Block Constraint

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abdullah
Posts: 2856
Joined: Sun May 04, 2014 3:16 pm

Block Constraint

Postby abdullah » Thu Jan 25, 2018 4:25 pm

Recently the Block Constraint has been merged.

Basically allows to block a geometric element in place with a single constraint. I should be particularly useful to work with B-Splines.

More here:
https://forum.freecadweb.org/viewtopic. ... 76#p205303

If you find bugs, let me know here or in the development forum (always quote me so that I get a notification), as I would like to solve any bug before 0.17 release.

Thanks,
abdullah
Marco_T
Posts: 213
Joined: Mon Jan 11, 2016 11:58 pm

Re: Block Constraint

Postby Marco_T » Thu Jan 25, 2018 10:40 pm

abdullah wrote:
Thu Jan 25, 2018 4:25 pm
Recently the Block Constraint has been merged.
Thanks abdullah,
good feature for lazy drafters as me... :D
I will test it as soon as possible.

--
Marco_T
triplus
Posts: 8278
Joined: Mon Dec 12, 2011 4:45 pm

Re: Block Constraint

Postby triplus » Thu Jan 25, 2018 10:52 pm

Thank you.
abdullah
Posts: 2856
Joined: Sun May 04, 2014 3:16 pm

Re: Block Constraint

Postby abdullah » Sun Jan 28, 2018 10:37 am

Marco_T wrote:
Thu Jan 25, 2018 10:40 pm
good feature for lazy drafters as me...
I am still to be surprised how people will use it, but for bsplines I think it is a must otherwise you may inadvertently drag a point, not realise it right away and ruin your b-spline contour.

Joel will probably use it in his Civil Engineering WB to freeze things in place and accelerate the solving of new addition in complex sketches...

I am sure people will come up with new uses.
triplus wrote:
Thu Jan 25, 2018 10:52 pm
Thank you.


Thanks to you too, as you are one of the guinea pigs that test my first concepts and helps shape the concepts into what is merged.

You, experienced during-development-testers, are vital for getting useful new features merged... What I want to say is that if what gets merged is not useful, it is not on me, you are to blame :lol:
triplus
Posts: 8278
Joined: Mon Dec 12, 2011 4:45 pm

Re: Block Constraint

Postby triplus » Sun Jan 28, 2018 10:02 pm

Fair enough.

P.S. But it ends at issue reports. Those are hopefully still on you. :lol:
abdullah
Posts: 2856
Joined: Sun May 04, 2014 3:16 pm

Re: Block Constraint

Postby abdullah » Mon Jan 29, 2018 1:19 pm

triplus wrote:
Sun Jan 28, 2018 10:02 pm

P.S. But it ends at issue reports. Those are hopefully still on you. :lol:
Yes, they are: triplus 1/Abdullah 0 :D
chrisb
Posts: 14502
Joined: Tue Mar 17, 2015 9:14 am

Re: Block Constraint

Postby chrisb » Tue Mar 06, 2018 4:43 pm

Abdullah, you have freed us from wrong usage of the tangent+coincidence constraint, but I'm afraid we will get more like this problem https://forum.freecadweb.org/viewtopic. ... 07#p218558 where the block constraint yields a solved sketch which pretends to be sensible.
But I will rather have a good tool with problems on wrong usage than a bad tool leading to bad results even on proper usage.
abdullah
Posts: 2856
Joined: Sun May 04, 2014 3:16 pm

Re: Block Constraint

Postby abdullah » Fri Mar 09, 2018 4:55 pm

chrisb wrote:
Tue Mar 06, 2018 4:43 pm
Abdullah, you have freed us from wrong usage of the tangent+coincidence constraint, but I'm afraid we will get more like this problem https://forum.freecadweb.org/viewtopic. ... 07#p218558 where the block constraint yields a solved sketch which pretends to be sensible.
But I will rather have a good tool with problems on wrong usage than a bad tool leading to bad results even on proper usage.
I have destroyed a fair amount of screws and forks using a fork as screwdriver and I have destroyed a fair amount of screwdrivers using them as chisels.

It has been interesting to see how the block constraint was being used in this case. It will have to be transmitted that blocking per se is not a meaningful way of constraining. It does not actually enforce a geometric relation. It just freezes the thing in place and you can not have enough precision to exactly locate things in place and block them.

What I was expecting is that people will (mostly wrongly) use it to remove those remaining DoF that are impossible to find. And I say wrongly because if you do not know when the DoF is missing is mostly a bad idea to use the block constraint to get away with a "fully constrained sketch". It is what triplus once said is an obsession to have "fully constrained sketches" for the sake of having them so. The DoF finder, when merged, will help a lot to avoid this (mis)use case.

I still think that the main use of the Block constraint is for "artistic work", when you do not care about a geometric definition, but you are happy about how it appears. Of course you do need at least coincidences so that things are closed.

Anyway, I still get mad when I need an screwdriver and the one I find is the one I used as a chisel... ;)
chrisb
Posts: 14502
Joined: Tue Mar 17, 2015 9:14 am

Re: Block Constraint

Postby chrisb » Fri Mar 09, 2018 6:01 pm

abdullah wrote:
Fri Mar 09, 2018 4:55 pm
I still think that the main use of the Block constraint is for "artistic work", when you do not care about a geometric definition, but you are happy about how it appears. Of course you do need at least coincidences so that things are closed.

Anyway, I still get mad when I need an screwdriver and the one I find is the one I used as a chisel... ;)
Very well said. Until now I have used block constraint successfully to find DOFs or to quickly freeze some elements. But the real use is e.g. after having imported e.g. an SVG with lots of points where some modifications have to be made. It's wonderful for that.
triplus
Posts: 8278
Joined: Mon Dec 12, 2011 4:45 pm

Re: Block Constraint

Postby triplus » Sat Mar 10, 2018 2:04 am

abdullah wrote:
Fri Mar 09, 2018 4:55 pm
It is what triplus once said is an obsession to have "fully constrained sketches" for the sake of having them so.
When a proposal is made it makes sense to think about it from more angles. If you want to evaluate it fully. Nice to see some assumptions where spot on. ;) But overall it's a nice addition. I have seen here on the forum some valid use cases already. Therefore clearly the potential pros outweigh the potential cons!
The DoF finder, when merged, will help a lot to avoid this (mis)use case.
+1
Anyway, I still get mad when I need an screwdriver and the one I find is the one I used as a chisel... ;)
That is the thing with FreeCAD tools. You find users are using screwdriver as a chisel at times. You tell them not to and point them to the right tool that does the job better. But if the original approach bare fruit that is OK in the end too. The tool did the job. And that is that. :idea:

P.S. Or you didn't speak metaphorically. And you had an actual screwdriver and a chisel in mind? :ugeek: