function  spaceframe_el_shrink (inc_e, inc_p, Type)
% Copyright 2000, J.E. Akin.  All rights reserved.
%  ------------------------------------------------------
%  Matlab program to calculate & plot 2-D FE meshes
%  If Type = 0, plot all elements, else only type
%  If inc_ < 0 show no numbers, = 0 show max of 10
%          > 0 use given increment in plotting numbers
%  ------------------------------------------------------
if ( nargin == 0 )
  inc_e = 1 ; inc_p = 1 ; Type = 0 ;
elseif ( nargin == 1 )
  inc_p = 1 ; Type = 0 ;
elseif ( nargin == 2 )
  Type = 0 ;
end % if nargin

% S_1    = Element shrink ratio, 1 = none
  S_1    = 0.8 ;
% S_2    = Gap size, = 1 - S_1
  S_2 = 1 - S_1 ;

% c_x    = x coordinates of nod_per_el line polygon
% c_y    = y coordinates of nod_per_el line polygon
% inc_e  = increment in element numbers on plot, if > 0
% inc_p  = increment in node numbers on plot, if > 0
% msh_typ_nodes   = connectivity list for elements, nt x nod_per_el
% loop   = corners for nod_per_el line polygon
% lab_p  = 1, if node points are circled
  lab_p  = 0;
% nod_per_el = Nodes per element
% nod_per_t  = Nodes per type
% np     = Number of Points
% nt     = Number of elements
% pre_e  = Element items before connectivity list
  pre_e  = 0 ;
% pre_p  = Nodal items before coordinates
% msh_bc_xyz = Nodal coordinates (with preceeding data)
% t_x    = x coordinates of nod_per_el corners
% t_y    = y coordinates of nod_per_el corners
% x_bar  = x-centroid of each element
% xy     = Coordinates of points, np x 2
% y_bar  = y-centroid of each element

%    Read coordinate file and connectivity file
%    integer bc code, real xy pairs for np points (pre_p = 1)

%    Set control data: number of points
  load msh_bc_xyz.tmp ;  pre_p = 1;
  np = size (msh_bc_xyz,1) ;   % number of nodal points  
  ns = size (msh_bc_xyz,2) - pre_p ;   % dimension of space
  if ( np == 0 )
    error ('Error missing file msh_bc_xyz.tmp')
  end % if error
  fprintf ('Read %g mesh coordinate pairs \n', np)
  % fprintf ('       x        y \n')

  x (np)      = 0.       ;       % pre-allocate array x
  y (np)      = 0.       ;       % pre-allocate array y
  z (np)      = 0.       ;       % pre-allocate array y

  % msh_bc_xyz has: pre_p items then: x, y
  x = msh_bc_xyz (1:np, (pre_p+1)) ; % extract x column of xyz
  y = msh_bc_xyz (1:np, (pre_p+2)) ; % extract y column of xyz
  z = msh_bc_xyz (1:np, (pre_p+3)) ; % extract z column of xyz
  
%    Set control data: number elements & nodes_per_element
  load  msh_typ_nodes.tmp ; % nod_per_el nodes per element
  nt         = size (msh_typ_nodes,1);           % number of elements 
  if ( nt == 0 )
    error ('Error missing file msh_typ_nodes.tmp')
  end % if error
  %b nod_per_el = size (msh_typ_nodes,2) - pre_e ; % nodes per element
  nod_per_el = size (msh_typ_nodes,2) - pre_e - 1 ; % nodes per element
  nod_per_t = nod_per_el ;
  fprintf ('Read %g elements with an element type \n', nt)
  fprintf ('and %g nodes each \n', nod_per_el)
  face_nodes = 4; faces=6;
  
