MATLAB对ply文件格式的读取和显示

在网上搜索这个题目可以找到一些类似的文章，其来源大致都是http://people.sc.fsu.edu/~jburkardt/m_src/ply_io/ply_io.html。但是并没有说明怎样运行和显示，因此我做这篇博客详细讲解一下。首先是这个ply_read.m文件

function [ Elements, varargout ] = PLY_READ ( Path, Str )%*****************************************************************************80%%% PLY_READ reads a PLY 3D data file.%%   [DATA,COMMENTS] = PLY_READ(FILENAME) reads a version 1.0 PLY file%   FILENAME and returns a structure DATA.  The fields in this structure%   are defined by the PLY header; each element type is a field and each%   element PRoperty is a subfield.  If the file contains any comments,%   they are returned in a cell string array COMMENTS.%%   [TRI,PTS] = PLY_READ(FILENAME,'tri') or%   [TRI,PTS,DATA,COMMENTS] = PLY_READ(FILENAME,'tri') converts vertex%   and face data into triangular connectivity and vertex arrays.  The%   mesh can then be displayed using the TRISURF command.%%   Note: This function is slow for large mesh files (+50K faces),%   especially when reading data with list type properties.%%   Example:%   [Tri,Pts] = PLY_READ('cow.ply','tri');%   [Tri,Pts] = PLY_READ('bunny.ply','tri');%   trisurf(Tri,Pts(:,1),Pts(:,2),Pts(:,3));%   colormap(gray); axis equal;%%  Discussion:%%    The original version of this program had a mistake that meant it%    did not properly triangulate files whose faces were not already triangular.%    This has been corrected (JVB, 25 February 2007).%%    Glenn Ramsey pointed out and corrected a problem that occurred%    with an uninitialized value of Type2, 27 August 2012.%%  Licensing:%%    This code is distributed under the GNU LGPL license.%%  Modified:%%    27 August 2012%%  Author:%%    Pascal Getreuer 2004%%  Parameters:%%  Local Parameters:%%    COMMENTS, any comments from the file.%%    ELEMENTCOUNT, the number of each type of element in file.%%    ELEMENTS, the element data.%%    PROPERTYTYPES, the element property types.%%    SIZEOF, size in bytes of each type.%%%  Open the input file in "read text" mode.%  [ fid, Msg ] = fopen ( Path, 'rt' );  if ( fid == -1 )    error ( Msg );  end  Buf = fscanf ( fid, '%s', 1 );  if ( ~strcmp ( Buf, 'ply' ) )    fclose ( fid );    error('Not a PLY file.');  end%%  Read the header.%  Position = ftell(fid);  Format = '';  NumComments = 0;  Comments = {};  NumElements = 0;  NumProperties = 0;  Elements = [];  ElementCount = [];  PropertyTypes = [];  ElementNames = {};  % list of element names in the order they are stored in the file  PropertyNames = [];  % structure of lists of property names  while ( 1 )%%  Read a line from the file.%    Buf = fgetl ( fid );    BufRem = Buf;    Token = {};    Count = 0;%%  Split the line into tokens.%    while ( ~isempty(BufRem) )      [ tmp, BufRem ] = strtok(BufRem);%%  Count the tokens.%      if ( ~isempty ( tmp ) )        Count = Count + 1;        Token{Count} = tmp;      end    end%%  Parse the line.%    if ( Count )      switch lower ( Token{1} )%%  Read the data format.%      case 'format'        if ( 2 <= Count )          Format = lower ( Token{2} );          if ( Count == 3 & ~strcmp ( Token{3}, '1.0' ) )            fclose ( fid );            error('Only PLY format version 1.0 supported.');          end        end%%  Read a comment.%      case 'comment'        NumComments = NumComments + 1;        Comments{NumComments} = '';        for i = 2 : Count          Comments{NumComments} = [Comments{NumComments},Token{i},' '];        end%%  Read an element name.%      case 'element'        if ( 3 <= Count )          if ( isfield(Elements,Token{2}) )            fclose ( fid );            error(['Duplicate element name, ''',Token{2},'''.']);          end          NumElements = NumElements + 1;          NumProperties = 0;          Elements = setfield(Elements,Token{2},[]);          PropertyTypes = setfield(PropertyTypes,Token{2},[]);          ElementNames{NumElements} = Token{2};          PropertyNames = setfield(PropertyNames,Token{2},{});          CurElement = Token{2};          ElementCount(NumElements) = str2double(Token{3});          if ( isnan(ElementCount(NumElements)) )            fclose ( fid );            error(['Bad element definition: ',Buf]);          end        else          error(['Bad element definition: ',Buf]);        end%%  Read an element property.