0022795: Make possible to display some presentable objects in overlay of others, groupped by display priority

src/AIS/AIS_InteractiveContext.cdl

@@ -406,6 +406,26 @@ is
     ---Purpose: Sets the display priority aPriority of the seen parts
 -- presentation of the entity anIobj.
 
+    SetZLayer( me         : mutable;
+               theIObj    : InteractiveObject from AIS;
+               theLayerId : Integer from Standard );
+    ---Purpose: Set Z layer id for interactive object. The layer can be
+    -- specified for displayed object only. The Z layers can be used to display
+    -- temporarily presentations of some object in front of the other objects
+    -- in the scene. The ids for Z layers are generated by V3d_Viewer.
+    -- Note that Z layers differ from under-/overlayer in V3d_View:
+    -- under-/overlayer are intended for specific 2D drawings that appear
+    -- behind/in front of all 3D presentations, while SetZLayer() method
+    -- applies to regular 3D presentations and does not imply any specific
+    -- drawing methods.
+
+    GetZLayer( me;
+               theIObj : InteractiveObject from AIS )
+      returns Integer from Standard;
+    ---Purpose: Get Z layer id set for displayed interactive object.
+    -- If the object doesn't exists in context or has no computed presentations,
+    -- the method returns -1.
+
     Redisplay(me     : mutable;
     	      aniobj : InteractiveObject from AIS;
 	      updateviewer : Boolean from Standard = Standard_True;

src/AIS/AIS_InteractiveContext.cxx

@@ -3147,3 +3147,54 @@ Standard_Boolean AIS_InteractiveContext::GetAutoActivateSelection() const
 {
   return myIsAutoActivateSelMode;
 }
+
+//=======================================================================
+//function : SetZLayer
+//purpose  : 
+//=======================================================================
+
+void AIS_InteractiveContext::SetZLayer (const Handle(AIS_InteractiveObject)& theIObj,
+                                        const Standard_Integer theLayerId)
+{
+  if (theIObj.IsNull ())
+    return;
+
+  if (myObjects.IsBound (theIObj))
+  {
+    switch (myObjects (theIObj)->GraphicStatus ())
+    {
+      case AIS_DS_Displayed:
+      {
+        theIObj->SetZLayer (myMainPM, theLayerId);
+        break;
+      }
+      case AIS_DS_Erased:
+      {
+        theIObj->SetZLayer (myCollectorPM, theLayerId);
+        break;
+      }
+      default:
+        break;
+    }
+  }
+  else if (HasOpenedContext ())
+  {
+    myLocalContexts (myCurLocalIndex)->SetZLayer (theIObj, theLayerId);
+  }
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  : 
+//=======================================================================
+
+Standard_Integer AIS_InteractiveContext::GetZLayer (const Handle(AIS_InteractiveObject)& theIObj) const
+{
+  if (theIObj.IsNull ())
+    return -1;
+
+  if (myObjects.IsBound (theIObj))
+    return theIObj->GetZLayer (myMainPM);
+
+  return myLocalContexts (myCurLocalIndex)->GetZLayer (theIObj);
+}

src/AIS/AIS_LocalContext.cdl

@@ -373,6 +373,26 @@ is
                        anObject: InteractiveObject from AIS;
                        Prior   : Integer from Standard);
 
+    SetZLayer( me         : mutable;
+               theIObj    : InteractiveObject from AIS;
+               theLayerId : Integer from Standard );
+    ---Purpose: Set Z layer id for interactive object. The layer can be
+    -- specified for displayed object only. The Z layers can be used to display
+    -- temporarily presentations of some object in front of the other objects
+    -- in the scene. The ids for Z layers are generated by V3d_Viewer.
+    -- Note that Z layers differ from under-/overlayer in V3d_View:
+    -- under-/overlayer are intended for specific 2D drawings that appear
+    -- behind/in front of all 3D presentations, while SetZLayer() method
+    -- applies to regular 3D presentations and does not imply any specific
+    -- drawing methods.
+
+    GetZLayer( me;
+               theIObj : InteractiveObject from AIS )
+      returns Integer from Standard;
+    ---Purpose: Get Z layer id set for displayed interactive object.
+    -- If the object doesn't exists in context or has no computed presentations,
+    -- the method returns -1.
+
     DisplayedObjects(me;theMapToFill : in out MapOfTransient from TColStd)
     returns Integer from Standard;
 

src/AIS/AIS_LocalContext.cxx

@@ -881,7 +881,6 @@ void AIS_LocalContext::SetDisplayPriority(const Handle(AIS_InteractiveObject)& a
   
 }
 
-
 //=======================================================================
 //function : DisplayedObjects
 //purpose  : 
@@ -1220,3 +1219,34 @@ void AIS_LocalContext::SetSensitivity(const Standard_Integer aPrecision) {
   myMainVS->Set(aPrecision);
 }
 #endif
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+
+void AIS_LocalContext::SetZLayer (const Handle(AIS_InteractiveObject)& theIObj,
+                                  const Standard_Integer theLayerId)
+{
+  if (!myActiveObjects.IsBound (theIObj)) 
+    return;
+
+  const Handle(AIS_LocalStatus)& aStatus = myActiveObjects (theIObj);
+  if (aStatus->DisplayMode () == -1)
+    return;
+
+  theIObj->SetZLayer (myMainPM, theLayerId);
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  : 
+//=======================================================================
+
+Standard_Integer AIS_LocalContext::GetZLayer (const Handle(AIS_InteractiveObject)& theIObj) const
+{
+  if (!myActiveObjects.IsBound (theIObj)) 
+    return -1;
+
+  return theIObj->GetZLayer (myMainPM);
+}

src/Graphic3d/Graphic3d_GraphicDriver.cdl

@@ -1287,6 +1287,52 @@ is
         -- <theCGroup>. This method is internal and should be used
         -- by Graphic3d_Group only.
 
+    AddZLayer( me         : mutable;
+               theCView   : CView from Graphic3d;
+               theLayerId : Integer from Standard )
+        is deferred;
+        ---Purpose: Add a new top-level z layer with ID <theLayerId> for
+        -- the view. Z layers allow drawing structures in higher layers
+        -- in foreground of structures in lower layers. To add a structure
+        -- to desired layer on display it is necessary to set the layer
+        -- ID for the structure.
+
+    RemoveZLayer( me         : mutable;
+                  theCView   : CView from Graphic3d;
+                  theLayerId : Integer from Standard )
+        is deferred;
+        ---Purpose: Remove Z layer from the specified view. All structures
+        -- displayed at the moment in layer will be displayed in default layer
+        -- ( the bottom-level z layer ). To unset layer ID from associated
+        -- structures use method UnsetZLayer (...).
+
+    UnsetZLayer( me         : mutable;
+                 theLayerId : Integer from Standard ) 
+        is deferred;
+        ---Purpose: Unset Z layer ID for all structures. The structure
+        -- indexes will be set to default layer ( the bottom-level z layer
+        -- with ID = 0 ).
+
+    ChangeZLayer( me            : mutable;
+                  theCStructure : CStructure from Graphic3d;
+                  theLayerId    : Integer from Standard )
+        is deferred;
+        ---Purpose: Change Z layer of a structure. The new z layer ID will
+        -- be used to define the associated layer for structure on display.
+
+    ChangeZLayer( me            : mutable;
+                  theCStructure : CStructure from Graphic3d;
+                  theCView      : CView from Graphic3d;
+                  theNewLayerId : Integer from Standard )
+        is deferred;
+        ---Purpose: Change Z layer of a structure already presented in view.
+
+    GetZLayer( me;
+               theCStructure : CStructure from Graphic3d )
+        returns Integer from Standard is deferred;
+        ---Purpose: Get Z layer ID of structure. If the structure doesn't
+        -- exists in graphic driver, the method returns -1.
+
     --------------------------
     -- Category: Class methods
     --------------------------

src/Graphic3d/Graphic3d_Structure.cdl

@@ -242,6 +242,19 @@ is
 	--	    method erase <me> and display <me> with the
 	--	    previous priority.
         
+        SetZLayer ( me         : mutable;
+                    theLayerId : Integer from Standard )
+           is static;
+        ---Purpose: Set Z layer ID for the structure. The Z layer mechanism
+        -- allows to display structures presented in higher layers in overlay
+        -- of structures in lower layers by switching off z buffer depth
+        -- test between layers
+
+        GetZLayer ( me )
+          returns Integer from Standard is static;
+        ---Purpose: Get Z layer ID of displayed structure. The method
+        -- returns -1 if the structure has no ID (deleted from graphic driver).
+
 	SetPick ( me		: mutable;
 		  AValue	: Boolean from Standard )
 		is static;

src/Graphic3d/Graphic3d_Structure.cxx

@@ -2553,3 +2553,27 @@ Standard_Address Graphic3d_Structure::CStructure () const {
   return Standard_Address (&MyCStructure);
 
 }
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+
+void Graphic3d_Structure::SetZLayer (const Standard_Integer theLayerId)
+{
+  // if the structure is not displayed, unable to change its display layer
+  if (IsDeleted ())
+    return;
+
+  MyStructureManager->ChangeZLayer (this, theLayerId);
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Integer Graphic3d_Structure::GetZLayer () const
+{
+  return MyStructureManager->GetZLayer (this);
+}

src/Graphic3d/Graphic3d_StructureManager.cdl

@@ -25,6 +25,7 @@ deferred class StructureManager from Graphic3d inherits TShared
 uses
 
