- Introduction
- Creating a New Drawing
- Model Space and Layout Space
- Communicating with AutoCAD
- Object Snaps, Ortho Mode, and Polar Tracking
- Undo/Redo
- Grid and Snap
- Draw a Circle
- Navigating Around the Drawing
- Object Properties
- Layers
- Dimension Styles
- Dimensioning
- Modifying Drawing Objects
- Grip Editing
- Introduction to Advanced Editing Techniques
- Cleaning Up Layout Space
- Plotting and Page Setups
- Chapter Summary
- Chapter Test Questions
This chapter is from the book
This chapter is from the book
This chapter is from the book
Layers
As you saw in the previous exercise, some properties are common to all objects. These include color, linetype, lineweight, layer, and transparency. Color is fairly obvious; it is the display color of the object on the screen. Linetype refers to how the line is displayed—for example, a dashed line, dotted line, or continuous line. Lineweight is the plotted width of the object (think of it as pen width). Transparency controls the visibility of objects so you can see through them.
You can assign a color, linetype, lineweight, and transparency level to each object individually; however, when your drawing grows in complexity, you can quickly find it difficult to manage each object individually. This is where layers come to the rescue.
Layers give you a way to group objects together logically. The objects are still separate but share common properties and can be manipulated as a group.
Each layer consists of a name, color, linetype, lineweight, transparency level, and a number of on/off settings. When you draw an object, the properties of the current layer are applied to that object. The quickest and easiest way to manage layers is via the Layers panel on the Home tab of the ribbon shown in Figure 2-20. The Layer drop-down list allows you to set the current drawing layer (see Figure 2-20). The Layer Properties Manager palette allows you to create and manage drawing layers.
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FIGURE 2-20 The Layers panel on the Home tab of the ribbon
EXERCISE 2-11 CREATING NEW LAYERS
Choose the Layer Properties tool from the Layers panel. The Layer Properties Manager palette appears (see Figure 2-21). There are three layers currently defined. Layer 0 is the default layer included in every drawing. The Title Block and Viewport layers came from the drawing template.
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FIGURE 2-21 The Layer Properties Manager palette
Choose the New Layer button at the top of the palette (see Figure 2-21). Type Dim<Enter> for the name.
Press <Enter> again. AutoCAD will create another new layer. Type Object <Enter> for the name.
Choose the color setting for the Object layer you just created. This will display the Select Color dialog box (see Figure 2-22). Choose the color red (index color 1) and choose OK to close the dialog box.
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FIGURE 2-22 The Select Color dialog box
Choose the New Layer button and create a layer named Center.
Select the color setting for the Center layer. Set the color to blue (index color 5) and choose OK to close the Select Color dialog box.
Choose the linetype setting for the Center layer. This displays the Select Linetype dialog box (see Figure 2-23).
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FIGURE 2-23 The Select Linetype dialog box
Choose the Load… button. This displays the Load or Reload Linetypes dialog box (see Figure 2-24).
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FIGURE 2-24 The Load or Reload Linetypes dialog box
Scroll down through the list to see the available linetypes. Next to each line is a text representation of what the linetype looks like. Select the CENTER2 linetype and choose OK. This loads this linetype definition into the drawing and returns you to the Select Linetype dialog box.
In the Select Linetype dialog box, select the CENTER2 linetype you just loaded and choose OK. This assigns the linetype you just loaded to the layer and returns you to the Layer Properties Manager palette.
Choose the Layer Properties button to close the Layer Properties Manager palette.
Save your drawing.
So far, the appearance of your drawing hasn’t changed. All you have done at this point is to define some new layers.
EXERCISE 2-12 DRAWING ON A LAYER
From the Layers panel, choose Center from the Layer drop-down list (see Figure 2-25). This sets the layer Center as the current drawing layer.
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FIGURE 2-25 The Layer drop-down list
Toggle the Ortho Mode drawing tool to on and choose the Line tool. Type 4.25,3<Enter> to specify the starting point.
Drag your cursor to the right and type 1.5<Enter> to specify the length and direction of the line segment.
Press <Esc> to end the LINE command.
Press the spacebar to restart the LINE command. Type 5,2.25<Enter> to specify the starting point.
Drag the cursor up and type 1.5<Enter> to specify the length and direction of the line segment.
Press <Esc> to end the LINE command. Your drawing should now resemble Figure 2-26.
Save your drawing.
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FIGURE 2-26 Adding centerlines to the drawing
The new lines have the color and linetype of the Center layer. The rest of the drawing was created on Layer 0. In the next exercise, you’ll move those objects from Layer 0 to the Object layer.
EXERCISE 2-13 MOVING OBJECTS TO ANOTHER LAYER
In the drawing area, pick a point in a blank area below and to the left of your figure. AutoCAD prompts you to Specify opposite corner or 
. Move your cursor up and to the right. A blue selection window will drag from the point you picked.
Pick a point above and to the right of your figure. This will select all the objects inside the box you just specified.
Hold down the <Shift> key and pick the two centerlines you just drew. This removes those lines from the selection.
Select the Object layer from the Layer drop-down list. The objects “move” to the Object layer and take on the properties of that layer.
Press <Esc> to clear the selection.
Save your drawing.
Of course, the objects didn’t actually move. Their layer property was simply changed from 0 to Object. However, you can think of this as the objects “floating” from one layer to another or (in the pin-board drafting world) moving the objects from one overlay sheet to another.
Freeze and Thaw a Layer
Your drawing objects are now organized into a few logical layers. Next we’ll look at some methods of manipulating layers in your drawing.
EXERCISE 2-14 FREEZING AND THAWING LAYERS
Select Layer 0 from the Layer drop-down list. This sets Layer 0 as the current layer.
From the Layer drop-down list, click on the sun icon next to layer Center (see Figure 2-27). The sun icon will change to a snowflake. Now pick anywhere in your drawing to close the Layer drop-down list. This freezes the Center layer and hides it from view.
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FIGURE 2-27 The Layer drop-down list
From the Layer drop-down list, click on the snowflake icon next to layer Center. The snowflake now turns back to a sun. Pick anywhere in the drawing area to close the Layer drop-down list. This thaws the Center layer, making it visible again.
Save your drawing.
When layers are frozen, AutoCAD acts as though the objects on those layers don’t exist. Objects on frozen layers are hidden from view and cannot be changed while the layer is frozen. The current drawing layer cannot be frozen.
AutoCAD also has an On/Off setting for layers (represented by the lightbulb in the Layer drop-down list). While turning layers off will hide them from view, objects on those layers can still be modified (i.e., erased). For this reason, freezing and thawing layers is generally preferred to turning layers on and off.
Lock and Unlock a Layer
Although the Freeze option will prevent objects from being modified, it also hides them from view. The Lock/Unlock setting allows you to prevent objects from being modified while still keeping them displayed on screen.
EXERCISE 2-15 LOCKING AND UNLOCKING LAYERS
From the Layer drop-down list, click on the open-lock icon next to layer Object (see Figure 2-28). The open-lock icon will change to a closed lock. Pick anywhere in your drawing to close the Layer drop-down list.
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FIGURE 2-28 Locking the Object layer
Double-click on the circle so the Quick Properties palette opens.
Change the Radius property of the circle to 1. AutoCAD rejects the input and maintains the 0.5 Radius value.
From the Layer drop-down list, click on the lock icon next to layer Object and pick anywhere in the drawing to close the Layer drop-down list. The Object layer is now unlocked.
Save your drawing.
This section has touched on only a few key elements of layering and AutoCAD’s layer management tools. Layer management is a crucial element of using AutoCAD effectively.