[solved] (Dangerous) behavior from the sketcher

Post here for help on using FreeCAD's graphical user interface (GUI).
Forum rules
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help

Also, be nice to others! Read the FreeCAD code of conduct!
User avatar
thomas-neemann
Veteran
Posts: 11730
Joined: Wed Jan 22, 2020 6:03 pm
Location: Osnabrück DE 🇩🇪
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by thomas-neemann »

openBrain wrote: Wed Jul 28, 2021 8:26 am
chrisb wrote: Wed Jul 28, 2021 8:15 am This is how it works on macOS and (currently, see above) on Ubuntu. I would prefer a point-on-object constraint for the third point as well, but tangent is ok too.
I think there is some misundertanding. (If I'm correct) OP is specifically talking about behavior of 3-pt circle, not 3-pt arc.
To me 3pt-arc is pretty correct, but 3-pt circle is indeed pretty weird.
Could you have a check on 3-pt circle too ?
3-pt arc also has a strange behavior on the axes, but this is not dangerous because it is noticed immediately. it is rather rare in daily work. but can't hurt if it gets cleaned up
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
openBrain
Veteran
Posts: 9031
Joined: Fri Nov 09, 2018 5:38 pm
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by openBrain »

chrisb wrote: Wed Jul 28, 2021 8:30 am I mixed things up: 3-point-circle acts as shown in your screen cast on macOS too. I don't think it's really weird. The only thing missing is a proposal for a tangent constraint for the first point.
Thx for feedback. At least all OSes behave the same, which is great.
thomas-neemann wrote: Wed Jul 28, 2021 8:31 am 3-pt arc also has a strange behavior on the axes, but this is not dangerous because it is noticed immediately. it is rather rare in daily work. but can't hurt if it gets cleaned up
Actually the more I think about it and the more I think current behavior is not so bad.

Regarding 3-pt arc, I think everything's actually correct. 1st and 2nd click are (real) endpoints, and 3rd click is a curve path.

Regarding 3-pt circle, I was fooled by the "name". We actually use points to define the circle, but all these points will have no real existence once circle is created and all that will remain is a curve. So we are actually manipulating a curve, and constraints are (pretty correctly) suggested as such.
Just I don't see why tangent constraint isn't suggested for 2 first clicks but only for third. My own opinion would be to suggest tangent for all 3 clicks (in regard of another curve) because I see no other sensible constraint between a circle and another curve.
Thoughts ?
User avatar
thomas-neemann
Veteran
Posts: 11730
Joined: Wed Jan 22, 2020 6:03 pm
Location: Osnabrück DE 🇩🇪
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by thomas-neemann »

openBrain wrote: Wed Jul 28, 2021 10:02 am
As long as the impression is not created that freecad has caught something even though it did not do it, everything is ok and no unnoticed errors can occur.
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
openBrain
Veteran
Posts: 9031
Joined: Fri Nov 09, 2018 5:38 pm
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by openBrain »

thomas-neemann wrote: Wed Jul 28, 2021 10:06 am As long as the impression is not created that freecad has caught something even though it did not do it, everything is ok and no unnoticed errors can occur.
I can't implement such a vague thing. :) I can change behavior, but I need to precisely know what is expected.
User avatar
thomas-neemann
Veteran
Posts: 11730
Joined: Wed Jan 22, 2020 6:03 pm
Location: Osnabrück DE 🇩🇪
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by thomas-neemann »

openBrain wrote: Wed Jul 28, 2021 10:21 am
thomas-neemann wrote: Wed Jul 28, 2021 10:06 am As long as the impression is not created that freecad has caught something even though it did not do it, everything is ok and no unnoticed errors can occur.
I can't implement such a vague thing. :) I can change behavior, but I need to precisely know what is expected.
i had the problem with referencing a step model. i didn't know the dimensions of the step model. When it was caught, circle 3 pts lit up the external geometry in yellow, so that I thought he caught it. but it didn't and the geometry that i then restricted was wrong.
later i noticed that when catching no restriction symbol appeared, like with all others e.g. arc, line, rectangle etc. with which it works wonderfully.
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
openBrain
Veteran
Posts: 9031
Joined: Fri Nov 09, 2018 5:38 pm
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by openBrain »

thomas-neemann wrote: Wed Jul 28, 2021 10:28 am i had the problem with referencing a step model. i didn't know the dimensions of the step model. When it was caught, circle 3 pts lit up the external geometry in yellow, so that I thought he caught it. but it didn't and the geometry that i then restricted was wrong.
later i noticed that when catching no restriction symbol appeared, like with all others e.g. arc, line, rectangle etc. with which it works wonderfully.
It doesn't help. My proposal is : for all 3 clicks, point-on-line with a vertex, tangent with a curve (any type). Would that be OK?
User avatar
thomas-neemann
Veteran
Posts: 11730
Joined: Wed Jan 22, 2020 6:03 pm
Location: Osnabrück DE 🇩🇪
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by thomas-neemann »

openBrain wrote: Wed Jul 28, 2021 10:35 am
thomas-neemann wrote: Wed Jul 28, 2021 10:28 am i had the problem with referencing a step model. i didn't know the dimensions of the step model. When it was caught, circle 3 pts lit up the external geometry in yellow, so that I thought he caught it. but it didn't and the geometry that i then restricted was wrong.
later i noticed that when catching no restriction symbol appeared, like with all others e.g. arc, line, rectangle etc. with which it works wonderfully.
It doesn't help. My proposal is : for all 3 clicks, point-on-line with a vertex, tangent with a curve (any type). Would that be OK?
in my opinion this is a good solution
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
chrisb
Veteran
Posts: 53789
Joined: Tue Mar 17, 2015 9:14 am

Re: [workaround] (Dangerous) behavior from the sketcher

Post by chrisb »

openBrain wrote: Wed Jul 28, 2021 10:35 am It doesn't help. My proposal is : for all 3 clicks, point-on-line with a vertex, tangent with a curve (any type). Would that be OK?
+1

Yellow highlight is not enough. The small symbols are important.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
openBrain
Veteran
Posts: 9031
Joined: Fri Nov 09, 2018 5:38 pm
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by openBrain »

I submitted a PR : https://github.com/FreeCAD/FreeCAD/pull/4945
See it in action below (on a simple test case) :
3pt_circle_fix.gif
3pt_circle_fix.gif (280.87 KiB) Viewed 1186 times
My only concern is that (believe me, but you can see it in the file diff of the PR), tangent constraint had been specifically removed for 1st and 2nd click. It was explicit in the code, but there was absolutely no explanation about the reason. And as far as I can think about it, I see no good reason why it could be harmful. If one can figure it out, please let me know and I will pause or kill the PR.
User avatar
thomas-neemann
Veteran
Posts: 11730
Joined: Wed Jan 22, 2020 6:03 pm
Location: Osnabrück DE 🇩🇪
Contact:

Re: [workaround] (Dangerous) behavior from the sketcher

Post by thomas-neemann »

openBrain wrote: Wed Jul 28, 2021 12:32 pm
i think the solution is very good. Many thanks
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
Post Reply