[Gate-users] A Warning

[Michael]

Dear Gaters:
I have solved the question about "material 'water'", thank you everyone, and now I go on following the UserGuide.
When I go to this part, a warning comes to, and I can not get the picture like the UserGuide(Figure1.2).

#  S Y S T E M
Idle> /gate/world/daughters/name cylindricalPET
Idle> /gate/world/daughters/insert cylinder
Idle> /gate/cylindricalPET/setMaterial Water
Idle> /gate/cylindricalPET/geometry/setRmax 100 mm
Idle> /gate/cylindricalPET/geometry/setRmin 86 mm
Idle> /gate/cylindricalPET/geometry/setHeight 18 mm
Idle> /gate/cylindricalPET/vis/forceWireframe
G4PhysicalVolumeModel::Validate() called.
  Volume of the same name and copy number ("world_phys", copy 0) still exists and is being used.
  WARNING: This does not necessarily guarantee it's the same
  volume you originally specified in /vis/scene/add/.

What happened? What should I do?

Another question,
how can I make a picture smaller, while I type "/vis/viewer/zoom " and it just makes a picture biger.

Thank you!!