more friendly draw_mesh, templates

Former-commit-id: 5994d3d632934aa28da4f55f8970b4b16bfa8db8

examples/principal_curvature/curvature.REMOVED.git-id

@@ -1 +1 @@
-71a9dea1fc763a1dc5caa543becdceaa9a7e391a
+69608d109a4c02e7dadad848f657b97f59239003

include/igl/draw_mesh.cpp

@@ -132,6 +132,9 @@ IGL_INLINE void igl::draw_mesh(
       }else if(N.rows() == F.rows())
       {
         glNormal3d(N(i,0),N(i,1),N(i,2));
+      }else
+      {
+        assert(N.size() == 0);
       }
       glVertex3d(V(F(i,j),0),V(F(i,j),1),V(F(i,j),2));
     }

include/igl/readDMAT.cpp

@@ -195,4 +195,5 @@ IGL_INLINE bool igl::readDMAT(
 template bool igl::readDMAT<Eigen::Matrix<double, -1, -1, 0, -1, -1> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> >&);
 template bool igl::readDMAT<double>(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::vector<std::vector<double, std::allocator<double> >, std::allocator<std::vector<double, std::allocator<double> > > >&);
 template bool igl::readDMAT<Eigen::Matrix<int, -1, -1, 0, -1, -1> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> >&);
+template bool igl::readDMAT<Eigen::Matrix<double, 4, 1, 0, 4, 1> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<double, 4, 1, 0, 4, 1> >&);
 #endif