Related to this topic we come to the conclusion that QCAD treats Linetypes differently compared with many other CAD applications.
Historically we can find the recurring statement that Linetypes are defined in millimeters or in inches.
I was totally convinced that this was true.
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Hatch patterns use parallel cloned custom Linetypes.For the pattern definitions the length of dash and space are expressed in drawing units (A dot = zero).
Cloning parameters for the pattern are in drawing units.
In About Simple Custom Linetypes is stated that:DASHDOT A,.5,-.25,0,-.25 has a dash that is 0.5 drawing units long and a space that is 0.25 drawing units long.
In AcDbLinetypeTableRecord Methods we can read that lengths are expressed as:in AutoCAD drawing units-the dash will appear this length when the linetype scale is 1.0
And that agrees with what is stated in LTSCALE and PSLTSCALE system variables in AutoCAD'The dash specifications in linetype definitions are given in terms of drawing units.'
I is not directly stated but from the Simple Line Type Tag Structure DXF R2000+ example we can deduct that:1.25+0.25+0.25+0.25 = 2.0 and group code 40 is said to be the overall pattern length in drawing units.
...I can not find a DXF specification that agrees with millimeters or inches.
Perhaps I am missing something.
For a drawing in meters the general advise is to use a Global Linetype Scale of 1000.
That is to scale pattern values up from millimeters to meters.
While that would never have been required when Linetype definitions were treated as expressed in drawing units to begin with.
It then boils down to: OR it looks good in QCAD, OR it looks good in other CAD applications.
Most reasons and explanations that you give are equally valid for mm or for drawing units.
-> In model space, there is no paper size,... etc, so it is simply not possible for QCAD to know how the line patterns should be displayed.
A line has a lenght and a dash itself too, I don't see why things would be impossible to render.
-> However, this is relatively costly since dashes have to be recalculated whenever the zoom level changes.
IMHO, with Screen-Based Linetypes OFF the length of a dash is steady and rendering it in any other zoom state requires recalculation.
In mm or in drawing units does not affect this.
-> It also makes line patterns unpredictable in model space
Again, mm or drawing units does not affect this.
With Screen-Based Linetypes OFF the text would align perfectly with the gap in any zoom state.
Still, perhaps I am missing something
Regards,
CVH