show how to mesh the volume from a surface STL

demos/sphere-discrete.geo

 // merge a surface mesh
 
-Merge "sphere-surf.msh";
-
-// delete all physical groups
-
-Delete Physicals;
+Merge "sphere-surf.stl";
 
 // add a geometrical volume
 
-Surface Loop(29) = {28,26,16,14,20,24,22,18};
-Volume(30) = {29};
+Surface Loop(1) = {1};
+Volume(1) = {1};