Hello, I need to do this kind of pillar with just 2 branch on the top (not three as in the picture) but I don’t know how to do!
I hope you can help me!
Thank you very much
Could you post the starting geometry - the cylinders you have to join. Someone will take a look.
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These are my cylinders. but I don’t know how to create the middle element. and I 'd prefer if it had a geometry like the first picture, i mean, more elegant than my trial cylinders
Changed the category to Rhino for Windows.
why? but it’s ok,thanks!
Hi michtat - if a mesh is OK, you can do this by starting with a crude mesh and, using the Weaverbird plug-in > WBCatmullClark command, smooth the mesh - it may take two or three applications of the command. In the attached file, I also made the mesh from the wbMeshFromLines command (One face at a time, then Join, as the command does not reliably find the ‘correct’ quads if all the lines are selected at once.
WB_Example.3dm (641.6 KB)
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This task is where T-Splines/Clayoo shines. Branching…
One of the methods I came up with is blending all three cylinders between them, finding the intersections between surfaces:
Intersection curves (green) I extended on surface, and trimmed the internal surfaces with them (trimming is optional).
After this you can pipe or offset on surface intersection curves, and split with pipes the main surfaces to get the secondary transitions.
(Pipe radius is too small in my example.)
I wouldn’t recommend this method to someone new to Rhino, though. You are better off either with T-Splines, or Weaverbird, as Pascal pointed.
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thank you very much to both! I used weaverbird, it’s very fast and the result is very nice! 
Just jumping in here, @Pascal. For those of us unfamiliar with Weaverbird, how does it compare to Tsplines?
@michtat were you familiar with Weaverbird or did you just pick it up? My experience with Tsplines is that it’s got quite a steep learning curve.
Thank you.
The classic and easy “branch” method works well and you end up with surfaces.
Turn on the layers one by one in the attached 3dm file to see the steps used.
Branch.3dm (1.8 MB)
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Weaverbird is nothing like T-Splines, and vice versa.
T-Splines emulates working with polygon mesh while underneath keeping a “t-spline” (mathematical) representation of an object. After you are done modeling, you can either transform “t-spline” representation to NURBS (and from NURBS to dense mesh), or save the control cage as a light polygon mesh (in OBJ format usually) for usage in another (Sub-D) program. The advantage of T-Splines - it lest you easily manipulate the control cage, allowing for extrudes, creating new faces, etc.
Weaverbird works with pure mesh objects. It lets you tessellate (triangulate) meshes, and subdivide them. Subdivision being the cool part. But meshes remain meshes, and there is no way to transform them to NURBS, unless you have T-Splines. Also there are no means to extrude in Weaverbird.
The best is to have them both.
As to “steep learning curve” of T-Splines 
You just need to know where to look, and you look in traditional polygonal modeling. The pols (stars), redirecting polygon flow, polygon loops, topology - all these rules are applicable in T-Splines too. It is very different way of thinking, though.
http://panoptic.com/rking/blender/GEN_SubD-ThreadHighlights.pdf
Hi Allyson - Weaverbird makes/works with meshes, but if has some nice tools for smoothing them - on the other hand, it does not have any UI to speak of , only a set of commands. I have not used it much myself but it seemed like an easy way out in this case - making the equivalent shape from surfaces would a long and tricky business.
-Pascal
Allyson, I already had weaverbird installed but I had never used it. the 2 commands that pascal suggested me are very simple
Hi,
This is the way the image looks to me. It’s much less of a challenge,
to model it this way as well. I used another program to apply the fillets.
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Hmmm… And I thought this week was going well up to press!
I’m just about to start working on something similar, Michtat… I have to model 2x interweaving coral forms that will be 3D printed for moulding and casting.
I’m Rhino for Mac so no hope of these plugins to aid me.
From a Rhino perspective I’m probably going to draw the centrelines/armature with splines in 3D space and then pipe a rudimentary form to get an idea of the core.
Secondly I’ll probably take sections through it and loose loft the curves with the history command to get it closer and then I’ll more than likely use Onetech’s proposal of splitting and blending surfaces.
It’s going to be a long and arduous task. I blame Steve Jobs (Johnny Ive) for making the Macbook so shiny and user friendly… The PC has the full version and countless plugins to help! 
Thanks for posting the question
Hi,
This looks so clean. What did you use for the fillets?
Thank you