It may sound easy, but it’s not: You have, for example for a computer game, two terrians which you need to connect with a path. The path should not be straight, but respect the curvature of both adjacent surfaces in order to keep a nice flow of lines.
If you have the choice between Mesh (polygons) and NURBS, I advice you to pick NURBS. In the tutorial I create two NURBS surfaces from four curves. For the connection I use fillet, projection and trimming techniques.
There are several tutorials about NURBS modeling in my channel. See for example this one about modeling a car fender:
And here is one about trimming NURBS surfaces:
The music is “Dubius 170” by my humble self.
If you wonder how the realtime rendering at the beginning and end of the tutorial is done, pls visit: