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TVirtualViewer3D Class Referenceabstract

Abstract 3D shapes viewer.

The concrete implementations are:

  • TViewerX3D : X3d viewer
  • TGLViewer : OpenGL viewer

3D Viewer Infrastructure Overview

The 3D Viewer infrastructure consists of:

  • TVirtualViewer3D interface: An abstract handle to the viewer, allowing client to test preferences, add objects, control the viewer via scripting (to be added) etc. -TBuffer3D class hierarchy: Used to describe 3D objects ("shapes")

Together these allow clients to publish objects to any one of the 3D viewers (currently OpenGL/x3d,TPad), free of viewer specific drawing code. They allow our simple x3d viewer, and considerably more sophisticated OpenGL one to both work with both geometry libraries (g3d and geom) efficiently.

Publishing to a viewer consists of the following steps:

  1. Create / obtain viewer handle
  2. Begin scene on viewer
  3. Fill mandatory parts of TBuffer3D describing object
  4. Add to viewer
  5. Fill optional parts of TBuffer3D if requested by viewer, and add again ... repeat 3/4/5 as required
  6. End scene on viewer

Creating / Obtaining Viewer

Create/obtain the viewer handle via local/global pad - the viewer is always bound to a TPad object at present [This may be removed as a restriction in the future] . You should perform the publishing to the viewer described below in the Paint() method of the object you attach to the pad (via Draw())

TVirtualViewer3D * v = gPad->GetViewer3D("xxxx");
#define gPad
Abstract 3D shapes viewer.

" xxxx" is viewer type: OpenGL "ogl", X3D "x3d" or Pad "pad" (default). The viewer is created via the plugin manager, attached to pad, and the interface returned.

Begin / End Scene

Objects must be added to viewer between BeginScene/EndScene calls e.g.


The BeginScene call will cause the viewer to suspend redraws etc, and after the EndScene the viewer will reset the camera to frame the new scene and redraw. [x3d viewer does not support changing of scenes - objects added after the first Open/CloseScene pair will be ignored.]

Filling TBuffer3D and Adding to Viewer

The viewers behind the TVirtualViewer3D interface differ greatly in their capabilities e.g.

  • Some know how to draw certain shapes natively (e.g. spheres/tubes in OpenGL) - others always require a raw tessellation description of points/lines/segments.
  • Some need the 3D object positions in the global frame, others can cope with local frames + a translation matrix - which can give considerable performance benefits.

To cope with these situations the object buffer is filled out in negotiation with the viewer. TBuffer3D classes are conceptually divided into enumerated sections Core, BoundingBox, Raw etc (see TBuffer3D.h for more details).

The SectionsValid() / SetSectionsValid / ClearSectionsValid() methods of TBuffer3D are used to test/set/clear these section valid flags.

The sections found in TBuffer3D (Core/BoundingBox/Raw Sizes/Raw) are sufficient to describe any tessellated shape in a generic fashion. An additional ShapeSpecific section in derived shape specific classes allows a more abstract shape description ("a sphere of inner radius x, outer radius y"). This enables a viewer which knows how to draw (tessellate) the shape itself to do so, which can bring considerable performance and quality benefits, while providing a generic fallback suitable for all viewers.

The rules for client negotiation with the viewer are:

  • If suitable specialized TBuffer3D class exists, use it, otherwise use TBuffer3D.
  • Complete the mandatory Core section.
  • Complete the ShapeSpecific section if applicable.
  • Complete the BoundingBox if you can.
  • Pass this buffer to the viewer using one of the AddObject() methods - see below.

