Drawing curve directly on a surface

Hi, I would like to know how does this guy in this video was able to draw curve on a surface instead of the curve being flat on the cplane. As you can see at 1:52 and 3:53 he was able to draw curve and circle from the top view directly onto the surface without having to use the command InterpCrvOnSrf and without having to project the curve on the surface. This seems really convenient. Does anyone know how to do this?

Hi Gusttie, I think He or She is just splitting that surface with a curve that is above his surface. Do some experimenting and see if it works. It is in the top view. The curve needs to be above the surface. —Mark

oh you’re right. thanks!

He probably uses PersistentOnSurface or PersistentOnPolysurface object snap at 1:52. He clearly uses project button at 3:53.