fully constrained sketch... or not?

[Janosik]

Hi all,
I want to start by saying that I'm absolutely new to FC, so maybe I'm just doing something wrong, maybe I'm misunderstanding something, or... maybe I'm having trouble wit a bug in FC...

If I understand correctly, a 'fully constrained sketch' means that it can be drawn in ONLY ONE WAY.

I now have a sketch, based on some numbers in a spreadsheet.
The value of the first cell can be freely chosen; the other cells are calculated by multiplying the first number with a certain factor.
Changing the first value will change the other values, but their ratio remains the same.

Changing the value in relatively small steps (usually) works fine, but when I change it in one big step, the sketch gets corrupted...

The sketch in the video below (about 4 minutes long) is isolated from a bigger project I'm working on.
I have tried constraining it in dozens different ways, but there's always something that goes wrong...

phpBB [video]

[freedman]

There is no golden rule that a sketch has to be fully constrained. It does make for a better understood, documented, locked in place, non-changable unless you change a number sketch. Are you getting broken constraints?

If I understand correctly, a 'fully constrained sketch' means that it can be drawn in ONLY ONE WAY.

Yes, I would say that's correct, "it can only be drawn to that size".

[kisolre]

Fully constrained does not mean it will have only one solution. From @ChrisB sketcher lecture:

A sketch is said to be solved, if all constraints are fulfilled and there is no other ”near-bysolution”, i.e. you cannot move some part of the sketch continuously while the solution is
still valid. This condition is a bit complicated, because a sketch can well be marked as solved
although the solution is not unique.

https://forum.freecadweb.org/viewtopic.php?f=36&t=30104