Felrakok egy képet, amit ma szedtem le egy külföldi fórumról.
Az úriember, aki csinálta, karoszéri elemek készítéséhez használja a módszert:
Bővebben: link

És a magyarázat:
Here is the example I promised. The Green transparent geometry are Surfaces used to project a curve. This is needed to create a curve with more than just a 2D profile unless you use tweak but you will ahve to learn that later but is not necessary to use to make a car. The blue lines are either curves made through two points or curves creat3ed or projected. You will see which are drawn and which are projected because I left the projected lines visible. The center curve is a through curve through two points and made normal to two planes. If the four boundaries are connected then you will be able to create a bondary blend through the four curves. Tangency is the most important thing is making a car. After you make your surface, morror it to a center plane as represented with the red surface. You have to be able to think ahead on what and where your surfaces will point to. Practice makes perfect. I taught myself and you can teach yourself too.

Remélem hasznát veszitek.
Nekem nagyon bejön, főleg, hogy a boundary blendet már használtam, de eszembe nem jutott volna, hogy ezt lehet vele művelni.