[Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

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In which position should be selected the center point of the symmetry ?

Poll ended at Tue Apr 28, 2020 3:14 pm

1st position / 1st click (first point)
0
No votes
2nd position / 2nd click (middle point)
2
17%
3rd position / 3rd click (last point)
10
83%
I like today's inconsistency, please don't change
0
No votes
 
Total votes: 12
openBrain
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[Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby openBrain » Tue Apr 14, 2020 3:14 pm

Hi all,

As of today, specifically when setting a point-point-point symmetry, the selection order differs depending of the active mode :
  • In single-shot mode (select points first then run command), the symmetry center is the 3rd (last) selected point
  • In continuous mode (select command --with nothing selected-- then select points, the symmetry center is the 2nd (middle) selected point
This has been discussed in the past as an inconsistency issue and recorder in issue #3746.

This quite easy to fix but ... in your opinion, what is the correct order ? I'll fix (or not) according poll result. :)
drmacro
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby drmacro » Tue Apr 14, 2020 3:22 pm

How that compare to point, point, center line?
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

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openBrain
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby openBrain » Tue Apr 14, 2020 3:29 pm

drmacro wrote:
Tue Apr 14, 2020 3:22 pm
How that compare to point, point, center line?
In the point-point-line variant, the order doesn't matter as FC deduces the line is the symmetry center. ;)
Same in the point-line variant.
Only the point-point-point is (can be) subject to that.
chrisb
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby chrisb » Tue Apr 14, 2020 3:32 pm

drmacro wrote:
Tue Apr 14, 2020 3:22 pm
How that compare to point, point, center line?
There are all three variants, as it's always the line that defines the sysmmetry: line-point-point, point-line-point or point-point-line.

Symmetry in the middle seems to be convenient, but is it consistent with other operations? I have the feeling that the distinguished item - which is here the point of symmetry - comes last.

Thanks that you work on this, and you will have to correct at least one of the two.
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drmacro
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby drmacro » Tue Apr 14, 2020 3:43 pm

I went and tinkered with it after I asked to see what I actually do...done it so many times it's muscle memory.

I think I learned early on that the point, point, point then select, the center point was last. And that's my go to flow. So I didn't really note the select, point, point, point was different. 8-)

And I asked because I didn't really find any docs about the line version that implied there'd be inconsistent difference between symmetry around a line opposed to point.
Last edited by drmacro on Tue Apr 14, 2020 5:05 pm, edited 1 time in total.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
chrisb
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby chrisb » Tue Apr 14, 2020 4:03 pm

drmacro wrote:
Tue Apr 14, 2020 3:43 pm
And I asked because I didn't really find any docs about the line version that implied there'd be inconsistent difference between symmetry around a line opposed to point.
Ha! It's documented in my sketcher document. I guess that openBrain, who kindly translated it to french, is running out of work and wants to make me change the document again :lol: .
A Sketcher Lecture with in-depth information is available in English, auf deutsch, en français, en español.
openBrain
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby openBrain » Tue Apr 14, 2020 4:28 pm

chrisb wrote:
Tue Apr 14, 2020 4:03 pm
Ha! It's documented in my sketcher document. I guess that openBrain, who kindly translated it to french, is running out of work and wants to make me change the document again :lol: .
No ... And no ... Respectively. :lol:

@all : could you please vote in the poll at the top of OP so hopefully there is a preferred option at the end of the discussion ? ;)
drmacro
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby drmacro » Tue Apr 14, 2020 5:07 pm

chrisb wrote:
Tue Apr 14, 2020 4:03 pm
drmacro wrote:
Tue Apr 14, 2020 3:43 pm
And I asked because I didn't really find any docs about the line version that implied there'd be inconsistent difference between symmetry around a line opposed to point.
Ha! It's documented in my sketcher document. I guess that openBrain, who kindly translated it to french, is running out of work and wants to make me change the document again :lol: .
Well, I admit, I looked at the wiki not your document. I assume you mean the sketcher tutorial...I have the pdf. :oops:
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freman
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby freman » Tue Apr 14, 2020 5:17 pm

Thanks for picking this up OpenBrain. I'd long forgot that I opened a bug about this but it annoys the hell out of me every time I try to use it on three dots. Especially since it changes from when you first try and then try again with the tool now active and get different results. I get the feeling the white mice put this together and are up in there studying how primitive terrian humanoids deal with inconsistent data.

I often just give up after about 5 annoying attempts and create a different geometry with a line or something. ( I have quite a nice hires monitor and would not want to see it get damaged ;) )

Folks may like to refer to the original thread which I opened before the bug.
https://forum.freecadweb.org/viewtopic.php?f=3&t=32997

It seems to me a good point to start is the hover hint ( although this could obviously be changes too , along with the doc ).
"Create a symmetry constraint between two points with respect to a line or a third point (S)"
That is quite clear and covers both line and point symmetries. It probably will translate well into most language that are not based on reverse Polish.

Being consistent between line and point symmetry is desirable ( we don't want to have a three line hint with an if then else clause ) . Being consistent w.r.t. the state of the tool is essential. It seems to me that third element fills that need and just tidies up the current confusion with a minimum of change.

My vote is for 3rd element to be the centre of the symmetry. :)
kisolre
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Re: [Community poll][Bug 3746][Sketcher] Inconsistent selection order in symmetry constraint

Postby kisolre » Tue Apr 14, 2020 7:15 pm

How often you create several symmetries one after another to justify the use the select tool. select elements approach? I look at the sketch, thinking how to constraint it. Since there are no automatic symmetries they need to be manually added every time. I see that I can constraint using symmetry (most of the time it is already planned). I select the elements and THEN start searching for the tool. Same with most other tools. Using the select tool/apply to elements is rare special case when I see that it will be faster.