Merge pull request #7392 from MaelRL/CGAL_IO-Obj_fixes-GF

Fix issues in OBJ I/O

Polygon_mesh_processing/examples/Polygon_mesh_processing/triangulate_faces_example.cpp

@@ -23,18 +23,32 @@ int main(int argc, char* argv[])
   Surface_mesh mesh;
   if(!PMP::IO::read_polygon_mesh(filename, mesh))
   {
-    std::cerr << "Invalid input." << std::endl;
-    return 1;
+    std::cerr << "Error: Invalid input." << std::endl;
+    return EXIT_FAILURE;
   }
 
+  if(is_empty(mesh))
+  {
+    std::cerr << "Warning: empty file?" << std::endl;
+    return EXIT_SUCCESS;
+  }
+
+  if(!CGAL::is_triangle_mesh(mesh))
+    std::cout << "Input mesh is not triangulated." << std::endl;
+  else
+    std::cout << "Input mesh is triangulated." << std::endl;
+
   PMP::triangulate_faces(mesh);
 
   // Confirm that all faces are triangles.
   for(boost::graph_traits<Surface_mesh>::face_descriptor f : faces(mesh))
+  {
     if(!CGAL::is_triangle(halfedge(f, mesh), mesh))
       std::cerr << "Error: non-triangular face left in mesh." << std::endl;
+  }
+
 
   CGAL::IO::write_polygon_mesh(outfilename, mesh, CGAL::parameters::stream_precision(17));
 
-  return 0;
+  return EXIT_SUCCESS;
 }

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/IO/polygon_mesh_io.h

@@ -105,7 +105,7 @@ bool read_polygon_mesh(const std::string& fname,
 
   std::vector<Point> points;
   std::vector<std::vector<std::size_t> > faces;
-  if(!CGAL::IO::read_polygon_soup(fname, points, faces))
+  if(!CGAL::IO::read_polygon_soup(fname, points, faces, CGAL::parameters::verbose(verbose)))
   {
     if(verbose)
       std::cerr << "Warning: cannot read polygon soup" << std::endl;

Stream_support/include/CGAL/IO/OBJ.h

@@ -24,6 +24,7 @@
 #include <boost/range/value_type.hpp>
 #include <CGAL/Named_function_parameters.h>
 
+#include <algorithm>
 #include <fstream>
 #include <iostream>
 #include <sstream>
@@ -67,12 +68,30 @@ bool read_OBJ(std::istream& is,
   bool tex_found(false), norm_found(false);
   while(getline(is, line))
   {
-    if(line.empty())
-      continue;
+    // get last non-whitespace, non-null character
+    auto last = std::find_if(line.rbegin(), line.rend(), [](char c) { return c != '\0' && !std::isspace(c); });
+    if(last == line.rend())
+      continue; // line is empty or only whitespace
+
+    // keep reading lines as long as the last non-whitespace, non-null character is a backslash
+    while(last != line.rend() && *last == '\\')
+    {
+      // remove everything from the backslash (included)
+      line = line.substr(0, line.size() - (last - line.rbegin()) - 1);
+
+      std::string next_line;
+      if(!getline(is, next_line))
+        break;
+
+      line += next_line;
+      last = std::find_if(line.rbegin(), line.rend(), [](char c) { return c != '\0' && !std::isspace(c); });
+    }
+
+    CGAL_assertion(!line.empty());
 
     std::istringstream iss(line);
     if(!(iss >> s))
-      continue; // can't read anything on the line, whitespace only?
+      continue;
 
     if(s == "v")
     {
@@ -122,8 +141,12 @@ bool read_OBJ(std::istream& is,
       }
 
       if(iss.bad())
+      {
+        if(verbose)
+          std::cerr << "error while reading OBJ face." << std::endl;
         return false;
       }
+    }
     else if(s.front() == '#')
     {
       // this is a commented line, ignored
@@ -148,15 +171,15 @@ bool read_OBJ(std::istream& is,
     else
     {
       if(verbose)
-        std::cerr << "error: unrecognized line: " << s << std::endl;
+        std::cerr << "Error: unrecognized line: " << s << std::endl;
       return false;
     }
   }
 
   if(norm_found && verbose)
-    std::cout<<"NOTE: normals were found in this file, but were discarded."<<std::endl;
+    std::cout << "NOTE: normals were found in this file, but were discarded." << std::endl;
   if(tex_found && verbose)
-    std::cout<<"NOTE: textures were found in this file, but were discarded."<<std::endl;
+    std::cout << "NOTE: textures were found in this file, but were discarded." << std::endl;
 
   if(points.empty() || polygons.empty())
   {