Using Layers to Organize Your Drawing - AutoCAD 2011 and AutoCAD LT 2011: No Experience Required - page 242

using Layers as an organizing tool
To understand what layers are and why they are so useful, think again about the
transparent overlay sheets used in hand drafting. Each overlay is designed to be
printed. The bottom sheet might be a basic floor plan. To create an overlay sheet
for a structural drawing, the drafter traces over only the lines of the floor plan
that the overlay needs and then adds new information pertinent to that sheet.
For the next overlay, the drafter performs the same task again. Each sheet, then,
contains some information in common as well as data unique to that sheet.
In AutoCAD, using layers allows you to generate all the sheets for a set of over-
lays from a single file (see Figure 6.1). Nothing needs to be drawn twice or traced.
The wall layout is on one layer and the rooflines are on another. Doors are on a
third. You can control the visibility of layers so that you can make all objects resid-
ing on a layer temporarily invisible. This feature lets you put all information keyed
to a particular floor plan in one .dwg file. From that drawing, you can produce a
series of derived drawings — such as the foundation plan, the second floor plan,
the reflected ceiling plan, and the roof plan — by making a different combina-
tion of layers visible for each drawing or drawing layout (layouts are covered in
Chapter 14, “Using Layouts to Set Up a Print”). When you make a print, you decide
which layers will be visible. Consequently, in a set of drawings, each sheet based on
the floor plan displays a unique combination of layers, all of which are in one file.
NOTE a typical project such as a building can easily amass more
than 100 layers. Managing so many layers from a single .dwg file can prove
tricky at times, and so layers are but one of several organizational methods
autoCaD provides. another method, using external references (xrefs) , is a
little more advanced, but provides an extra level of flexibility needed for
many real-world projects. You'll have the chance to explore xrefs in detail in
Chapter 13, “Managing external references.”
As an organizing tool, layers allow you to classify the various objects in a com-
puterized drawing — lines, arcs, circles, and so on — according to the compo-
nent of the building they represent, such as doors, walls, windows, dimensions,
and notes. Each layer is assigned a color, and all objects placed on the layer take
on that assigned default color unless you specify a different color for the objects.
This lets you easily distinguish between objects that represent separate compo-
nents of the building (see Figure 6.2). You can quickly tell which layer a given
object or group of objects is on.