Is my surface smooth or not?

Hey everyone,
I am still learning rhino and I am confused about my 3-pipe-connection:
I want to make sure the surfaces are smooth / tangential to each other.
The zebra analysis shows me smooth lines in horizontal direction but not in vertical directions. See screenshots below
And when I turn on the curvature analysis, there are some hard color differences. What do these indicate?
Then I tried to ExtractIsocurve and see the curvature continuity and they are G0?? Even tho they are touching… Can someone help me?
I will upload the file in case you want to take a closer look :blush:
Thank you for your time!

pipes.3dm (876.6 KB)

Hi Niklas - for tangency, you’ll want the zebra stripes to fully ‘connect’ at the edges


See also EdgeContinuity.


I know, but how did you make them “connect” like this?

Hi Niklas - MatchSrf the trasnsition surfaces - for tangency. match ‘by closest points’ and ‘match target isocurve direction’


You can check the following tutorial for creation of Y-branch models:

Keep in mind that in my example all 3 pipes were equal size and arranged at 120 degrees each, so it was easy to use Rhino’s History to automatically match the rest surfaces while modifying just one of them.
In your example, however, your pipes are not equal, hence you have to manually adjust the control points of every surface. It’s slower but the general logic is the same as shown in my video. Make sure that you convert your blend surfaces to Degree 5 with 6 control points, then use “Match surface” (History recording must be turned on) and then manually adjust the control points via the “MoveUVN” tool.

Note that once I was satisfied with the general shape, I added one extra row of control points (7 in total) in order to have a greater control over the curvature of the surfaces. This is totally optional and you can make smooth transitions with G2 even with 6 control points.

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