I found this when working in grasshopper, but it seems to generalize to Rhino also. I was trying to sweep between the two short curves using the longer curves as rails.
The curve directions are as shown, and pick points on the curves consistent:
But the sweep comes out like this:
In grasshopper, it hasn’t happened with every set of curves, probably less than 20% of the time.
Sweep2.3dm (38.8 KB)
Sweep2 is usually used with the section curves running between the rails, with the each end of the sections either on a rail or close to a rail. My guess is the Sweep algorithm has logic for deciding which end of each section to associate with which rail, and in this unusual situation that logic is making a decision different than your intent.
What are you trying to accomplish with this unusual use of Sweep2? There may be another way to accomplish it.
They’re not, you’re focusing on the wrong sections. Please refer to the images above. Sorry for including extra geometry in the file.
Tbh, 2-rail sweep was a workaround for grashopper not having an equivalent to Rhino’s Sweep1/Align with Surface.
In my case, Sweep1 gives me the same result that I wanted, so additional work-arounds aren’t needed.
But I don’t beleieve I’m mis-using the tool, nor am I wrong to expect consistent results with consistent inputs.
Here’s a corrected file [eyeroll].
Sweep2.3dm (20.3 KB)
