function ply_write ( Elements, Path, Format, Str )

%*****************************************************************************80
%
%% ply_write() writes 3D data as a PLY file.
%
%   PLY_WRITE(DATA,FILENAME) writes the structure DATA as a binary
%   PLY file.  Every field of DATA is interpreted as an element
%   and every subfield as an element property.  Each subfield of
%   property data must either be an array or a cell array of
%   arrays.  All property data in an element must have the same
%   length.
%
%   A common PLY data structure has the following fields:
%      DATA.vertex.x = x coordinates, [Nx1] real array
%      DATA.vertex.y = y coordinates, [Nx1] real array
%      DATA.vertex.z = z coordinates, [Nx1] real array
%
%      DATA.face.vertex_indices = vertex index lists,
%         an {Mx1} cell array where each cell holds a one-
%         dimesional array (of any length) of vertex indices.
%   Some other common data fields:
%      DATA.vertex.nx = x coordinate of normal, [Nx1] real array
%      DATA.vertex.ny = y coordinate of normal, [Nx1] real array
%      DATA.vertex.nz = z coordinate of normal, [Nx1] real array
%
%      DATA.edge.vertex1 = index to a vertex, [Px1] integer array
%      DATA.edge.vertex2 = second vertex index, [Px1] integer array
%   Many other fields and properties can be added.  The PLY format
%   is not limited to the naming in the examples above -- they are
%   only the conventional naming.
%
%   PLY_WRITE(DATA,FILENAME,FORMAT) write the PLY with a specified
%   data format, where FORMAT is
%      'ascii'                  ASCII text data
%      'binary_little_endian'   binary data, little endian
%      'binary_big_endian'      binary data, big endian (default)
%
%   PLY_WRITE(DATA,FILENAME,FORMAT,'double') or
%   PLY_WRITE(DATA,FILENAME,'double') write floating-point data as
%   double precision rather than in the default single precision.
%
%   Example:
%   % make a cube
%   clear Data;
%   Data.vertex.x = [0;0;0;0;1;1;1;1];
%   Data.vertex.y = [0;0;1;1;0;0;1;1];
%   Data.vertex.z = [0;1;1;0;0;1;1;0];
%   Data.face.vertex_indices = {[0,1,2,3],[7,6,5,4], ...
%         [0,4,5,1],[1,5,6,2],[2,6,7,3],[3,7,4,0]};
%   ply_write(Data,'cube.ply','ascii');
%
%  Modified:
%
%    01 March 2007
%
%  Author:
%
%    Original MATLAB version by Pascal Getreuer 2004.
%    This version by John Burkardt.
%
  if ( nargin < 4 )

    Str = '';

    if ( nargin < 3 )
      Format = 'binary_big_endian';
    elseif strcmpi(Format,'double')
      Str = 'double';
      Format = 'binary_big_endian';
    end

  end

  [ fid, Msg ] = fopen ( Path, 'wt' );

  if ( fid == -1 )
    error(Msg);
  end

  PlyTypeNames = {'char','uchar','short','ushort','int','uint','float','double', ...
    'char8','uchar8','short16','ushort16','int32','uint32','float32','double64'};
  FWriteTypeNames = {'schar','uchar','int16','uint16','int32','uint32','single','double'};
  MatlabTypeNames = {'int8','uint8','int16','uint16','int32','uint32','single','double'};
  PrintfTypeChar = {'%d','%u','%d','%u','%d','%u','%-.6f','%-.14e'};
  IntegerDataMin = [-128,0,-2^15,-2^31,0];
  IntegerDataMax = [127,255,2^16-1,2^31-1,2^32-1];
%
%  write PLY header
%
  fprintf(fid,'ply\nformat %s 1.0\ncomment created by MATLAB ply_write\n',Format);
  ElementNames = fieldnames(Elements);
  NumElements = length(ElementNames);
  Data = cell(NumElements,1);

  for i = 1 : NumElements

    eval(['tmp=isa(Elements.',ElementNames{i},',''struct'');']);

    if ( tmp )
      eval(['PropertyNames{i}=fieldnames(Elements.',ElementNames{i},');']);
    else
      PropertyNames{i} = [];
    end

    if ( ~isempty(PropertyNames{i}) )
      eval(['Data{i}{1}=Elements.',ElementNames{i},'.',PropertyNames{i}{1},';']);
      ElementCount(i) = prod(size(Data{i}{1}));
      Type{i} = zeros(length(PropertyNames{i}),1);
    else
      ElementCount(i) = 0;
    end

    fprintf(fid,'element %s %u\n',ElementNames{i},ElementCount(i));

    for j = 1 : length(PropertyNames{i})

      eval(['Data{i}{j}=Elements.',ElementNames{i},'.',PropertyNames{i}{j},';']);

      if ( ElementCount(i) ~= prod(size(Data{i}{j})) )
        fclose(fid);
        error('All property data in an element must have the same length.');
      end

      if ( iscell(Data{i}{j}) )
        Type{i}(j) = 9;
        Data{i}{j} = Data{i}{j}{1};
      end