 	Array2OfReal		from TColStd,
+        SequenceOfInteger       from TColStd,
 
 	GenId			from Aspect,
 	GraphicDevice           from Aspect,
@@ -272,6 +273,43 @@ is
 	---Purpose: Changes the display priority of the structure <AStructure>.
 	---Category: Private methods
 
+        ChangeZLayer ( me           : mutable;
+                       theStructure : Structure from Graphic3d;
+                       theLayerId   : Integer from Standard )
+           is deferred;
+        ---Purpose: Change Z layer for structure. The z layer mechanism allows
+        -- to display structures in higher layers in overlay of structures in
+        -- lower layers.
+
+        GetZLayer ( me;
+                    theStructure : Structure from Graphic3d )
+           returns Integer from Standard is deferred;
+        ---Purpose: Get Z layer ID assigned to structure. If the structure
+        -- has no layer ID (deleted from graphic driver), the method returns -1.
+
+        AddZLayer ( me : mutable;
+                    theLayerId : in out Integer from Standard )
+           returns Boolean from Standard is deferred;
+        ---Purpose: Add a new top-level Z layer and get its ID as
+        -- <theLayerId> value. The method returns Standard_False if the layer
+        -- can not be created. The z layer mechanism allows to display
+        -- structures in higher layers in overlay of structures in lower layers.
+
+        RemoveZLayer ( me : mutable;
+                       theLayerId : Integer from Standard )
+           returns Boolean from Standard is deferred;
+        ---Purpose: Remove Z layer with ID <theLayerId>. Method returns
+        -- Standard_False if the layer can not be removed or doesn't exists.
+        -- By default, there is always a default bottom-level layer that can't
+        -- be removed.
+
+        GetAllZLayers ( me;
+                        theLayerSeq : out SequenceOfInteger from TColStd )
+           is deferred;
+        ---Purpose: Return all Z layer ids in sequence ordered by level
+        -- from lowest layer to highest. The first layer ID in sequence is
+        -- the default layer that can't be removed.
+
 	CurrentId ( myclass )
 		returns Integer from Standard;
 	---Level: Internal

src/OpenGl/FILES

@@ -124,3 +124,5 @@ OpenGl_Context.hxx
 OpenGl_Context.cxx
 OpenGl_ArbVBO.hxx
 OpenGl_ExtFBO.hxx
+OpenGl_LayerList.cxx
+OpenGl_LayerList.hxx

src/OpenGl/OpenGl_GraphicDriver.hxx

@@ -285,6 +285,47 @@ public:
   Standard_EXPORT void FBOChangeViewport(const Graphic3d_CView& view,Graphic3d_PtrFrameBuffer& fboPtr,const Standard_Integer width,const Standard_Integer height);
   Standard_EXPORT Standard_Boolean Export(const Standard_CString theFileName,const Graphic3d_ExportFormat theFormat,const Graphic3d_SortType theSortType,const Standard_Integer theWidth,const Standard_Integer theHeight,const Graphic3d_CView& theView,const Aspect_CLayer2d& theLayerUnder,const Aspect_CLayer2d& theLayerOver,const Standard_Real thePrecision = 0.005,const Standard_Address theProgressBarFunc = NULL,const Standard_Address theProgressObject = NULL);
   
+  //! Add a new top-level z layer with ID <theLayerId> for <br>
+  //! the view. Z layers allow drawing structures in higher layers <br>
+  //! in foreground of structures in lower layers. To add a structure <br>
+  //! to desired layer on display it is necessary to set the layer <br>
+  //! index for the structure. <br>
+  Standard_EXPORT void AddZLayer(const Graphic3d_CView& theCView,
+                                 const Standard_Integer theLayerId);
+
+  //! Remove Z layer from the specified view. All structures <br>
+  //! displayed at the moment in layer will be displayed in default layer <br>
+  //! ( the bottom-level z layer ). To unset layer index from associated <br>
+  //! structures use method UnsetZLayer (...). <br>
+  Standard_EXPORT void RemoveZLayer(const Graphic3d_CView& theCView,
+                                    const Standard_Integer theLayerId);
+
+  //! Unset Z layer ID for all structures. The structure <br>
+  //! indexes will be set to default layer ( the bottom-level z layer with <br>
+  //! ID = 0 ). <br>
+  Standard_EXPORT void UnsetZLayer(const Standard_Integer theLayerId);
+
+  //! Change Z layer of a structure. The new z layer ID will <br>
+  //! be used to define the associated layer for structure on display. <br>
+  //! It is recommended to take care of redisplaying the structures already <br>
+  //! presented in view with previously set layer index. This is usually <br>
+  //! done by viewer manager. Z layers allow drawing structures in <br>
+  //! higher layers in foreground of structures in lower layers. <br>
+  Standard_EXPORT void ChangeZLayer(const Graphic3d_CStructure& theCStructure,
+                                    const Standard_Integer theLayerId);
+
+  //! Change Z layer of a structure already presented in view. <br>
+  //! It is recommended to update z layer of already <br>
+  //! displayed structures with this method before setting new z layer <br>
+  //! index to the structure. This is usually done by viewer manager. <br>
+  Standard_EXPORT void ChangeZLayer(const Graphic3d_CStructure& theCStructure,
+                                    const Graphic3d_CView& theCView,
+                                    const Standard_Integer theNewLayerId);
+
+  //! Get Z layer ID of the structure. If the structure doesn't exists in <br>
+  //! graphic driver, the method returns -1. <br>
+  Standard_EXPORT Standard_Integer GetZLayer(const Graphic3d_CStructure& theCStructure) const;
+
 public:
 
   //! Returns true if VBO usage does not forbidden.

src/OpenGl/OpenGl_GraphicDriver_4.cxx

@@ -115,3 +115,74 @@ void OpenGl_GraphicDriver::Structure (Graphic3d_CStructure& theCStructure)
   OpenGl_GraphicDriver::GetMapOfStructures().Bind (theCStructure.Id, aStructure);
   InvalidateAllWorkspaces();
 }
+
+//=======================================================================
+//function : ChangeZLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_GraphicDriver::ChangeZLayer (const Graphic3d_CStructure& theCStructure,
+                                         const Standard_Integer theLayer)
+{
+  if (!GetMapOfStructures().IsBound (theCStructure.Id))
+    return;
+
+  OpenGl_Structure* aStructure =
+    OpenGl_GraphicDriver::GetMapOfStructures().Find (theCStructure.Id);
+
+  aStructure->SetZLayer (theLayer);
+}
+
+//=======================================================================
+//function : ChangeZLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_GraphicDriver::ChangeZLayer (const Graphic3d_CStructure& theCStructure,
+                                         const Graphic3d_CView& theCView,
+                                         const Standard_Integer theNewLayerId)
+{
+  const OpenGl_CView *aCView = (const OpenGl_CView *)theCView.ptrView;
+
+  if (!GetMapOfStructures().IsBound (theCStructure.Id) || !aCView)
+    return;
+
+  OpenGl_Structure* aStructure =
+    OpenGl_GraphicDriver::GetMapOfStructures().Find (theCStructure.Id);
+
+  aCView->View->ChangeZLayer (aStructure, theNewLayerId);
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Integer OpenGl_GraphicDriver::GetZLayer (const Graphic3d_CStructure& theCStructure) const
+{
+  if (!GetMapOfStructures().IsBound (theCStructure.Id))
+    return -1;
+
+  OpenGl_Structure* aStructure = 
+    OpenGl_GraphicDriver::GetMapOfStructures().Find (theCStructure.Id);
+
+  return aStructure->GetZLayer();
+}
+
+//=======================================================================
+//function : UnsetZLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_GraphicDriver::UnsetZLayer (const Standard_Integer theLayerId)
+{
+  NCollection_DataMap<Standard_Integer, OpenGl_Structure*>::Iterator
+    aStructIt (GetMapOfStructures ());
+  
+  for( ; aStructIt.More (); aStructIt.Next ())
+  {
+    OpenGl_Structure* aStruct = aStructIt.ChangeValue ();
+    if (aStruct->GetZLayer () == theLayerId)
+      aStruct->SetZLayer (0);
+  }
+}

src/OpenGl/OpenGl_GraphicDriver_7.cxx

@@ -496,3 +496,29 @@ void OpenGl_GraphicDriver::SetBackFacingModel (const Graphic3d_CView& ACView)
   if (aCView)
     aCView->View->SetBackfacing(ACView.Backfacing);
 }
+
+//=======================================================================
+//function : AddZLayer
+//purpose  : 
+//=======================================================================
+
+void OpenGl_GraphicDriver::AddZLayer (const Graphic3d_CView& theCView,
+                                      const Standard_Integer theLayerId)
+{
+  const OpenGl_CView *aCView = (const OpenGl_CView *)theCView.ptrView;
+  if (aCView)
+    aCView->View->AddZLayer (theLayerId);
+}
+
+//=======================================================================
+//function : RemoveZLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_GraphicDriver::RemoveZLayer (const Graphic3d_CView& theCView,
+                                         const Standard_Integer theLayerId)
+{
+  const OpenGl_CView* aCView = (const OpenGl_CView *)theCView.ptrView;
+  if (aCView)
+    aCView->View->RemoveZLayer (theLayerId);
+}

