Changing parameter name changes sketch geometry

[TRIALCAD2014]

As title says renaming a parameter changes the geometry. Where the were 2mm between vertical lines in Figure 1

we now have  now have 1 mm. Renaming is not supposed to change so is a bug and the project unusable now. Days of work gone to waste.
s

After renaming:

[rohit.bapat]

Hello @TRIALCAD2014 

Can you please provide us the f3d file that produces this issue? It will help us get to the bottom of this issue

[TRIALCAD2014]

Hi,

I cleared out most of the project to isolate the issue. Rename BoneCornerToCenter to anything like BoneCornerToCenterX to see how the circle dimension moves to the other side while maintaining the value. So it seems to be an issue with redrawing as it the value change sign.

Cheers,
Adrian

[KristianLaholm]

You hade the same dimension (thickness) in 2 places due to missed constrain on one line.

But the cause of you problem I think is this:

The dimension parameter "boneCenterToCenterSide" had a negative value, fixed with abs().

https://knowledge.autodesk.com/community/screencast/c29b54f6-3882-405b-a4c4-3ea1f6bcc5d1 

[TRIALCAD2014]

Thank you for noticing the unusual use of dimension instead of constraints. This is not the full project and that element gets mirrored and projected a number of times. I noticed that the constraints are not reliably carried with these operations but dimensions are so I had to use the dimension as a work around.
As you stated that is not related to this problem with variable renaming.
Of course we can always appy abs in front of all the parameters as a potential workaround but that would not work with parameters that can be positive and negative
The issue is that he renaming of a parameter changes its value and I cannot see any other interpretation to this except for a bug which should be submitted to dev.
Thank you

[KristianLaholm]

Some of the devs/experts will have a better answer but to my knowledge negative dimensions will cause this behavior.

I can trigger the same behavior as parameter name change by drawing a line from center of one circle to the other and the sketch will flip due to the sketch engine recalculating the constraints and interpreting the negative dimension.

[TRIALCAD2014]

LOL
Imagine creating a game that has a child face in a window. Somebody
renames one of the variables in the game and the child face disappears
from the window!

[jeff_strater · Accepted solution]

@KristianLaholm is correct - negative values for a sketch dimension is unsupported (and why it is prohibited in the Edit Dimension workflow - there is a loophole in the parameter dialog/system).  However, the behavior of a sketch with negative dimensions is highly undesirable - each successive compute will "flip" the direction of the dimension.  This is why it is prohibited when editing a dimension.  The screencast below illustrates the problem.

So, why is rename involved?  Any change to the parameters, even a rename of the parameter, triggers a compute, which will trigger this bad behavior.

Yes, this is a bug, and it is already recorded (many times, to be honest).  The large percentage of users do not encounter this bug, ever.

[TRIALCAD2014]

Hi,

Yeah, I would have been surprised if many users would not have ran into this issue.

I was too often there triaging and prioritizing issues to be fixed so I understand that most of the time there are not enough resources. Yet, it will continue to drain resources every time somebody runs into it. The fix could be a simple check for negative values for dimensions, a relevant error message and a junior dev could be assigned to it to put it to RIP pile.

Cheers,
Adrian