How to smoothly connect these surfaces?

I’ve tried Blend, Sweep, Network, Patch … with split edges. Noun of them really worked : (

How to Smoothly Connect the Surfaces.3dm (2.7 MB)


Update a satisfying result.

How to Smoothly Connect the Surfaces.3dm (4.2 MB)

Nice work… depending on the shape I might use NetworkSrf for the corner surfaces if you find Patch doesn’t join.

How did you get this result?

Thanks Brian,
Yes, I tried NetworkSrf first (love this function so much), but it gave me a weird distortion at one corner…
NetworkSrf seems not so good for corner surfaces? Not sure, but I had similar issues with it before.
Patch worked fine with UV set to 50; it’s a completely different story if set to 10 :smile:

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The rounded-rectangle surfaces have conic corners with rho set to 0.9, and they are tangent at the mid point of each edge. So basically the gap is a combination of 8 clean rounded corners, nothing else in-between corners. Therefore, I needed to figure out where to split the edges.

I did it like the image showed, for all the 6 faces (then realized I only needed to prepare for one corner…).

Then, I used Blend (and tried many times to adjust tangency or curvature to allow Patch to work better).

Then, cut the corner straight from each view, and Patch

Finally, I cut out one corner and mirror to the rest to get the acceptable result.


A result (not necessarily better) can be obtained with the NetworkSrf but with 4 edges (bend continuity on all sides except the top one that is position) instead of the patch.
You must use the “UntrimAll” command “keep all cuts” on the upper surface to retrieve the edges.

The attachment file contains the parts used to get the result.

How to Smoothly Connect the Surfaces.3dm (5.9 MB)

Any finishing … (to be applied manually on each edge of the parallelepiped. Otherwise, with the mirror there will be open edges.)


Hi @Zsimon, really really appreciate the help. Are the top split points at the particular positions, or roughly decided just to add a little spacing for the NetworkSrf? Also how to get these two curves/edges?

Create 2 lines. A line that is perpendicular to point A, the other with “normal” option from the B surface. Then Sweep 1 binary. Extends surfaces

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I get it now. Thank you @Zsimon !

Hi Zhao,

for these “setback” corners, there is another solution, with G2 and less isocurves, often making for a better surface. Please find a quick take on a typical solution; maybe it is useful for your purpose (or anyone else, for that matter).

Typical solution.3dm (95.2 KB)

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I like the result.
I have some questions about the result obtained: 1) creating control isocurve I see continuity G1.
2) Since it is important for everyone to get this result, could they share building curves and how they were created?



Sure. Here’s the file with the curves used in the process… by the way, all surfaces do join ok on my end.

Typical solution.3dm (95.4 KB)

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Maybe a matter of tolerance. Here I see many open edges.
With what command have the 3 surfaces been generated?
Thank you

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Hi @Lagom the surface looks great.
I also like to know as @Zsimon how you made the surfaces. Patch doesn’t join many times and solution to this kind of multiblend is appreciated.

You would use the Curve Network surface. You select G2 against the two already adjacent surfaces and the two lilac curves. Then you copy, paste and rotate the surface around the setback-cap’s centre (where the lilac curves are intersecting) to fill the void.

At last, some UVN control point massage is necessary.


@Lagom Thank you for the tutorial!

Interesting. The procedure reminds me of something Alias (especially G2 continuity of the curve network). Just thoughts.

Hi Lagom - in the more general case, where there is no symmetry on the corner (i.e. the pink curves across the corner do not intersect) how do you reliably find the middle point where all the squares converge? I usually end up averaging some closest points among the blend curves but this always seems a little ‘iffy’ to me - do you have a better way?


It does indeed. Whether in Alias, Rhino or ICEM, but also in Creo or SolidWorks - if you design consumer products for good brands, it’s all about G2, just like in the car industry (where G2 is often not even sufficient). On some of the more expensive Electrolux or MIELE vacuum cleaners, one can see where even G2 fails to convey the visual impression of a shell appearing as a single monolithic surface.

The good thing about all NURBS surface modellers is, in my view, that once you know the typical solutions (patch layout principles, so to speak), you can switch and mix software depending on the task at hand.

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