Creating Dashed Polylines- MapScenes Pro only | Back to User Tips
We have all had the need to make a
smoothed polyline a dashed linetype. The problem is that the CAD engine
does not permit this option to be shown correctly. It draws the linetype
based upon each short segment in the polyline, each being too short to maintain
the linetype, so no linetype is displayed.
We now have a work around solution
to assist you. The new Divide and Measure commands may make life easier
for you. See below for an example of how you may use these commands to
help draw a dashed line to follow a smoothed polyline.
Before we get started - an updated
program file to run the new Divide and Measure commands, must be downloaded and copied to your computer.
Copy the file MESDIV2.LSP to the C:\MapScenesPro\Common folder and replace the existing file. This
only needs to be done once on each computer.
Example:
In the following sample drawing, the
red line is a smoothed polyline. You wouldn't know it but the red line
has a dashed linetype assigned to it with a linetype scale of 50. You
can't see the linetype at all due to the way the CAD engine works.
So what can we do? The new
Divide and Measure commands will allow us to draw short line segments along the
polyline, to approximate a dashed linetype.
Step 1)
We need to draw a temporary, short
line, the length required.
In this example we will draw a line
10 feet long, horizontal on screen, using the line command.
> Line
Type in LINE or pick it from the menu or toolbar.
From point:
Pick an arbitrary location off to one side of the drawing.
To point: @10<0
this draws a line 10 feet long, to the right
To point:
Press enter to complete the line.
What you will see is a short line
like this:
Step 2)
To use this line in the Divide and
Measure commands, it must be saved as a Block or Part. To do this we need
to convert this to a Block or Part.
Go under the Symbols menu ->
Define Symbol. (or type in PARTDEF)
The following dialog box comes up:
This dialog allows us to assign a
name to the part - in this case we called it DASH.
A list of other parts already in
this drawing is also provided in the bottom left portion of the dialog.
On the right bottom, you have 3 options to choose from. In this case we
wish to delete the original dash, once the part is defined. Set the
dialog as shown and pick OK to continue.
Next you will be asked for the
"Insertion base point:" Type in MID
and press enter.
When asked "of object:", take your crosshair and pick on the short dash we
drew earlier. You will see the triangle object snap and the tooltip
confirming the midpoint snap being used.
Next you will be asked to
"Select objects:"
Pick the same dash once again.
After picking the line and pressing
enter, you will see "*** 1 selected.
***" in the command line, and the dash will
vanish off the screen. It has been saved to a block in this drawing, for
future use.
Here is all you will see left on the
command line to confirm what you have done.
> PARTDEF
Insertion base point: mid
of object:
Select objects:
1
selected.
Select objects:
*** 1
selected. ***
Step 3)
Now that we have the block created,
let us use it in the Measure command.
Type in MEASURE or pick it from the
menu or toolbar.
> MEASURE
Select a line/circle/2d-polyline or
an arc to measure:
In this example we picked the red
polyline.
Block or Distance: B
We typed in B so the command knew we
wished to place a block along the polyline.
Name of the block to insert (or ? to list): DASH
We type in the name of the block we
created above, DASH.
Offset angle for alignment the block
along the object (or ENTER for none alignment): 0
We type in an angle of zero (0) so
the DASH block will follow the polyline.
Distance: 20
Wishing to have a dash then a blank,
then a dash, etc., with a spacing of 10 between each dash, we add the dash
length and the space to get 20 as the distance to enter.
There will now be short dashes on
top of the red polyline.
To see them clearly, you need to
erase the red polyline and then refresh the screen.
What you will be left with is a
series of short dashes following the original smoothed polyline.
The first and last dash may not line
up perfectly for the starting and ending location of the polyline because the
dash was placed based upon the MIDpoint of the dash. You can do any edits
required to clean up the drawing to your satisfaction.
The Divide command works exactly the
same way except it does not ask you for the distance between each dash
placement, it asks for the number of dashes to place along the polyline.
It then divides the length up to place those dashes correctly.
Feel free to experiment a bit to get
a result that you are happy with.
Glen W.
Cameron, C.E.T.
Technical Support Manager