src/OpenGl/OpenGl_LayerList.cxx

@@ -0,0 +1,243 @@
+// File:      OpenGl_LayerList.hxx
+// Created:   2 February 2012
+// Author:    Anton POLETAEV
+// Copyright: OPEN CASCADE 2012
+
+#include <OpenGl_LayerList.hxx>
+#include <OpenGl_tgl_all.hxx>
+#include <OpenGl_Structure.hxx>
+
+#include <InterfaceGraphic_Graphic3d.hxx>
+#include <InterfaceGraphic.hxx>
+
+//=======================================================================
+//function : OpenGl_LayerList
+//purpose  : Constructor
+//=======================================================================
+
+OpenGl_LayerList::OpenGl_LayerList (const Standard_Integer theNbPriorities)
+ : myNbPriorities (theNbPriorities),
+   myNbStructures (0)
+{
+  // insert default priority layer
+  myLayers.Append (OpenGl_PriorityList (myNbPriorities));
+  myLayerIds.Bind (0, myLayers.Length());
+}
+
+//=======================================================================
+//function : ~OpenGl_LayerList
+//purpose  : Destructor
+//=======================================================================
+
+OpenGl_LayerList::~OpenGl_LayerList ()
+{
+}
+
+//=======================================================================
+//function : defaultLayer
+//purpose  :
+//=======================================================================
+
+OpenGl_PriorityList& OpenGl_LayerList::defaultLayer()
+{
+  return myLayers.ChangeValue (1);
+}
+
+//=======================================================================
+//function : NbPriorities
+//purpose  : Method returns the number of available priorities
+//=======================================================================
+
+Standard_Integer OpenGl_LayerList::NbPriorities () const
+{
+  return myNbPriorities;
+}
+
+//=======================================================================
+//function : NbStructures
+//purpose  : Method returns the number of available structures
+//=======================================================================
+
+Standard_Integer OpenGl_LayerList::NbStructures () const
+{
+  return myNbStructures;
+}
+
+//=======================================================================
+//function : AddLayer
+//purpose  : 
+//=======================================================================
+
+void OpenGl_LayerList::AddLayer (const Standard_Integer theLayerId)
+{
+  if (HasLayer (theLayerId))
+    return;
+
+  // add the new layer
+  myLayers.Append (OpenGl_PriorityList (myNbPriorities));
+  myLayerIds.Bind (theLayerId, myLayers.Length());
+}
+
+//=======================================================================
+//function : HasLayer
+//purpose  : 
+//=======================================================================
+
+Standard_Boolean OpenGl_LayerList::HasLayer 
+  (const Standard_Integer theLayerId) const
+{
+  return myLayerIds.IsBound (theLayerId);
+}
+
+//=======================================================================
+//function : RemoveLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_LayerList::RemoveLayer (const Standard_Integer theLayerId)
+{
+  if (!HasLayer (theLayerId) || theLayerId == 0)
+    return;
+
+  Standard_Integer aRemovePos = myLayerIds.Find (theLayerId);
+  
+  // move all displayed structures to first layer
+  const OpenGl_PriorityList& aList = myLayers.Value (aRemovePos);
+  defaultLayer ().Append (aList);
+
+  // remove layer
+  myLayers.Remove (aRemovePos);
+  myLayerIds.UnBind (theLayerId);
+
+  // updated sequence indexes in map
+  OpenGl_LayerSeqIds::Iterator aMapIt (myLayerIds);
+  for ( ; aMapIt.More (); aMapIt.Next ())
+  {
+    Standard_Integer& aSeqIdx = aMapIt.ChangeValue ();
+    if (aSeqIdx > aRemovePos)
+      aSeqIdx--;
+  }
+}
+
+//=======================================================================
+//function : AddStructure
+//purpose  :
+//=======================================================================
+
+void OpenGl_LayerList::AddStructure (const OpenGl_Structure *theStructure,
+                                     const Standard_Integer  theLayerId,
+                                     const Standard_Integer  thePriority)
+{
+  // add structure to associated layer,
+  // if layer doesn't exists, display structure in default layer
+  OpenGl_PriorityList& aList = !HasLayer (theLayerId) ? defaultLayer () :
+    myLayers.ChangeValue (myLayerIds.Find (theLayerId));
+
+  aList.Add (theStructure, thePriority);
+  myNbStructures++;
+}
+
+//=======================================================================
+//function : RemoveStructure
+//purpose  : 
+//=======================================================================
+
+void OpenGl_LayerList::RemoveStructure (const OpenGl_Structure *theStructure,
+                                        const Standard_Integer  theLayerId)
+{
+  Standard_Integer aSeqPos = !HasLayer (theLayerId) ?
+    1 : myLayerIds.Find (theLayerId);
+  
+  OpenGl_PriorityList& aList = myLayers.ChangeValue (aSeqPos);
+
+  // remove structure from associated list
+  // if the structure is not found there,
+  // scan through layers and remove it
+  if (aList.Remove (theStructure) >= 0)
+  {
+    myNbStructures--;
+    return;
+  }
+  
+  // scan through layers and remove it
+  Standard_Integer aSeqId = 1;
+  OpenGl_SequenceOfLayers::Iterator anIts;
+  for (anIts.Init (myLayers); anIts.More (); anIts.Next (), aSeqId++)
+  {
+    OpenGl_PriorityList& aScanList = anIts.ChangeValue ();
+    if (aSeqPos == aSeqId)
+      continue;
+  
+    if (aScanList.Remove (theStructure) >= 0)
+    {
+      myNbStructures--;
+      return;
+    }
+  }
+}
+
+//=======================================================================
+//function : ChangeLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_LayerList::ChangeLayer (const OpenGl_Structure *theStructure,
+                                    const Standard_Integer  theOldLayerId,
+                                    const Standard_Integer  theNewLayerId)
+{
+  Standard_Integer aSeqPos = !HasLayer (theOldLayerId) ?
+    1 : myLayerIds.Find (theOldLayerId);
+  
+  OpenGl_PriorityList& aList = myLayers.ChangeValue (aSeqPos);
+  Standard_Integer aPriority;
+
+  // take priority and remove structure from list found by <theOldLayerId>
+  // if the structure is not found there, scan through all other layers
+  if ((aPriority = aList.Remove (theStructure)) >= 0)
+  {
+    myNbStructures--;
+    AddStructure (theStructure, theNewLayerId, aPriority);
+  }
+  else
+  {
+    // scan through layers and remove it
+    Standard_Integer aSeqId = 1;
+    OpenGl_SequenceOfLayers::Iterator anIts;
+    for (anIts.Init (myLayers); anIts.More (); anIts.Next (), aSeqId++)
+    {
+      OpenGl_PriorityList& aScanList = anIts.ChangeValue ();
+      if (aSeqPos == aSeqId)
+        continue;
+  
+      // try to remove structure and get priority value from this layer
+      if ((aPriority = aList.Remove (theStructure)) >= 0)
+      {
+        myNbStructures--;
+        AddStructure (theStructure, theNewLayerId, aPriority);
+        break;
+      }
+    }
+  }
+}
+
+//=======================================================================
+//function : Render
+//purpose  : Render this element
+//=======================================================================
+
+void OpenGl_LayerList::Render (const Handle(OpenGl_Workspace) &theWorkspace) const
+{
+  OpenGl_SequenceOfLayers::Iterator anIts;
+  for(anIts.Init (myLayers); anIts.More (); anIts.Next ())
+  {
+    const OpenGl_PriorityList& aList = anIts.Value ();
+    if (aList.NbStructures () > 0)
+    {
+      // separate depth buffers
+      glClear (GL_DEPTH_BUFFER_BIT);
+
+      // render priority list
+      aList.Render (theWorkspace);
+    }
+  }
+}

src/OpenGl/OpenGl_LayerList.hxx

@@ -0,0 +1,85 @@
+// File:      OpenGl_LayerList.hxx
+// Created:   2 February 2012
+// Author:    Anton POLETAEV
+// Copyright: OPEN CASCADE 2012
+
+#ifndef _OpenGl_LayerList_Header
+#define _OpenGl_LayerList_Header
+
+#include <OpenGl_PriorityList.hxx>
+
+#include <InterfaceGraphic_telem.hxx>
+
+#include <NCollection_Sequence.hxx>
+#include <NCollection_DataMap.hxx>
+
+class OpenGl_Structure;
+class Handle(OpenGl_Workspace);
+
+typedef NCollection_Sequence<OpenGl_PriorityList> OpenGl_SequenceOfLayers;
+typedef NCollection_DataMap<int, int> OpenGl_LayerSeqIds;
+
+class OpenGl_LayerList
+{
+ public:
+  
+  //! Constructor
+  OpenGl_LayerList (const Standard_Integer theNbPriorities = 11);
+  
+  //! Destructor
+  virtual ~OpenGl_LayerList ();
+  
+  //! Method returns the number of available priorities
+  Standard_Integer NbPriorities () const;
+
+  //! Number of displayed structures
+  Standard_Integer NbStructures () const;
+
+  //! Insert a new layer with id.
+  void AddLayer (const Standard_Integer theLayerId);
+  
+  //! Check whether the layer with given id is already created.
+  Standard_Boolean HasLayer (const Standard_Integer theLayerId) const;
+  
+  //! Remove layer by its id.
+  void RemoveLayer (const Standard_Integer theLayerId);
+  
+  //! Add structure to list with given priority. The structure will be inserted
+  //! to specified layer. If the layer isn't found, the structure will be put
+  //! to default bottom-level layer.
+  void AddStructure (const OpenGl_Structure *theStructure,
+                     const Standard_Integer  theLayerId,
+                     const Standard_Integer  thePriority);
+  
+  //! Remove structure from structure list and return its previous priority
+  void RemoveStructure (const OpenGl_Structure *theStructure,
+                        const Standard_Integer  theZLayerId);
+  
+  //! Change structure z layer
+  //! If the new layer is not presented, the structure will be displayed
+  //! in default z layer
+  void ChangeLayer (const OpenGl_Structure *theStructure,
+                    const Standard_Integer  theOldLayerId,
+                    const Standard_Integer  theNewLayerId);
+  
+  //! Render this element
+  void Render (const Handle(OpenGl_Workspace) &theWorkspace) const;
+  
+ private:
+  
+  //! Get default layer
+  OpenGl_PriorityList& defaultLayer ();
+  
+ protected:
+
+  // number of structures temporary put to default layer
+  OpenGl_SequenceOfLayers myLayers;
+  OpenGl_LayerSeqIds      myLayerIds;
+  Standard_Integer        myNbPriorities;
+  Standard_Integer        myNbStructures;
+
+ public:
+  IMPLEMENT_MEMORY_OPERATORS
+};
+
+#endif //_OpenGl_LayerList_Header

src/OpenGl/OpenGl_PriorityList.cxx

@@ -20,7 +20,7 @@ void OpenGl_PriorityList::Add (const OpenGl_Structure *AStructure,const Standard
 
