Daniel John Stine
Schroff Development Corporation
Crash Course Introduction (the Basics)
This lesson is meant to give you a brief introduction to a few of the
most used commands. You will be walked through each drawing, in
this lesson,step-by-step. The intent is for the user to get some of the
basic concepts in mind before going through subsequent chapters.
Lines and Shapes
The number one command in AutoCAD is the Line command. Lines in
AutoCAD are extremely precise drawing elements. This means you can
create very accurate drawings. Lines, or any drawn object, can beas
precise as eight decimal places (i.e., 24.999999999) or 1/256.
AutoCAD is a vector based program. That means each drawn object is
stored in a numerical database. For example, a line is stored in the
drawing’s database as the X, Y, Z coordinates for its starting point and
the X,Y,Z, coordinates for its endpoint. These coordinates are all
relative to the drawings 0, 0, 0 position; calledthe Origin.
When a line needs to be displayed on the screen, AutoCAD reads the
line’s coordinates from the drawing database and displays a line
between those two points on the screen. This means that the line will
be very accurate at any scale or zoom magnification.
A raster based program, in contrast to vector based, is comprised of
dots that infill a grid. Thegrid can vary in density, and is typically
referred to as resolution (e.g., 600x800, 1600x1200, etc.). This file
type is used by graphics programs that typically deal with
photographs; such as Adobe Photoshop. There are two reasons this
type of file is not appropriate for CAD programs:
1. A raster based line is composed of many dots on a grid (which
also representsthe line’s width). When you zoom in (or magnify)
the line, it becomes pixilated and you actually start to see each
dot in the grid. In a vector file you can “infinitely” zoom in on a
line and it will never become pixilated because the program
recalculates the line each time you zoom in.
Residential Design using AutoCAD 2007
2. A CAD program, such as AutoCAD,only needs to store the
starting point and end point coordinates for each line; the dots
needed to draw the line are calculated on the fly for the current
screen resolution. Whereas a raster file has to store each dot
that represents the full length and width of the line. This can
vary from a few hundred dots to several thousand dots,
depending on the resolution, for the same line.
Thefollowing graphic illustrates this point:
Vector vs. Raster lines
Figure 2-1.1a Vector Line Enlarged 1600%
Figure 2-1.1 Vector Line Example
File Size: approx. 33kb
Figure 2-1.2a Raster Line Enlarged 1600%
Figure 2-1.2 Raster Line Example
File Size: approx. 4.4MB
Crash Course Introduction (the Basics)Copyrighted
The Line Command:
You will now study the Line command.
Close the empty drawing automatically opened by AutoCAD.
The empty startup drawing that is opened by default when you start AutoCAD,
does not have the various variables preset for architectural CAD use.
So you should make sure you start with thecorrect template file whenever
instructed to start a new drawing file in this book.
Select New from the File menu.
Use the following Template file to start your new drawing from:
Architectural Imperial.dwt (in the SheetSets sub-folder).
Click on the Model Tab to switch to Model Space (which is
where all the drawing is done as previously mentioned).
Leer documento completo
Regístrate para leer el documento completo.