Mantis#2796. Thank you kindly, Gerhard for a patch that addresses:

On a call of llVolumeDetect(1) (or any other number !=0) volume 
detection is enabled. Together with VD, the phantom flag is set to the GUI.
On a call of llVolumeDetect(0), vd detection is switched of again, 
also the phantom state is removed. On a call to llSetState(STATE_PHANTOM, 
false) while VD is active, also VD is switched off. The same is true for 
unchecking the phantom flag via GUI. This allows to take back VD without 
the need to script just by removing the phantom flag.
Things missing in this patch: persistance of the volume-detection flag. 
This needs more discussion and will be included in another patch soon.

1 files changed, 3 insertions, 1 deletions

diff --git a/OpenSim/Region/Environment/Scenes/SceneGraph.cs b/OpenSim/Region/Environment/Scenes/SceneGraph.cs
index b373c09..d261e2d 100644
--- a/OpenSim/Region/Environment/Scenes/SceneGraph.cs
+++ b/OpenSim/Region/Environment/Scenes/SceneGraph.cs
@@ -1203,6 +1203,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// <param name="localID"></param>
         /// <param name="packet"></param>
         /// <param name="remoteClient"></param>
+        /// This routine seems to get called when a user changes object settings in the viewer.
+        /// If some one can confirm that, please change the comment according.
         protected internal void UpdatePrimFlags(uint localID, bool UsePhysics, bool IsTemporary, bool IsPhantom, IClientAPI remoteClient)
         {
             SceneObjectGroup group = GetGroupByPrim(localID);
@@ -1210,7 +1212,7 @@ namespace OpenSim.Region.Environment.Scenes
             {
                 if (m_parentScene.Permissions.CanEditObject(group.UUID, remoteClient.AgentId))
                 {
-                    group.UpdatePrimFlags(localID, UsePhysics, IsTemporary, IsPhantom);
+                    group.UpdatePrimFlags(localID, UsePhysics, IsTemporary, IsPhantom, false); // VolumeDetect can't be set via UI and will always be off when a change is made there
                 }
             }
         }