Editing
Polylines
Sacramento City College
Engineering Design Tecnology
Editing Polylines
1
Objectives
 Use
the PLINE command to draw polylines
and polyarcs.
 Edit existing polylines with the PEDIT
command.
 Describe the function of each PEDIT
command option.
 Use the EXPLODE command to change
polylines into individual line and arc
segments.
Editing Polylines
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Objectives
 Draw
and edit spline curves.
 Create a polyline boundary.
Editing Polylines
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The PLINE Command
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PLINE Command
 The
PLINE command can be accessed by:
 Picking
the Polyline button in the Draw toolbar
 OR
 Selecting
Polyline from the Draw pull-down
menu
 OR
 Type
PL or PLINE at the Command: prompt.
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PLINE Command - The Arc option
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PLINE Command
 The
Arc option of the PLINE command
 Is
similar to the ARC command
 The PLINE Width and Halfwidth options can
be used to set an arc width.
 The
arc width can range from 0 up to the
radius of the arc.
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PLINE Command
A
polyline arc with different end widths is
drawn by
 accessing
the Width option and
 changing the width values.
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Drawing a Continuous Polyline Arc
A
polyline arc continued from a previous
line or polyline is tangent to the last object
drawn.
 The
arc's center is determined automatically
 You can pick a new center.
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Drawing a Continuous Polyline Arc
 If
a straight polyline is continued from a
polyline arc, the arc's tangent direction
remains the same as that of the previous
line, arc, or polyline.
 This
may not be what you want.
 Specify a different setting with one of the
PLINE Arc options.
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Drawing a Continuous Polyline Arc
 Arc
Options:
 Angle
 Center
 Close
 Direction
 Radius
 Second
pt (second point).
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Specifying the Included Angle
 Angle
option
 You
can specify the angle for a PLINE arc by
using the Angle option.
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Specifying the Included Angle
 Center
option
 When
a polyline arc is continued from a
drawn object, the center point is calculated
automatically.
 You can to pick a new center point.
 The
CEnter option allows you to specify a
new center point for the arc.
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Specifying the Included Angle
 If
A is entered, the next prompt is:
 Specify
included angle: (enter an included angle
and press [Enter])
 If
L is entered, the next prompt is:
 Specify
length of chord: (enter a chord length and
press [Enter])
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The Direction Option
 The
Direction option
 changes
the bearing of the arc.
 It changes the default option of placing a
polyline arc tangent to the last polyline, arc, or
line.
 The Direction option functions much like the
Direction option of the ARC command.
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Drawing a Polyline Arc by Radius
 Radius
Option
 Polyline
arcs can be drawn by giving the arc's
radius.
 Enter the Radius option inside the PLINE Arc
command.
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Three-Point Polyline Arc
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Three-Point Polyline Arc
A
three-point polyline arc can be drawn by
using the Second pt option.
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Three-Point Polyline Arc
 The
CLose option
 adds
the last segment to close a polygonal
shape.
 Used inside the PLINE Arc command
sequence closes the shape with a polyline arc
segment, rather than a straight polyline.
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Three-Point Polyline Arc
 Two
letters are required
 CL
= CLose
 CE = CEnter option.
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Presetting Polyline Widths
The PLINEWID System Variable
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Presetting Polyline Widths
 The
PLINEWID system variable
 Sets
the constant width for polylines.
 To change a PLINE width
 Enter
PLINEWID at the Command: prompt and
 enter a new value.
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Presetting Polyline Widths
 Polygons
 are
NOT affected by the PLINEWID system
variable.
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Editing Polylines
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Editing Polylines
 Polylines
are drawn as single segments.
 Even though you draw connecting segments,
AutoCAD puts them all together.
 The result is one polyline treated as a single
object.
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Editing Polylines
 When
 Edit
editing a polyline, you must
it as one object
 OR
 Divide
it into its individual segments.
 This
method destroys the PLINE (!)
 Not recommended.
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Editing Polylines
 The
PEDIT (PE) command is accessed by:
 Picking
the Edit Polyline button from the
Modify II toolbar
 OR
 By
typing PE or PEDIT at the Command:
prompt,
 OR
 By
selecting Polyline from the Modify pulldown menu.
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Editing Polylines
 PEDIT
 You
can also
 select
a polyline and
 then right-click in the drawing area to display a
shortcut menu.
