AutoCAD linetype customizing facilities
31 Aug, 1999 By: Bill FaneOnce upon a time, a long time ago, in an AutoCAD release very far away, someone decided that AutoCAD should draw using a variety of noncontinuous linetype styles. Someone further decided that the people at Autodesk, as smart as they were, could not forsee every possible type of noncontinuous linetype that users might desire or require, so in their great wisdom they allowed users to create their own custom line definitions.
AutoCAD has 46 standard
linetypes defined. For the most part, the 46 cover every conceivable situation.
We will begin by looking at the current ones and then investigate the
need for and method of defining other styles.
Whats available
As usual these days, AutoCAD has umpteen different ways start a specific
command. Whenever I mention a specific way in a column, I get inundated
with e-mail telling me about the other umpteen minus one ways. I know,
but I dont have space to list them all here.
Anyway, issue either the Layer or Linetype command from the Command prompt,
or go to Format|Layer, or Format|Linetype, or use the Object properties
toolbar and pick Layer or Linetype, or whatever.
Pick the Linetype tab of the Layer and linetype dialog box to see the
46 linetypes.
What 46? I see only three.
Youre right. Initially, new drawings show only three types. First, the
explanation of continuous is pretty obvious. In fact, its definition is
built in by default.
Two other names also turn up, but they are not really linetypes. Bylayer
simply means that the object takes on the linetype properties of the layer
on which it resides. Byblock means that if you use an object in
a block definition, the object within the block takes on the linetype
properties of the layer in which you insert the block.
To see the other 45 linetypes, load the definitions from an external file.
From the Linetype tab of the Layer and Linetype dialog box, pick Load.
This defaults to the linetype definitions stored in the external file
called ACAD.LIN, as shown in figure 1 below.
![]() Figure 1. Each linetype definition has a name and a description in ACAD.LIN. |
Each linetype definition
has a name and a description. The description includes a series of dashes
and dots that show approximately what the linetype looks like. As you
can see, linetypes cover ISO (metric) styles and Imperial styles for things
such as hidden, section, center, and phantom lines. Most are also available
in regular, half, and double scales.
You usually use the Ltscale and Celtscale commands to set a specific linetype
scale for all objects globally or for specific objects within the drawing,
but you can also select fine and coarse variants of linetypes.
Select one or more linetypes, click OK, and the selected linetypes become
available in your drawing.
Cool, but for drawing schematic drawings I need linetypes to indicate
different line contents such as pneumatic, hydraulic, hot water, cold
water, and so on.
Season of our dis-contents
Note that you had to load the desired linetypes from an external file.
That file is a simple text file. To add or create custom linetype definitions,
you can either edit the external file with Notepad or create your own
separate file. If you edit the standard ACAD.LIN
file, save an original copy somewhere so you can go back. If you dont,
the file is always available from the install CD-ROM.
The standard ACAD.LIN
file resides in the AutoCAD Program files\
\Support directory. In Notepad
you;ll see that the first portion looks almost exactly like this:
AutoCAD ignores anything that follows a semicolon (;) and blank lines. ;;
;; AutoCAD Linetype Definition file
;; Version 2.0
;; Copyright 1991, 1992, 1993, 1994, 1996 by Autodesk
;;
*BORDER,Border __ __ . __ __ . __ __ . __ __ . __ __ .
A,.5,-.25,.5,-.25,0,-.25
*BORDER2,Border (.5x) __.__.__.__.__.__.__.__.__.__.__.
A,.25,-.125,.25,-.125,0,-.125
*BORDERX2,Border (2x) ____ ____ . ____ ____ . ___
A,1.0,-.5,1.0,-.5,0,-.5
*CENTER,Center ____ _ ____ _ ____ _ ____ _ ____ _ ____
A,1.25,-.25,.25,-.25
*CENTER2,Center (.5x) ___ _ ___ _ ___ _ ___ _ ___ _ ___
A,.75,-.125,.125,-.125
*CENTERX2,Center (2x) ________ __ ________ __ _____
A,2.5,-.5,.5,-.5
The basic format of a linetype definition is simplethey always consist
of two lines. The first line exists mostly for the benefit of humans while
the second line does the work. Lets start by studying the Center linetype
and its first line.
As cribbed straight from the AutoCAD Help function, This line must begin
with an asterisk and must be immediately followed by the linetype name.
If the description is provided, it must be separated from the name by a
comma and be no more than 47 characters. The description is not used by
AutoCAD; it is intended to help you visualize the appearance of the linetype.
The description is the words and/or dash-dot symbols in the dialog box.*CENTER,Center ____ _ ____
____ _ ____ _ ____ _
The second line does the work:
The first character is an alignment code. It is mandatory, but since day
one the only allowable value has been A. Hmm, a mandatory optionsounds
like something government would do.A,2.5,-.5,.5,-.5
The rest of this line includes the actual definition of the linetype segments. The definition of each segment is a simple numeric value, separated by a comma (no spaces) from its neighbors, that indicates its nominal length. Positive values indicate pen down, or draw a line. Negative values indicate pen up, or leave a blank segment. A length of zero indicates a dot.
The definition for
a Center linetype thus indicates that it consists of a line 2.5 units
long followed by a space of 0.5 units, then a line of 0.5 units, and a
space of 0.5 units. The pattern repeats automatically to fill the allocated
total line length, so that although the file defines only two lines and
two spaces, a center line looks like this:
In line definitions, the A alignment code indicates that:- - - - - - - - -
- -
A specific line always ends with a repeat of one of the first segments.
Great! I want to define a linetype that consists of a long segment,
a short gap, a medium segment, a tiny gap, a dot, a large gap, a medium
line, a. . .
Note a couple of limitations. A linetype definition cannot exceed
12 segments and 80 characters, whichever comes first. It is also normal
to end up with a space segment so the terminating segment is the correct
length.
And that is all there is to it! You can edit any of the existing definitions,
add your own to ACAD.LIN, or create one or more
separate files to hold them. If you use a file other than ACAD.LIN,
you must specifically browse for it when you load it into your drawing.
Get it right the first time
Hold it! I just had a terrible thought. Do I have to load linetypes
manually each time? And what happens if I send a drawing file to someone
else?
They both have the same solution. Linetype definitions read in from
the *.LIN file become part of the current drawing.
The *.LIN file needs to be present only when
you load the linetypes the first time. Any drawings you send elsewhere
or any existing drawings you reopen later carry their custom linetype
definitions with them and dont need the *.LIN
pattern file. The only time you need the *.LIN
file for an existing drawing is if you want to change the definition.
Simply load the new definition, and all existing lines update.
You can also load your usual definitions into a drawing template file
so that every drawing you start from that template will have the linetypes
defined without need for the *.LIN file.
Be sure to come back next time when I promise to cover the text and
symbols that you see in seven of the linetypes.
And now for something completely different
If you buy a used Hobie Cat sailboat, be sure to check out the rudder
settings before you go sailing. The previous owner may have taken them apart
and then swapped them right for left when reassembling them. The rudder
heads are not quite symmetrical. If they are backwards, the two rudder blades
splay outwards. This makes it almost impossible to keep the boat the right
way up in gusty weather.
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