      for k = 1 : length(MatlabTypeNames)
        if ( isa(Data{i}{j},MatlabTypeNames{k}) )
          Type{i}(j) = Type{i}(j) + k;
          break;
        end
      end

      if ( ~rem(Type{i}(j),9) )
        fclose(fid);
        error('Unsupported data structure.');
      end
%
%  Try to convert float data to integer data
%
%  Array data.
%
      if ( Type{i}(j) <= 8 )
        if any(strcmp({'single','double'},MatlabTypeNames{Type{i}(j)}))
          if ~any(floor(Data{i}{j}) ~= Data{i}{j})  % data is integer
            MinValue = min(min(Data{i}{j}));
            MaxValue = max(max(Data{i}{j}));

               % choose smallest possible integer data format
            tmp = max(min(find(MinValue >= IntegerDataMin)),min(find(MaxValue <= IntegerDataMax)));

            if ~isempty(tmp)
              Type{i}(j) = tmp;
            end
          end
        end
      else        % cell array data
        eval(['Data{i}{j}=Elements.',ElementNames{i},'.',PropertyNames{i}{j},';']);
        tmp = 1;

        for k = 1:prod(size(Data{i}{j}))
          tmp = tmp && all(floor(Data{i}{j}{k}) == Data{i}{j}{k});
        end

        if tmp  % data is integer
          MinValue = inf;
          MaxValue = -inf;

          for k = 1:prod(size(Data{i}{j}))
            MinValue = min(MinValue,min(Data{i}{j}{k}));
            MaxValue = max(MaxValue,max(Data{i}{j}{k}));
          end

            % choose smallest possible integer data format
          tmp = max(min(find(MinValue >= IntegerDataMin)),min(find(MaxValue <= IntegerDataMax)));

          if ~isempty(tmp)
            Type{i}(j) = tmp + 9;
          end

        end
      end

      % convert double to single if specified
      if rem(Type{i}(j),9) == 8 && ~strcmpi(Str,'double')
        Type{i}(j) = Type{i}(j) - 1;
      end

      if Type{i}(j) <= 8
        fprintf(fid,'property %s %s\n',PlyTypeNames{Type{i}(j)},PropertyNames{i}{j});
      else
        fprintf(fid,'property list uchar %s %s\n',PlyTypeNames{Type{i}(j)-9},PropertyNames{i}{j});
      end
    end
  end

  fprintf(fid,'end_header\n');

  switch Format
    case 'ascii'
      Format = 0;
    case 'binary_little_endian'
      fclose(fid);
      fid = fopen(Path,'a','ieee-le');
      Format = 1;
    case 'binary_big_endian'
      fclose(fid);
      fid = fopen(Path,'a','ieee-be');
      Format = 2;
  end

  for i = 1 : NumElements
    if ~isempty(PropertyNames{i})
      if ~Format          % write ASCII data
        for k = 1:ElementCount(i)
          for j = 1:length(PropertyNames{i})
            if Type{i}(j) <= 8
              fprintf(fid,[PrintfTypeChar{Type{i}(j)},' '],Data{i}{j}(k));
            else
              fprintf(fid,'%u%s ',length(Data{i}{j}{k}),sprintf([' ',PrintfTypeChar{Type{i}(j)-9}],Data{i}{j}{k}));
            end
          end

          fprintf(fid,'\n');
        end
      else            % write binary data
        if all(Type{i} <= 8) && all(Type{i} == Type{i}(1))
          % property data without list types (fast)
          tmp = zeros(length(PropertyNames{i}),ElementCount(i));

          for j = 1:length(PropertyNames{i})
            tmp(j,:) = Data{i}{j}(:)';
          end

          fwrite(fid,tmp,FWriteTypeNames{Type{i}(j)});
        elseif all(Type{i} > 8)
        % only list types
          Type{i} = Type{i} - 9;

          if length(PropertyNames{i}) == 1
           % only one list property
            tmp = FWriteTypeNames{Type{i}(1)};

            for k = 1:ElementCount(i)
              fwrite(fid,length(Data{i}{1}{k}),'uchar');
              fwrite(fid,Data{i}{1}{k},tmp);
            end
          else
           % multiple list properties
            for k = 1:ElementCount(i)
              for j = 1:length(PropertyNames{i})
                fwrite(fid,length(Data{i}{j}{k}),'uchar');
                fwrite(fid,Data{i}{j}{k},FWriteTypeNames{Type{i}(j)});
              end
            end
          end
        else
        % mixed type
          for k = 1:ElementCount(i)
            for j = 1:length(PropertyNames{i})
              if Type{i}(j) <= 8
                fwrite(fid,Data{i}{j}(k),FWriteTypeNames{Type{i}(j)});
              else
                fwrite(fid,length(Data{i}{j}{k}),'uchar');
                fwrite(fid,Data{i}{j}{k},FWriteTypeNames{Type{i}(j)-9});
              end
            end
          end
        end
      end
    end
  end

  fclose(fid);

  return
end