 /*----------------------------------------------------------------------*/
 
-void OpenGl_PriorityList::Remove (const OpenGl_Structure *AStructure)
+Standard_Integer OpenGl_PriorityList::Remove (const OpenGl_Structure *AStructure)
 {
   const Standard_Integer aNbPr = myArray.Length();
   Standard_Integer i = 0;
@@ -34,10 +34,12 @@ void OpenGl_PriorityList::Remove (const OpenGl_Structure *AStructure)
       {
         aSeq.Remove(its);
         myNbStructures--;
-        return;
+        return i;
       }
     }
   }
+
+  return -1;
 }
 
 /*----------------------------------------------------------------------*/
@@ -54,4 +56,37 @@ void OpenGl_PriorityList::Render (const Handle(OpenGl_Workspace) &AWorkspace) co
   }
 }
 
-/*----------------------------------------------------------------------*/
+//=======================================================================
+//function : Append
+//purpose  : 
+//=======================================================================
+
+Standard_Boolean OpenGl_PriorityList::Append (const OpenGl_PriorityList& theOther)
+{
+  // the source priority list shouldn't have more priorities
+  const Standard_Integer aNbPriorities = theOther.NbPriorities ();
+  if (aNbPriorities > NbPriorities ())
+    return Standard_False;
+
+  // add all structures to destination priority list
+  Standard_Integer aIdx = 0;
+  OpenGl_SequenceOfStructure::Iterator anIts;
+  for (; aIdx < aNbPriorities; aIdx++)
+  {
+    const OpenGl_SequenceOfStructure& aSeq = theOther.myArray (aIdx);
+    for (anIts.Init (aSeq); anIts.More (); anIts.Next ())
+      Add (anIts.Value (), aIdx);
+  }
+
+  return Standard_True;
+}
+
+//=======================================================================
+//function : NbPriorities
+//purpose  : 
+//=======================================================================
+
+Standard_Integer OpenGl_PriorityList::NbPriorities() const
+{
+  return myArray.Length();
+}

src/OpenGl/OpenGl_PriorityList.hxx

@@ -23,15 +23,26 @@ class OpenGl_PriorityList
  public:
 
   OpenGl_PriorityList (const Standard_Integer ANbPriorities = 11) : myArray(0,(ANbPriorities-1)), myNbStructures(0) {}
+
   virtual ~OpenGl_PriorityList () {}
 
   void Add (const OpenGl_Structure *AStructure, const Standard_Integer APriority);
-  void Remove (const OpenGl_Structure *AStructure);
+
+  //! Remove structure and returns its priority, if the structure is not found,
+  //! method returns negative value
+  Standard_Integer Remove (const OpenGl_Structure *AStructure);
 
   Standard_Integer NbStructures () const { return myNbStructures; }
 
   void Render (const Handle(OpenGl_Workspace) &AWorkspace) const;
 
+  //! Returns the number of available priority levels
+  Standard_Integer NbPriorities() const;
+
+  //! Append priority list of acceptable type (with similar number of priorities
+  //! or less). Returns Standard_False if the list can not be accepted.
+  Standard_Boolean Append (const OpenGl_PriorityList& theOther);
+
  protected:
 
   OpenGl_ArrayOfStructure myArray;

src/OpenGl/OpenGl_Structure.cxx

@@ -36,7 +36,8 @@ OpenGl_Structure::OpenGl_Structure ()
   myAspectText(NULL),
   myHighlightBox(NULL),
   myHighlightColor(NULL),
-  myNamedStatus(0)
+  myNamedStatus(0),
+  myZLayer(0)
 {
 }
 
@@ -445,4 +446,22 @@ void OpenGl_Structure::Render (const Handle(OpenGl_Workspace) &AWorkspace) const
   AWorkspace->NamedStatus = named_status;
 }
 
-/*----------------------------------------------------------------------*/
+//=======================================================================
+//function : SetZLayer
+//purpose  : 
+//=======================================================================
+
+void OpenGl_Structure::SetZLayer (const Standard_Integer theLayerIndex)
+{
+  myZLayer = theLayerIndex;
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  : 
+//=======================================================================
+
+Standard_Integer OpenGl_Structure::GetZLayer () const
+{
+  return myZLayer;
+}

src/OpenGl/OpenGl_Structure.hxx

@@ -52,6 +52,12 @@ class OpenGl_Structure : public OpenGl_Element
   void RemoveGroup (const OpenGl_Group *);
   void Clear ();
 
+  //! Set z layer ID to display the structure in specified layer
+  void SetZLayer (const Standard_Integer theLayerIndex);
+
+  //! Get z layer ID
+  Standard_Integer GetZLayer () const;
+
   virtual void Render (const Handle(OpenGl_Workspace) &AWorkspace) const;
   
  protected:
@@ -70,6 +76,7 @@ class OpenGl_Structure : public OpenGl_Element
   //Structure_LABVisibility
   //Structure_LABPick
   int myNamedStatus; //Structure_LABNameSet
+  int myZLayer;
 
   OpenGl_ListOfStructure myConnected;
 

src/OpenGl/OpenGl_View.hxx

@@ -26,9 +26,8 @@
 #include <Visual3d_TypeOfSurfaceDetail.hxx>
 
 #include <OpenGl_telem_view.hxx>
-
+#include <OpenGl_LayerList.hxx>
 #include <OpenGl_Light.hxx>
-#include <OpenGl_PriorityList.hxx>
 
 #include <Handle_OpenGl_Trihedron.hxx>
 #include <Handle_OpenGl_GraduatedTrihedron.hxx>
@@ -135,8 +134,27 @@ class OpenGl_View : public MMgt_TShared
   const TEL_TRANSFORM_PERSISTENCE * BeginTransformPersistence ( const TEL_TRANSFORM_PERSISTENCE *ATransPers );
   void EndTransformPersistence ();
 
-  void DisplayStructure (const OpenGl_Structure *AStructure, const Standard_Integer APriority) { myStructures.Add(AStructure,APriority); }
+  //! Add structure to display list with specified priority.
-  void EraseStructure (const OpenGl_Structure *AStructure) { myStructures.Remove(AStructure); }
+  //! The structure will be added to associated with it z layer.
+  //! If the z layer is not presented in the view, the structure will
+  //! be displayed in default bottom-level z layer.
+  void DisplayStructure (const OpenGl_Structure *theStructure,
+                         const Standard_Integer  thePriority);
+
+  //! Erase structure from display list.
+  void EraseStructure (const OpenGl_Structure *theStructure);
+
+  //! Insert a new top-level z layer with ID <theLayerId>
+  void AddZLayer (const Standard_Integer theLayerId);
+
+  //! Remove a z layer with ID <theLayerId>
+  void RemoveZLayer (const Standard_Integer theLayerId);
+
+  //! Display structure in z layer with ID <theNewLayerId>
+  //! If the layer with ID <theNewLayerId> is not presented in the view,
+  //! the structure will be displayed in default bottom-level layer.
+  void ChangeZLayer (const OpenGl_Structure *theStructure,
+                     const Standard_Integer  theNewLayerId);
 
   void CreateBackgroundTexture (const Standard_CString AFileName, const Aspect_FillMethod AFillStyle);
   void SetBackgroundTextureStyle (const Aspect_FillMethod FillStyle);
@@ -197,7 +215,7 @@ class OpenGl_View : public MMgt_TShared
 
   //View_LABDepthCueing - fixed index used
 
-  OpenGl_PriorityList myStructures;
+  OpenGl_LayerList myZLayers;
 
   int myAnimationListIndex;
   Standard_Boolean myAnimationListReady;

src/OpenGl/OpenGl_View_2.cxx

@@ -33,6 +33,7 @@
 #include <OpenGl_Trihedron.hxx>
 #include <OpenGl_GraduatedTrihedron.hxx>
 #include <OpenGl_PrinterContext.hxx>
+#include <OpenGl_Structure.hxx>
 
 /*----------------------------------------------------------------------*/
 /*
@@ -1231,7 +1232,8 @@ D = -[Px,Py,Pz] dot |Nx|
 //ExecuteViewDisplay
 void OpenGl_View::RenderStructs (const Handle(OpenGl_Workspace) &AWorkspace)
 {
-  if ( myStructures.NbStructures() <= 0 ) return;
+  if ( myZLayers.NbStructures() <= 0 )
+    return;
 
   glPushAttrib ( GL_DEPTH_BUFFER_BIT );
 
@@ -1261,7 +1263,7 @@ void OpenGl_View::RenderStructs (const Handle(OpenGl_Workspace) &AWorkspace)
     }
   }
 
-  myStructures.Render(AWorkspace);
+  myZLayers.Render (AWorkspace);
 
   //TsmPopAttri(); /* restore previous graphics context; before update lights */
 
@@ -1511,4 +1513,57 @@ void OpenGl_View::SetBackgroundGradientType (const Aspect_GradientFillMethod ATy
   myBgGradient.type = AType;
 }
 
-/*----------------------------------------------------------------------*/
+//=======================================================================
+//function : AddZLayer
+//purpose  : 
+//=======================================================================
+
+void OpenGl_View::AddZLayer (const Standard_Integer theLayerId)
+{
+  myZLayers.AddLayer (theLayerId);
+}
+
+//=======================================================================
+//function : RemoveZLayer
+//purpose  : 
+//=======================================================================
+
+void OpenGl_View::RemoveZLayer (const Standard_Integer theLayerId)
+{
+  myZLayers.RemoveLayer (theLayerId);
+}
+
+//=======================================================================
+//function : DisplayStructure
+//purpose  : 
+//=======================================================================
+
+void OpenGl_View::DisplayStructure (const OpenGl_Structure *theStructure,
+                                    const Standard_Integer  thePriority)
+{
+  Standard_Integer aZLayer = theStructure->GetZLayer ();
+  myZLayers.AddStructure (theStructure, aZLayer, thePriority);
+}
+
+//=======================================================================
+//function : EraseStructure
+//purpose  : 
+//=======================================================================
+
+void OpenGl_View::EraseStructure (const OpenGl_Structure *theStructure)
+{
+  Standard_Integer aZLayer = theStructure->GetZLayer ();
+  myZLayers.RemoveStructure (theStructure, aZLayer);
+}
+
+//=======================================================================
+//function : ChangeZLayer
+//purpose  :
+//=======================================================================
+
+void OpenGl_View::ChangeZLayer (const OpenGl_Structure *theStructure,
+                                const Standard_Integer  theNewLayerId)
+{
+  Standard_Integer anOldLayer = theStructure->GetZLayer ();
+  myZLayers.ChangeLayer (theStructure, anOldLayer, theNewLayerId);
+}

src/PrsMgr/PrsMgr_PresentableObject.cdl

@@ -234,7 +234,21 @@ is
     
    UpdateLocation(me:mutable;P : mutable Presentation from Prs3d) is virtual;
     
+   SetZLayer ( me         : mutable;
+               thePrsMgr  : PresentationManager from PrsMgr;
+               theLayerId : Integer from Standard )
+     is virtual;
+   ---Purpose: Set Z layer ID and update all presentations of
+   -- the presentable object. The layer can be set only for displayed object.
+   -- If all object presentations are removed, the layer ID will be set to 
+   -- default value when computing presentation. The layers mechanism allows
+   -- drawing objects in higher layers in overlay of objects in lower layers.
     
+   GetZLayer ( me;
+               thePrsMgr  : PresentationManager from PrsMgr )
+     returns Integer from Standard is static;
+   ---Purpose: Get ID of Z layer. If no presentations of object is displayed,
+   -- and layer ID is unavailable, the -1 value is returned.
  
 fields
     myPresentations: Presentations from PrsMgr is protected;

src/PrsMgr/PrsMgr_PresentableObject.cxx

@@ -335,3 +335,28 @@ gp_Pnt  PrsMgr_PresentableObject::GetTransformPersistencePoint() const
 {
   return gp_Pnt( myTransformPersistence.Point.x, myTransformPersistence.Point.y, myTransformPersistence.Point.z );
 }
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+void PrsMgr_PresentableObject::SetZLayer 
+  (const Handle(PrsMgr_PresentationManager)& thePrsMgr,
+   const Standard_Integer theLayerId)
+{
+  if (!thePrsMgr.IsNull())
+    thePrsMgr->SetZLayer (this, theLayerId);
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :
+//=======================================================================
+Standard_Integer PrsMgr_PresentableObject::GetZLayer 
+  (const Handle(PrsMgr_PresentationManager)& thePrsMgr) const
+{
+  if (!thePrsMgr.IsNull())
+    return thePrsMgr->GetZLayer (this);
+
+  return -1;
+}

src/PrsMgr/PrsMgr_Presentation.cdl

@@ -48,6 +48,15 @@ is
     SetDisplayPriority(me:mutable;aNewPrior:Integer from Standard)
     is deferred private;
 
+    SetZLayer ( me : mutable;
+                theLayerId : Integer from Standard )
+      is deferred private;
+    ---Purpose: Set Z layer ID for the presentation
+
+    GetZLayer ( me )
+      returns Integer from Standard is deferred private;
+    ---Purpose: Get Z layer ID for the presentation
+
     Clear(me: mutable) 
     is deferred private;
     

src/PrsMgr/PrsMgr_Presentation2d.cdl

@@ -51,6 +51,14 @@ is
     SetDisplayPriority(me:mutable;aNewPrior:Integer from Standard)
     is redefined static private;
    
+    SetZLayer ( me : mutable;
+                theLayerId : Integer from Standard )
+      is redefined static private;
+    ---Purpose: Set Z layer ID for the presentation
+
+    GetZLayer ( me )
+      returns Integer from Standard is redefined static private;
+    ---Purpose: Get Z layer ID for the presentation
 
     Clear(me:mutable)
     	---Purpose: removes the whole content of the presentation.

src/PrsMgr/PrsMgr_Presentation2d.cxx

@@ -78,3 +78,22 @@ Standard_Integer PrsMgr_Presentation2d::Offset () const {
 
 void PrsMgr_Presentation2d::Destroy () {
 }
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+
+void PrsMgr_Presentation2d::SetZLayer (Standard_Integer theLayer)
+{
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Integer PrsMgr_Presentation2d::GetZLayer () const
+{
+  return 0;
+}

src/PrsMgr/PrsMgr_Presentation3d.cdl

@@ -58,6 +58,15 @@ is
     SetDisplayPriority(me:mutable;aNewPrior:Integer from Standard)
     is redefined static private;
 
+    SetZLayer ( me : mutable;
+                theLayerId : Integer from Standard )
+      is redefined static private;
+    ---Purpose: Set Z layer ID for the presentation
+
+    GetZLayer ( me )
+      returns Integer from Standard is redefined static private;
+    ---Purpose: Get Z layer ID for the presentation
+
     Clear(me:mutable)
     ---Purpose: removes the whole content of the presentation.
     --          Does not remove the other connected presentations.

src/PrsMgr/PrsMgr_Presentation3d.cxx

@@ -308,3 +308,23 @@ void PrsMgr_Presentation3d::Destroy () {
     myStructure->Clear();
   myStructure.Nullify();
 }
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+
+void PrsMgr_Presentation3d::SetZLayer (Standard_Integer theLayerId)
+{
+  myStructure->SetZLayer (theLayerId);
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :  
+//=======================================================================
+
+Standard_Integer PrsMgr_Presentation3d::GetZLayer () const
+{
+  return myStructure->GetZLayer ();
+}

src/PrsMgr/PrsMgr_PresentationManager.cdl

@@ -79,6 +79,19 @@ is
 	-- aPresentableObject in this framework with the
 	-- display mode aMode.
     
+    SetZLayer ( me                   : mutable;
+                thePresentableObject : PresentableObject from PrsMgr;
+                theLayerId           : Integer from Standard )
+      is static;
+    ---Purpose: Set Z layer ID for all presentations of the object.
+
+    GetZLayer ( me;
+                thePresentableObject : PresentableObject from PrsMgr )
+      returns Integer from Standard is static;
+    ---Purpose: Get Z layer ID assigned to all presentations of the object.
+    -- Method returns -1 value if object has no presentations and is
+    -- impossible to get layer index.
+    
     IsDisplayed(me;aPresentableObject: PresentableObject from PrsMgr;
                 aMode: Integer from Standard = 0) 
         ---Purpose: Returns true if the presentation of the presentable

src/PrsMgr/PrsMgr_PresentationManager.cxx

@@ -204,6 +204,12 @@ void PrsMgr_PresentationManager::AddPresentation
     Handle(PrsMgr_Presentation) P = newPresentation(aPresentableObject);
     aPresentableObject->Presentations().Append(PrsMgr_ModedPresentation(P,aMode));
     aPresentableObject->Fill(this,P,aMode);
+
+    // set layer index accordingly to object's presentations
+    Standard_Integer aZLayerId = GetZLayer (aPresentableObject);
+    if (aZLayerId >= 0)
+      P->SetZLayer (aZLayerId);
+
     P->SetUpdateStatus(Standard_False);
 }
 
@@ -222,3 +228,39 @@ void PrsMgr_PresentationManager::RemovePresentation(const Handle(PrsMgr_Presenta
   }
 }
 
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+
+void PrsMgr_PresentationManager::SetZLayer 
+  (const Handle(PrsMgr_PresentableObject)& thePresentableObject,
+   const Standard_Integer theLayerId)
+{
+  PrsMgr_Presentations& aPresentations = thePresentableObject->Presentations();
+  for (Standard_Integer aIdx = 1; aIdx <= aPresentations.Length (); aIdx++)
+  {
+    Handle(PrsMgr_Presentation) aPrs = aPresentations (aIdx).Presentation ();
+    if (aPrs->PresentationManager () == this)
+      aPrs->SetZLayer (theLayerId);
+  }
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Integer PrsMgr_PresentationManager::GetZLayer 
+  (const Handle(PrsMgr_PresentableObject)& thePresentableObject) const
+{
+  PrsMgr_Presentations& aPresentations = thePresentableObject->Presentations();
+  for (Standard_Integer aIdx = 1; aIdx <= aPresentations.Length (); aIdx++)
+  {
+    Handle(PrsMgr_Presentation) aPrs = aPresentations (aIdx).Presentation ();
+    if (aPrs->PresentationManager () == this)
+      return aPrs->GetZLayer ();
+  }
+  
+  return -1;
+}

src/SelectMgr/SelectMgr_EntityOwner.cdl

@@ -134,6 +134,12 @@ is
     --          Hilight for SelectableObject when the owner is detected. By default 
     --          it always return FALSE.  
     