If the viewer requires more sections to be completed (Raw/RawSizes) AddObject() will return flags indicating which ones, otherwise it returns kNone. You must fill the buffer and mark these sections valid, and pass the buffer again. A typical code snippet would be:

TBuffer3DSphere sphereBuffer;
// Fill out kCore...
// Fill out kBoundingBox...
// Fill out kShapeSpecific for TBuffer3DSphere
// Try first add to viewer
Int_t reqSections = viewer->AddObject(buffer);
if (reqSections != TBuffer3D::kNone) {
if (reqSections & TBuffer3D::kRawSizes) {
// Fill out kRawSizes...
if (reqSections & TBuffer3D::kRaw) {
// Fill out kRaw...
// Add second time to viewer - ignore return cannot do more
Sphere description class - see TBuffer3DTypes for producer classes Supports hollow and cut spheres.
Definition TBuffer3D.h:130

ShapeSpecific: If the viewer can directly display the buffer without filling of the kRaw/kRawSizes section it will not need to request client side tessellation. Currently we provide the following various shape specific classes, which the OpenGL viewer can take advantage of (see TBuffer3D.h and TBuffer3DTypes.h)

OpenGL only supports solid spheres at present - cut/hollow ones will be requested tessellated.

Anyone is free to add new TBuffer3D classes, but it should be clear that the viewers require updating to be able to take advantage of them. The number of native shapes in OpenGL will be expanded over time.

BoundingBox: You are not obliged to complete this, as any viewer requiring one internally (OpenGL) will build one for you if you do not provide. However to do this the viewer will force you to provide the raw tessellation, and the resulting box will be axis aligned with the overall scene, which is non-ideal for rotated shapes.

As we need to support orientated (rotated) bounding boxes, TBuffer3D requires the 6 vertices of the box. We also provide a convenience function, SetAABoundingBox(), for simpler case of setting an axis aligned bounding box.

Master/Local Reference Frames

The Core section of TBuffer3D contains two members relating to reference frames: fLocalFrame & fLocalMaster. fLocalFrame indicates if any positions in the buffer (bounding box and tessellation vertexes) are in local or master (world frame). fLocalMaster is a standard 4x4 translation matrix (OpenGL column major ordering) for placing the object into the 3D master frame.

If fLocalFrame is kFALSE, fLocalMaster should contain an identity matrix. This is set by default, and can be reset using SetLocalMasterIdentity() function.

Logical & Physical Objects

There are two cases of object addition:

  • Add this object as a single independent entity in the world reference frame.
  • Add a physical placement (copy) of this logical object (described in local reference frame).

The second case is very typical in geometry packages, GEANT4, where we have very large number repeated placements of relatively few logical (unique) shapes. Some viewers (OpenGL only at present) are able to take advantage of this by identifying unique logical shapes from the fID logical ID member of TBuffer3D. If repeated addition of the same fID is found, the shape is cached already - and the costly tessellation does not need to be sent again. The viewer can also perform internal GL specific caching with considerable performance gains in these cases.

For this to work correctly the logical object in must be described in TBuffer3D in the local reference frame, complete with the local/master translation. The viewer indicates this through the interface method

virtual Bool_t PreferLocalFrame() const =0

If this returns kTRUE you can make repeated calls to AddObject(), with TBuffer3D containing the same fID, and different fLocalMaster placements.

For viewers supporting logical/physical objects, the TBuffer3D content refers to the properties of logical object, with the fLocalMaster transform and the fColor and fTransparency attributes, which can be varied for each physical object.

As a minimum requirement all clients must be capable of filling the raw tessellation of the object buffer, in the master reference frame. Conversely viewers must always be capable of displaying the object described by this buffer.

Scene Rebuilds

It should be understood that AddObject is not an explicit command to the viewer

  • it may for various reasons decide to ignore it:
  • It already has the object internally cached .
  • The object falls outside some 'interest' limits of the viewer camera.
  • The object is too small to be worth drawing.

In all these cases AddObject() returns kNone, as it does for successful addition, simply indicating it does not require you to provide further information about this object. You should not try to make any assumptions about what the viewer did with it.

This enables the viewer to be connected to a client which sends potentially millions of objects, and only accept those that are of interest at a certain time, caching the relatively small number of CPU/memory costly logical shapes, and retaining/discarding the physical placements as required. The viewer may decide to force the client to rebuild (republish) the scene (via a TPad repaint at present), and thus collect these objects if the internal viewer state changes. It does this presently by forcing a repaint on the attached TPad object - hence the reason for putting all publishing to the viewer in the attached pad objects Paint() method. We will likely remove this requirement in the future, indicating the rebuild request via a normal ROOT signal, which the client can detect.

