Add material surface mesh reader

ChangeLog.md

@@ -98,6 +98,11 @@
     Action instead of Appeveyor  (David Coeurjolly,
     [#1689](https://github.com/DGtal-team/DGtal/pull/1689))
 
+- *IO*
+  - Add reading material indices in SurfaceMeshReader::readOBJ
+    (Jacques-Olivier Lachaud, [#1677](https://github.com/DGtal-team/DGtal/pull/1677))
+
+
 ## Bug fixes
 - *General*
   - Missing `boost/next_prior.hpp` includes in ReverseIterator, Melkman and Convex

src/DGtal/io/readers/SurfaceMeshReader.h

@@ -73,7 +73,8 @@ namespace DGtal
     typedef typename SurfaceMesh::Index          Index;
     typedef typename SurfaceMesh::Vertices       Vertices;
     typedef typename SurfaceMesh::Faces          Faces;
-
+    typedef std::vector<int>                     Materials;
+
     /// Checks that every index in \a indices are different from the others.
     /// @param indices a vector of integer indices
     /// @return 'true' iff the integer indices are all pairwise different.
@@ -97,6 +98,18 @@ namespace DGtal
     /// created mesh is ok.
     static
     bool readOBJ( std::istream & input, SurfaceMesh & smesh );
+
+    /// Reads an input file as an OBJ file format and outputs the
+    /// corresponding surface mesh.
+    ///
+    /// @param[in,out] input the input stream where the OBJ file is read.
+    /// @param[out] smesh the output surface mesh.
+    /// @param[out] materials a vector containing the material of each face (an index).
+    ///
+    /// @return 'true' if both reading the input stream was ok and the
+    /// created mesh is ok.
+    static
+    bool readOBJ( std::istream & input, SurfaceMesh & smesh, Materials& materials );
   };
 
 } // namespace DGtal

src/DGtal/io/readers/SurfaceMeshReader.ih

@@ -65,6 +65,15 @@ template <typename TRealPoint, typename TRealVector>
 bool
 DGtal::SurfaceMeshReader<TRealPoint, TRealVector>::
 readOBJ( std::istream & input, SurfaceMesh & smesh )
+{
+  Materials materials;
+  return readOBJ( input, smesh, materials );
+}
+//-----------------------------------------------------------------------------
+template <typename TRealPoint, typename TRealVector>
+bool
+DGtal::SurfaceMeshReader<TRealPoint, TRealVector>::
+readOBJ( std::istream & input, SurfaceMesh & smesh, Materials& materials )
 {
   std::vector<RealPoint>  vertices;
   std::vector<RealVector> normals;
@@ -77,6 +86,7 @@ readOBJ( std::istream & input, SurfaceMesh & smesh )
   RealVector n;
   std::getline( input, linestr );
   Index l = 0;
+  int mat = 0; // current material
   for ( ; input.good() && ! input.eof(); std::getline( input, linestr ), l++ )
     {
       if ( linestr.empty() ) continue; // skip empty line
@@ -89,6 +99,11 @@ readOBJ( std::istream & input, SurfaceMesh & smesh )
       } else if ( keyword == "vn" ) {
         lineinput >> n[ 0 ] >> n[ 1 ] >> n[ 2 ];
         normals.push_back( n );
+      } else if ( keyword == "usemtl" )  {
+        std::string strmat;
+        std::operator>>( lineinput, strmat ); // lineinput >> keyword;
+        auto matinfo = split( strmat, '_' );
+        mat = matinfo.size() >= 2 ? std::stoi( matinfo[ 1 ] ) : 0;
       } else if ( keyword == "f" ) {
         std::vector< Index > face, face_normals;
         while ( ! lineinput.eof() ) {
@@ -109,6 +124,7 @@ readOBJ( std::istream & input, SurfaceMesh & smesh )
           {
             faces.push_back( face );
             faces_normals_idx.push_back( face_normals );
+            materials.push_back( mat );
           }
       }
       // Weird: necessary to clear them.