topic Re: Profile Reference Lost Scale User Param in Fusion Support Forum

Profile Reference Lost Scale User Param

hernandez.frank — Mon, 28 Sep 2020 22:33:49 GMT

Hi,

I am encountering what seems to be a bug.

The steps to reproduce are as follows:

Create a user parameter called ScaleFactor, default value of 1.
Create two fully constrained sketches where each dimension is multiplied by ScaleFactor.
Loft between the two sketches created in step 2.
Change the ScaleFactor user param to something larger like 5.
Observe warning "The profile reference is lost".

Expected behavior: Profile reference should not be lost.

Minimal Fusion 360 file presenting the issue: https://a360.co/3ibWoqP

Screencast URL: https://autode.sk/2EGgbAW

Fusion 360 Version: 2.0.9006

OS Version: Windows 7

Does anyone know what could be causing this?

Thanks,

Re: Profile Reference Lost Scale User Param

jhackney1972 — Mon, 28 Sep 2020 22:38:42 GMT

Is there some reason you are posting the same forum question as you did before? You had it answered then and you Accepted the Solution.

Re: Profile Reference Lost Scale User Param

hernandez.frank — Mon, 28 Sep 2020 22:51:39 GMT

Hi @jhackney1972 ,

Thank you for your reply.

This post and the one linked are about two different issues. Although they both involved a user parameter for scale the post you are linking to is about a failure with the Emboss feature and this one is about the Loft feature.

Re: Profile Reference Lost Scale User Param

jhackney1972 — Mon, 28 Sep 2020 22:57:56 GMT

The situation is surely the same. The developers probably use the same coding for the dialog boxes so I am sure the same situation applies. Fix one, you will fix them all.

Re: Profile Reference Lost Scale User Param

hernandez.frank — Mon, 28 Sep 2020 23:07:45 GMT

Hi @jhackney1972 ,

While I agree with you that they may have the same root cause only the development team can say for sure since they are the ones who know the code.

This is why I felt it would be beneficial to bring this specific case to the attention of @jeff.strater and the rest of team in the event the root causes are not the same.

Thanks again for taking the time to respond to my post,

Re: Profile Reference Lost Scale User Param

jeff_strater — Mon, 28 Sep 2020 23:46:14 GMT

I know in broad strokes what is going on here. In short, it is the purple projected lines in the sketch. At scale == 1, this is what those sketches look like:

but, at scale == 5, they look like this:

the topology of the first sketch has changed. That purple line is now wholly contained inside of the other sketch lines, and I think this is throwing off the profile recognition algorithm. I suspect it's because it was using the purple line in the profile, and assumed that the adjacent line intersected the purple line, which, after the scale, it does not. Note that the second sketch does NOT have this problem, which is why it does not fail.

The fix (or more accurately, the prevention) here is to make those purple lines construction geometry:

Then, they do not get taken into consideration in the profiles. You have to re-create the loft to do this. But, if you do that, then the loft works at scale == 1:

and, also at scale == 5:

regardless of the topology changes.

Re: Profile Reference Lost Scale User Param

hernandez.frank — Tue, 29 Sep 2020 00:04:05 GMT

Hi @jhackney1972 ,

Thank you for the detailed look at the issue.

The purples lines are the projected Z axis from origin into the sketch.

Why would the Z axis projection be affected by the scale?

Re: Profile Reference Lost Scale User Param

jeff_strater — Tue, 29 Sep 2020 20:07:56 GMT

@hernandez.frank - the projected Z axes are NOT affected by the scale. In fact, that is the point. They stay the same size and position while the rest of the sketch is scaled. That is what leads to the change in topology.

Re: Profile Reference Lost Scale User Param

hernandez.frank — Tue, 29 Sep 2020 21:55:19 GMT

Hi @jeff_strater ,

Thank you for your response and for the clarification.

Based on the information would the recommendation be to stay away from projecting geometry all together if I am modifying me sketches via user parameters like I am doing with scale?

Re: Profile Reference Lost Scale User Param

jeff_strater — Tue, 29 Sep 2020 23:46:56 GMT

I would not really recommending completely avoiding projected geometry. Sometimes it is very necessary to achieve your design intent. I've been trying, myself, to decide what the overall lesson here is, and I'm not 100% sure. Definitely avoid overlapping "normal" sketch profile geometry - I know that can confuse the profile detection code, and was a factor here. So, in this case, converting the projected geometry to construction avoided that overlapping problem. But, I cannot say "always convert projected geometry to construction", because that is, also, not always a good thing. Sometimes you NEED that projected geometry in your profile.

Re: Profile Reference Lost Scale User Param

hernandez.frank — Wed, 30 Sep 2020 00:46:45 GMT

Understood, I'll approach it on a case by case basis moving forward.

Thanks again for looking into this @jeff_strater really appreciate all the help.