MESH2D: 2D unstructured mesh generation for a polygon.

MESH2D generates a 2D unstructured triangular mesh based on a piecewise
linear geometry input. The polygon can contain an arbitrary number of 
cavities.  An iterative method is implemented to optimise mesh quality. 

If you wish to mesh multiple connected faces, use MESHFACES instead!

OUTPUTS

  P     = Nx2 array of nodal XY co-ordinates.
  T     = Mx3 array of triangles as indices into P, defined with a
         counter-clockwise node ordering.

SHORT SYNTAX:

  [p,t] = mesh2d(node);

NODE defines the geometry nodes as an Nx2 array:

  node  = [x1 y1; x2 y2; etc], geometry nodes specified in consecutive
                               order, such that NODE(2,:) is joined with
                               NODE(1,:) etc.

An element size function is automatically generated based on the 
complexity of the geometry. Generally this produces meshes with the 
fewest number of triangles.

LONG SYNTAX:

  [p,t] = mesh2d(node,edge,hdata,options);

Blank arguments can be passed using the empty placeholder "[]".

EDGE defines the connectivity between the points in NODE as a list of
edges:

  edge = [n1 n2; n2 n3; etc], connectivity between nodes to form
                              geometry edges. If EDGE is specified it is
                              not required that NODE be consectutive.

HDATA is a structure containing user defined element size information. 
HDATA can include the following fields:

  hdata.hmax  = h0;                   Max allowable global element size.
  hdata.edgeh = [e1,h1; e2,h2; etc];  Element size on specified geometry 
                                      edges.
  data.fun   = 'fun' or @fun;         User defined size function.
  hdata.args  = {arg1, arg2, etc};    Additional arguments for HDATA.FUN.

Calls to user specified functions must accept vectorised input of the 
form H = FUN(X,Y,ARGS{:}), where X,Y are the xy coordinates where the
element size will be evaluated and ARGS are optional additional arguments 
as passed by HDATA.ARGS.

An automatic size function is always generated to ensure that the
geometry is adequately resolved. The overall size function is the minimum
of the user specified and automatic functions.

OPTIONS is a structure array that allows some of the "tuning" parameters
used in the solver to be modified:

  options.mlim   : The convergence tolerance. The maximum percentage 
                   change in edge length per iteration must be less than 
                   MLIM { 0.02, 2.0}. 
  options.maxit  : The maximum allowable number of iterations { 20 }.
  options.dhmax  : The maximum allowable (relative) gradient in the size 
                   function { 0.3, 30.0}.
  options.output : Displays the mesh and the mesh statistics upon
                   completion { TRUE }.

EXAMPLE:

  meshdemo                  Will run the standard demos
  mesh_collection(n)        Will run some additional demos