How can I loft curve A & B but with a undulation in between!
Loft.gh (13.0 KB)
Is this what you want? You’re going to end up with an open brep because of the polyline. Also, note that in Loft, the Aligned Sections option is checked.
Loft-b.gh (20.1 KB)
If is something like this, you can easily do it without grasshopper using a BlendSurface
If you want to do it using grasshopper, you can use a intermediate curves in the Loft for create that curvature. That means to take the diamond curve, move it in Z position (negativa) and scale it as you prefer.
For example:
Can you please post the GH script for the same. I am not able to get it!
Sorry, I just saw this. But @HS_Kim did just what I said so I hope that was what you meant. 