+    SetZLayer ( me         : mutable;
+                thePrsMgr  : PresentationManager from PrsMgr;
+                theLayerId : Integer from Standard )
+      is virtual;
+    ---Purpose: Set Z layer ID and update all presentations.
+
 fields
 
     mySelectable        : SOPtr;

src/SelectMgr/SelectMgr_EntityOwner.cxx

@@ -134,3 +134,13 @@ Standard_Boolean SelectMgr_EntityOwner::IsForcedHilight () const
 {
   return Standard_False;
 }
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+void SelectMgr_EntityOwner::SetZLayer 
+  (const Handle(PrsMgr_PresentationManager)& thePrsMgr,
+   const Standard_Integer theLayerId)
+{
+}

src/SelectMgr/SelectMgr_SelectableObject.cdl

@@ -26,6 +26,7 @@ uses
     SequenceOfSelection   from SelectMgr,
     TypeOfPresentation3d  from PrsMgr,
     Presentation          from Prs3d,
+    PresentationManager   from PrsMgr,
     PresentationManager3d from PrsMgr,
     SequenceOfOwner       from SelectMgr,
     NameOfColor           from Quantity,
@@ -170,6 +171,16 @@ is
     GetSelectPresentation(   me: mutable;
     	    	    	     TheMgr:  PresentationManager3d from PrsMgr )  returns Presentation from Prs3d  is  static; 
 	
+   SetZLayer ( me         : mutable;
+               thePrsMgr  : PresentationManager from PrsMgr;
+               theLayerId : Integer from Standard )
+     is redefined virtual;
+   ---Purpose: Set Z layer ID and update all presentations of
+   -- the selectable object. The layer can be set only for displayed object.
+   -- If all object presentations are removed, the layer ID will be set to 
+   -- default value when computing presentation. The layers mechanism allows 
+   -- drawing objects in higher layers in overlay of objects in lower layers.
+
 fields
 
     myselections        : SequenceOfSelection is protected;

src/SelectMgr/SelectMgr_SelectableObject.cxx

@@ -307,3 +307,42 @@ Handle(Prs3d_Presentation) SelectMgr_SelectableObject::GetSelectPresentation( co
   return mySelectionPrs;
 }
 
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+void SelectMgr_SelectableObject::SetZLayer 
+  (const Handle(PrsMgr_PresentationManager)& thePrsMgr,
+   const Standard_Integer theLayerId)
+{
+  if (thePrsMgr.IsNull())
+    return;
+
+  // update own presentations
+  PrsMgr_PresentableObject::SetZLayer (thePrsMgr, theLayerId);
+
+  // update selection presentations
+  if (!mySelectionPrs.IsNull())
+    mySelectionPrs->SetZLayer (theLayerId);
+
+  if (!myHilightPrs.IsNull())
+    myHilightPrs->SetZLayer (theLayerId);
+
+  // update all entity owner presentations
+  for (Init (); More () ;Next ())
+  {
+    const Handle(SelectMgr_Selection)& aSel = CurrentSelection();
+    for (aSel->Init (); aSel->More (); aSel->Next ())
+    {
+      Handle(Select3D_SensitiveEntity) aEntity = 
+        Handle(Select3D_SensitiveEntity)::DownCast (aSel->Sensitive());
+      if (!aEntity.IsNull())
+      {
+        Handle(SelectMgr_EntityOwner) aOwner = 
+          Handle(SelectMgr_EntityOwner)::DownCast (aEntity->OwnerId());
+        if (!aOwner.IsNull())
+          aOwner->SetZLayer (thePrsMgr, theLayerId);
+      }
+    }
+  }
+}

src/StdSelect/StdSelect_BRepOwner.cdl

@@ -134,6 +134,12 @@ is
     SetLocation(me:mutable; aLoc : Location from TopLoc) is redefined;
     ResetLocation(me:mutable) is redefined;
 
+    SetZLayer ( me         : mutable;
+                thePrsMgr  : PresentationManager from PrsMgr;
+                theLayerId : Integer from Standard )
+      is redefined virtual;
+    ---Purpose: Set Z layer ID and update all presentations.
+
 fields
     myPrsSh   		: Shape   from StdSelect; 
     myCurMode 		: Integer from Standard;

src/StdSelect/StdSelect_BRepOwner.cxx

@@ -89,15 +89,28 @@ void StdSelect_BRepOwner::Hilight(const Handle(PrsMgr_PresentationManager)& PM,
         myPrsSh.Nullify();
     }
 
+    // generate new presentable shape
     if(myPrsSh.IsNull())
       myPrsSh = new StdSelect_Shape (myShape);
-  }  
 
+    // highlight and set layer
+    PM->Highlight (myPrsSh, M);
+    Handle(SelectMgr_SelectableObject) aSel = Selectable();
+    if (!aSel.IsNull())
+    {
+      Standard_Integer aLayer = aSel->GetZLayer (PM);
+      if (aLayer >= 0)
+        PM->SetZLayer (myPrsSh, aLayer);
+    }
+  }  
+  else
+  {
     if(myPrsSh.IsNull())
       PM->Highlight(Selectable(),M);
     else
       PM->Highlight(myPrsSh,M);
   }
+}
 
 void StdSelect_BRepOwner::Hilight()
 {}
@@ -122,8 +135,11 @@ void StdSelect_BRepOwner::HilightWithColor(const Handle(PrsMgr_PresentationManag
         myPrsSh.Nullify();
     }
 
-    if(myPrsSh.IsNull()){
+    // generate new presentable shape
-      if(HasLocation()){
+    if(myPrsSh.IsNull())
+    {
+      if(HasLocation())
+      {
         TopLoc_Location lbid = Location() * myShape.Location();
         TopoDS_Shape ShBis = myShape.Located(lbid);
         myPrsSh = new StdSelect_Shape(ShBis);
@@ -131,12 +147,25 @@ void StdSelect_BRepOwner::HilightWithColor(const Handle(PrsMgr_PresentationManag
       else
         myPrsSh = new StdSelect_Shape(myShape);
     }
+
+    // highlight with color and set layer
+    PM->Color (myPrsSh, aCol, M);
+    Handle(SelectMgr_SelectableObject) aSel = Selectable();
+    if (!aSel.IsNull())
+    {
+      Standard_Integer aLayer = aSel->GetZLayer (PM);
+      if (aLayer >= 0)
+        PM->SetZLayer (myPrsSh, aLayer);
     }
+  }
+  else
+  {
     if(myPrsSh.IsNull())
       PM->Color(Selectable(),aCol,M);
     else
       PM->Color(myPrsSh,aCol,M);
   }
+}
 
 void StdSelect_BRepOwner::Unhilight(const Handle(PrsMgr_PresentationManager)& PM,
 				    const Standard_Integer aMode)
@@ -173,8 +202,8 @@ void StdSelect_BRepOwner::SetLocation(const TopLoc_Location& aLoc)
   // set the update flag and then recompute myPrsSh on hilighting
   if (!myPrsSh.IsNull())
     myPrsSh->SetToUpdate();
- 
 }
+
 void StdSelect_BRepOwner::ResetLocation()
 {
   SelectMgr_EntityOwner::ResetLocation();
@@ -183,5 +212,16 @@ void StdSelect_BRepOwner::ResetLocation()
   // set the update flag and then recompute myPrsSh on hilighting
   if (!myPrsSh.IsNull())
     myPrsSh->SetToUpdate();
-
+}
+
+//=======================================================================
+//function : SetZLayer
+//purpose  :
+//=======================================================================
+void StdSelect_BRepOwner::SetZLayer 
+  (const Handle(PrsMgr_PresentationManager)& thePrsMgr,
+   const Standard_Integer theLayerId)
+{
+  if (!myPrsSh.IsNull())
+    thePrsMgr->SetZLayer (myPrsSh, theLayerId);
 }

src/V3d/V3d_Viewer.cdl

@@ -43,6 +43,7 @@ uses
         Plane from V3d,
         ListOfTransient from V3d,
         ListIteratorOfListOfTransient from TColStd,
+        SequenceOfInteger from TColStd,
         TypeOfView from V3d,
         Vector from Graphic3d,
         ViewManager from Visual3d,
@@ -656,6 +657,31 @@ is
         ---Purpose:
         -- Display grid echo at requested point in the view.
 
