Sweep1 creates 4 surfaces?

Not sure why this is creating 4 surfaces when sweeping a simple circle…?

always hard or impossible to guess from a screenshot.
there is
_torus as command.
if your rail is a circle - use
_revolve

if you use _sweep1 or _sweep2 best practice is, that startpoints of curves meet.

EDIT:

torus_with_sweep1.3dm (2.7 MB)

ok - 2 circles that meet at their endpoints.
can be checked with
_gcon
_sweep1
I also get a Polysurface with 4 Surfaces.
(mac os x, rhino Version 8 (8.16.25021.13002, 2025-01-21))

I agree that this is not 100% expected - but I guess _sweep1 does not like the knot-Structure of a circle.

does _torus or _revolve do the job for you ?

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Ill give that a shot… Just thought it was weird as i dont remember that being an issue before…

Thank you!

The multiple surfaces is probably due to circles being rational.

Creating surfaces from rational curves can be difficult. It looks the Sweep1 command creates a separate surface for each span of a multi-span rail. A circle is rational with 4 spans, hence 4 surfaces when the rail is a circle.

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but isn t the knot-style of a circle (interpreted as nurbs curve) more special.
basically a circle has 4 kinks - that are not visible because of the CV-Structure… - the kinks are 180 degree / tangent.

EDIT:
setting the weight of all CVs of the circles to 1.0 - still 4 surfaces