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Editing Polylines
 Use
the pick box to select a polyline to be
edited.
 If you use the pick box on a wide polyline, you
must pick it on the edge of a polyline
segment, rather than in the center.
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Editing Polylines
 If
the object you select is a line or arc
object (not a polyline), the following
message is displayed:
 Object
selected is not a polyline
 Do you want to turn it into one? <Y>
 Entering
Y or pressing [Enter] turns the
selected object into a polyline.
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Editing Polylines
 Join
Option
 Allows
a group of connected lines and arcs
can be turned into a continuous polyline.
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Editing Polylines
 There
is no default option for the PEDIT
command
 You
must enter one of the options.
 Pressing [Enter] returns you to the Command:
prompt.
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Opening and Closing a Polyline
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Opening and Closing a Polyline
 Open
PLINEs can be Closed.
 Closed PLINEs can be Opened.

hese functions are performed with the Open
and Close options of the PEDIT command.
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Opening and Closing a Polyline
 If
the PLINE is OPEN
 It
 If
can only be CLOSED
the PLINE is CLOSED
 It
can only be OPENed
 AutoCAD
displays only the appropriate
option – NOT both options.
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Opening and Closing a Polyline
 The
Open option is not displayed if you
select a polyline that was closed by
manually drawing the final segment.
 It
is only available if the polygon was
closed using the Close option of the PLINE
command.
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Joining Polylines to Other Polylines
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Joining Polylines to Other Polylines
 Join
Option
 Allows
polylines, lines, and arcs that share an
EXACT endpoint can be joined to create a
single polyline.
 AutoCAD computes line vertices to 25
decimal places
 Lines
may appear to have the same endpoints,
BUT in reality, do NOT.
 You CANNOT join objects with PEDIT unless the
endpoints match EXACTLY.
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Joining Polylines to Other Polylines
 This
option works only if the polyline and
other existing objects meet exactly.
 They
cannot cross.
 There cannot be any spaces or breaks
between the objects.
 Select
each object to be joined
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Joining Polylines to Other Polylines
 To
get the endpoints to match EXACTLY
 You
may have to MOVE an object
 Turn OSNAP on
 And MOVE the object using the ENDPOINT
OSNAP to get the endpoints aligned.
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Changing the Polyline Width
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Changing the Polyline Width
 The
Width Option
 of
the PEDIT command
 allows you to change a polyline width to a
new width.
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Editing a Polyline Vertex
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Editing a Polyline Vertex
 The
Edit vertex option of the PEDIT
command is used to
 Edit
polyline vertices and
 Points of tangency.
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Editing a Polyline Vertex
A
polyline vertex
 is
A
where straight polyline segments meet.
point of tangency
 is
where straight polyline segments or polyline
arcs join other polyline arcs.
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Editing a Polyline Vertex
 When
you enter the Edit vertex option,
 an
"X" marker
 appears on screen at the first polyline vertex
or point of tangency.
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Editing a Polyline Vertex
The Edit vertex option has 10 options
Next
 Previous
 Break
 Insert
 Move

 Regen
 Straighten
 Tangent
 Width
 eXit
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Editing a Polyline Vertex
 Next
 Moves
the "X" marker on screen to the next
vertex or point of tangency on the polyline.
 Previous
 Moves
the marker to the previous vertex or
point of tangency on the polyline.
 Break
 Breaks
a portion out of the polyline.
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Editing a Polyline Vertex
 Insert
 Adds
a new polyline vertex.
 Move

Moves a polyline vertex to a new location.
 Regen
 Generates
the revised version of the polyline.
 Straighten
 Straightens
polyline segments.
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Editing a Polyline Vertex
 Tangent
 Specifies
a tangent direction for curve fitting
when using the PEDIT Fit option.
 Width
 Changes
a polyline segment width.
 eXit
 Returns
the PEDIT command prompt.
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Editing a Polyline Vertex
 Only
the current point identified by the "X"
marker is affected by editing functions.
 The marker is moved
 Clockwise
using the Next option (N)
 Counterclockwise using the Previous option.
(P)
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Making Breaks in a Polyline
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Making Breaks in a Polyline
 Break
option
 Breaks
out a portion of a polyline
 Use the Next or Previous option to move the
"X" marker to the correct vertex.
 AutoCAD
accepts the highlighted vertex as the first
break point.
