Lineweights and drawing units

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ChrisDancer
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Posts: 3
Joined: Fri Sep 07, 2007 11:35 am

Lineweights and drawing units

Post by ChrisDancer » Mon Sep 10, 2007 4:23 am

I have a question about how lineweights relate to the drawing scale / units.

From what I have read here and in the help file, the drawing scale is unitless, ie. a distance of 1.000 in the drawing does not necessarily mean 1 cm or 1 inch, etc.
Why then is lineweight specified in mm?
I want to use 1 drawing unit = 1mm, and I want lineweights to display on screen, but I can see no way to specify that a drawing unit equals 1mm.

Perhaps lineweight actually means "pen width" and refers to the width of the line when it is printed. If so, changing the print scale should affect the appearance of lineweights on screen. I just tried setting print scale to 1:1 and units to mm. Lineweights still don't display correctly.

I notice that there is also a property called "width", which seems to behave sensibly - ie. if you set the width to 0.1, you get a line on screen 0.1 drawing units wide. By experimentation I found out how to create arcs and splines with wide lines. It's not the most intuitive process though.
John Finlay

Post by John Finlay » Mon Sep 10, 2007 5:17 pm

ChrisDancer,

In CAD most people draw full size and scale their plots to suit the paper size and printer they use.
CAD uses vectors to display lines and the like where you can zoom in and the line width remains the same on the screen.
This enables fine details to be accurately drawn then printed with different line thickness (pen width is from hand drafting and pen plotting).
When printing the vectors in CAD are converted to raster images (a series of dots) so the printer can understand and produce the final output.


From ICAD Help:

If entities are assigned lineweights, you can control whether they print with the assigned lineweights. If you turn off lineweight printing, entities print with a default outline. You can also control whether lineweights print in proportion to the scale you set on the Scale/View tab.

As an example:
1/ First draw two lines that cross each other.
2/ Select one line and right click then select properties.
3/ On the properties form select lineweights and select the thickest line available.
4/ Print preview the lines and you will see the difference.

If you type LWDisplay at the command prompt you can turn the lineweight display on or off. By selecting on, the line that you have assigned the thicker lineweight will display thicker than the other.

You have raised a few issues here and apart from the lineweights there are printing issues.

You need to set up printing where the color of each line has a default linewidth (pen width and these range from 0.0 to 2.11 mm)

To set these:
1/ Select print (select mm check box).
2/ Then on the form select the Advanced tab.
3/ Select your print style table name (Monochrome prints all colors black).
4/ Select Edit and select a color from the pulldown and choose a lineweight from the pulldown, which is the default for that color.
Save the changes and print some colored lines to see the result.

You can create and save different style table names depending on the colors you intend to draw and remember you can override this by selecting a linewidth property for each entity as in the first example.

The next issue is the “width” property and this is different from linewidth as it refers to polylines, which can have differing starting and ending widths.

All this may appear confusing at first as CAD is a large program with many settings in both system variables and specific entities with their own different properties.

I have covered a number of issues and please post if you need further assistance.
ChrisDancer
Newbie
Posts: 3
Joined: Fri Sep 07, 2007 11:35 am

Post by ChrisDancer » Wed Sep 12, 2007 3:44 am

Thanks John.

I should explain why I asked this. I appreciate that a CAD drawing is basically a wireframe model of an object, where the lines represent edges, so the line width is not really important, except for clarity of printing.
However, I am evaluating whether I can use Intellicad for things like creating instrument panel artwork. In this case it is very important that the artwork appears on the screen exactly the way it will print.
I was barking up the wrong tree with lineweight. I realised this when I selected show lineweights, zoomed in and out on a line, and the thickness of the line on screen did not change!
I need to use polylines to create lines of controlled thickness that will display correctly on screen. In which case, my next questions would be: can I convert an existing line to a polyline, and can I define a default start and end width for all polylines?
John Finlay

Post by John Finlay » Wed Sep 12, 2007 3:52 pm

ChrisDancer,

A line can be converted to a polyline using the pedit command.

You can type in pedit or on the modify toolbar there is a button named Edit Polyline.

When you execute pedit and select a line the line is converted to a polyline and a range of options are displayed on the command line.

the options are:
Edit polyline: Edit vertices/Close/Decurve/Fit/Join/Linetype-mode/Reverse/Spline/Taper/Width/Undo/<eXit>:

If you select Taper by typing t you will be prompted for a starting width then an ending width.

When you select a polyline to draw you get the following options: Arc/Distance/Follow/Halfwidth/Width/<Next point>:

By typing W after selecting the starting point you will be asked for the starting and then the ending width.

From Help in IntelliCAD

PLINEGEN Determines whether the linetype used around the vertices of a polyline are continuous or dashed. The default value (0) sets the linetype around the vertex to a dash. Setting the value to 1 changes the linetype to a continuous pattern around the vertex of the polyline.

PLINETYPE Controls the use of optimized 2-D polylines in IntelliCAD. You can save disk space and memory by using the optimized format. PLINETYPE controls the use of optimized polylines for creating new polylines using the PLINE command and converting previously created polylines.

PLINEWID Sets the default polyline width to a value of 0 (the default) or greater.

As you can see by typing PLineWid you can set the default width when you draw polylines.

Try this out:
Draw a polyline with say 5 points in an irregular shape then select pedit then type S for the Spline and press Enter or right click the mouse.
You can have hours of fun in 2D - Just imagine what you can do in 3D.
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