[Gmsh] Surface mesh refinement

[John Purdue]

Hi,
I've been using Gmsh to create a surface mesh on a complicated 3D geometry.
 I have three questions that I could do with some help.

1.  What is the most suitable file extension to use if I want to import a
mesh and edit it with Gmsh?  The object does not originally come from a CAD
source or anything like it.  I'm currently using a .stl file but had to
convert to that anyway so if there is a more suitable version please
advise.

2.  In the .stl format I am easily able to refine my mesh however not
locally.  Ideally I would like the option of picking areas on my surface
mesh that would have a higher refinement.  Or put another way, points from
which the mesh initiates from.

3.  The mesh I'm importing isn't necessarily perfect.  Is there a way
re-creating the mesh to essentially 'clean' it of any hard edges or
overlapping that might be present with it?

Any help with this would be greatly appreciated.  Great application by the
way.

John
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