Weird tube surface


i managed to model this weird tube which comes from an offset process of a filletedge surface. Tube has weird control points. i tried “TestRemoveNakedMicroLoops” “untrimall”.

i noticed that, even if the tube diameter is 10mm, i need to “extend surface edge” minimum 10000 to see a difference.

this may be a bug or a bad modelling approach, i like to hear your thoughts.


weird_tube.3dm (89.1 KB)

Wow, that is completely bizarre… Normally you can’t have a larger than 90° arc section with only 3 control points… Do you have a “recipe” to re-create this reliably? I’m sure @chuck at McNeel would be interested…


Thank you mitch, did you also noticed that the control points are not over the surface.

this is the recipe, weird_tube_recipe.3dm (224.1 KB)


The initial fillet is pretty weird,(but kinda cool, I’ve never noticed so large an arc made with only three points) I’d say it all starts there…


Rhino doesn’t normally create them, but one can manually create arcs up to 180 degrees by placing the mid control point at the intersection of end tangents and weighing it at cos() of half the angular span.