topic Re: G1 or g2 doesn't work on loft in Fusion Design, Validate & Document Forum

G1 or g2 doesn't work on loft

kahjun1991 — Tue, 18 May 2021 05:23:11 GMT

Hello guys

I'm a industrial designer and now I've been considering to change the 3D tool to Fusion 360

So I've practiced Fusion 360 and i have an issue with loft modeling

Re: G1 or g2 doesn't work on loft

TrippyLighting — Tue, 18 May 2021 11:46:12 GMT

If you use circular curves that are only tangent (G1) you will have problems achieving G2.

Also if you are surfacing you need only a surface, not a solid body to be able to define tangency toward.

Re: G1 or g2 doesn't work on loft

kahjun1991 — Tue, 18 May 2021 12:59:32 GMT

none

Re: G1 or g2 doesn't work on loft

kahjun1991 — Tue, 18 May 2021 12:59:01 GMT

That mean if I make a loft face from surface to surface, I can use G1 or G2 on loft right?

So I tried to make a surface only using surface to surface. But still G1 and G2 doesn't work.

I attach the 3D file. Please check it.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Tue, 18 May 2021 13:11:53 GMT

I really don't have the tie to sort through all the unneeded stuff in your timeline to decipher what you want to achieve.

Then, please create a screencast and show the loft creation process you are having a problem with.

My gut feeling is that you are tying to venture too far too soon into unfamiliar territory.

Here are 2 resources you should give a thorough read before continuing:

Autodesk Alias Theory Builders

Autodesk Alias Golden Rules

Re: G1 or g2 doesn't work on loft

kahjun1991 — Tue, 18 May 2021 14:05:34 GMT

I am a NX UG user as a industrial designer. I know g1 and g2 on logically.

Just i wanna know why it doesn't show up on Loft menu even I made curves from connected surface.

I made same thing same way from NX UG and It totally worked. And Rhino as well.

Is this program bug or something problem?

Re: G1 or g2 doesn't work on loft

TrippyLighting — Tue, 18 May 2021 14:48:03 GMT

Assuming that you can do the same thing the same way using different software packages is simply not a good approach. I work with several different software packages and they all want to handled in a particular way 😉

I still don't exactly know how the screenshots match what I see in your design. I don't see the little strip you are showing the lofting process of in the design file you shared. As such I cannot help analyzing what the problem might be.

Something you should never do in Fusion 360 without checking the curvature is working with projected (purple) curves. In Fusion 360 projected curves almost always have broken curvature. I just randomly grabbed a sketch from your design:

Re: G1 or g2 doesn't work on loft

kahjun1991 — Tue, 18 May 2021 18:12:02 GMT

Ok here is the thing.

I wanna make this vertical mouse and problem is the patterns

First i made a body.

And cut this for making the patterns

After that i sketch the patterns on Y section.

Then made intersection curves on surface.

And made on more curve for circular curve middle of intersection curves for pattern

But it doesn't show up G1 of G2 on Rail menu, So the loft surface is not connected softly with other bodys.

If the intersection(purple) curve have a problem with Loft menu, how can I make this patterns with out intersection curve.

Do I have to sketch it on 3D sketch one by one? I think it doesn't make sense.

I know some guy make this patterns using T-spline but I wanna make with out T-spline.

Please let me know how can I handle this one. I'm really considering to change tool NX UG from Fusion 360

but this problems make me still using NX UG.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Tue, 18 May 2021 19:10:51 GMT

Ahh, yes, now this makes sense.

My apologies for assuming you were new to the surfacing world. I should have taken a closer look at your model!

I managed to get one of these lofts to be G2at the two transitions at the top and bottom. But give me a day, or two to investigate. I'll need to go back through the timeline and see how you constructed this to make a recommendation for a better workflow.

You probably try to follow the workflow you are used to from NX, which does not serve you well in this case.

I can see one thing already. You cut up (split body) the solid to get a particular surface. A better workflow is to copy the surfaces by creating a zero offset and then work with those surfaces. That way your original geometry remains intact. You never know when you might need to go back in the timeline needing the original surface.

Re: G1 or g2 doesn't work on loft

kahjun1991 — Wed, 19 May 2021 06:34:56 GMT

Thank you for your support sir.

I will wait for your solution.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Wed, 19 May 2021 12:01:33 GMT

@kahjun1991 I have looked at this into a bit more detail and I am wondering if there is a regression in the loft code!