+        AddZLayer ( me : mutable;
+                    theLayerId : in out Integer from Standard )
+           returns Boolean from Standard is static;
+        ---Purpose: Add a new top-level Z layer to all managed views and get
+        -- its ID as <theLayerId> value. The Z layers are controlled entirely
+        -- by viewer, it is not possible to add a layer to a
+        -- particular view. The method returns Standard_False if the layer can
+        -- not be created. The layer mechanism allows to display structures
+        -- in higher layers in overlay of structures in lower layers.
+
+        RemoveZLayer ( me : mutable;
+                       theLayerId : Integer from Standard )
+           returns Boolean from Standard is static;
+        ---Purpose: Remove Z layer with ID <theLayerId>. Method returns
+        -- Standard_False if the layer can not be removed or doesn't exists.
+        -- By default, there are always default bottom-level layer that can't
+        -- be removed.
+
+        GetAllZLayers ( me;
+                        theLayerSeq : out SequenceOfInteger from TColStd )
+           is static;
+        ---Purpose: Return all Z layer ids in sequence ordered by overlay level
+        -- from lowest layer to highest ( foreground ). The first layer ID
+        -- in sequence is the default layer that can't be removed.
+
 fields
 
         MyViewer:               ViewManager from Visual3d ;

src/V3d/V3d_Viewer.cxx

@@ -366,3 +366,33 @@ void V3d_Viewer::DelPlane( const Handle(V3d_Plane)& ThePlane ) {
   
   MyDefinedPlanes.Remove(ThePlane);
 }
+
+//=======================================================================
+//function : AddZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Boolean V3d_Viewer::AddZLayer (Standard_Integer& theLayerId)
+{
+  return MyViewer->AddZLayer (theLayerId);
+}
+
+//=======================================================================
+//function : RemoveZLayer
+//purpose  : 
+//=======================================================================
+
+Standard_Boolean V3d_Viewer::RemoveZLayer (const Standard_Integer theLayerId)
+{
+  return MyViewer->RemoveZLayer (theLayerId);
+}
+
+//=======================================================================
+//function : GetAllZLayers
+//purpose  :
+//=======================================================================
+
+void V3d_Viewer::GetAllZLayers (TColStd_SequenceOfInteger& theLayerSeq) const
+{
+  MyViewer->GetAllZLayers (theLayerSeq);
+}

src/ViewerTest/ViewerTest_ObjectCommands.cxx

@@ -4198,6 +4198,71 @@ static Standard_Integer VSegment (Draw_Interpretor& di,
   return 0;
 }
 
+//=======================================================================
+//function : VObjZLayer
+//purpose  : Set or get z layer id for presentable object
+//=======================================================================
+
+static Standard_Integer VObjZLayer (Draw_Interpretor& di,
+                                    Standard_Integer argc,
+                                    const char ** argv)
+{
+  Handle(AIS_InteractiveContext) aContext = ViewerTest::GetAISContext();
+  if (aContext.IsNull())
+  {
+    di << argv[0] << "Call 'vinit' before!\n";
+    return 1;
+  }
+
+  // get operation
+  TCollection_AsciiString aOperation;
+  if (argc >= 2)
+    aOperation = TCollection_AsciiString (argv [1]);
+
+  // check for correct arguments
+  if (!(argc == 4 && aOperation.IsEqual ("set")) &&
+      !(argc == 3 && aOperation.IsEqual ("get")))
+  {
+    di << "Usage : " << argv[0] << " set/get object [layerid]\n";
+    di << " set - set layer id for interactive object, layerid - z layer id\n";
+    di << " get - get layer id of interactive object\n";
+    di << " argument layerid should be passed for set operation only\n";
+    return 1;
+  }
+
+  // find object
+  TCollection_AsciiString aName (argv[2]);
+  ViewerTest_DoubleMapOfInteractiveAndName& aMap = GetMapOfAIS();
+  if (!aMap.IsBound2 (aName))
+  {
+    di << "Use 'vdisplay' before" << "\n";
+    return 1;
+  }
+
+  // find interactive object
+  Handle(Standard_Transient) anObj = GetMapOfAIS().Find2 (aName);
+  Handle(AIS_InteractiveObject) anInterObj =
+    Handle(AIS_InteractiveObject)::DownCast (anObj);
+  if (anInterObj.IsNull())
+  {
+    di << "Not an AIS interactive object!\n";
+    return 1;
+  }
+
+  // process operation
+  if (aOperation.IsEqual ("set"))
+  {
+    Standard_Integer aLayerId = atoi (argv [3]);
+    aContext->SetZLayer (anInterObj, aLayerId);
+  }
+  else if (aOperation.IsEqual ("get"))
+  {
+    di << "Z layer id: " << aContext->GetZLayer (anInterObj);
+  }
+  
+  return 0;
+}
+
 //=======================================================================
 //function : ObjectsCommands
 //purpose  :
@@ -4302,4 +4367,8 @@ void ViewerTest::ObjectCommands(Draw_Interpretor& theCommands)
   theCommands.Add("vsegment",
     "vsegment Name PointName PointName", 
     __FILE__, VSegment,group);
+
+  theCommands.Add("vobjzlayer",
+    "vobjzlayer : set/get object [layerid] - set or get z layer id for the interactive object",
+    __FILE__, VObjZLayer, group);
 }

src/ViewerTest/ViewerTest_ViewerCommands.cxx

@@ -26,6 +26,7 @@
 #include <Draw_Appli.hxx>
 #include <Aspect_PrintAlgo.hxx>
 #include <Image_PixMap.hxx>
+#include <TColStd_SequenceOfInteger.hxx>
 
 #ifndef WNT
 #include <Graphic3d_GraphicDevice.hxx>
@@ -2060,6 +2061,86 @@ static int VPrintView (Draw_Interpretor& di, Standard_Integer argc,
 #endif
 }
 
+//==============================================================================
+//function : VZLayer
+//purpose  : Test z layer operations for v3d viewer
+//==============================================================================
+static int VZLayer (Draw_Interpretor& di, Standard_Integer argc, const char** argv)
+{
+  Handle(AIS_InteractiveContext) aContextAIS = ViewerTest::GetAISContext ();
+  if (aContextAIS.IsNull())
+  {
+    di << "Call vinit before!\n";
+    return 1;
+  }
+  else if (argc < 2)
+  {
+    di << "Use: vzlayer " << argv[0];
+    di << " add/del/get [id]\n";
+    di << " add - add new z layer to viewer and print its id\n";
+    di << " del - del z layer by its id\n";
+    di << " get - print sequence of z layers in increasing order of their overlay level\n";
+    di << "id - the layer identificator value defined when removing z layer\n";
+    return 1;
+  }
+
+  const Handle(V3d_Viewer)& aViewer = aContextAIS->CurrentViewer();
+  if (aViewer.IsNull())
+  {
+    di << "No active viewer!\n";
+    return 1;
+  }
+
+  // perform operation
+  TCollection_AsciiString anOp = TCollection_AsciiString (argv[1]);
+  if (anOp == "add")
+  {
+    Standard_Integer aNewId;
+    if (!aViewer->AddZLayer (aNewId))
+    {
+      di << "Impossible to add new z layer!\n";
+      return 1;
+    }
+
+    di << "New z layer added with index: " << aNewId << "\n";
+  }
+  else if (anOp == "del")
+  {
+    if (argc < 3)
+    {
+      di << "Please also provide as argument id of z layer to remove\n";
+      return 1;
+    }
+
+    Standard_Integer aDelId = atoi (argv[2]);
+    if (!aViewer->RemoveZLayer (aDelId))
+    {
+      di << "Impossible to remove the z layer or invalid id!\n";
+      return 1;
+    }
+
+    di << "Z layer " << aDelId << " has been removed\n";
+  }
+  else if (anOp == "get")
+  {
+    TColStd_SequenceOfInteger anIds;
+    aViewer->GetAllZLayers (anIds);
+    for (Standard_Integer aSeqIdx = 1; aSeqIdx <= anIds.Length(); aSeqIdx++)
+    {
+      di << anIds.Value (aSeqIdx) << " ";
+    }
+
+    di << "\n";
+  }
+  else
+  {
+    di << "Invalid operation, please use { add / del / get }\n";
+    return 1;
+  }
+
+  return 0;
+}
+
 //=======================================================================
 //function : ViewerCommands
 //purpose  :
@@ -2140,5 +2221,7 @@ void ViewerTest::ViewerCommands(Draw_Interpretor& theCommands)
   theCommands.Add("vprintview" ,
     "vprintview : width height filename [algo=0] : Test print algorithm: algo = 0 - stretch, algo = 1 - tile",
     __FILE__,VPrintView,group);
-
+  theCommands.Add("vzlayer",
+    "vzlayer : add/del/get [id] : Z layer operations in v3d viewer: add new z layer, delete z layer, get z layer ids",
+    __FILE__,VZLayer,group);
 }

src/Visual3d/Visual3d_View.cdl

@@ -887,6 +887,27 @@ is
 	---Purpose: Changes the display priority of the structure <AStructure>.
 	---Category: Private methods
 