Physical IDs

TVirtualViewer3D provides for two methods of object addition:virtual Int_t AddObject(const TBuffer3D & buffer, Bool_t * addChildren = 0)

virtual Int_t AddObject(UInt_t physicalID, const TBuffer3D & buffer, Bool_t * addChildren = 0)
Generic 3D primitive description class.
Definition TBuffer3D.h:18
virtual Int_t AddObject(const TBuffer3D &buffer, Bool_t *addChildren=nullptr)=0

If you use the first (simple) case a viewer using logical/physical pairs will generate IDs for each physical object internally. In the second you can specify a unique identifier from the client, which allows the viewer to be more efficient. It can now cache both logical and physical objects, and only discard physical objects no longer of interest as part of scene rebuilds.

Child Objects

In many geometries there is a rigid containment hierarchy, and so if the viewer is not interested in a certain object due to limits/size then it will also not be interest in any of the contained branch of descendents. Both AddObject() methods have an addChildren parameter. The viewer will complete this (if passed) indicating if children (contained within the one just sent) are worth adding.

Recycling TBuffer3D

Once add AddObject() has been called, the contents are copied to the viewer internally. You are free to destroy this object, or recycle it for the next object if suitable.

Definition at line 33 of file TVirtualViewer3D.h.

Public Member Functions

virtual ~TVirtualViewer3D ()
virtual void AddCompositeOp (UInt_t operation)=0
virtual Int_t AddObject (const TBuffer3D &buffer, Bool_t *addChildren=nullptr)=0
virtual Int_t AddObject (UInt_t physicalID, const TBuffer3D &buffer, Bool_t *addChildren=nullptr)=0
virtual void BeginScene ()=0
virtual Bool_t BuildingScene () const =0
virtual Bool_t CanLoopOnPrimitives () const
virtual void CloseComposite ()=0
virtual void DrawViewer ()
virtual void EndScene ()=0
TClassIsA () const override
virtual void ObjectPaint (TObject *, Option_t *="")
virtual Bool_t OpenComposite (const TBuffer3D &buffer, Bool_t *addChildren=nullptr)=0
virtual void PadPaint (TVirtualPad *)
virtual Bool_t PreferLocalFrame () const =0
virtual void PrintObjects ()
virtual void ResetCameras ()
virtual void ResetCamerasAfterNextUpdate ()
virtual TObjectSelectObject (Int_t, Int_t)
void Streamer (TBuffer &) override
 Stream an object of class TObject.
void StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
- Public Member Functions inherited from TObject
 TObject ()
 TObject constructor.
 TObject (const TObject &object)
 TObject copy ctor.
virtual ~TObject ()
 TObject destructor.
void AbstractMethod (const char *method) const
 Use this method to implement an "abstract" method that you don't want to leave purely abstract.
virtual void AppendPad (Option_t *option="")
 Append graphics object to current pad.
virtual void Browse (TBrowser *b)
 Browse object. May be overridden for another default action.
ULong_t CheckedHash ()
 Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object.
virtual const char * ClassName () const
 Returns name of class to which the object belongs.
virtual void Clear (Option_t *="")
virtual TObjectClone (const char *newname="") const
 Make a clone of an object using the Streamer facility.
virtual Int_t Compare (const TObject *obj) const
 Compare abstract method.
virtual void Copy (TObject &object) const
 Copy this to obj.
virtual void Delete (Option_t *option="")
 Delete this object.
virtual Int_t DistancetoPrimitive (Int_t px, Int_t py)
 Computes distance from point (px,py) to the object.
virtual void Draw (Option_t *option="")
 Default Draw method for all objects.
virtual void DrawClass () const
 Draw class inheritance tree of the class to which this object belongs.
virtual TObjectDrawClone (Option_t *option="") const
 Draw a clone of this object in the current selected pad with: gROOT->SetSelectedPad(c1).
virtual void Dump () const
 Dump contents of object on stdout.
virtual void Error (const char *method, const char *msgfmt,...) const
 Issue error message.
virtual void Execute (const char *method, const char *params, Int_t *error=nullptr)
 Execute method on this object with the given parameter string, e.g.
virtual void Execute (TMethod *method, TObjArray *params, Int_t *error=nullptr)
 Execute method on this object with parameters stored in the TObjArray.
virtual void ExecuteEvent (Int_t event, Int_t px, Int_t py)
 Execute action corresponding to an event at (px,py).
virtual void Fatal (const char *method, const char *msgfmt,...) const
