Hi Jesse - your "central rail" there is not entirely smooth - it comes to a sharp point where it starts the upward bulge. Generally those types of sharp points are not going to work well in a scaling rail.

Your network layout is very clear there, MoI is not getting confused about the directions, instead it is having a hard time combining the multiple curves together into one single surface, the resulting surface is getting too dense. I should be able to do some work that will help to solve this and also for other areas that combine multiple curves together into a single surface such as loft and sweep.

I thought a bit about putting in some sort of "manual direction" picking like Rhino has an option for, but I haven't yet seen the type of network that would need it. I'll add it later if something like that shows up, but I think that anything that can't be sorted automatically probably won't be a valid grid network for this command anyway.

I tried your curves in Rhino, and got a nice smooth surface result, but it is also a bit strange in a couple of aspects, it seems to ignore the sharp corner in your central section, and seems to sag away from some spots nearby that by more than the allowed tolerance:



Do you think it is better for creases in your input curves to be ignored like this and sort of automatically smoothed out?

I kind of would expect for there to be a crease in the resulting surface corresponding to the crease in your input curve...

- Michael