Sweep2, Output SubD - Same Options, Diff Output

[Jonathan_Hutchinson (Jonathan)]

sweep2_setup.3dm (171.3 KB)

Maybe I’ve missed something. But something seems up with the Sweep2 Output SubD option. It seems to sort of remember the structure of making a NURBS surface, and applies to the next created SubD. And actually even creates two different surfaces from the same picked stuff. SO maybe something under the hood going on? Guessing it’s something to do with refit maybe - the dense SubD fits the rail, the other maps CVs to Cage points

[Trav (Travis Serio)]

Hi @Jonathan_Hutchinson

Thanks for the find. I am able to repeat here as well.

I have created a bug report here.
https://mcneel.myjetbrains.com/youtrack/issue/RH-58540

[Jonathan_Hutchinson (Jonathan)]

Hi @Trav

You’re welcome - glad to have noticed, and thanks for taking the time to repeat. I had noticed sometimes I got SubD Sweep2s that followed the rails and some that didn’t at random.

Do you think the Output SubD will remain integrated within vanilla Sweep2, or that a SubD Sweep might be peeled off like for loft?

[Trav (Travis Serio)]

Hi @Jonathan_Hutchinson the reason some of your curves fit and some do not depends on the curve structures. We call these “SubDFriendlyCurves”. You can read more about what makes a curve SubD Friendly here.

SubD Friendly Curve

Hi David - from a presentation that Dale Lear gave us a while back: Curves that give exact matches when using Loft, ExtrudeCrv, and Revolve to make SubDs are called SubDFriendly. SubDFriendly curves are: NURBS degree 3 uniform non-rational natural or periodic [image] Friendly curves have zero end curvature. Because it is very easy to mess up these end conditions, the SubDFriendly curves hide those two “extra” points. HTH, -wim

[Jonathan_Hutchinson (Jonathan)]

Cheers Trav for the link.

Yeah I think I’ve noticed the trick for SubD friendly - is it the little grey dot when points are on? (and SubDfriendly+ in _What)

Edit: I posted that image BEFORE reading the link

[brian (Brian Gillespie)]

RH-58540 is fixed in the latest WIP

[Jonathan_Hutchinson (Jonathan)]

Hi Trav - this seems to be halfway there. The surface output is coming out right everytime as it would be expected, regardless of whether or not you have output a SubD the previous time.

But with the SubD output, only the dense version is possible (albeit, a version which doesn’t fit the rails perfectly as your example).

What are your thoughts ?

[Trav (Travis Serio)]

Hi @Jonathan_Hutchinson

@lowell may have some more insight here.

[lowell (Lowell Walmsley)]

No more insight.
Simple sweep is prohibited for subd output because it usually doesn’t hit the rails.

[Jonathan_Hutchinson (Jonathan)]

Thanks for the info - got it. I would maybe argue for allowing the simple option - it wasn’t so much that the result was a problem in the reported bug, but rather that it would yield completely different results with the same options. Someone mixing workflows might end up with an unnecessarily complex NURBS result.

Maybe someone else will chime in if they would like having that cleaner option available, if explicitly desired. @BrianJ ?