-workers) that use the old way, as described in the “About colors and lineweights” sidebar.

AutoCAD gives you two different ways of controlling object properties:

By layer: Each layer has a default color, linetype, lineweight, and plot style property. Unless you tell AutoCAD otherwise, objects inherit the properties of the layers on which they’re created. AutoCAD calls this approach controlling properties by layer.

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By object: AutoCAD also enables you to override an object’s layer’s property setting and give the object a specific color, linetype, lineweight, or plot style that differs from the layer’s. AutoCAD calls this approach controlling properties by object.

If you’ve worked with other graphics programs, you may be used to assigning properties such as color to specific objects. If so, you’ll be tempted to use the by object approach to assigning properties in AutoCAD. Resist the temptation. In almost all cases, it’s better to create layers, assign properties to each layer, and let the objects on each layer inherit that layer’s properties. Here are some benefits of using the by layer approach:

You can easily change the properties of a group of related objects that you put on one layer. You simply change the property for the layer, not for a bunch of separate objects.

Experienced drafters use the by layer approach, so if you work with drawings from other people, you’ll be much more compatible with them if you do it the same way. You’ll also avoid getting yelled at by irate CAD managers, whose jobs include haranguing any hapless newbies who assign properties by object.

About colors and lineweights

AutoCAD drafters traditionally have achieved different printed lineweights by mapping various on-screen display colors of drawing objects to different plotted lineweights. An AutoCAD-using company may decide that red lines are to be plotted thin, green lines are to be plotted thicker, and so on. This indirect approach sounds strange, but until AutoCAD 2000, it was the only practical way to plot from AutoCAD with a variety of lineweights. Also, not many people plotted in color until recently, so few folks minded the fact that color was used to serve a different master.

AutoCAD 2000 added lineweight as an inherent property of objects and the layers that they live on. Thus, object display color can revert to being used for — surprise! — color. You can use display colors to control plot colors, of course. But even if you make monochrome plots, you can use color to help you distinguish

different kinds of objects when you view them on-screen or to make jazzy on-screen presentations of drawings for others.

Lineweights are handy, but they have quirks. Watch for these problems as you work with them:

Although lineweights may have been assigned to objects in a drawing that you open, you won’t necessarily see them on the screen. You must turn on the Show/Hide Lineweight button on the AutoCAD status bar (the button labeled LWT).

On a slow computer or a complex drawing, showing lineweights may cause AutoCAD to redraw the screen more slowly when you zoom and pan.

You may need to zoom in on a portion of the drawing before the differing lineweights become apparent.

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If you take my advice and assign properties by layer, all you have to do is set layer properties in the Layer Properties Manager dialog box, as shown in Figure 4-3. Before you draw any objects, make sure the Color Control, Linetype Control, Lineweight Control, and Plotstyle Control drop-down lists on the Properties toolbar are set to ByLayer, as shown in Figure 4-4.

Figure 4-3:
Use layer
properties
to control
object
properties.
							Plotstyle control
	Layer control					Linetype control
Figure 4-4:
ByLayer all
the way.
			Color control				Lineweight control

If the drawing is set to use color-based plot styles instead of named plot styles (see Chapter 12), the Plotstyle Control drop-down list will be inactive and will display ByColor.

If you don’t like doing things the wrong way and getting yelled at by CAD managers, don’t assign properties to objects in either of these ways:

Don’t choose a specific color, linetype, lineweight, or plot style from the appropriate drop-down list on the Object Properties toolbar, and then draw the objects.

Don’t draw the objects, select them, and then choose a property from the same drop-down lists.

If you prefer to do things the right way, assign these properties by layer, as I describe in this section.