@jeff_strater It might make sense to discuss this n the EE Slack channel.

We would use the two vertical edges of the red surfaces as the loft profiles and the two horizontal yellow edges and the little sketch arc as the rail. We should be able to get G1/G2 options for the rails when all the surfaces are individual, non stitched surfaces.

However, I can only get this to work if I stitch together all of the surfaces that would define the loft boundaries.

That would make this model incredibly tedious and I don't remember it being that way.

It would also be impossible to use curves as loft profiles for this design.

Re: G1 or g2 doesn't work on loft

jeff_strater — Wed, 19 May 2021 16:26:06 GMT

There is no regression in the loft functionality that I am aware of.

A couple of points:

the conditions continuity (G1/G2) are only available when model edges are selected (in surface loft) as profiles. If you select sketch curves for profiles or rails, these conditions are not available. For profiles, sketch curves allow a "direction".
For rails, even if you select a model edge as a rail, the continuity controls are only available in certain cases. I'm not completely certain what all the limitations are but it is designed for this kind of case:

where the rails are on the outer boundaries of the loft (as opposed to internal rails):
It is possible to create conflicting requirements when using rails. In your case, the continuity between profiles is somewhat determined by the rail curves. At the point indicated, the shape of the result is influenced by the rail. If the rail is not G1/G2 to the adjacent loft, but you specify G1/G2, (assuming you were lofting between surface and not sketches), then Loft has to choose one or the other.

Not sure this answers all your questions, but hopefully sheds some light.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Wed, 19 May 2021 19:00:16 GMT

@jeff_strater thanks for the prompt response.

I don't think I've explained this well so will create a screencast later today to do so.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Thu, 20 May 2021 01:30:40 GMT

@jeff_strater

Here's the screencast:

Re: G1 or g2 doesn't work on loft

kahjun1991 — Fri, 21 May 2021 01:20:03 GMT

@TrippyLighting Wow thank you!! This is what I want to say about it!! Your explain is perfect

@jeff_strater And This is what makes me bother. Please tell me a solution about it Thanks. I will wait for it!!

Re: G1 or g2 doesn't work on loft

TrippyLighting — Sat, 22 May 2021 21:25:52 GMT

I thought I had found a workflow that works but got stopped by another issue. @kahjun1991 can you actually create this model in NX the way you demonstrate in teh screenshots above ?

In Fusion 360 the surface quality of these lofts already does not look exactly great.

And the loft in the open space I cannot create as Fusion 360 complains that the loft would self intersect.

Re: G1 or g2 doesn't work on loft

kahjun1991 — Tue, 25 May 2021 07:23:05 GMT

@TrippyLighting Hello again sir. I made this in NX UG as same way which i tried to make on Fusion 360.

And It works perfectly as you can see. i don't know how i analyze surface in NX UG and Fusion 360

I will upload the STEP file on here. Please check it out.

And @jeff_strater sir. Still I'm waiting for your solution.

Please let me know how can I make it in Fusion 360 without T-spline.

I don't think it is something hard modeling.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Tue, 25 May 2021 12:30:28 GMT

I personally don't think that there is a solution for this that will allow you to model this the same way you model it in NX. You might have to change your modeling strategy.

For example lofts where the rails and profiles meet at angles closer to 90 degrees will have better chance of succeeding.

Only using tangency (G1) will create a very strong pinching effect on the loft section in this image.

In tis case I am lofting from the upper short edge to the lower short edge, which then allows me to adjust the tangency weights. However, that appears to make almost no difference.

Changing this to G2 then the loft outright fails.

My observation is - and this might be completely wrong - is that Fusion 360 applies the weights strictly perpendicular to the loft edge.

Re: G1 or g2 doesn't work on loft

TrippyLighting — Wed, 26 May 2021 11:44:02 GMT

@kahjun1991 wrote:

TrippyLighting Hello again sir. I made this in NX UG as same way which i tried to make on Fusion 360.

And It works perfectly as you can see. i don't know how i analyze surface in NX UG and Fusion 360

In the "Inspect" menu you can use the curvature map and zebra stripe analysis tools. You have equivalent tools in NX.

Re: G1 or g2 doesn't work on loft

cekuhnen — Wed, 23 Jun 2021 21:56:33 GMT

Hi there

one practice is to work with target surface

in your case I slice the target surfaces so I can easily loft all

those duplicate / target surfaces can later be removed before stitching all together

did you try that ?

the tricky part will later be filleting the sharp edges