 Issue fatal error message.
virtual TObjectFindObject (const char *name) const
 Must be redefined in derived classes.
virtual TObjectFindObject (const TObject *obj) const
 Must be redefined in derived classes.
virtual Option_tGetDrawOption () const
 Get option used by the graphics system to draw this object.
virtual const char * GetIconName () const
 Returns mime type name of object.
virtual const char * GetName () const
 Returns name of object.
virtual char * GetObjectInfo (Int_t px, Int_t py) const
 Returns string containing info about the object at position (px,py).
virtual Option_tGetOption () const
virtual const char * GetTitle () const
 Returns title of object.
virtual UInt_t GetUniqueID () const
 Return the unique object id.
virtual Bool_t HandleTimer (TTimer *timer)
 Execute action in response of a timer timing out.
virtual ULong_t Hash () const
 Return hash value for this object.
Bool_t HasInconsistentHash () const
 Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e.
virtual void Info (const char *method, const char *msgfmt,...) const
 Issue info message.
virtual Bool_t InheritsFrom (const char *classname) const
 Returns kTRUE if object inherits from class "classname".
virtual Bool_t InheritsFrom (const TClass *cl) const
 Returns kTRUE if object inherits from TClass cl.
virtual void Inspect () const
 Dump contents of this object in a graphics canvas.
void InvertBit (UInt_t f)
Bool_t IsDestructed () const
virtual Bool_t IsEqual (const TObject *obj) const
 Default equal comparison (objects are equal if they have the same address in memory).
virtual Bool_t IsFolder () const
 Returns kTRUE in case object contains browsable objects (like containers or lists of other objects).
R__ALWAYS_INLINE Bool_t IsOnHeap () const
virtual Bool_t IsSortable () const
R__ALWAYS_INLINE Bool_t IsZombie () const
virtual void ls (Option_t *option="") const
 The ls function lists the contents of a class on stdout.
void MayNotUse (const char *method) const
 Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary).
virtual Bool_t Notify ()
 This method must be overridden to handle object notification (the base implementation is no-op).
void Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
 Use this method to declare a method obsolete.
void operator delete (void *ptr)
 Operator delete.
void operator delete (void *ptr, void *vp)
 Only called by placement new when throwing an exception.
void operator delete[] (void *ptr)
 Operator delete [].
void operator delete[] (void *ptr, void *vp)
 Only called by placement new[] when throwing an exception.
void * operator new (size_t sz)
void * operator new (size_t sz, void *vp)
void * operator new[] (size_t sz)
void * operator new[] (size_t sz, void *vp)
TObjectoperator= (const TObject &rhs)
 TObject assignment operator.
virtual void Paint (Option_t *option="")
 This method must be overridden if a class wants to paint itself.
virtual void Pop ()
 Pop on object drawn in a pad to the top of the display list.
virtual void Print (Option_t *option="") const
 This method must be overridden when a class wants to print itself.
virtual Int_t Read (const char *name)
 Read contents of object with specified name from the current directory.
virtual void RecursiveRemove (TObject *obj)
 Recursively remove this object from a list.
void ResetBit (UInt_t f)
virtual void SaveAs (const char *filename="", Option_t *option="") const
 Save this object in the file specified by filename.
virtual void SavePrimitive (std::ostream &out, Option_t *option="")
 Save a primitive as a C++ statement(s) on output stream "out".
void SetBit (UInt_t f)
void SetBit (UInt_t f, Bool_t set)
 Set or unset the user status bits as specified in f.
virtual void SetDrawOption (Option_t *option="")
 Set drawing option for object.
virtual void SetUniqueID (UInt_t uid)
 Set the unique object id.
void StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
virtual void SysError (const char *method, const char *msgfmt,...) const
 Issue system error message.
R__ALWAYS_INLINE Bool_t TestBit (UInt_t f) const
Int_t TestBits (UInt_t f) const
virtual void UseCurrentStyle ()
 Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked.
virtual void Warning (const char *method, const char *msgfmt,...) const
 Issue warning message.
virtual Int_t Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
 Write this object to the current directory.
virtual Int_t Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0) const
 Write this object to the current directory.