 Move the marker to the vertex you want to
designate as the second break point.
 Enter G for Go.
 AutoCAD
removes the portion of the polyline
between the two selected points.
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Inserting a New Polyline Vertex
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Inserting a New Polyline Vertex
 To
add a new vertex
 Use
the Insert vertex option.
 Use
the Next or Previous option to locate the
vertex next to where you want the new vertex
to be.
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Moving a Polyline Vertex
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Moving a Polyline Vertex
 To
move a polyline vertext
 Use
the Move vertex option.
 This option is similar to the Insert option.
 Place the "X" marker on the vertex you want
to move with Next or Previous.
 Then, enter the Move option and
 Specify the new location.
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Straightening Polyline Segments or
Arcs
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Straightening Polyline Segments or Arcs
 The
Straighten vertex option
 allows
you to straighten polyline segments or
arcs between two points.
 Place the "X" marker on the vertex you want
to move with Next or Previous.
 Then, enter Straighten option.
 If
the 'X" marker is not moved before G is entered,
AutoCAD straightens the segment from the first
marked point to the next vertex.
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Changing Polyline Segment Widths
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Changing Polyline Segment Widths
 To
change the width of an individual
polyline segment
 Use
the Width vertex option
 Move the "X" marker to the beginning vertex
of the segment to be altered.
 Enter the Width option and
 Specify the new width.
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Changing Polyline Segment Widths
 The
starting width default value is the current
width of the segment to be changed.
 The
ending width default value is the same as
the revised starting width.
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Making Smooth Curves
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Making Smooth Curves
 You
can convert a polyline into a series of
smooth curves.
 Example:
a graph.
 A graph may show a series of plotted points
as a smooth curve rather than straight
segments.
 This process is called curve fitting.
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Making Smooth Curves
 Example:
a curved landscape border.
 The
landscape border can be drawn with
straight polyline segments and
 then converted to a smooth curve.
 If the curvature is not correct,
 Decurve
the line
 Adjust the verticees
 Recurve the line
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Making Smooth Curves
 To
curve a PLINE
 Use
the PEDIT
 Fit option
 Spline option.
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Making Smooth Curves
 The
Fit option
 allows
you to construct pairs of arcs passing
through control points.
 You can specify the control points
 Closely spaced control points produce a
smooth curve.
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Making Smooth Curves
 If
the resulting curve does not look like
what you had anticipated,
 Decurve
the PLINE
 Enter the Edit vertex option.
 Make changes using the various vertex
editing options as necessary.
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The PEDIT Spline Option
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The PEDIT Spline Option
 The
PEDIT Fit option,
 Causes
the resulting curve to pass through
polyline vertices.
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The PEDIT Spline Option
 The
PEDIT Spline option
 makes
the resulting curve pass through the
first and last control points or vertices only.
 The
curve pulls toward the other vertices (but
does not pass through them).
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The PEDIT Spline Option
 The
SPLINETYPE system variable
 determines
whether AutoCAD draws cubic or
quadratic curves.
 Default
= 6 = cubic curve
 5 = quadratic curve
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Straightening All Polyline Segments
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Straightening All Polyline Segments
 The
PEDIT Decurve option
 returns
a polyline edited with the Fit or Spline
options to its original form.
 You
can also use the Decurve option to
straighten the segments of a polyarc.
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The Undo Option
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The Undo Option
 If
you make a mistake while editing a
polyline, use the Undo option.
 Using
the Undo option more than once allows
you to step backward through each option
used.
 Press
[Enter] to return to the Command:
prompt.
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The Undo Option
 The

UNDO command
can also be used at the Command: prompt to
undo the effects of the last PEDIT command.
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The SPLINE Command
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The SPLINE Command
 The
SPLINE command
 is
used to create a special type of curve called
a “non-uniform rational B-spline” (NURBS).
A
NURBS curve is a “true spline”.
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The SPLINE Command
 To
access the SPLINE command:
 Pick
SPLINE button in the Draw toolbar
 OR
 Pick
SPLINE from the Draw pull-down menu.
 OR
 Type
SPL or SPLINE at the the Command:
prompt.
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Drawing Closed Splines
 Use
the Close option to draw a closed spline.
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The Fit Tolerance Specification
 Different
results can be achieved when
drawing splines by altering the
specifications used with the Fit Tolerance
option.
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