topic Re: Extend - patch feature edge not tangent in Fusion Design, Validate & Document Forum

Extend - patch feature edge not tangent

Anonymous — Sun, 16 Sep 2018 14:44:29 GMT

I'm doing some surface modeling and need to extend a surface to cut another surface. It would be helpful to have the extended surface have somewhat of an extension that replicated the curvature of the edge of the surface body it is extending. In the picture you can see while the surface may be extending a tangent surface body, the resulting edge curve is not tangent. Is this a functionality that anyone else would prefer and/or am I missing a quick fix on how to accomplish this? Thanks.

Re: Extend - patch feature edge not tangent

mavigogun — Sun, 16 Sep 2018 15:00:30 GMT

I produced even worse results with 2 simple curves extended further- the surface curvature actually inverts!

Re: Extend - patch feature edge not tangent

mavigogun — Sun, 16 Sep 2018 15:15:27 GMT

Extending ALL edges tells a clearer story about what is happening- and might allow us to predict results. Check out the side extended toward the more curved edge- it features the most intuitive result. It might help to think of this behavior akin to the way Splines interact- the first curve being forced through the lens of the second, tension retained.

Re: Extend - patch feature edge not tangent

TrippyLighting — Sun, 16 Sep 2018 15:16:34 GMT

I ti very easy to create broken edges in Fusion 360 with no tools to repair edges. In ZW3D for example I can concatenate edges. However, similar to stitching in Fusion 360 if care is not taken this also can result in deteriorating the curvature of as it can modify the edge within the specified tolerance.

Depending on how the initial surface was created, extending an edge is also the wrong technique. Not that one has a chance in Fusions 360 to do this, but the right technique would actually be to un-trim the NURBS surface. In ZW3D this is called "delete loop". I believe this is also possible in Autodesk Inventor and has a similar name to "delete loop" which refers to the trimming loop/curve.

As always, check the curvature on edges and splines frequently and avoid working with projected sketches when working with surfaces!

Re: Extend - patch feature edge not tangent

mavigogun — Sun, 16 Sep 2018 15:24:18 GMT

@TrippyLighting wrote:
*snip* Not that one has a chance in Fusions 360 to do this, but the right technique would actually be to un-trim the NURBS surface. In ZW3D this is called "delete loop". I believe this is also possible in Autodesk Inventor and has a similar name to "delete loop" which refers to the trimming loop/curve.

Is that to say Fusion actually views these curves surfaces as part of a Loop I might consider in the Sculpt workspace?

As always, check the curvature on edges and splines frequently and avoid working with projected sketches when working with surfaces!

Could you qualify that last caution- what are the ramifications of Sketch Projections interacting with Surfaces? Do we risk slowing calculations down to a virtual stop as complexity is piled on?

Re: Extend - patch feature edge not tangent

TrippyLighting — Sun, 16 Sep 2018 16:03:03 GMT

@mavigogun As you often work with surfacing techniques in Fusion 360 the Autodesk Alias Theory Builders are an absolute MUST READ.

The "loop"I was referring to has absolutely no relation with edge loops in Sub-D modeling. Int's a trimming curve.

Projected geometry in sketches when coming from curved shapes are approximations and are NOT splines.

As such building curved surfaces from sketch projections that might come from trimmed surfaces compound curvature issues and the curvature deteriorates quickly. That in turn leads to problems.

It is better to work with body edges than with projected sketch objects.

Re: Extend - patch feature edge not tangent

cekuhnen — Sun, 16 Sep 2018 17:06:16 GMT

@TrippyLighting @Anonymous @mavigogun

What Trippy refers to is a common tool set in NURBS surface freeform modelers like Alias Rhino etc.

Look at how extend in Alias reduces or extends the surface making sure the curvature is perfect.

As you can the CV points of the original surface are re-positioned.

Extend in Fusion does not work in my opinion to the same depth basically offering only a tangent continuation but ignores the side edges.

Look at the images below so you can see what Fusion does not do

now consider a very complex organic shape being extended. that is in fusion not a good idea.

Thus the best path is to always overbuild so you have extra material to manipulate.

Re: Extend - patch feature edge not tangent

TrippyLighting — Sun, 16 Sep 2018 21:14:45 GMT

Also, for the ones so inclined Claas has a YouTube channel with a wealth of information on how to model "stuff" in Fusion 360 from the perspective of a Industrial Designer. Worth watching!

Re: Extend - patch feature edge not tangent

lichtzeichenanlage — Sun, 16 Sep 2018 21:57:03 GMT

Thx for mentioning this. He has a new subscriber.

@TrippyLighting wrote:
Also, for the ones so inclined Claas has a YouTube channel with a wealth of information on how to model "stuff" in Fusion 360 from the perspective of a Industrial Designer. Worth watching!