Printing dashed lines

[Ted the Bear]

Hello:
I am using windows 11 and version 3.27.8.0 (3.27.8) of Qcad. I do a lot of DIY projects and find QCAD extremely helpful to draw my project before actually building anything. I find it very intuitive and do not have any formal CAD training. I have read the previous posts / threads about this issue and still I am unable to get it sorted (Sorry!). I am preparing drawings for a home renovation and have drawn the plan at full scale (1'-0" = 1'-0"). I export the cad file to a pdf in order to print. I can only print on 8.5" x 11" paper. I have used the property editor to change some lines to dashed lines and adjusted the linetype scale and the dashed lines appear fine on the screen and even in print preview they look fine but when they are exported to a pdf drawing they always print as a solid line. In reading the various threads I enabled screen based line type mode and this got me closer to the result I am requiring because before enabling this mode the dashed lines on screen were shown as solid lines in pdf export view but now they still show as dashed lines in pdf export view but they still print as solid lines.
I have attached the drawing for your review..... Hoping the fix can be explained so my simple brain can understand what to do....
Thank you in advance!

[CVH]

Hi, and welcome to the QCAD forum.

I am using windows 11 and version 3.27.8.0 (3.27.8 ) of Qcad.

A) That is an older version of QCAD (>2 years), not that it should matter in this case.
B) Are you using QCAD Pro or the CE version? ... Because the file is in the R15 (2000) format.

the dashed lines appear fine on the screen and even in print preview they look fine but when they are exported to a pdf drawing they always print as a solid line.

I can't really agree with the second of 3 statements.
In my case, dashed lines already appear as continuous in Print Preview mode.
But there are some settings and preferences that have an influence.

Typically we use Screen-based Linetypes (LN) when working in Model_Space.
That is a pixel based hybrid so that Linetypes are rendered somewhat dashed/dotted and/or thick/thin on screen and that in any zoom state.
With real combinations of dashes and spaces it would otherwise be possible to Zoom OUT so far that a space is less than a pixel.
Such a line would then appear to be continuous on screen while it is not.
Or when Zooming IN deep, we would only see one of the dashes or the spacing between them.
Again resembling a (fat) continuous line but also nothing at all if the view only displays the void in this zoom state.

Auto-switching to Screen-based when in Model view is configurable by Preference, active is the default.
See menu Edit .. Application Preferences .. Graphics View .. Appearance

The bottom line here is that you don't have to worry about how Linetypes appear on the screen in Model view.
But remember that it is only intended to display things on screen, it will never be printed or exported to PDF as such.

- - - - - - - - -

When Screen-based is not active, the weight should be rendered as they are and types as defined and scaled.

If we switch to paper view (Print Preview, Layouts) then Screen-based is automatically turned off.
Things may look a little different with a paper scale other than 1:1.
Because unlike the patterns, the sizes of former physical pens with ink are never scaled.
A line using a 1mm pen is always printed or exported as 1mm wide (~0.04").

In your drawing I see the use of ISO types, typically only used for metric drawings in the ISO standard.
As by standard these should be scaled by line weight what can also be set by preference. (.. Appearance)
This is an application wide setting and your preference may be set different from mine.
This would mean that an additional factor is applied, proportional to pattern of a 1 mm wide line.


At this point it becomes debatable.
Linetypes are said to be defined in mm.
'Dashed' for example is defined as 12.7 ON and 6.35 OFF in metric and that correlates with 0.5 and 0.25 for imperial patterns.
Thus, imperial patterns are defined in inch and not in mm.
In both systems the dash is exactly 12,7mm = 0.5" long.

The exceptions are the ISO types.
'ISO dash' is defined as 12 ON and 3 OFF in both systems.
Long story short, these seem to be defined in mm in both systems.
Or ... Imperial patterns of this sort will not be converted from inch to mm (Educated assumption).


From the above ...
For your drawing: Weight = 'By Layer' = 0.25mm (ISO), Scaling by weight active, Linetype Scale 100 and pattern 'ISO dash' ...
... I expect dashes that are 12 x 0.25 x 100 = 300mm (11.811") long when Screen-based is NOT active in Model view.
And the dashes are exactly that long if we account for the round end-butts of the line segments.
Continuous lines or those using a Linetype pattern are drawn with round pens, Polylines with (a) custom width(s) are drawn with a flat pen.

