Strange behaviour when changing parameters back and forth

[Anonymous]

So I am trying to draw a paramteric board game. But when I change some paramters from 120mm to 200mm back and forth some times it gets screwed up:

Until now everything looks nice. But when I do it again: 

Everything is screwed up. I have no idea why. 

Any help is appreciated!

[macmanpb]

Try to constrain your sketcher right. In your screens i see alot of uncontrained sketches. On parameter changes fusion cannot map these changes to the other sketches. 

[Anonymous]

How can I reconize which elements are unconstrained?

[macmanpb]

Go to the preferences and check this:

Then you can see all sketches that are fully constrained are black. The others blue. That might help you to get a better sketch behaviour 😉

[Anonymous]

Thanks for your answer. I can now see, which elements are not constrained enough. But I have no idea how to fix it. Everything i try seems to overconstrain it.. For example i tried to fix their length to the define constant MiddlePartDistanceBetweenCornerFields. Do you have any suggestions on how I should tackle this problem? How can I see the degrees of freedom of the lines, which are not constrained enough? Basically the solution should allow me to set the BoardRadius to any value and everything else should get scaled accordingly so that it looks just like a scaled version. All angles and proportions should stay the same.

[Anonymous]

I changed the file a little bit: 

[macmanpb]

Thats a limitation in Fusion. The sketch that is not enougth constrained is blue but fusion dont tell u why 🙂

The best is, to set dimensions from the orgin to the starting point of your sketch. The rest is to analyse the free sketch elements and try to constrain them.

Hope the fusion team has a better solution but that is my way to get rid with that.

If i have move time i will take a look into your design.

[macmanpb]

I take a look into your file and see a lot is black. But i dont figure out why the zigzag's are blue. For my opinion there are enought constrained.

[Anonymous]

Ok. Thank you very much for your time! 🙂

I hope some one else sees what we are missing.

[jeff_strater]

That is just a limitation/bug in the "fully constrained display color" option.  Those zig-zag lines are, indeed, fully constrained and should display as such.  I'll add that bug to the system.  I've found that the fully constrained analysis code does not seem to handle midpoint constraints very well, so that is probably what we are seeing here.  That's partially why it is still in the "preview" state.

The good news is that this sketch does perform well now that it is fully constrained.  Changing the BoardRadius parameter seems to update correctly, from what I can tell.

Thanks for bringing this to our attention,  It is a  good test case.  Is it OK if we add it to our test suite?

Jeff

[Anonymous]

@jeff_straterThanks for your answer. But I still experience the same issue:

If I change the parameter BoardRadius from 200 to 100 to 200 to 100 to 200 it doesn't look like before. The first few tmes it works, but then everything gets messed up suddenly.

Can you explain why this happens?

Yes. Feel free to add this to your internal test suite!

[jeff_strater]

that looks like another bug.  No, I cannot explain it, but we'll look into it.  I only changed it once when I tried it...

In general I try to avoid large-size changes all at once, but that's just from working with sketch solvers for a long time.  They tend to react slightly better if you go slowly.  So, if you want to go from 100 to 200, I would probably stop at 150 on the way, or even a couple of times.  I don't know that this would help in this case, but it is a good general technique.

Jeff

[Anonymous]

Ok. Thanks for your help! It is especially strange because it works as expected the first few times...

I usually changed the parameters back and forth to check if the constrains work as expected.

Can you say anything about the release cycle of Fusion360 at which such bugs get fixed?

[jeff_strater]

I just heard that the fully constrained analysis on this model works correctly in our current development build, so the next major update should fix the analysis bug.  The editing of parameters back and forth is still being looked at.

Jeff

[jeff_strater]

I also heard today that the "editing the parameter value back and forth" problem has also been solved.  No ETA on when these will be released, they need bake time and QA validation, but it's good news that these have both been fixed.  Thanks again for reporting these.

Jeff