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## Copyright (C) 2024 David Legland
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
## documentation and/or other materials provided with the distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function mesh = readMesh_obj(fileName)
%READMESH_OBJ Read mesh data stored in OBJ format.
%
% MESH = readMesh_obj(FILENAME)
% Read the data stored in file FILENAME and return the mesh into a struct
% with fields 'vertices' and 'faces'.
%
% Example
% mesh = readMesh_obj('teapot.obj');
% figure; drawMesh(mesh, 'facecolor', [.5 .5 .5]);
% axis equal; light;
%
% References
% Adapted from Bernard Abayowa (2022). readObj
% (https://www.mathworks.com/matlabcentral/fileexchange/18957-readobj),
% MATLAB Central File Exchange. Retrieved September 8, 2022.
%
% See also
% meshes3d, readMesh, readMesh_off, drawMesh
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2022-09-08, using Matlab 9.9.0.1570001 (R2020b) Update 4
% Copyright 2022-2023 INRAE - BIA Research Unit - BIBS Platform (Nantes)
%% initialisations
% open file
fid = fopen(fileName);
if fid == -1
error('matGeom:readMesh_obj:FileNotFound', ...
['Could not open input file: ' fileName]);
end
% create result arrays for vertices
v = []; % vertices
vt = []; % vertex textures
vn = []; % vertex normals
% create result arrays for faces
% (uses cell arrays as face may have variable number of vertices)
fv = {}; % face vertices
fvt = {}; % face texture coordinates
fvn = {}; % face normals
%% File parsing
% parse lines of OBJ file within infinite loop
lineIndex = 0;
while true
% read current line
line = fgetl(fid);
lineIndex = lineIndex + 1;
% check end of file to break the loop
if ~ischar(line)
break;
end
% parse element type
type = sscanf(line, '%s', 1);
if strcmp(type, 'v')
% parse vertex
v = [v; sscanf(line(2:end), '%f')']; %#ok<AGROW>
elseif strcmp(type, 'vt')
% parse texture coordinate
vt = [vt; sscanf(line(3:end), '%f')']; %#ok<AGROW>
elseif strcmp(type, 'vn')
% parse normal coordinates
vn = [vn; sscanf(line(3:end), '%f')']; %#ok<AGROW>
elseif strcmp(type, 'f')
% parse face data
% transform current line into a matrix of tokens with as many rows
% as face vertices, and as many columns as face data type
str = textscan(line(2:end), '%s');
tokenMatrix = split(str{1}, '/');
% parse vertex indices (first column of matrix)
fv = [fv; {str2double(tokenMatrix(:,1))'}]; %#ok<AGROW>
% parse texture coordinates (second column of matrix)
if size(tokenMatrix, 2) > 1 && ~isempty(tokenMatrix{1,2})
fvt = [fvt; {str2double(tokenMatrix(:,2))'}]; %#ok<AGROW>
end
% parse normal coordinates (third column of matrix)
if size(tokenMatrix, 2) > 2 && ~isempty(tokenMatrix{1,3})
fvn = [fvn ; str2double(tokenMatrix(:,3)')]; %#ok<AGROW>
end
% The following code is slightly faster, but does not manage
% all possible cases (in particular when face texture is empty)
% and is more complicated to maintain.
% str = textscan(line(2:end), '%s');
% str = str{1};
% fvi = []; fvti = []; fvni = [];
%
% % number of fields with this face vertices
% nf = length(strfind(str{1}, '/'));
%
% % vertex indices
% [tok, str] = strtok(str, '//'); %#ok<STTOK>
% for k = 1:length(tok)
% fvi = [fvi str2double(tok{k})]; %#ok<AGROW>
% end
% fv = [fv; fvi]; %#ok<AGROW>
%
% % vertex texture coordinates
% if nf > 0
% [tok, str] = strtok(str, '//'); %#ok<STTOK>
% for k = 1:length(tok)
% fvti = [fvti str2double(tok{k})]; %#ok<AGROW>
% end
% fvt = [fvt; fvti]; %#ok<AGROW>
% end
%
% % vertex normal coordinates
% if nf > 1
% tok = strtok(str, '//');
% for k = 1:length(tok)
% fvni = [fvni str2double(tok{k})]; %#ok<AGROW>
% end
% fvn = [fvn; fvni]; %#ok<AGROW>
% end
elseif any(strcmp(type, {'g', 'o', 's', 'usemtl'}))
warning('matGeom:readMesh_obj:UnsupportedElement', ......
'Element %s at line %d is not (yet) managed', type, lineIndex);
elseif isempty(type) || any(strcmp(type(1), {'#', ' '}))
% comment or empty line -> do nothing
else
warning('matGeom:readMesh_obj:UnknownElement', ......
'Unknown element type at line %d: %s', lineIndex, type);
end
end
% close file
fclose(fid);
%% Format output
% create mesh structure
mesh = struct('vertices', v);
% add optional vertex data
if ~isempty(vn)
mesh.vertexNormals = vn;
end
if ~isempty(vt)
mesh.vertexTexture = vt;
end
mesh.faces = fv;
% add optional face data
if ~isempty(fvn)
mesh.faceVertexNormals = fvn;
end
if ~isempty(fvt)
mesh.faceVertexTexture = fvt;
end
% if faces have all the same number of vertices, convert to numeric arrays
nvf = cellfun(@length, fv);
if all(nvf == nvf(1))
mesh.faces = cell2mat(mesh.faces(:));
if ~isempty(fvn)
mesh.faceVertexNormals = cell2mat(fvn(:));
end
if ~isempty(fvt)
mesh.faceVertexTexture = cell2mat(fvt(:));
end
end
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