%      case 'property'        if ( ~isempty(CurElement) & Count >= 3 )          NumProperties = NumProperties + 1;          eval(['tmp=isfield(Elements.',CurElement,',Token{Count});'],...            'fclose(fid);error([''Error reading property: '',Buf])');          if ( tmp )            error(['Duplicate property name, ''',CurElement,'.',Token{2},'''.']);          end%%  Add property subfield to Elements.%          eval(['Elements.',CurElement,'.',Token{Count},'=[];'], ...            'fclose(fid);error([''Error reading property: '',Buf])');%%  Add property subfield to PropertyTypes and save type.%          eval(['PropertyTypes.',CurElement,'.',Token{Count},'={Token{2:Count-1}};'], ...            'fclose(fid);error([''Error reading property: '',Buf])');%%  Record property name order.%          eval(['PropertyNames.',CurElement,'{NumProperties}=Token{Count};'], ...            'fclose(fid);error([''Error reading property: '',Buf])');         else           fclose ( fid );           if ( isempty(CurElement) )             error(['Property definition without element definition: ',Buf]);           else             error(['Bad property definition: ',Buf]);           end         end%%  End of header.%        case 'end_header'          break;      end    end  end%%  Set reading for specified data format.%  if ( isempty ( Format ) )    warning('Data format unspecified, assuming ASCII.');    Format = 'ascii';  end  switch Format    case 'ascii'      Format = 0;    case 'binary_little_endian'      Format = 1;    case 'binary_big_endian'      Format = 2;    otherwise      fclose ( fid );      error(['Data format ''',Format,''' not supported.']);  end%%  Read the rest of the file as ASCII data...%  if ( ~Format )    Buf = fscanf ( fid, '%f' );    BufOff = 1;  else%%  ...or, close the file, and reopen in "read binary" mode.%    fclose ( fid );%%  Reopen the binary file as LITTLE_ENDIAN or BIG_ENDIAN.%    if ( Format == 1 )      fid = fopen ( Path, 'r', 'ieee-le.l64' );    else      fid = fopen ( Path, 'r', 'ieee-be.l64' );    end%%  Find the end of the header again.%  Using ftell on the old handle doesn't give the correct position.%    BufSize = 8192;    Buf = [ blanks(10), char(fread(fid,BufSize,'uchar')') ];    i = [];    tmp = -11;    while ( isempty(i) )      i = findstr(Buf,['end_header',13,10]);   % look for end_header + CR/LF      i = [i,findstr(Buf,['end_header',10])];  % look for end_header + LF      if ( isempty(i) )        tmp = tmp + BufSize;        Buf = [Buf(BufSize+1:BufSize+10),char(fread(fid,BufSize,'uchar')')];      end    end%%  seek to just after the line feed%    fseek ( fid, i + tmp + 11 + (Buf(i + 10) == 13), -1 );  end%%  Read element data.%%  PLY and MATLAB data types (for fread)%  PlyTypeNames = {'char','uchar','short','ushort','int','uint','float','double', ...    'char8','uchar8','short16','ushort16','int32','uint32','float32','double64'};  MatlabTypeNames = {'schar','uchar','int16','uint16','int32','uint32','single','double'};  SizeOf = [1,1,2,2,4,4,4,8];  for i = 1 : NumElements%%  get current element property information%    eval(['CurPropertyNames=PropertyNames.',ElementNames{i},';']);    eval(['CurPropertyTypes=PropertyTypes.',ElementNames{i},';']);    NumProperties = size(CurPropertyNames,2);%   fprintf('Reading %s.../n',ElementNames{i});%%  Read ASCII data.%    if ( ~Format )      for j = 1 : NumProperties        Token = getfield(CurPropertyTypes,CurPropertyNames{j});        if ( strcmpi(Token{1},'list') )          Type(j) = 1;        else          Type(j) = 0;        end%%  Glenn Ramsey 20120827 %  Initialise Type2{} to prevent uninitialised value error.%        Type2{j} = '';      end%%  Parse the buffer.%      if ( ~any(Type) )         % no list types        Data = reshape ( ...          Buf(BufOff:BufOff+ElementCount(i)*NumProperties-1), ...          