Actually, i was using 3D spline line in modeling my geometry.However, when I trying to convert to surface, it doesn't function.It's required to convert those lines into regions and from the region convert to surface.But, the problem is that 3D spline lines can not be used to form a region.So, here, I would like to ask is there any ways to:1- convert 3D spline lines into 3D polylines?2- form a region using 3D spline line directly?thank you for all of your professional helps.

Ways to convert a spline to a polyline.
 
http://cadpanacea.com/node/70

hi, i have successfully convert the 3D spline lines to 3D polylines.But, i still not be able to turn the 3D polylines to region.When i selected for example 3 polylines to form a region, it stated that '0 regions created'.Is that not possible to use 3D polylines to form a region?This is because after formed regions, only then i can convert those regions into surfaces.Thank you for all your kindly help.