Added simple 3d hexahedra output

Should differentiate a bit more dimensional outputs

src/output/VTKWriter.hpp

@@ -55,8 +55,12 @@ public:
         fout << "0 "; // VTK requires 3 components
       }
     } else {
-      std::cerr << "VTKWriter not implemented in dimension " << MeshType::dimension << '\n';
-      std::exit(1);
+      const Kokkos::View<const TinyVector<3>*> xr = mesh.xr();
+      for (unsigned int r=0; r<mesh.numberOfNodes(); ++r) {
+        for (unsigned short i=0; i<3; ++i) {
+          fout << xr[r][i] << ' ';
+        }
+      }
     }
     fout << '\n';
     fout << "</DataArray>\n";
@@ -101,6 +105,10 @@ public:
           fout << "9 ";
           break;
         }
+        case 8: {
+          fout << "12 ";
+          break;
+        }
         default: {
           fout << "7 ";
           break;