General function for modification of a mesh object.
PIDs = gf_mesh_set(mesh M, 'pts', mat PTS)
PIDs = gf_mesh_set(mesh M, 'add point', mat PTS)
gf_mesh_set(mesh M, 'del point', ivec PIDs)
CVIDs = gf_mesh_set(mesh M, 'add convex', geotrans GT, mat PTS)
gf_mesh_set(mesh M, 'del convex', mat CVIDs)
gf_mesh_set(mesh M, 'del convex of dim', ivec DIMs)
gf_mesh_set(mesh M, 'translate', vec V)
gf_mesh_set(mesh M, 'transform', mat T)
gf_mesh_set(mesh M, 'boundary', int rnum, mat CVFIDs)
gf_mesh_set(mesh M, 'region', int rnum, mat CVFIDs)
gf_mesh_set(mesh M, 'extend region', int rnum, mat CVFIDs)
gf_mesh_set(mesh M, 'region intersect', int r1, int r2)
gf_mesh_set(mesh M, 'region merge', int r1, int r2)
gf_mesh_set(mesh M, 'region subtract', int r1, int r2)
gf_mesh_set(mesh M, 'delete boundary', int rnum, mat CVFIDs)
gf_mesh_set(mesh M, 'delete region', ivec RIDs)
gf_mesh_set(mesh M, 'merge', mesh m2[, scalar tol])
gf_mesh_set(mesh M, 'optimize structure')
gf_mesh_set(mesh M, 'refine'[, ivec CVIDs])
General function for modification of a mesh object.
PIDs = gf_mesh_set(mesh M, 'pts', mat PTS)
Replace the coordinates of the mesh points with those given in PTS.
PIDs = gf_mesh_set(mesh M, 'add point', mat PTS)
Insert new points in the mesh and return their #ids.
    PTS should be an nxm matrix , where n is the mesh
    dimension, and m is the number of points that will be
    added to the mesh. On output, PIDs contains the point #ids
    of these new points.
    Remark: if some points are already part of the mesh (with a small
    tolerance of approximately 1e-8), they won't be inserted again,
    and PIDs will contain the previously assigned #ids of these
    points.
gf_mesh_set(mesh M, 'del point', ivec PIDs)
Removes one or more points from the mesh.
    PIDs should contain the point #ids, such as the one returned by
    the 'add point' command.
CVIDs = gf_mesh_set(mesh M, 'add convex', geotrans GT, mat PTS)
Add a new convex into the mesh.
    The convex structure (triangle, prism,...) is given by GT
    (obtained with gf_geotrans('...')), and its points are given by
    the columns of PTS. On return, CVIDs contains the convex #ids.
    PTS might be a 3-dimensional array in order to insert more than
    one convex (or a two dimensional array correctly shaped according
    to Fortran ordering).
gf_mesh_set(mesh M, 'del convex', mat CVIDs)
Remove one or more convexes from the mesh.
    CVIDs should contain the convexes #ids, such as the ones
    returned by the 'add convex' command.
gf_mesh_set(mesh M, 'del convex of dim', ivec DIMs)
Remove all convexes of dimension listed in DIMs.
    For example; gf_mesh_set(mesh M, 'del convex of dim', [1,2]) remove
    all line segments, triangles and quadrangles.
gf_mesh_set(mesh M, 'translate', vec V)
Translates each point of the mesh from V.
gf_mesh_set(mesh M, 'transform', mat T)
Applies the matrix T to each point of the mesh.
    Note that T is not required to be a NxN matrix (with
    N = gf_mesh_get(mesh M, 'dim')). Hence it is possible to transform
    a 2D mesh into a 3D one (and reciprocally).
gf_mesh_set(mesh M, 'boundary', int rnum, mat CVFIDs)
DEPRECATED FUNCTION. Use 'region' instead.
gf_mesh_set(mesh M, 'region', int rnum, mat CVFIDs)
Assigns the region number rnum to the set of convexes or/and convex
    faces provided in the matrix CVFIDs.
    The first row of CVFIDs contains convex #ids, and the second row
    contains a face number in the convex (or 0
    for the whole convex (regions are usually used to store a list of
    convex faces, but you may also use them to store a list of convexes).
    If a vector is provided (or a one row matrix) the region will represent
    the corresponding set of convex.
gf_mesh_set(mesh M, 'extend region', int rnum, mat CVFIDs)
Extends the region identified by the region number rnum to include
    the set of convexes or/and convex faces provided in the matrix
    CVFIDs, see also gf_mesh_set(mesh M, 'set region).
gf_mesh_set(mesh M, 'region intersect', int r1, int r2)
Replace the region number r1 with its intersection with region number r2.
gf_mesh_set(mesh M, 'region merge', int r1, int r2)
Merge region number r2 into region number r1.
gf_mesh_set(mesh M, 'region subtract', int r1, int r2)
Replace the region number r1 with its difference with region
    number r2.
gf_mesh_set(mesh M, 'delete boundary', int rnum, mat CVFIDs)
DEPRECATED FUNCTION. Use 'delete region' instead.
gf_mesh_set(mesh M, 'delete region', ivec RIDs)
Remove the regions whose #ids are listed in RIDs
gf_mesh_set(mesh M, 'merge', mesh m2[, scalar  tol])
Merge with the mesh m2.
      
      Overlapping points, within a tolerance radius tol, will not be
      duplicated. If m2 is a mesh_fem object, its linked mesh will be used.
gf_mesh_set(mesh M, 'optimize structure')
Reset point and convex numbering. After optimisation, the points (resp. convexes) will be consecutively numbered from 1 to gf_mesh_get(mesh M, 'max pid') (resp. gf_mesh_get(mesh M, 'max cvid')).
gf_mesh_set(mesh M, 'refine'[, ivec CVIDs])
Use a Bank strategy for mesh refinement.
    If CVIDs is not given, the whole mesh is refined. Note
    that the regions, and the finite element methods and
    integration methods of the mesh_fem and mesh_im objects linked
    to this mesh will be automagically refined.
Y. Collette