added quick obj reader

src/polymesh/formats/obj.cc

@@ -301,3 +301,9 @@ void obj_reader::parse(std::istream &in, Mesh &mesh)
         }
     }
 }
+
+void polymesh::read_obj(const std::string &filename, Mesh &mesh, vertex_attribute<glm::vec3> &position)
+{
+    obj_reader reader(filename, mesh);
+    position = reader.positions_vec3();
+}

src/polymesh/formats/obj.hh

@@ -14,6 +14,7 @@ void write_obj(std::string const& filename,
                vertex_attribute<glm::vec3> const& position,
                vertex_attribute<glm::vec2> const* tex_coord = nullptr,
                vertex_attribute<glm::vec3> const* normal = nullptr);
+void read_obj(std::string const& filename, Mesh& mesh, vertex_attribute<glm::vec3>& position);
 
 struct obj_writer
 {