Blend challenge - multiblend - patch issue - G2

Dear Everybody
several times i come across similar issues like the one (a reduced / simplyfied version) you find attached.
how to fill the hole between the surfaces with a G2 surface / surface combination?

In the .3dm file you will find a t-spline - solution.
rhino patch fails.
i managed to get some acceptable but painful solutions with some of the blend commands.

looking for a pure rhino-commands-solution. - or a link to similar, solved problems

handleConnection_02.3dm (2.1 MB)

thanks, best, Tom

I guess @Stratosfear is the right man for the job

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How about something like this:
G2handle.3dm (296.8 KB)

Personally, I think one could make a lot nicer looking model (and more robust model too) if G1 transitions were used.
. Making G2 transitions between a bunch of planar surfaces seems silly, but that’s just my opinion.

I notice the Tsplines version doesn’t come close to matching the input curves and some surfaces don’t match.

My go…
handleConnection-PG.3dm (144.6 KB)


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@pascal @jim
thanks a lot for your suggestions.
I hoped that there could be a solution with a topology similar to the t-spline sketch ( wich i just include to show roughly what i am searching.)

(@) jim:
i agree that g1 vs g2 can be discussed - but the problem is more an extract / reduced version of a larger context - with curved surfaces.

thanks & best regards - Tom

@Tom_ What is the design intent? Can you sketch what you want? Do you want the tight 90 degree blend to follow the curve as in Pascal’s solution?

I don’t think you are going to find an acceptable looking Class-A solution to this form. I had to use another Cad modeler to do the 5 sided patches. Rhino’s patch command just can’t handle them. It’s not perfect but it produces a clean flowing form. I would modify the topology to get a clean result. Without the need for complex trim surfaces or n-side patches. Hopefully this will spark someone to come up with something better.

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dear everybody - many thanks for your support, input, approaches.
(where can i mark the topic as solved ?)

the design-intent is close to the tspline surface in the initial post - rhino-file
similar to Stratosfear s solution

Thanks - which Cad did you use ?

this is the solution i will finally use - the pity is, that it is not a bush of one / a few buttons - solution.
i started with a _sweep1 (simple sweep) for the main surface and then stepwise added more Knots and moved the CVs…

handleConnection_03_.3dm (153.8 KB)

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Gave it some more thought and came up this better simpler result. I tried to do a cordial/constant width fillet/blend. The results looked a little wonky as it went over the accelerated blend surfaces. I decided it looked better with a rolling ball style.

Nice looking! The surface to the far right seems to be a five edge surface?

Using MOI for that one?

// Rolf

I got this one, by starting diagonally from the red corners, and BlendCrv/Isocurves (Tangent) which I pulled out a bit in the lower end (arrow head). Finished off with MatchSrf.

U9 V9 Degree 3 :

// Rolf


Here is similar structure made with degree 5 single span surfaces.

G2handle02.3dm (137.1 KB)

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every time i open one of your models @jim i have the feeling i am somwhere in outerspace where up and down has no relevancy :joy:

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That’s clean! Beautiful work!
How’d you do this?

i think the people with files like that (where the ‘ground’ isn’t horizontal) are rotating relative to view.

try jim’s file with (on mac) Preferences-> View-> Rotate relative… it will make more sense then and feel less outerspacey.


either this or he is using a spacemouse but at least he could make it straight before submitting i get dizzy each time :smiley:

Very nice surfaces.

But I noticed one thing which I don’t understand how it is configured. I tried to show isocurves, but I found no way to display them, not in any display mode. What is the magic behind that?

// Rolf

My model is in the same location and orientation as the original.

If the view angle and cplane orientation has some relevance to the problem posed I would appreciate if somebody would explain that relevance so that I might avoid whatever problem my failure to understand the relevance is causing.

@jim thats how i see it every time i open one of your models, in parallel view and weirdly rotated

fwiw, a quick reset is via the red car icon then ‘perspective view’ (which runs a little built in macro of SetView)