Boundary edge extraction from surface mesh

I have open SURFACE- NOT SOLID (say a hemisphere) represented using mesh (imported as obj). I want to extract the boundary of the open surface(circle in the case of a hemisphere). i.e. the set of boundary edges which are 3 dimensional. Is there any function which can do this? Please have a look at the attached image

Answer 1

[Sami Väänänen]

You can use e.g. surfedge function in iso2mesh toolbox (<http://iso2mesh.sourceforge.net/cgi-bin/index.cgi)>. If you give triangulation as an argument, it returns the indices of the open edges.