NumProperties, ElementCount(i) )';        BufOff = BufOff + ElementCount(i) * NumProperties;      else        ListData = cell(NumProperties,1);        for k = 1 : NumProperties          ListData{k} = cell(ElementCount(i),1);        end%% list type%        for j = 1 : ElementCount(i)          for k = 1 : NumProperties            if ( ~Type(k) )              Data(j,k) = Buf(BufOff);              BufOff = BufOff + 1;            else              tmp = Buf(BufOff);              ListData{k}{j} = Buf(BufOff+(1:tmp))';              BufOff = BufOff + tmp + 1;            end          end        end      end%%  Read binary data.%    else% translate PLY data type names to MATLAB data type names      ListFlag = 0;  % = 1 if there is a list type      SameFlag = 1;     % = 1 if all types are the same      for j = 1 : NumProperties        Token = getfield(CurPropertyTypes,CurPropertyNames{j});%%  Non-list type.%        if ( ~strcmp(Token{1},'list' ) )          tmp = rem(strmatch(Token{1},PlyTypeNames,'exact')-1,8)+1;          if ( ~isempty(tmp) )            TypeSize(j) = SizeOf(tmp);            Type{j} = MatlabTypeNames{tmp};            TypeSize2(j) = 0;            Type2{j} = '';            SameFlag = SameFlag & strcmp(Type{1},Type{j});          else            fclose(fid);            error(['Unknown property data type, ''',Token{1},''', in ', ...              ElementNames{i},'.',CurPropertyNames{j},'.']);          end        else           % list type          if ( length(Token) == 3 )            ListFlag = 1;            SameFlag = 0;            tmp = rem(strmatch(Token{2},PlyTypeNames,'exact')-1,8)+1;            tmp2 = rem(strmatch(Token{3},PlyTypeNames,'exact')-1,8)+1;            if ( ~isempty(tmp) & ~isempty(tmp2) )              TypeSize(j) = SizeOf(tmp);              Type{j} = MatlabTypeNames{tmp};              TypeSize2(j) = SizeOf(tmp2);              Type2{j} = MatlabTypeNames{tmp2};            else              fclose(fid);              error(['Unknown property data type, ''list ',Token{2},' ',Token{3},''', in ', ...                ElementNames{i},'.',CurPropertyNames{j},'.']);            end          else            fclose(fid);            error(['Invalid list syntax in ',ElementNames{i},'.',CurPropertyNames{j},'.']);          end        end      end% read file      if ( ~ListFlag )%%  No list types, all the same type (fast)%        if ( SameFlag )          Data = fread(fid,[NumProperties,ElementCount(i)],Type{1})';%%  No list types, mixed type.%        else          Data = zeros(ElementCount(i),NumProperties);          for j = 1 : ElementCount(i)            for k = 1 : NumProperties              Data(j,k) = fread(fid,1,Type{k});            end          end        end      else        ListData = cell(NumProperties,1);        for k = 1 : NumProperties          ListData{k} = cell(ElementCount(i),1);        end        if ( NumProperties == 1 )          BufSize = 512;          SkipNum = 4;          j = 0;%%  List type, one property (fast if lists are usually the same length)%          while ( j < ElementCount(i) )            BufSize = min(ElementCount(i)-j,BufSize);            Position = ftell(fid);%%  Read in BufSize count values, assuming all counts = SkipNum%            [Buf,BufSize] = fread(fid,BufSize,Type{1},SkipNum*TypeSize2(1));            Miss = find(Buf ~= SkipNum);     % find first count that is not SkipNum            fseek(fid,Position + TypeSize(1),-1);   % seek back to after first count            if ( isempty(Miss) )% all counts are SkipNum              Buf = fread(fid,[SkipNum,BufSize],[int2str(SkipNum),'*',Type2{1}],TypeSize(1))';              fseek(fid,-TypeSize(1),0);     % undo last skip              for k = 1:BufSize                ListData{1}{j+k} = Buf(k,:);              end              j = j + BufSize;              BufSize = floor(1.5*BufSize);            else%%  Some counts are SkipNum.%              if ( 1 < Miss(1) )                Buf2 = fread(fid,[SkipNum,Miss(1)-1],[int2str(SkipNum),'*',Type2{1}],TypeSize(1))';                for k = 1:Miss(1)-1                  ListData{1}{j+k} = Buf2(k,:);                end                j = j + k;              end%%  Read in the list with the missed count.