It happened several times to me now that points or lines switched places when changing constraints in a sketch.
Check this starting sketch, especially the horizontal constraint of 20mm:
- orig_20.png (20.02 KiB) Viewed 568 times
If I change it to 60mm, the shape is the same, except being longer (as expected):
- const_60.png (20 KiB) Viewed 568 times
But if I change the constraint to 70mm (from 20mm only; it does not do that when going from 60mm), the two right vertical lines "switch" sides:
- const_70.png (20.22 KiB) Viewed 568 times
This is a simple sketch, the "problem" is easily visible and there are other ways this sketch could be constrained that would most likely not lead to the "switch". But with more complicated sketches, especially when using parameters from a spreadsheet or referencing constraints of another sketch, it's much worse, because then things go wrong somewhere and you don't even notice it until it's way too late (e. g. when a part is not visible currently, because you work on something else). Quite often even changing back to the original constraint doesn't revert all the "switches" that happened. Pretty much the only hope at that point is that I didn't save my model and make the changes "permanent".
I know that there will often be multiple "solutions" for the constraints given in a sketch, but unfortunately it is not obvious while drawing a sketch where they can hit you. What is the best way to avoid something like this happening? Would it be possible to create constraints (or more like hints for the solver) like "this line should be longer than that line" or "this point should always be left of that point" or similar?
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