No simple sweep - command feedback / naming

dear mc neel
dear community to discuss
dear @pascal as we discussed:

since rhino 6 we miss a simple sweep option in _sweep1 and _sweep2
we should get a simple sweep if it is possible.
for complex surfaces or surfaces that will get modified after the initial sweep it is essential to get a simple sweep.

In my opinion it would be very helpful to have some kind of feedback, if simple sweep fails:
(A) my favourite would be an option in _sweep1 and _sweep2
simpleSweepFeedback = On/Off
(B) a separate command to focus on creating simple sweeps
_sweep1simple _sweep2simple
(C) an analysing-command _testForSimpleSweep

my main aim would be to get some easy visual / text feedback:
simpleSweep failed because of cross curve not touching rail at Knot, out of tolerance, cross curves structure vary …

and a second aspect:
maybe the naming “simple” (wich is quite complex to get) is not chosen well for non-technical users ?
“use same nurbs-structure as input curves” = rigid ? loose ? preserve structure, structure inheritance … (i am not a native speaker so maybe someone else has nicer suggestions).

attached some curves - a minimal set of 3 - that sometimes nearly not every time do simple sweep - in this case because of _Gcon G0 with 0.00099

simpleSweepChallenge.3dm (6.3 MB)

and some video with that file - that shows how unexpected a simple-sweep fails and takes quite some afford to fix… and for sure more work if there are 4 or 5 cross curves

in my mind, the dialog that does not update always is a bug - using Version 6 on mac os X 10.15.6 (19G2021)
(6.29.20239.15172, 2020-08-26)

looking forward to read other opinions.

kind regards -tom

Sorry, I meant I’m going to take a “wait and see” approach on this to see what reaction there is from other users.

Since many years i do an exercise, where my students have to model a Bottle.
The exercise is inspired by the “rhino level 2 training” Chapter 11 “make a detergent bottle” and Chapter 12 surface analysis.
Each year my students hate me because of those ugly, precise workflows that are necessary to get a simple sweep and are not supported by any tools. - But give really great surfaces.

todays example (CV was away 0.01 mm from the knot /edit point)

@carlosperez (as an example of a lost topic…)

and as a back-link… the issue is similar to this topic

would appreciate if this aspect is not getting lost. thanks. kind regards -tom

Simple sweeps should be available.

and easily accessible !

1 Like

why did this get worse ?

I am angry about this topic.

I have some old exercises where the curves allowed a simpleSweep in 2020.
It s a exercise where I teach the student to build some surfaces with the smallest amount of CVs and modify them after. But if sweep2 messes up with to many CV s this is not possible.

(left Surface done in Rhino Version 7 (7.25.22313.11002, 2022-11-09) on a mac)

NoSimpleSweep2022.3dm (3.9 MB)

@theoutside maybe you are the right person to look at this ?

@Rhino_Bulgaria I would appreciate your commend as well. - thanks

Hi Tom - here is what I get in the latest V7

That is Windows - it should not be any different on Mac but I’ll check in a moment.
OK on Mac as well here.


I get the simple result with the “Refit rails” option turned off. I get the overlycomplicated result with the “Refit rails” option turned on.

thanks for having a look at this - maybe a mac problem ?

thanks for having a look.
i do a restart later and check again.

ok after a restart i get the expected simple-sweep surface.

I ll do the exercise next week in class and report back how many students get it right.

Also this strange focus-bug still exists sometimes and of course disappears after a restart (of rhino only is enough)

Dear @pascal and @dan
It looks like those 2 problems occur after Rhino Mac wasn t restartet for a while (2 hours or something like this)
(1) setPt needs extra click to get focus in viewport.
(2) sweep2 does not do a simple-sweep.

hard to reproduce - i am preparing a tutorial video - first walk-trough for warmup everything worked fine, second … while recording (grrrr… :cold_face: ) it did not work.

the only thing that allows to solve it is to restart rhino.

those little nasty things feel a bit like alchemy … sorry to bother you with this topics

Thanks, I’ll try to reproduce this.


restart rhino - problem gone.
so after a 4h Rhino session without restart using sweep maybe 12 or 16 times the problem is there again.
restart solves it again…
did not find any specific action that courses the problem.
my guess - as sometime the sweep2 do not update, maybe the _sweep2 opens are not saved / restored in a proper way between sweep2 usage. Looks like refit rail is (always) used after a certain time. … sorry that i can not offer a simple way to reproduce.

I had the same just yet and restarting Rhino indeed fixes it. What’s odd on the mac is that with two curves as rails there is still options to change continuity on the rails. Might be related @pascal

edit: definitely got something repeatable: @Tom can you try this: set both rails to tangency, then click ok (you will get a complicated sweep regardless of the Refit rail setting), then undo, restart the sweep2, Edge Continuity will revert back to Position, but clicking Sweep will not make a simple sweep.

Yes i can repeat this.
first time tangent, second time position, no simple sweep.

nice catch …


Do you find a short workflow to repeat this focus problem as well ?

in fact, yes, see other thread

for now I’ve logged this as RH-71505 Sweep2 rail options for curves show invalid options

not sure if it’s related