Uneven Isocurves in PIPE or SWEEP commands

In Rhino7 when doing a SWEEP or PIPE command the resultant solid has an imbalanced distribution of isocurves. When changing a Polysurface to SubD (OR when generating in SubD) the location of the isocurves can be very important. Anyone find out why this is so, or how to correct it? I did not go back and try in V6 but can’t recall it happening there.! Here is photo of a Sweep of a modified rectangle.


Post a Rhino file with the rail and section if you want any help.

Hello - RebuildUV may help.


I may not understand all the options on RebuildUV but that didn’t seem to work to change the imbalance of isocurves. Martin wanted a file so that is now included other than just a photo. I also sent the file to Tech@McNeel and am hoping that provides more info on a couple more issues as well. The imbalance is shown on the polysurface in the view that comes up when you open the file . Layer 03 has the rail and curve…Nurbs base layer has the SWEEP1 result - shown.

Also, no one seemed to say whether the isocurves should or should not be evenly spaced around a circle PIPE or SWEEP1…my expectation is that they should be evenly spaced.

(Totally off-subject for my issue but it is SO nice the forum allows a LOT of edits prior to a Reply!!!)

2mm setting SAVE for copy and paste.3dm (1.9 MB)

Just to be sure - is there some reason not to use a Revolve here?
In any case, all surfaces rebuilt in U to 12 points and re-joined -


Pascal, As you have noted in the past……I get into pilot error very easily. I think I could fly an airplane better than I fly Rhino!!! (actually in college ROTC I aced all my pilot exams to see if i could be an AF pilot)

Nope………there is no reason to not use REVOLVE. My thought train was originally in the process of learning SubD….so I tried a PIPE in SubD and got the uneven distribution of isocurves. So, I then went to Nurbs to see what I could achieve and got the same results. My design path did not take me to Nurbs first with REVOLVE, then create the SubD from Nurbs….then go back to meshing with face deletion and BRIDGE command legs to the Torus in SubD. I am going through Andres’ SubD course to learn SubD…… I’m at about 80% finished.

Thanks also for the short course in REBUILDUV……

But I am still puzzled…. Is it to be expected that PIPE and SWEEP1 will not give evenly distributed isocurves….and if so why is that the case?

Now my Gumball decides to drag…any idea as to what pilot error would cause that?

Thanks again………

In many situations it is more straightforward to build a SubD with a mesh instead of trying to convert Nurbs into SubD. Or in your case you could also use _SubDSweep1 and forget about the Nurbs convertion.

Thanks for all the help. I went through ALL the options on REBUILDUV and nothing worked. So, after re-reading the instructions on that command by Martin it hit me EXPLODE needed to be used so that JOIN could be used after the rebuild. That worked. Working in MESH mode is rather difficult for my brain to comprehend - I have to do it some for 3D printing…learning SubD is a huge stretch. Thanks for the help and I can now proceed.

1 Like