I get the following error in unimesh.py:
nr_tpolys = sum([len(actor.Geometry().TexPolygons())
TypeError: len() of unsized object

I fixed that for me by changing lines 106-109 like this:

        nr_polys = sum([len(actor.Geometry().Polygons())
                        for actor in actors if actor.Geometry().Polygons() and actor.Geometry().TexPolygons()])
        nr_tpolys = sum([len(actor.Geometry().TexPolygons())
                         for actor in actors if actor.Geometry().Polygons() and actor.Geometry().TexPolygons()])

and adding the following after line 125:   if not geom.Polygons() or not geom.TexPolygons(): continue