All fine up to now but further as this I have the same issue.

If I switch to Print Preview mode (Ctrl+Shift+P) the dashed line becomes continuous.
Paper size is ANSI A, in Portrait and Paper Scale 0.0119.
We would then expect a dash that is 300 x 0.0119 = 3,57mm (0.14") long on paper.
On screen, the pattern should simply remain the same because it is the paper that is displayed 84 times larger.


IT IS patterned when we use the sequence Ctrl+Shift+P and then QQ (a few times if required).
Or swap briefly to another drawing and back (A new drawing (Ctrl+N) for example).
It is again wrong if we swap briefly to another application, QQ will fix that again.
Still in preview mode and displayed as dashed, a single line turns continuous after selection.
...
..
.

I can replicate this behavior in QCAD 3.27.6.0 and just the same in the latest stable version 3.31.2.0 on a Win7 system.

From left to right:
- Model view + Screen-based Linetypes ON (dash/space not relevant)
- Model view + Screen-based Linetypes OFF
- Paper view after Ctrl+Shift+P (Screen-based automatically OFF)
- Paper view after QQ
The red marker points to a single dash 300mm (11.811") long.
Remark that the pen looks thicker on paper, it is in the actual pen size, in Model View there is no known Paper Scale.

Display_vs_Print_&_ISO.png (44.87 KiB) Viewed 62999 times

Hoping the fix can be explained so my simple brain can understand what to do....

Explained in detail how it is expected to work, but it is not or it is not consistent.
I think that this should be reported as a bug on QCAD bugtracker.
Seems to be related with re-rendering patterns when something changes with the focus, view or individual entities.

I was unable to export to PDF with dashes this way, probably because the focus first shifts to the file dialog widget.
ISO types or not or stored in a newer format is just the same.


This method did work and only successful for me as described below:
Closed all files in QCAD, terminated QCAD.
Re-downloaded the file from the forum.
Started QCAD with opening your file in the download folder (A duplicate called 'Proposed Foundation Plan (1).dxf' this time)
Selection Filter >> Linetype Scale equal to 100 >> Replace current selection.
Changed scale of all selected from 100 to 1 in the Property Editor with a single action.
Ctrl+Shift+P and exported to PDF with the button on the Option Toolbar when in Print Preview mode.

Proposed Foundation Plan3.pdf

(70.39 KiB) Downloaded 1128 times

Now they turn continuous after QQ but not with briefly swapping application, drawing and so on.


Regards,
CVH

[Ted the Bear]

Good morning and thank you for the very detailed review and explanation of what is going on. To answer your question I am using the CE version of QCad and yes it is an older version, which until now has performed very well for me. If I understand correctly you note that the behavior I am experiencing should be reported as a bug, and I can do that unless you already have.
Also not sure if downloading the current version would resolve this issue or not.

Thanks again, Ted

[CVH]

o answer your question I am using the CE version of QCad

This forum is intended for users of the Pro version but the behavior is just the same using Pro or Trial.

Also not sure if downloading the current version would resolve this issue or not.

I can replicate this behavior in QCAD 3.27.6.0 and just the same in the latest stable version 3.31.2.0 on a Win7 system.

The above screenshots (Display_vs_Print_&_ISO.png) where collected using the latest version.

But I was able to export the PDF with setting the Linetype Scale to 1 as explained.
I am missing the logic supporting this work around.
To clearly understand what is going on and when, I have to test that further in detail.

Printed or exported to PDF this way I get 20 dashes (ISO) per 75mm.
That correlates with 20 times (10 ON + 3 OFF) times 0.25 (Weight factor) times 1(Linetype Scale) = 75mm
And not at all with 20 x (10 + 3) x 0.25 x 100 (Linetype Scale) x 0.0119 (Paper Scale) = 77.35mm

As if a Linetype is defined as 'mm on paper' and disregards paper scale.
And that throws me off even further from understanding.
Because we can clearly see the length of a dash changing with increasing or decreasing the paper scale.

I also did a test with a Global Linetype scale as it is the standard advice to enlarge that for larger designs.
But that is practically the same as setting an individual Linetype scale.

TBC

Regards,
CVH

[Ted the Bear]

Thank you again for your reply and sorry I don't know how I missed the "setting linetype scale to 1" in your first reply. I tried this and yes it is working for me also. Much appreciate the support and timely replies.