I select the whole curves first, then hit the network of curves command, what I get is a ‘‘select first curve in first direction’’ warning in the command line, instead of a succesfuly networked surface.

and I don’t understand how to select which line in which direction.

In every tutorial on the web it is just easy as selecting and hittin the button and having the options but I could not see that little window.falan.3dm (958.5 KB)

All curves use as input to NetworkSrf must be open. Your lower curve and the edge of the surface are closed. Also the curves must be in two groups with a requirement that “all curves in one direction must cross all curves in the other direction and cannot cross each other”.

The message ‘‘select first curve in first direction’’ appears because Rhino cannot automatically sort the curves into two groups of open curves with all curves in one direction crossing all curves in the other direction and not crossing each other. It is giving the user the opportunity to sort the curves.‘

thank you very much for the solution, I finally figured it out thanks to you.