Feature request: equality constraint between lines and arcs in the Sketcher

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chrili_rakete
Posts: 11
Joined: Thu May 15, 2014 11:51 am

Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrili_rakete » Thu Jan 26, 2017 11:10 am

Hello!

It would be extremely helpful for me to constrain the length of also a line and an arc in the sketcher. So I could generate (rather trivial) sheet metal unroll jobs in the sketcher.

Thank you!
--
Christoph
chrisb
Posts: 1630
Joined: Tue Mar 17, 2015 9:14 am

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrisb » Thu Jan 26, 2017 6:40 pm

I have needed this from time to time too.
hokieengr
Posts: 9
Joined: Sat Dec 31, 2016 5:09 pm

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby hokieengr » Thu Jan 26, 2017 7:54 pm

As in set the line length and the length between the two end points of the arc to the same value?
chrisb
Posts: 1630
Joined: Tue Mar 17, 2015 9:14 am

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrisb » Thu Jan 26, 2017 8:03 pm

hokieengr wrote:As in set the line length and the length between the two end points of the arc to the same value?

Yes, although that is a constraint which I can set but it does nothing.
chrili_rakete
Posts: 11
Joined: Thu May 15, 2014 11:51 am

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrili_rakete » Thu Jan 26, 2017 8:07 pm

No, I would rather suggest that the line length should be equal to the length of the arc. Thank you!
chrili_rakete
Posts: 11
Joined: Thu May 15, 2014 11:51 am

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrili_rakete » Thu Mar 02, 2017 4:34 pm

I posted this as a feature request into the bugtracker: http://freecadweb.org/tracker/view.php?id=2939
triplus
Posts: 4833
Joined: Mon Dec 12, 2011 4:45 pm

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby triplus » Thu Mar 02, 2017 4:44 pm

chrili_rakete wrote:I posted this as a feature request into the bugtracker: http://freecadweb.org/tracker/view.php?id=2939


I asked Abdullah on his opinion about this:

https://forum.freecadweb.org/viewtopic. ... 90#p161448

And in the past there was a discussion on how such constraint could be useful in for example creating belt length:

https://forum.freecadweb.org/viewtopic.php?f=24&t=17372

Bottom line it doesn't look like such constrain will be made anytime soon. But i guess you never know what the future holds.
chrili_rakete
Posts: 11
Joined: Thu May 15, 2014 11:51 am

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrili_rakete » Thu Mar 02, 2017 5:22 pm

Thank you triplus – I did not know about this interesting discussion. I am not absolutely sure, but I think that my request is similar, but much more trivial, as I was asking for the length of a simple arc (given e.g. center, starting and end-point geometry, radius) to constrain. Compared to splines or other complex curved geometry as it is discussed in your post, the algorithm of constraining the length of an arc to another length might be considerably simpler. And for me: very useful ;)
triplus
Posts: 4833
Joined: Mon Dec 12, 2011 4:45 pm

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby triplus » Thu Mar 02, 2017 6:03 pm

chrili_rakete wrote:Thank you triplus – I did not know about this interesting discussion. I am not absolutely sure, but I think that my request is similar, but much more trivial, as I was asking for the length of a simple arc (given e.g. center, starting and end-point geometry, radius) to constrain. Compared to splines or other complex curved geometry as it is discussed in your post, the algorithm of constraining the length of an arc to another length might be considerably simpler. And for me: very useful ;)


Unfortunately i explicitly asked about Arc length constraint. And the answer was it wouldn't be trivial to implement such constraint.

P.S. I am wondering if expressions could be used in combination with existing constraints. I guess it depends on the use case.
chrili_rakete
Posts: 11
Joined: Thu May 15, 2014 11:51 am

Re: Feature request: equality constraint between lines and arcs in the Sketcher

Postby chrili_rakete » Thu Mar 02, 2017 6:44 pm

triplus wrote:Unfortunately i explicitly asked about Arc length constraint. And the answer was it wouldn't be trivial to implement such constraint.


Oh yes, I did notice that – but I think that microelly2 and abdullah continued to talk about "curves" in their answers. (Sorry if I might be wrong!)

triplus wrote:P.S. I am wondering if expressions could be used in combination with existing constraints. I guess it depends on the use case.


Yes, this is possible, at least in 0.17 – for example you can constrain the length of a line in a sketch to the length of an arc (Draft) via the expression "=Arc.Shape.Length"