Nicer 3D colors and lighting

utils/view-mesh.pl

@@ -27,6 +27,9 @@ my %opt = ();
 {
     my $model = Slic3r::Model->read_from_file($ARGV[0]);
     
+    # make sure all objects have at least one defined instance
+    $model->add_default_instances;
+    
     $Slic3r::ViewMesh::object = $model->objects->[0];
     my $app = Slic3r::ViewMesh->new;
     $app->MainLoop;