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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 varargout = readMesh_stl(fName)
%READMESH_STL Read mesh data stored in STL format.
%
% [VERTICES, FACES] = readMesh_stl(FNAME)
%
% MESH = readMesh_stl(FNAME)
%
% See also
% meshes3d, readMesh, readMesh_off, readMesh_ply, writeMesh_stl
%
% Source
% Functions of the stlTools toolbox by Pau Micó are used for STL files
% in ASCII format:
% https://mathworks.com/matlabcentral/fileexchange/51200-stltools
% MATLAB's build-in stlread is used for STL files in binary format.
% ------
% Author: oqilipo
% E-mail: N/A
% Created: 2021-02-12, using Matlab 9.9.0.1538559 (R2020b)
% Copyright 2021-2023
format = stlGetFormat(fName);
if strcmp(format,'ascii')
[vertices,faces] = stlReadAscii(fName);
elseif strcmp(format,'binary')
TR = stlread(fName);
vertices = TR.Points;
faces = TR.ConnectivityList;
end
varargout = formatMeshOutput(nargout, vertices, faces);
end
function format = stlGetFormat(fileName)
%STLGETFORMAT identifies the format of the STL file and returns 'binary' or
%'ascii'
fid = fopen(fileName);
% Check the file size first, since binary files MUST have a size of 84+(50*n)
fseek(fid,0,1); % Go to the end of the file
fidSIZE = ftell(fid); % Check the size of the file
if rem(fidSIZE-84,50) > 0
format = 'ascii';
else
% Files with a size of 84+(50*n), might be either ascii or binary...
% Read first 80 characters of the file.
% For an ASCII file, the data should begin immediately (give or take a few
% blank lines or spaces) and the first word must be 'solid'.
% For a binary file, the first 80 characters contains the header.
% It is bad practice to begin the header of a binary file with the word
% 'solid', so it can be used to identify whether the file is ASCII or
% binary.
fseek(fid,0,-1); % go to the beginning of the file
header = strtrim(char(fread(fid,80,'uchar')')); % trim leading and trailing spaces
isSolid = strcmp(header(1:min(5,length(header))),'solid'); % take first 5 char
fseek(fid,-80,1); % go to the end of the file minus 80 characters
tail = char(fread(fid,80,'uchar')');
isEndSolid = contains(tail,'endsolid');
% Double check by reading the last 80 characters of the file.
% For an ASCII file, the data should end (give or take a few
% blank lines or spaces) with 'endsolid <object_name>'.
% If the last 80 characters contains the word 'endsolid' then this
% confirms that the file is indeed ASCII.
if isSolid && isEndSolid
format = 'ascii';
else
format = 'binary';
end
end
fclose(fid);
end
function [v, f, n, name] = stlReadAscii(fileName)
%STLREADASCII reads a STL file written in ASCII format
%V are the vertices
%F are the faces
%N are the normals
%NAME is the name of the STL object (NOT the name of the STL file)
%======================
% STL ascii file format
%======================
% ASCII STL files have the following structure. Technically each facet
% could be any 2D shape, but in practice only triangular facets tend to be
% used. The present code ONLY works for meshes composed of triangular
% facets.
%
% solid object_name
% facet normal x y z
% outer loop
% vertex x y z
% vertex x y z
% vertex x y z
% endloop
% endfacet
%
% <Repeat for all facets...>
%
% endsolid object_name
fid = fopen(fileName);
cellcontent = textscan(fid,'%s','delimiter','\n'); % read all the file and put content in cells
content = cellcontent{:}(logical(~strcmp(cellcontent{:},''))); % remove all blank lines
fclose(fid);
% read the STL name
line1 = char(content(1));
if (size(line1,2) >= 7)
name = line1(7:end);
else
name = 'Unnamed Object';
end
% read the vector normals
normals = char(content(logical(strncmp(content,'facet normal',12))));
n = str2num(normals(:,13:end)); %#ok<ST2NM>
% read the vertex coordinates (vertices)
vertices = char(content(logical(strncmp(content,'vertex',6))));
v = str2num(vertices(:,7:end)); %#ok<ST2NM>
nvert = size(v,1); % number of vertices
nfaces = sum(strcmp(content,'endfacet')); % number of faces
if (nvert == 3*nfaces)
f = reshape(1:nvert,[3 nfaces])'; % create faces
end
end
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