%              SkipNum = Buf(Miss(1));              j = j + 1;              ListData{1}{j} = fread(fid,[1,SkipNum],Type2{1});              BufSize = ceil(0.6*BufSize);            end          end        else%%  List type(s), multiple properties (slow)%          Data = zeros(ElementCount(i),NumProperties);          for j = 1:ElementCount(i)            for k = 1:NumProperties              if ( isempty(Type2{k}) )                Data(j,k) = fread(fid,1,Type{k});              else                tmp = fread(fid,1,Type{k});                ListData{k}{j} = fread(fid,[1,tmp],Type2{k});              end            end          end        end      end    end%%  Put data into Elements structure%    for k = 1 : NumProperties      if ( ( ~Format && ~Type(k) ) || (Format && isempty(Type2{k})) )        eval(['Elements.',ElementNames{i},'.',CurPropertyNames{k},'=Data(:,k);']);      else        eval(['Elements.',ElementNames{i},'.',CurPropertyNames{k},'=ListData{k};']);      end    end  end  clear Data  clear ListData;  fclose ( fid );%%  Output the data as a triangular mesh pair.%  if ( ( nargin > 1 & strcmpi(Str,'Tri') ) || nargout > 2 )%%  Find vertex element field%    Name = {'vertex','Vertex','point','Point','pts','Pts'};    Names = [];    for i = 1 : length(Name)      if ( any ( strcmp ( ElementNames, Name{i} ) ) )        Names = getfield(PropertyNames,Name{i});        Name = Name{i};        break;      end    end    if ( any(strcmp(Names,'x')) & any(strcmp(Names,'y')) & any(strcmp(Names,'z')) )      eval(['varargout{1}=[Elements.',Name,'.x,Elements.',Name,'.y,Elements.',Name,'.z];']);    else      varargout{1} = zeros(1,3);    end    varargout{1} = varargout{1}';    varargout{2} = Elements;    varargout{3} = Comments;    Elements = [];%% Find face element field%    Name = {'face','Face','poly','Poly','tri','Tri'};    Names = [];    for i = 1 : length(Name)      if ( any(strcmp(ElementNames,Name{i})) )        Names = getfield(PropertyNames,Name{i});        Name = Name{i};        break;      end    end    if ( ~isempty(Names) )      % find vertex indices property subfield      PropertyName = {'vertex_indices','vertex_indexes','vertex_index','indices','indexes'};      for i = 1 : length(PropertyName)        if ( any(strcmp(Names,PropertyName{i})) )          PropertyName = PropertyName{i};          break;        end      end%%  Convert face index list to triangular connectivity.%      if ( ~iscell(PropertyName) )        eval(['FaceIndices=varargout{2}.',Name,'.',PropertyName,';']);        N = length(FaceIndices);        Elements = zeros(3,N*2);        Extra = 0;        for k = 1 : N          Elements(1:3,k) = FaceIndices{k}(1:3)';%%  The original code had an error in the following loop.%          for j = 4 : length(FaceIndices{k})            Extra = Extra + 1;            Elements(1,N + Extra) = FaceIndices{k}(1);            Elements(2,N + Extra) = FaceIndices{k}(j-1);            Elements(3,N + Extra) = FaceIndices{k}(j);          end        end%%  Add 1 to each vertex value; PLY vertices are zero based.%        Elements = Elements(:,1:N+Extra) + 1;      end    end  else    varargout{1} = Comments;  end  returnend输入的参数是两个，一个是ply文件的位置，另一个是打开方式，一般为'tri'
对于ply格式的解答这里有几篇文章可以参考：PLY文件格式剖析(一)，PLY文件格式剖析(二)
PLY_DISPLAY这个函数也是类似的
但是事实上用txt直接读取ply格式确是有可能出现乱码的
但是某些只有点和面的信息的格式是被允许的
例如下图的棱锥
plyformat ascii 1.0comment created by MATLAB ply_writeelement vertex 5property float xproperty float yproperty float zelement face 6property list uchar char vertex_indicesend_header0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 1.000000 1.000000 0.000000 0.000000 1.000000 0.000000 0.500000 0.500000 1.600000 3 1 0 3 3 1 3 2 3 0 1 4 3 0 4 3 3 3 4 2 3 1 2 4 
此外，更为复杂的cow可以在我的资源页处下载，下面就是读取ply格式的文件了，这里文中给定的例子略微有点问题，应该调用的是矩阵的转置
[Tri,Pts] = PLY_READ('coww.ply','tri');Pts=Pts';trisurf(Tri',Pts(:,1),Pts(:,2),Pts(:,3));
cow
MATLAB绘制效果
meshlab显示效果
但是对于一般的ply文件利用这个函数却不能正确读出Tri来。。可能他的代码还有待改善吧。。