Render Rage

Is there a way to stop Rhino’s display and renderer doing this? As far as I can see all the surfaces are tangent.
Here is the file (v5.0 windows service 11)y pipe.3dm (5.4 MB)

The surface is indeed tangent, but only at the very edge - use CurvatureAnalysis/Gaussian to check this. The triangular patch is, for the most part, flat. This is what you see.
Unfortunately, there is no easy way to do this kind of Y-pipe in Rhino and have it come out looking nice.

Rhino can’t join a bunch of tangential surfaces together and come out looking nice. What a wonderful modeller it is. Thank god I only use it in my work for the import and export of dwg files.

Yes good for you!


with all due respect, rhino is showing it exactly the way you modeled it, if you want it smoother, model it smoother,…

If I’m joining a flat surface to a curved surface then tangent is as smooth as it gets unless the flat surface takes on a little curvature.

and you dont want the flat surface to have some curvature?..

No. I would be increasing the width of the pipes being joined together but this is neither here nor there, I was just hoping there was a setting somewhere I had missed that would eliminate that horrible rendering effect.

You can use locally applied Gaussian Blur in Photoshop. May be faster than fixing the model.

don’t blame the tool ( well most of the time)
your secondary srf. are less than optimal as are the primary srf; i`ve replaced the secondary srf, so the edges are not positional to the original. the end result is also not perfect ( srf dips a litte before spliting into the y) but I think that the way to go

y pipe2.3dm (5.6 MB)

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Thanks for the input eleven10. I had tried something similar but with a patch over the central parts. It didn’t work so well. Your way looks more promising. I’ll see what I can do.

Hi Tony

Here an example with patch
Ciao Vittorio

i thought you didnt want curvature because eleven10’s has curvature, the surface isnt flat anymore,…

@eleven10 great going, ive been using vsr alot and barely ever use multisurface blend, i really should use that alot more,…

I ended up with flat because when I tried Vittorio’s way, it bulged too much and I didn’t want the pipes getting wider. Although looking at his results here, they look pretty good but hard to see from this angle.

Hi Tony
The workFlow is to create a blend curve green color.
Ciao Vittorio

i think we are on the same page when it comes to rhino: clean, low cv geometry with g2+ continuity/nice reflections, right :slight_smile: ? do you know of any good resources regading this topic? I`ve been searching for ages but I don’t find good tutorials/ nurbs theory.
anyway here are some links that helped me a lot:

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Yeah, i do alot of surfacing so g2 low span is all very much what i aim for.

well had alot of videos but alot are gone, though the latest aston vids are very nice,…

Not G2 yet, but the idea of subdividing surfaces…

y pipe my way.3dm (269.2 KB)

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I think this is the easiest way to do it, you blend the left and right branch with the center one, then split both and do a sweep2, very easy to edit and only 3 surfaces,…not perfect but with some editing you can get there,…y pipe easy.3dm (311.2 KB)


Thanks for this. I really like this approach. I do have a few criticisms. Your display settings are problematic. The unit tolerance should be set to 0.001 not 5. Your display mesh setting is too dense. Lastly two of the surfaces are made from unnecessarily high degrees 9 and 7. I never exceed 5 you’re just asking for problems when you do. I rebuilt it with my settings and achieved a water tight polysurface with curvature continuity.