A request for more variety in Arrows

[DerekGove]

Afternoon,

As I mentioned in my introduction, I trained in technical drawing in the pre-computer era. This is probably why I developed a preference for open arrows, rather than the closed and filled style. As far as I know, there are still a variety of arrow styles allowed in the ISO standards, and it would be great if we had some more options in QCAD.

Arrowheads.png (37.62 KiB) Viewed 8883 times

Of all these options, we only have the filled arrow and the oblique stroke. It's be lovely to have the full range.

This isn't an issue which prevents QCAD from doing it's job, it's purely a preference issue which would make it more 'comfy', for want of a better word. Hopefully it is so simple to implement it might be considered.

Cheers,
Derek

[CVH]

Derek,
Welcome to the QCAD forum.

The best place for a new feature request is: https://www.ribbonsoft.com/bugtracker/
You need a separate account there or create a new one.

A quick search on the term 'arrow' returns these open feature requests:
FS#695, FS#757, FS#952, FS#1157
And I find about 37 open tickets on 'dimension'.

Yes, there is room for improvements.
But I think that the main question remains if it is workable as it is.
Not so long ago Andrew implemented Dimension Styles and Style overrides in QCAD pro.

QCAD supports the default filled arrowhead, but not the 30 degree type, here the ratio is 3:1 or 3 long for 1 unit wide.
I suppose that other 'arrows' are defined by blocks.
https://help.autodesk.com/view/ACD/2022 ... 1B512B9CC9
Further, QCAD supports the oblique stroke but then simply as a custom generated line-piece.
(And thus not with a block called '_OBLIQUE')

One can not edit the Block Name field in the Property Editor but it should be available by scripting:
https://qcad.org/doc/qcad/3.0/developer ... ca74b044b5
https://qcad.org/doc/qcad/3.0/developer ... ec32c5f54f
Even then I am not sure that QCAD will render that as intended.
I need to test that.

Remind also that there are 2 distinct methods in the DXF standard:
DIMSAH = 0 >> Use arrowhead blocks set by DIMBLK
DIMSAH = 1 >> Use arrowhead blocks set by DIMBLK1 and DIMBLK2
Thus one could use 2 different arrow blocks but there is just one property.

Hopefully it is so simple to implement it might be considered.

Everything is simple until it gets too complex to cover only the needs of a few.

Regards,
CVH

[CVH]

Even then I am not sure that QCAD will render that as intended.
I need to test that

No, this is not intended to use as 'arrow' blocks.

Regards,
CVH

[DerekGove]

Hi CVH,

Thanks for the information about the bug tracker, I wasn't aware of that, which is why I thought the 'Suggestions and feedback' bit of the forum was a good place for my thoughts. I see others have also requested similar.

I was fully aware that it isn't a high priority, but I think it fell squarely in the category of "If you don't ask, you don't get.."

I can see how it might be considered a feature to accommodate 'a few', but another way of looking at it is that it makes this functionality fully ISO compliant, which has to be a good thing for everybody.

It actually highlights another very minor difference I hadn't noticed earlier. You mentioned a 3:1 ratio for the arrowhead; where the ISO standard I have has the arrowhead the same length as the height of the text, and with a 30 degree angle, which would make the ratio pretty much 2:1.

Arrowhead-dimensions.png (12.81 KiB) Viewed 8762 times

Of course in the days of paper and pencil, arrowheads just had to be neat and clear. I was told to draw them 2mm long, though I'm pretty sure that if they looked about right, no-one ever measured the size or angles of them.

Thanks for highlighting options in the DXF standards for alternative blocks for arrowheads. I'll maybe investigate those at some point, but right now I think I shall leave that alone because I'm not really much good at scripting beyond fairly basic tasks.

Perhaps instead of providing umpteem different arrowheads for different preferences, an option for a 'user-defined' arrowhead might work better, then anybody interested could customise to use whatever standard or convention they prefer. I won't hold my breath though.

Thanks again,
Derek

[Husky]

I was fully aware that it isn't a high priority, but I think it fell squarely in the category of "If you don't ask, you don't get.."

I second that. We have here in the States the saying: "The squeaky wheel gets the grease".

Thanks for the information about the bug tracker, I wasn't aware of that, which is why I thought the 'Suggestions and feedback' bit of the forum was a good place for my thoughts. I see others have also requested similar.

Actually you were right but the bugtracker/feature request is a permanent (maybe) todo list. Every entry which is an open ticket has the chance to be considered for implementation. The forum 'Suggestions and feedback' section will most likely loose attention over time ...

[CVH]

You mentioned a 3:1 ratio for the arrowhead; where the ISO standard I have has the arrowhead the same length as the height of the text, and with a 30 degree angle, which would make the ratio pretty much 2:1.

In DXF the text height and the arrow length are unrelated.
To be correct the QCAD ratio is almost 3:1 ... 18.9246°, for some reason it always turns out to be 18.9076°
And after I looked it up, it does match perfectly.
The half arrow is considered to be 0.165 rad, times two is 0.33 rad and that is 18.9076072.. degrees.
https://github.com/qcad/qcad/blob/f4b8b ... le.cpp#L83

To make it 30 degrees the half arrow should be PI/12 or about 0.2618 rad.
I am not aware if this is intentionally or by mistake/misinterpretation.

