topic Curve smoothing & merging / concatenate segmented curves for surface creation in Fusion Design, Validate & Document Forum

Curve smoothing & merging / concatenate segmented curves for surface creation

lubos.ulovec — Fri, 14 Mar 2025 17:43:59 GMT

Hello,

In some CAD systems, I have found it useful to concatenate specific curves, then interpolate/smooth them out with a given deviation. This helps e.g. in rebuilding areas with larger, smoother surfaces instead of dealing with too many small segments.

Is there an efficient workaround in Fusion 360 to achieve this? Or could a feature like this be considered for future implementation?

A related topic: Sometimes, surface boundaries are created from segmented curves (e.g. after merging two surfaces together). Even if these segments maintain curvature continuity, the resulting surface still inherits those divisions, rather than forming a single smooth surface. Is there a way to replace such segmented boundary curves with a single unified curve (either identical or smoothed out if necessary) before generating the surface? And I don't mean fit point spline approach because it does not really guarantee deviation limits (without potentially multiple reiteration loops) which can result in a surface which cannot be sewn together with the adjacent one.

This actually has use for many applications in Fusion (sweep/loft guide/rails/path) when there is an error "curve not continuous in tangency/curvature"

I think it would be a fantastic improvement in already great Fusion functionality.

Thanks for any insights!

Best regards,

Lubos

Re: Curve smoothing & merging / concatenate segmented curves for surface creation

johnsonshiue — Mon, 17 Mar 2025 20:28:05 GMT

Hi Lubos,

I suspect the example was done by using a Loft feature. You may want to edit the Loft feature and make sure "Merge" is enabled in Tangent Edges option.

Another approach to consider is to use Guide Rail Sweep, which may also yield decent shape.

Please share the design here. The forum experts can help take a look to see if there are better alternatives.

Many thanks!

Re: Curve smoothing & merging / concatenate segmented curves for surface creation

lubos.ulovec — Mon, 17 Mar 2025 22:23:38 GMT

Hello Johnson,

Thank you for your feedback!

The feature was actually done by "ruled" command. And thanks for pointing out that the "loft" command has the option to "merge" the curves if they are tangent but "ruled" "sweep" "patch" etc. commands do not have this option.

I understand that design can be done via multiple approaches but my point is I think merging/joining curves in to a single one and smoothing/interpolating the result if necessary should be a common functionality when creating surfaces. Also - with current setup the surface boundaries can be split (split face + merge surface gives a single surface with segmented boundary like in my example) but the boundary cannot be "unsplit".

Let say, I need to make this corner (blue) on a tool more smooth (similar to the bottom one):

So I create nice blend curve:

and then want to create the new surfaces and instead of a simplified smooth result get something like this:

All these small segments on the yellow surface comes from the fact that the bottom edge wasn't continuous in tangency and now I have to start working on it. It sure can be fixed done but it is and inefficient work. And when you are working with surfaces these situations are happening way too often and it takes too much productivity away.

What I would like to be able is to pick the curves, get some warning they are not connected or do not have tangent/curvature continuity with a prompt to correct/replace it with connectivity/tangency/curvature with clear deviation goals (because sometimes they can't be alternated "too much") and create the surface. Right now the process is to work in eventually multiple iterations to get to the result.

Please let me know if it doesn't make sense, thank you Johnson

Best Regards,

Lubos

P.S.: data available here https://a360.co/42aNaFk

Re: Curve smoothing & merging / concatenate segmented curves for surface creation

TrippyLighting — Tue, 18 Mar 2025 00:35:30 GMT

@lubos.ulovec wrote:

...

What I would like to be able is to pick the curves, get some warning they are not connected or do not have tangent/curvature continuity with a prompt to correct/replace it with connectivity/tangency/curvature with clear deviation goals (because sometimes they can't be alternated "too much") and create the surface. Right now the process is to work in eventually multiple iterations to get to the result.

That makes sense, but I would not expect that to be implemented in at least the next 4-5 years!

Re: Curve smoothing & merging / concatenate segmented curves for surface creation

lubos.ulovec — Tue, 18 Mar 2025 03:06:26 GMT

That would be a pity, because similar or related functionality is already available in “Fit Curve To Mesh Section” command

and it works great.

We need in my opinion something similar for wireframe or “normal” sketching environment to make the designing process faster, more robust and user friendly.