+        AddZLayer ( me         : mutable;
+                    theLayerId : Integer from Standard )
+          is static private;
+        ---Purpose: Add a new top-level Z layer to the view with ID
+        -- <theLayerId>. The z layer mechanism allows to display
+        -- structures in higher layers in overlay of structures in lower layers.
+        -- The layers in a particular view should be managed centrally
+        -- by its view manager so to avoid IDs mismatching and provide correct
+        -- display of graphics in all views.
+
+        RemoveZLayer ( me         : mutable;
+                       theLayerId : Integer from Standard )
+          is static private;
+        ---Purpose: Remove z layer from the view by its ID.
+
+        ChangeZLayer ( me           : mutable;
+                       theStructure : Structure from Graphic3d;
+                       theLayerId   : Integer from Standard )
+           is static private;
+        ---Purpose: Change Z layer of already displayed structure in the view.
+
 	Clear ( me		: mutable;
 		AStructure	: Structure from Graphic3d;
 		WithDestruction	: Boolean from Standard )

src/Visual3d/Visual3d_View.cxx

@@ -4311,3 +4311,35 @@ Standard_Boolean Visual3d_View::Export (const Standard_CString       theFileName
                                   aWidth, aHeight, MyCView, anUnderCLayer, anOverCLayer,
                                   thePrecision, theProgressBarFunc, theProgressObject);
 }
+
+//=======================================================================
+//function : AddZLayer
+//purpose  :
+//=======================================================================
+
+void Visual3d_View::AddZLayer (const Standard_Integer theLayerId)
+{
+  MyGraphicDriver->AddZLayer (MyCView, theLayerId);
+}
+
+//=======================================================================
+//function : RemoveZLayer
+//purpose  : 
+//=======================================================================
+
+void Visual3d_View::RemoveZLayer (const Standard_Integer theLayerId)
+{
+  MyGraphicDriver->RemoveZLayer (MyCView, theLayerId);
+}
+
+//=======================================================================
+//function : ChangeZLayer
+//purpose  : 
+//=======================================================================
+
+void Visual3d_View::ChangeZLayer (const Handle(Graphic3d_Structure)& theStructure,
+                                  const Standard_Integer theLayerId)
+{
+  MyGraphicDriver->ChangeZLayer (
+    (*(Graphic3d_CStructure*)theStructure->CStructure()), MyCView, theLayerId);
+}

src/Visual3d/Visual3d_ViewManager.cdl

@@ -18,6 +18,8 @@ class ViewManager from Visual3d inherits StructureManager from Graphic3d
 uses
 
 	Array2OfReal		from TColStd,
+        SequenceOfInteger       from TColStd,
+        MapOfInteger            from TColStd,
 
 	GenId			from Aspect,
 	GraphicDevice           from Aspect,
@@ -275,6 +277,48 @@ is
 	---Purpose: Changes the display priority of the structure <AStructure>.
 	---Category: Private methods
 
+        ChangeZLayer ( me           : mutable;
+                       theStructure : Structure from Graphic3d;
+                       theLayerId   : Integer from Standard )
+           is redefined static;
+        ---Purpose: Change Z layer for structure. The layer mechanism allows
+        -- to display structures in higher layers in overlay of structures in
+        -- lower layers.
+
+        GetZLayer ( me;
+                    theStructure : Structure from Graphic3d )
+           returns Integer from Standard is redefined static;
+        ---Purpose: Get Z layer ID assigned for the structure.
+
+        AddZLayer ( me : mutable;
+                    theLayerId : in out Integer from Standard )
+           returns Boolean from Standard is redefined static;
+        ---Purpose: Add a new top-level Z layer and get its ID as
+        -- <theLayerId> value. The method returns Standard_False if the layer
+        -- can not be created. The layer mechanism allows to display
+        -- structures in higher layers in overlay of structures in lower layers.
+
+        RemoveZLayer ( me : mutable;
+                       theLayerId : Integer from Standard )
+           returns Boolean from Standard is redefined static;
+        ---Purpose: Remove Z layer with ID <theLayerId>. Method returns
+        -- Standard_False if the layer can not be removed or doesn't exists.
+        -- By default, there are always default bottom-level layer that can't
+        -- be removed.
+
+        GetAllZLayers ( me;
+                        theLayerSeq : out SequenceOfInteger from TColStd )
+           is redefined static;
+        ---Purpose: Return all Z layer ids in sequence ordered by overlay level
+        -- from lowest layer to highest ( foreground ). The first layer ID
+        -- in sequence is the default layer that can't be removed.
+
+        getZLayerGenId ( myclass )
+        ---Purpose: Returns global instance of z layer ids generator.
+        ---C++: return &
+           returns GenId from Aspect is protected;
+        
+
 	Clear ( me		: mutable;
 		AStructure	: Structure from Graphic3d;
 		WithDestruction	: Boolean from Standard )
@@ -431,7 +475,7 @@ is
 	--	    is managed automatically.
 	--	    Default Standard_False
 	---Category: Internal methods
---
+--
 
 fields
 
@@ -460,6 +504,10 @@ fields
 	MyZBufferAuto			:	Boolean from Standard;
 	MyTransparency			:	Boolean from Standard;
 
+        -- Z layer indexes
+        myLayerIds                      :       MapOfInteger from TColStd;
+        myLayerSeq                      :       SequenceOfInteger from TColStd;
+
 friends
 
 	class View from Visual3d,

src/Visual3d/Visual3d_ViewManager.cxx

@@ -48,6 +48,7 @@
 #include <Standard_ErrorHandler.hxx>
 
 #include <Aspect.hxx>
+#include <Aspect_IdentDefinitionError.hxx>
 
 #include <Graphic3d_GraphicDriver.hxx>
 #include <Graphic3d_MapOfStructure.hxx>
@@ -81,11 +82,14 @@ MyViewGenId (View_IDMIN+((View_IDMIN+View_IDMAX)/(Visual3d_ViewManager::Limit ()
 MyZBufferAuto (Standard_False),
 MyTransparency (Standard_False)
 {
+  // default layer is always presented in display layer sequence
+  // it can not be removed
+  myLayerIds.Add (0);
+  myLayerSeq.Append (0);
 
   Handle(Aspect_GraphicDriver) agd = aDevice->GraphicDriver ();
 
   MyGraphicDriver = *(Handle(Graphic3d_GraphicDriver) *) &agd;
-
 }
 
 //-Destructors
@@ -1339,3 +1343,120 @@ const Handle(Visual3d_Layer)& Visual3d_ViewManager::OverLayer () const {
 	return (MyOverLayer);
 
 }
+
+//=======================================================================
+//function : ChangeZLayer
+//purpose  : 
+//=======================================================================
+
+void Visual3d_ViewManager::ChangeZLayer (const Handle(Graphic3d_Structure)& theStructure,
+                                         const Standard_Integer theLayerId)
+{
+  if (!myLayerIds.Contains (theLayerId))
+    return;
+  
+  // change display layer for structure in all views
+  if (MyDisplayedStructure.Contains (theStructure))
+  {
+    Visual3d_SetIteratorOfSetOfView aViewIt(MyDefinedView);
+    for ( ; aViewIt.More (); aViewIt.Next ())
+      (aViewIt.Value ())->ChangeZLayer (theStructure, theLayerId);
+  }
+  
+  // tell graphic driver to update the structure's display layer
+  MyGraphicDriver->ChangeZLayer (
+    (*(Graphic3d_CStructure*)theStructure->CStructure ()), theLayerId);
+}
+
+//=======================================================================
+//function : GetZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Integer Visual3d_ViewManager::GetZLayer (const Handle(Graphic3d_Structure)& theStructure) const
+{
+  Graphic3d_CStructure& aStructure =
+    (*(Graphic3d_CStructure*)theStructure->CStructure ());
+
+  return MyGraphicDriver->GetZLayer (aStructure);
+}
+
+//=======================================================================
+//function : AddZLayer
+//purpose  :
+//=======================================================================
+
+Standard_Boolean Visual3d_ViewManager::AddZLayer (Standard_Integer& theLayerId)
+{
+  try
+  {
+    OCC_CATCH_SIGNALS
+    theLayerId = getZLayerGenId ().Next ();
+    myLayerIds.Add (theLayerId);
+    myLayerSeq.Append (theLayerId);
+  }
+  catch (Aspect_IdentDefinitionError)
+  {
+    // new index can't be generated
+    return Standard_False;
+  }
+
+  // tell all managed views to remove display layers
+  Visual3d_SetIteratorOfSetOfView aViewIt(MyDefinedView);
+  for ( ; aViewIt.More (); aViewIt.Next ())
+    (aViewIt.Value ())->AddZLayer (theLayerId);
+
+  return Standard_True;
+}
+
+//=======================================================================
+//function : RemoveZLayer
+//purpose  : 
+//=======================================================================
+
+Standard_Boolean Visual3d_ViewManager::RemoveZLayer (const Standard_Integer theLayerId)
+{
+  if (!myLayerIds.Contains (theLayerId) || theLayerId == 0)
+    return Standard_False;
+
+  // tell all managed views to remove display layers
+  Visual3d_SetIteratorOfSetOfView aViewIt(MyDefinedView);
+  for ( ; aViewIt.More (); aViewIt.Next ())
+    (aViewIt.Value ())->RemoveZLayer (theLayerId);
+
+  MyGraphicDriver->UnsetZLayer (theLayerId);
+
+  // remove index
+  for (int aIdx = 1; aIdx <= myLayerSeq.Length (); aIdx++)
+    if (myLayerSeq(aIdx) == theLayerId)
+    {
+      myLayerSeq.Remove (aIdx);
+      break;
+    }
+
+  myLayerIds.Remove (theLayerId);
+  getZLayerGenId ().Free (theLayerId);
+
+  return Standard_True;
+}
+
+//=======================================================================
+//function : GetAllZLayers
+//purpose  :
+//=======================================================================
+
+void Visual3d_ViewManager::GetAllZLayers (TColStd_SequenceOfInteger& theLayerSeq) const
+{
+  theLayerSeq.Assign (myLayerSeq);
+}
+
+//=======================================================================
+//function : getZLayerGenId
+//purpose  :
+//=======================================================================
+
+Aspect_GenId& Visual3d_ViewManager::getZLayerGenId ()
+{
+  static Aspect_GenId aGenId (1, IntegerLast());
+  return aGenId;
+}