Pretty much 2:1, I agree, but in my book that is equal to 28.072487°.

Regards,
CVH

[DerekGove]

In DXF the text height and the arrow length are unrelated.

I'm sure the QCAD ratio is right for a 3:1 dimension arrow. I'm just a bit puzzled. I haven't worked much with the .dxf format, but is it the dxf format itself which controls the dimension arrows? I'm struggling to accept the notion that the most common format for technical drawings can't easily do arrows which follow the ISO conventions.
Any idea where the 3:1 arrow originates from? A particular field (general technical, mechanical engineering, shipbuilding.. etc?) or a geographic region? Or just some random programmer at Autodesk..?

To make it 30 degrees the half arrow should be PI/12 or about 0.2618 rad.
I am not aware if this is intentionally or by mistake/misinterpretation.

Pretty much 2:1, I agree, but in my book that is equal to 28.072487°.

- Yeah, to get a total 30 degree angle, the arrowhead should be treated not as one isosceles triangle ,but two right angled ones, with an angle of 15degrees at the point. Sin(15) is 0.2588, which doubled is 0.5176; so not quite half the length, but to be fair, I did say "pretty much 2:1".

Thanks for the responses.
After having had a quick glance at other forums using different software, but also the dxf format, I'm not the only one who has noticed that the 3:1 arrows are not ISO compliant, which is very odd for technical software which does follow other ISO conventions in many other areas. Odd. But it does appear to be a dxf issue, not QCAD, so I'll leave this for now, because I have other questions...

Regards,
Derek

[CVH]

Yeah, to get a total 30 degree angle, the arrowhead should be treated not as one isosceles triangle ,but two right angled ones, with an angle of 15degrees at the point. Sin(15) is 0.2588, which doubled is 0.5176;

Not sure where you get the Sin(15) from ... 15 degrees is 0.2617993.. rad, 30 degrees is 0.5235987.. rad, ... Ok 1/0.5176 is about 2:1 ...
It is treated as two right angled triangles.
I included a link to where the arrowhead shape is created.
This code written by Andrew uses 0.165 rad for defining two vectors at both sides.
The arrow end position and the two new vectors then make up an RTriangle shape.

BTW, the only method in QCAD to draw a custom 3 point solid is by exploding a dimension and dragging the solid its endpoints.
Apart from DrawFromCSV that does support these too.

But it does appear to be a dxf issue

I think the DXF standard keeps all doors open, ISO or not.
Here it is definitely hardcoded.
There is a 'ToDo' in https://github.com/qcad/qcad/blob/df269 ... .cpp#L1137 concerning arrow blocks.

Regards,
CVH

[Husky]

Any idea where the 3:1 arrow originates from? A particular field (general technical, mechanical engineering, shipbuilding.. etc?) or a geographic region? Or just some random programmer at Autodesk..?

German norm - DIN 406 (Deutsche Industrie Norm 406). Mostly used in mechanical engineering. If that format would be a programmer exercise by AC and co. it would most likely never be accepted as a Germany standard ...
DIN and ISO are pretty similar for various reasons.

[DerekGove]

Not sure where you get the Sin(15) from ...

- Oh that's easy. It was late, and my brain grabbed onto sin30 as a quick approximation because I know that sin30 is 0.5. Then when I meant to work it out properly, I never noticed that my initial quick guess was fundamentally flawed. Here's my proper workings out to prove I'm not a complete moron... LOL

Arrow-15degrees.png (24.01 KiB) Viewed 8576 times

So. 0.5358. Still close(ish) to 2:1

I included a link to where the arrowhead shape is created.
This code written by Andrew uses 0.165 rad for defining two vectors at both sides.
The arrow end position and the two new vectors then make up an RTriangle shape.

- The only issue here is, to paraphrase Doctor McCoy, "Dammit Jim, I'm an artist, not a programmer!". I have no idea what to do with any of that information, although I'm sure is incredibly helpful to many other people. If it's something embedded in the .dxf file I could edit in a text editor, I might be up for that. If it means changing code for QCAD and recompiling it, then that's beyond me.

There is a 'ToDo' in https://github.com/qcad/qcad/blob/df269 ... .cpp#L1137 concerning arrow blocks.

- I understood this bit. No idea what the timescale is of the 'to-do' list, but it's encouraging that it's there.

Thanks for all your assistance CVH, even though much of it went over my head.

Cheers,
Derek

[DerekGove]

German norm - DIN 406 (Deutsche Industrie Norm 406). Mostly used in mechanical engineering.

-Cheers Husky, Nice to know.

If that format would be a programmer exercise by AC and co. it would most likely never be accepted as a Germany standard ...

I can imagine. In my previous job I had quite a lot of interaction with a German software company. Let's just say that our experience with that particular company and their development team pretty much destroyed the notion we previously had of 'German efficiency.'
LOL.