% if ( nod_per_el ~= 8 ) 
%   error ('This is not a hexahedra mesh') 
% end % if H8

  el_type (nt) = 0       ;       % pre-allocate array el_type
  x_bar (nt)  = 0.       ;       % pre-allocate array x_bar
  y_bar (nt)  = 0.       ;       % pre-allocate array y_bar
  z_bar (nt)  = 0.       ;       % pre-allocate array y_bar
  t_nodes (nod_per_el) = 0 ;    % Optional pre-allocation
  t_x (nod_per_el) = 0 ;        % Optional pre-allocation
  t_y (nod_per_el) = 0 ;        % Optional pre-allocation
  t_z (nod_per_el) = 0 ;        % Optional pre-allocation
  c_x (nod_per_el + 1) = 0 ;    % Optional pre-allocation
  c_y (nod_per_el + 1) = 0 ;    % Optional pre-allocation
  c_z (nod_per_el + 1) = 0 ;    % Optional pre-allocation
  loop (nod_per_el + 1) = 0 ;   % Optional pre-allocation
% c_x (face_nodes + 1) = 0 ;    % Optional pre-allocation
% c_y (face_nodes + 1) = 0 ;    % Optional pre-allocation
% c_z (face_nodes + 1) = 0 ;    % Optional pre-allocation
% loop (face_nodes + 1) = 0 ;   % Optional pre-allocation

  fprintf ('Begin element plots:')

%    Initialize plots
  xmax = max (x)      ; xmin = min (x) ;
  ymax = max (y)      ; ymin = min (y) ;
  zmax = max (z)      ; zmin = min (z) ;
  clf                               % clear graphics
  axis ([xmin, xmax, ymin, ymax, zmin, zmax])   % set axes
  axis ('equal')                    % true shape style
  hold on                           % hold image for plots
  grid                              % add grid dots
  xlabel ('X')
  ylabel ('Y')
  zlabel ('Z')

%   get the element types
  Max_type = max (el_type) ;
  fprintf (' Maximum element type number is %g \n', Max_type)
  if ( Type < 0 | Type > Max_type )
   error ('Error requested type not available')
  end % if error

%   count various types
  Type_count (1:Max_type) = 0 ;
  if ( Max_type > 1 )
    for j = 1:nt       
      k = el_type (j) ;
      Type_count ( k ) = Type_count ( k ) + 1 ;
    end % for j
    for j = 1:Max_type
      fprintf ('Type %g has %g elements \n', j, Type_count (j))
    end % for j
  end % if Max_typ

%%    Show 10 nodes and 10 elements, or all for small mesh
   if ( inc_e == 0 )
     nt_show = nt ;
     if ( Type > 0 )
       nt_show = Type_count (Type) ;
     end % if Type
     if ( nt_show <= 10 )
       inc_e = 1 ;
%    else 
%      inc_e = floor(nt_show/10) ;
     end % if show
   end % if inc_e
   if (inc_p == 0 ) 
    if ( np <= 10 )
      inc_p = 1 ;
%   else                
%     inc_p = floor(np/10) ;
    end % if np
  end % if inc_p
  if ( inc_p > 0 ) 
    in_mesh (1:np) = 0 ; % assume nodes absent
  end % if
  
%      Plot input mesh points & label them
  if (lab_p == 1)                   % plot all points
    plot3 (x, y, z, 'b.')               % mark each node
  end % if show labels

%    Loop over all elements
  [loop] = get_El_Loop (nod_per_el) ;
  Old_type = 0;
  for it = 1:nt  ;
   This_type = el_type (it) ;
   if ( This_type == Type | Type == 0 ) % then plot it

%      Extract corner connectivity 
    t_nodes = msh_typ_nodes (it, (pre_e+2):(nod_per_el+pre_e+1)); 

%      Get the type, nodes per type and loop array
    if ( Old_type ~= This_type  )
      Old_type = This_type    ;
      nod_per_t = nod_per_el ;
      [Low_node, Low_I] = min (t_nodes) ;
      if ( Low_node <= 0 )
        nod_per_t = Low_I - 1 ;
      end % if shorter topology list
 
%                set constants
%     clear loop;
%     if ( nod_per_t == 8 ) % then solid
%       [loop] = get_Solid_El_Loop (nod_per_t) ;
%     elseif ( nod_per_t == 4 ) % then face
%       [loop] = [1, 2, 3, 4, 1] ;
%     elseif ( nod_per_t == 2 ) % then line
%       [loop] = [1,2] ;
%     else % point
%       [loop] = [1];
%     end % if
    end % if a new type

