Sketcher destroys topology

[ulrich1a]

ulrich1a wrote:The solver replaced the 180° angle constraint with a parallel constraint.


I can't imagine how such behavior could be possible. I don't think that this can happen unless there are changes in the sketcher during the last year that I am not aware of.

Ok, to be correct: The sketcher joined the lines, that made up the angle before. So the 180°-angle-constraint became redundant. The change could not applied, until deletion of the angle constraint, but that converted the fully constrained sketch in an underconstrained sketch.
I will test tomorrow in an old version.
Ulrich

[triplus]

This is the reason why you could not change angle constraint after you entered corner case scenario (180 degrees):



Simply put leaving corner case scenario puts one construction line on one side and second one on the opposite side of Y axis (of 4 possible outcomes) and with (because of) combination of other constraints used this prevents different angle (180 degrees) to be formed between the lines. Using this constraints instead:



Simply put leaving corner case scenario (180 degrees) will always put construction lines on the same side of Y axis and that enables you to use angle constraint on both lines because only 2 possible outcomes are possible and both enable to form an angle between two lines.

But that will not solve all the issues you are having with original sketch. For that you will need to set different set of constraints in the first place:



And you will not be able to change the angle in steps bigger then 179 degrees for now if you do not want flipping. That last part i do see as a bug everything else discussed not all that much!

[ulrich1a]

And you will not be able to change the angle in steps bigger then 179 degrees for now if you do not want flipping. That last part i do see as a bug everything else discussed not all that much!

I had a further look and I agree to this.
The question is, if step sizes for angles greater than 179° can occur in the solving process for a complicated sketch. The solver will be more reliable, if the arc flipping is avoided also for this step size.

[triplus]

The question is, if step sizes for angles greater than 179° can occur in the solving process for a complicated sketch.

Sure. This will happen in simple or complex sketches i do not see the reason why it should not.