Block Constraint

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chrisb
Posts: 16352
Joined: Tue Mar 17, 2015 9:14 am

Re: Block Constraint

Postby chrisb » Sat Dec 08, 2018 11:15 am

paullee wrote:
Sat Dec 08, 2018 10:50 am
Hi, it seems Block Constraint does not work on a point.
It is slightly inconsistent, but the point is a bit special, as it is always construction geometry, which is not exposed to the outside world. So you usually have some edges related to it, otherwise the point is useless. And those edges can be block constrained.
abdullah
Posts: 3174
Joined: Sun May 04, 2014 3:16 pm

Re: Block Constraint

Postby abdullah » Sat Dec 08, 2018 2:19 pm

paullee wrote:
Sat Dec 08, 2018 10:50 am
abdullah wrote:
Hi, it seems Block Constraint does not work on a point.

So, can only use Lock Constraint as alternative?

Thanks!
Interesting!! I am not sure ATM why. I will add it as an issue for v0.19.

I am not sure what you are trying to do, but Block Constraint is rarely what you want to lock a point, because generally you need to lock a point at an exact value position. In any case, locking a point without editing the values will get you the same behaviour as using the block constraint.
paullee
Posts: 1545
Joined: Wed May 04, 2016 3:58 pm

Re: Block Constraint

Postby paullee » Sat Dec 08, 2018 11:55 pm

chrisb wrote:
Sat Dec 08, 2018 11:15 am
It is slightly inconsistent, but the point is a bit special, as it is always construction geometry, which is not exposed to the outside world. So you usually have some edges related to it, otherwise the point is useless. And those edges can be block constrained.
abdullah wrote:
Sat Dec 08, 2018 2:19 pm

Interesting!! I am not sure ATM why. I will add it as an issue for v0.19.

I am not sure what you are trying to do, but Block Constraint is rarely what you want to lock a point, because generally you need to lock a point at an exact value position. In any case, locking a point without editing the values will get you the same behaviour as using the block constraint.
Thanks all! Noted abdullah has put it in Mantis.

If possible, a block constraint is better as it do not create dimension line object occupying the screen.

'Better Option'?

Even better, I was thinking (forget if asked in forum) if it is possible in e.g. Sketcher::SketchObjectPython, that some edges could 'turn' into status like the H-Axis/V-Axis that it no longer be 'editable', rather than having a 'constraint' which seem take solver time to process - seems when there is more Block Constraints added, the sketch become sluggish.

Usecase of Block Constraints

BTW, I am using Block Constraints because I find Link to External Geometry is Extremely Vulnerable - a change in the reference object (even the referenced object is sketch) probably break the Link.

Workflow Attempting
  1. I just make the Link to External Geometry as required.
  2. Duplicate the edge with normal edge with say coincidence
  3. Then add Block Constraints to freeze the latter
  4. Remove the External Link so whatever the change in external it does affect the current sketch
  5. Downside is if that particular 'External Edge' is expected to change and need updating and referenced in current sketch, need to do it again manually
  6. At least, it would not 'unexpectedly' frustrate the current sketch when the external geometry is 'updated' without aware of knock-on effect
Realthunder's Assembly 3 branch I remember make some new Sketch Edge Index which is persistent and it no longer 'change' and break link.
chrisb
Posts: 16352
Joined: Tue Mar 17, 2015 9:14 am

Re: Block Constraint

Postby chrisb » Sun Dec 09, 2018 12:14 am

Interesting workaround for topological naming issues. And I see that here a block constraint for a point would be sensible.