%      Extract corner coordinates
    t_x  = x (t_nodes (1:nod_per_t)) ;  % x at those nodes, only
    t_y  = y (t_nodes (1:nod_per_t)) ;  % y at those nodes, only
    t_z  = z (t_nodes (1:nod_per_t)) ;  % z at those nodes, only

%      Flag these element's nodes as present in the mesh
    if ( inc_p > 0 ) 
      in_mesh (t_nodes (1:nod_per_t)) = 1 ;
    end % if inc_p

%      Get the centroid
    x_bar (it) = sum (t_x (1:nod_per_t)' )/nod_per_t  ;
    y_bar (it) = sum (t_y (1:nod_per_t)' )/nod_per_t  ;
    z_bar (it) = sum (t_z (1:nod_per_t)' )/nod_per_t  ;

%      Plot this polygon
    if (nod_per_t == 8 ) % then brick
%      Loop over each face
      for jf = 1:faces
%      Extract face nodes
        [loop] = get_H8_Face_Loop (jf) ;
%      continue if normal vector is visible
%        Plot this polygon
        c_x  = t_x (loop) ;       % x for nod_per_el line polygon
        c_y  = t_y (loop) ;       % y for nod_per_el line polygon
        c_z  = t_z (loop) ;
        c_x = S_1 * c_x + S_2 * x_bar (it) ; % shrink x
        c_y = S_1 * c_y + S_2 * y_bar (it) ; % shrink y
        c_z = S_1 * c_z + S_2 * z_bar (it) ; % shrink z
        plot3 (c_x, c_y, c_z)           % plot nod_per_el lines
      end % for faces
    else % face, edge, or point
      c_x  = t_x (loop) ;       % x for nod_per_el line polygon
      c_y  = t_y (loop) ;       % y for nod_per_el line polygon
      c_z  = t_z (loop) ;
      c_x = S_1 * c_x + S_2 * x_bar (it) ; % shrink x
      c_y = S_1 * c_y + S_2 * y_bar (it) ; % shrink y
      c_z = S_1 * c_z + S_2 * z_bar (it) ; % shrink z
      plot3 (c_x, c_y, c_z)           % plot nod_per_el lines
    end % if brick

   end % if the right type
  end % for over all elements

%   Add the node numbers if requested
  if ( inc_p > 0 ) % show labels
    for i = 1:inc_p:np                 % convert to string
      if ( in_mesh (i) > 0 )           % it is present
       p_text = sprintf ('  %g', i);   % offset # from pt
       text (x(i), y(i), z(i), p_text)       % plot pt number
      end % if present
    end % for all points
  end % if show labels
 
%    Finish the plots with polygon numbers
  if (inc_e > 0)                     % plot elem number, inclined
    % plot3 (x_bar, y_bar, z_bar, 'g.')        % centroid of each element
    for it = 1:inc_e:nt               % convert to string
      This_type = el_type (it) ;
      if ( This_type == Type | Type == 0 ) % then plot it
        t_text = sprintf ('   %g', it);  % offset # from pt
        text (x_bar(it),y_bar(it),z_bar(it),t_text,'Rotation',45) % incline
        plot3 (x_bar(it),y_bar(it),z_bar(it),'g.') % centroid 
      end % if right type
    end % for all polygons
  end % if show labels

  if ( Type == 0 )
    title (['Space Frame Mesh Geometry: ',  ...
            int2str(nt), ' Elements, ', int2str(np),' Nodes', ...
            ' (', int2str(nod_per_el), ' per element)'])
  else
    title (['Type ', int2str(Type), ' FE 3D Mesh Geometry: ', ...
            int2str(Type_count (Type)), ' of ', ...
            int2str(nt), ' Elements, ', int2str(np),' Nodes', ...
            ' (', int2str(nod_per_t), ' per element)'])
  end % if

%       -depsc -tiff            % for an eps version
  %bprint -dpsc spaceframe_el_shrink
  hold off
  %bfprintf ('Created file spaceframe_el_shrink.ps \n')
% end of spaceframe_el_shrink