Fusion crashes every time manipulating spline points of continuously constrained spline

[maxpoetter]

Hello everyone,

I am experiencing this bug, that Fusion crashes every time I try to manipulate a spline that connects two other splines with a “continuous” constraint. I have ideas for workarounds, but it is really annoying. Connecting splines continuously should be straightforward imho and would speed up my process a lot. I have experienced this for quite a while on two computers.

In the following guide, similar strategies are applied, so this should definitely work:

https://www.autodesk.com/products/fusion-360/blog/sketch-control-point-splines-faq/#How_do_I_constra...

As I get an error every time I try to add the screencast, due to „invalid html”:

https://autode.sk/36XR5LS

Just some additional thought, which might be related:

It is kind of strange, that there is a kink at the first control point of the filling spline on both sides. In the guide above the lines connecting the endpoint to the first and second control points are straight. So, maybe there's is just something wrong with continuous constraints on Mac in general?

My Example:

Kink in my own example

Screenshot from the guide (link above):

No Kink in the Guide

BTW: The Screencast app for Mac is terrible. Doesn't grab the commands from Fusion and is annoyingly slow. Also, Fusion should finally get their window management on Mac right.

[TheCADWhisperer]

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

[maxpoetter]

Trying to manipulate the control points of the connecting spline always leads to a crash of fusion.

I also added a link to a screencast to my initial message, as I couldn't add it in the “intended way”.

[TheCADWhisperer]

Will a Fit Point Spline work for your Design Intent (see Attached).

[maxpoetter]

Thank you for your suggestion. As I said I have ideas for workarounds. Just wanted to report this bug to a imho very basic feature.

Also, from what I can tell, your solution doesn't provide continuous curvature. Probably fine for most use cases, but not what I would call a “best practice”.

[TrippyLighting]

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@maxpoetter wrote:

Also, from what I can tell, your solution doesn't provide continuous curvature. Probably fine for most use cases, but not what I would call a “best practice”.

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Thanks for reporting this!

@Phil.E @jeff_strater Can you look at this please ?

A fit point spline will be G2 curvature continuous when you apply the same constraint you applied to the CV spline.

[TrippyLighting]

It seems using a fit point spline (which is a 5-degree multi span spline in Fusion 360) provide better curvature than a control point spline.

Due to the odd and almost dysfunctional controls in Fusion 360 I rarely use a control, point spline as a blend curve.

The image above was created with the attached file. In that file I replaced the "fix" constraints with dimensions. 

No crashes, so the crashes seem to be related to the fix constraint.

However, I then used a fit point spline with G2 constraints. Now I cannot scale the tangent handles!

Disappointing!

Edit: the more I dig into this, the more embarrassing it gets. I created this from scratch just to avoid inheriting any remnants and still cannot scale the tangent handles. 

So I added another spline control point to the right spline. I cannot move either of the two control points,, but the spline tuned blue indicating it is not fully constrained.

[Phil.E]

@maxpoetter unfortunately you have not sent in any recent crash reports. This is unfortunate because the only way for an engineer like me to know you are crashing and work on fixing problems like this comes from reading the reports that are sent in. No report means the problem is not known.

I'm going to send this to a QA on the sketch team to have a look at the spline complaints.

The crash is indeed repeatable and is now logged with the sketch team. Thanks @maxpoetter for providing the .f3d file and video.

[jiang_peng · Accepted solution]

Sorry for the incovieniece!

As a workaround, please fix the control points instead of fixing the whole spline:

The curvature issue is logged as FUS-101838, thanks

[maxpoetter]

Thanks for the tip! Can you also adjust the weight of the curve? This is what I am trying to do by manipulating the handles, which causes the crash.

For me, the handles of the fit point spline are fixed after applying the continuous curvature constraint.

[maxpoetter]

Thanks a lot for your exploration. Very interesting!

[maxpoetter]

I am not sure wether I put my mail address in, but I definitely described the steps necessary to recreate the issue and send the report!

Thanks a lot for forwarding this issue to the responsible team.

[TrippyLighting]

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@maxpoetter wrote:
Thanks for the tip! Can you also adjust the weight of the curve? This is what I am trying to do by manipulating the handles, which causes the crash.

For me, the handles of the fit point spline are fixed after applying the continuous curvature constraint.

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No, I cannot adjust the tangent handles, which is another bug.

[TrippyLighting]

So, I added another control point to the left spline. That drops the two dimensions associated with the first control spline, because Fusion 360 attempts to maintain the shape of the spline while adding the additional  control point.

So the spline turns blue to indicate that it is not fully constrained. Yet, I cannot move any of the two spline control points. That's another bug.

So we're counting 4 bugs in a simple sketch with three curves, and I am not done playing with it. There are signs there is more misbehavior!