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CADD PRIMER
Chapter 6: Working with Layers

Contents

Key Terms in this Chapter
The Concept of Layers in CADD
Creating Layers for an Engineer’s Office
The Tools to Work with Layers
  • Creating New Layers
  • Setting a Layer Current
  • Changing Color and Line Type of Layers
  • Turning Layers On or Off
  • Locking and Unlocking Layers
Are Layers Absolutely Necessary?
AutoCAD, MicroStation and Cadkey Terms


About This Chapter

This chapter describes how to create different layers within a drawing and manipulate data using the layering capabilities of CADD. Most of the leading CADD programs offer layering capabilities that enable you to group specific data on different layers. This enables you to organize data within a drawing, which makes it easier to work with CADD drawings. Some CADD programs allow you to create only a limited number of layers in a drawing while the others allow creating as my layers as you like. Some programs offer elaborate layering functions than the others. This chapter describes the commonly used layering functions available in most programs.

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Key Terms in this Chapter
 
Term
Description
Composite drawing A drawing that contains multiple drawings created with the help of CADD layers. 
Layer or

level

A transparent surface created within a drawing.
Layer color A color assigned to a layer.
Layer off Making the drawing objects on a layer invisible.
Layer on Making the drawing objects on a layer visible.
Layer line type A line type assigned to a layer.
Locking a layer Making the drawing objects on a layer permanent and non-editable.
Macro A recorded set of instructions that can be used to repeat a task.

The Concept of Layers in CADD AutoCAD Forum

Layers are imaginary transparent surfaces that can be created within a CADD drawing. You can draw on these imaginary surfaces and group drawing objects on different layers (Fig. 6.1). This helps to organize CADD drawings and makes editing much easier. You can turn the layers on or off to view or edit specific objects. When you turn a layer off, the objects on that layer disappear from the screen; when you turn it back on, they are displayed. Using layers enables you to control the display of specific information on the screen by turning a combination of layers on or off.

You may create dozens of layers in a drawing to segregate drawing objects. You may create separate layers to show dimensions, hatch patterns and for any drawing objects that are different in nature. This provides a great convenience in editing drawings. When drawings are complex and a number of drawing objects are overlapping, you can turn off the unwanted layers. This makes it much easier to select the desired objects for editing. When you are finished editing, you can turn the layers back on.

Layers are commonly used in professional architecture and engineering drawings. Architects and engineers often need to coordinate different engineering services in a plan. They can illustrate different engineering services on the same drawing using different layers. This helps them understand how one engineering service relates to another.

Note:

Layers are given specific characteristics that distinguish them from each other. Each layer has a specific color and line type. Whatever you draw on a layer is drawn with that color and line type. This color coding helps to identify which drawing objects are placed on which layer.
 

The Tools to Work with Layers  
CADD provides a number of tools that allow you to work efficiently with layers. Most programs use a layer control window that allows you to manage all aspects of working with layers.

The following are the basic tools for working with layers:
 

  • Creating new layers
  • Setting a layer current
  • Changing color and line type for a layer
  • Turning layers on or off
  • Locking and unlocking layers


Creating New Layers

CADD allows you to create a number of layers in a drawing. To create a new layer you need to enter the name of the layer and assign a color and line type to it. The layer name should reflect the kind of information it contains.

Most companies follow standard guidelines in naming layers and placing specific information on specific layers. This allows CADD users to efficiently coordinate information. Professional institutes such as the American Institute of Architects (AIA) and the American Institute of Engineers (AIE) have developed standard naming conventions for layers that are commonly used by CADD professionals.

AIA layers constitute hundreds of names that accommodate all disciplines of the building trade. The first letter of the layer name identifies a building trade; for example, A for architectural, E for electrical, I for interior design, S for structural, L for landscape and G for general drawings. There are dozens of layer names established for each engineering discipline.

Setting a Layer Current

When you need to work on a specific layer, you must set that layer to be current by selecting it in the layer control window (Fig. 6.3). When a layer is set current, whatever you draw is drawn on that layer. The current layer name or number is displayed in the status bar.

Let's say you want to add some new furniture to the diagram as shown in Fig. 6.2. In order to maintain consistency, the new furniture must be drawn on the same layer as the existing furniture. You can set the furniture layer as the current layer. Subsequently, all the drawing work will be drawn on the furniture layer and should appear in the same color as the other furniture. If the color or line type are different, you may be working on the wrong layer.

Changing Color and Line Type of Layers

You can change the color and line type of layers at any time. When you change the color and line type of layers, all the drawing objects on that layer are displayed with the new color and line type. You can instantly make adjustments to colors and line types by selecting the layer from the layer control window (Fig. 6.3, 6.4) and choosing a color and line type for the layer.

Note: The colors used in a CADD drawing represent certain line weights and pen numbers when the drawings are plotted. More on colors and line weights is discussed in Chapter 8, "Printing and Plotting."

Turning Layers On or Off

You can turn any number of layers on or off by selecting them from the layer control window. To turn on a layer, highlight it in the layer control window and press the ON button. Similarly, you can turn the layers off when needed.

Turning layers on and off provides a great convenience for drawing and editing, as well as for plotting. To plot selected layers, simply turn off the rest of the layers. When drawing and editing, it is also a good idea to turn off unwanted layers, particularly when there is a lot of information on the screen. This speeds up the display process.

Locking and Unlocking Layers

Most CADD programs allow you to assign a lock or unlock status to layers. If a layer is locked, it means that you can't erase, move, or copy anything on that layer. To erase any drawing object from that layer, you must first unlock it. If there are certain drawing objects that are of a permanent nature and you don't want to run the risk of accidentally erasing or moving them, you can lock that layer.
 

Are Layers Absolutely Necessary?  
Layers are not absolutely necessary, however they provide a convenient way to manage information in CADD drawings. For example, in the engineer's office example, without the help of this function you may have to create separate drawings to show the furniture plan, lighting plan, etc. With the help of layers, you can create just one composite drawing. The composite drawing can contain all the plans. It makes it easier to correlate information from one plan to another.

For complex drawings, layers are a must because they make editing much easier. Often you need to select only specific drawing objects for editing, and the use of layers makes its very easy to select them.

Refer to CADD PRIMER for details on the topics listed above.


Note: CADD PRIMER is illustrated with more than 100 diagrams. The above diagram is an example from CADD PRIMER illustrating the concept of layers in CADD.

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