Static Public Member Functions

static TClassClass ()
static const char * Class_Name ()
static constexpr Version_t Class_Version ()
static const char * DeclFileName ()
static TVirtualViewer3DViewer3D (TVirtualPad *pad=nullptr, Option_t *type="")
 Create a Viewer 3D of specified type.
- Static Public Member Functions inherited from TObject
static TClassClass ()
static const char * Class_Name ()
static constexpr Version_t Class_Version ()
static const char * DeclFileName ()
static Longptr_t GetDtorOnly ()
 Return destructor only flag.
static Bool_t GetObjectStat ()
 Get status of object stat flag.
static void SetDtorOnly (void *obj)
 Set destructor only flag.
static void SetObjectStat (Bool_t stat)
 Turn on/off tracking of objects in the TObjectTable.

Additional Inherited Members

- Public Types inherited from TObject
enum  {
  kIsOnHeap = 0x01000000 , kNotDeleted = 0x02000000 , kZombie = 0x04000000 , kInconsistent = 0x08000000 ,
  kBitMask = 0x00ffffff
enum  { kSingleKey = (1ULL << ( 0 )) , kOverwrite = (1ULL << ( 1 )) , kWriteDelete = (1ULL << ( 2 )) }
enum  EDeprecatedStatusBits { kObjInCanvas = (1ULL << ( 3 )) }
enum  EStatusBits {
  kCanDelete = (1ULL << ( 0 )) , kMustCleanup = (1ULL << ( 3 )) , kIsReferenced = (1ULL << ( 4 )) , kHasUUID = (1ULL << ( 5 )) ,
  kCannotPick = (1ULL << ( 6 )) , kNoContextMenu = (1ULL << ( 8 )) , kInvalidObject = (1ULL << ( 13 ))
- Protected Types inherited from TObject
enum  { kOnlyPrepStep = (1ULL << ( 3 )) }
- Protected Member Functions inherited from TObject
virtual void DoError (int level, const char *location, const char *fmt, va_list va) const
 Interface to ErrorHandler (protected).
void MakeZombie ()

#include <TVirtualViewer3D.h>

Inheritance diagram for TVirtualViewer3D:

Constructor & Destructor Documentation

◆ ~TVirtualViewer3D()

TVirtualViewer3D::~TVirtualViewer3D ( )

Definition at line 276 of file TVirtualViewer3D.cxx.

Member Function Documentation

◆ AddCompositeOp()

virtual void TVirtualViewer3D::AddCompositeOp ( UInt_t  operation)
pure virtual

Implemented in TViewer3DPad, TGLScenePad, and TGLViewer.

◆ AddObject() [1/2]

virtual Int_t TVirtualViewer3D::AddObject ( const TBuffer3D buffer,
Bool_t addChildren = nullptr 
pure virtual

Implemented in TGLViewer, TViewer3DPad, and TGLScenePad.

◆ AddObject() [2/2]

virtual Int_t TVirtualViewer3D::AddObject ( UInt_t  physicalID,
const TBuffer3D buffer,
Bool_t addChildren = nullptr 
pure virtual

Implemented in TGLScenePad, TViewer3DPad, and TGLViewer.

◆ BeginScene()

virtual void TVirtualViewer3D::BeginScene ( )
pure virtual

Implemented in TViewer3DPad, TGLScenePad, and TGLViewer.

◆ BuildingScene()

virtual Bool_t TVirtualViewer3D::BuildingScene ( ) const
pure virtual

Implemented in TViewer3DPad, TGLScenePad, and TGLViewer.

