readMesh_off

READMESH_OFF Read mesh data stored in OFF format.

   [VERTICES, FACES] = readMesh_off(FILENAME)
   Read the data stored in file FILENAME and return the vertex and face
   arrays as NV-by-3 array and NF-by-N array respectively, where NV is the
   number of vertices and NF is the number of faces.

   MESH = readMesh_off(FILENAME)
   Read the data stored in file FILENAME and return the mesh into a struct
   with fields 'vertices' and 'faces'.

   Example
     [v, f] = readMesh_off('mushroom.off');
     figure; drawMesh(v, f, 'faceColor', [0 1 0], 'edgeColor', 'none')
     view([5 80]); light; lighting gouraud

   See also
     meshes3d, readMesh, writeMesh_off, readMesh_obj, drawMesh

0001 function varargout = readMesh_off(fileName)
0002 %READMESH_OFF Read mesh data stored in OFF format.
0003 %
0004 %   [VERTICES, FACES] = readMesh_off(FILENAME)
0005 %   Read the data stored in file FILENAME and return the vertex and face
0006 %   arrays as NV-by-3 array and NF-by-N array respectively, where NV is the
0007 %   number of vertices and NF is the number of faces.
0008 %
0009 %   MESH = readMesh_off(FILENAME)
0010 %   Read the data stored in file FILENAME and return the mesh into a struct
0011 %   with fields 'vertices' and 'faces'.
0012 %
0013 %   Example
0014 %     [v, f] = readMesh_off('mushroom.off');
0015 %     figure; drawMesh(v, f, 'faceColor', [0 1 0], 'edgeColor', 'none')
0016 %     view([5 80]); light; lighting gouraud
0017 %
0018 %   See also
0019 %     meshes3d, readMesh, writeMesh_off, readMesh_obj, drawMesh
0020 %
0021 
0022 % ------
0023 % Author: David Legland
0024 % E-mail: david.legland@inrae.fr
0025 % Created: 2011-12-20, using Matlab 7.9.0.529 (R2009b)
0026 % Copyright 2011-2024 INRA - Cepia Software Platform
0027 
0028 %% Read header
0029 
0030 % open file
0031 f = fopen(fileName, 'r');
0032 if f == -1 
0033     error('matGeom:readMesh_off:FileNotFound', ...
0034         ['Could not open input file: ' fileName]);
0035 end
0036 
0037 % check format
0038 line = fgetl(f);   % -1 if eof
0039 if ~strcmp(line(1:3), 'OFF')
0040     error('matGeom:readMesh_off:FileFormatError', ...
0041         'Not a valid OFF file');    
0042 end
0043 
0044 % number of faces and vertices
0045 line = fgetl(f);
0046 vals = sscanf(line, '%d %d');
0047 nVertices = vals(1);
0048 nFaces = vals(2);
0049 
0050 
0051 %% Read vertex data
0052 [vertices, count] = fscanf(f, '%f ', [3 nVertices]);
0053 if count ~= nVertices * 3
0054     error('matGeom:readMesh_off:FileFormatError', ...
0055         ['Could not read all the ' num2str(nVertices) ' vertices']);
0056 end
0057 vertices = vertices';
0058 
0059 
0060 %% Read Face data
0061 % First try to read faces as an homogeneous array. It if fails, start from
0062 % face offset and parse each face individually. In the latter case, faces
0063 % can have different number of vertices.
0064 
0065 % keep position of face info within file
0066 faceOffset = ftell(f);
0067 
0068 % read first face to assess number of vertices per face
0069 line = fgetl(f);
0070 if line == -1
0071     error('matGeom:readMesh_off:FileFormatError', ...
0072         'Unexpected end of file');
0073 end
0074 tokens = split(line);
0075 face1 = str2double(tokens(2:end))' + 1;
0076 nv = length(face1);
0077 
0078 try 
0079     % attempt to read the remaining faces assuming they all have the same
0080     % number of vertices
0081     pattern = ['%d' repmat(' %d', 1, nv) '\n'];
0082     [faces, count] = fscanf(f, pattern, [(nv+1) (nFaces-1)]);
0083     if count ~= (nFaces-1) * (nv+1)
0084         error('matGeom:readMesh_off:FileFormatError', ...
0085             'Could not read all the %d faces', nFaces);
0086     end
0087 
0088     % transpose, remove first column, use 1-indexing, and concatenate with
0089     % first face
0090     faces = [face1 ; faces(2:end,:)'+1];
0091 
0092 catch
0093     % if attempt failed, switch to slower face-by-face parsing
0094     disp('readMesh_off: Inhomogeneous number of vertices per face, switching to face-per-face parsing');
0095     
0096     fseek(f, faceOffset, 'bof');
0097     
0098     % allocate cell array
0099     faces = cell(1, nFaces);
0100     
0101     % iterate over faces
0102     for iFace = 1:nFaces
0103         % read next line
0104         line = fgetl(f);
0105         if line == -1
0106             error('matGeom:readMesh_off:FileFormatError', ...
0107                 'Unexpected end of file');
0108         end
0109 
0110         % parse vertex indices for current face
0111         tokens = split(line);
0112         faces{iFace} = str2double(tokens(2:end))' + 1;
0113     end
0114 end
0115 
0116 
0117 %% Post-processing
0118 
0119 % close the file
0120 fclose(f);
0121 
0122 % format output arguments
0123 if nargout < 2
0124     mesh.vertices = vertices;
0125     mesh.faces = faces;
0126     varargout = {mesh};
0127 else
0128     varargout = {vertices, faces};
0129 end