◆ CanLoopOnPrimitives()

virtual Bool_t TVirtualViewer3D::CanLoopOnPrimitives ( ) const

Reimplemented in TGLScenePad, and TGLViewer.

Definition at line 45 of file TVirtualViewer3D.h.

◆ Class()

static TClass * TVirtualViewer3D::Class ( )
TClass describing this class

◆ Class_Name()

static const char * TVirtualViewer3D::Class_Name ( )
Name of this class

◆ Class_Version()

static constexpr Version_t TVirtualViewer3D::Class_Version ( )
Version of this class

Definition at line 76 of file TVirtualViewer3D.h.

◆ CloseComposite()

virtual void TVirtualViewer3D::CloseComposite ( )
pure virtual

Implemented in TViewer3DPad, TGLScenePad, and TGLViewer.

◆ DeclFileName()

static const char * TVirtualViewer3D::DeclFileName ( )
Name of the file containing the class declaration

Definition at line 76 of file TVirtualViewer3D.h.

◆ DrawViewer()

virtual void TVirtualViewer3D::DrawViewer ( )

Definition at line 68 of file TVirtualViewer3D.h.

◆ EndScene()

virtual void TVirtualViewer3D::EndScene ( )
pure virtual

Implemented in TViewer3DPad, TGLScenePad, and TGLViewer.

◆ IsA()

TClass * TVirtualViewer3D::IsA ( ) const
TClass describing current object

Reimplemented from TObject.

Definition at line 76 of file TVirtualViewer3D.h.

◆ ObjectPaint()

virtual void TVirtualViewer3D::ObjectPaint ( TObject ,
Option_t = "" 

Reimplemented in TGLScenePad.

Definition at line 49 of file TVirtualViewer3D.h.

◆ OpenComposite()

virtual Bool_t TVirtualViewer3D::OpenComposite ( const TBuffer3D buffer,
Bool_t addChildren = nullptr 
pure virtual

Implemented in TGLViewer, TViewer3DPad, and TGLScenePad.

◆ PadPaint()

virtual void TVirtualViewer3D::PadPaint ( TVirtualPad )

Reimplemented in TGLScenePad, and TGLViewer.

Definition at line 48 of file TVirtualViewer3D.h.

◆ PreferLocalFrame()

virtual Bool_t TVirtualViewer3D::PreferLocalFrame ( ) const
pure virtual

Implemented in TViewer3DPad, TGLScenePad, and TGLViewer.

◆ PrintObjects()

virtual void TVirtualViewer3D::PrintObjects ( )

Reimplemented in TGLViewer.

Definition at line 70 of file TVirtualViewer3D.h.

◆ ResetCameras()

virtual void TVirtualViewer3D::ResetCameras ( )

Reimplemented in TGLViewer.

Definition at line 71 of file TVirtualViewer3D.h.

◆ ResetCamerasAfterNextUpdate()

virtual void TVirtualViewer3D::ResetCamerasAfterNextUpdate ( )

Reimplemented in TGLViewer.

Definition at line 72 of file TVirtualViewer3D.h.

◆ SelectObject()

virtual TObject * TVirtualViewer3D::SelectObject ( Int_t  ,

Definition at line 67 of file TVirtualViewer3D.h.

◆ Streamer()

void TVirtualViewer3D::Streamer ( TBuffer R__b)

Stream an object of class TObject.

Reimplemented from TObject.

◆ StreamerNVirtual()

void TVirtualViewer3D::StreamerNVirtual ( TBuffer ClassDef_StreamerNVirtual_b)

Definition at line 76 of file TVirtualViewer3D.h.

◆ Viewer3D()

TVirtualViewer3D * TVirtualViewer3D::Viewer3D ( TVirtualPad pad = nullptr,
Option_t type = "" 

Create a Viewer 3D of specified type.

Definition at line 281 of file TVirtualViewer3D.cxx.

  • core/base/inc/TVirtualViewer3D.h
  • core/base/src/TVirtualViewer3D.cxx