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class TBuffer3D: public TObject


Generic 3D primitive description class - see TBuffer3DTypes for
producer classes

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

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)

  • TBuffer3DSphere - solid, hollow and cut spheres*
  • TBuffer3DTubeSeg - angle tube segment
  • TBuffer3DCutTube - angle tube segment with plane cut ends.

*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 colum 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


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)

If you use the first (simple) case a viewer using logical/physical pairs SetSectionsValid(TBuffer3D::kBoundingBox); 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.

Recyling 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.

Function Members (Methods)

TBuffer3D(Int_t type, UInt_t reqPnts = 0, UInt_t reqPntsCapacity = 0, UInt_t reqSegs = 0, UInt_t reqSegsCapacity = 0, UInt_t reqPols = 0, UInt_t reqPolsCapacity = 0)
voidTObject::AbstractMethod(const char* method) const
virtual voidTObject::AppendPad(Option_t* option = "")
virtual voidTObject::Browse(TBrowser* b)
static TClass*Class()
virtual const char*TObject::ClassName() const
virtual voidTObject::Clear(Option_t* = "")
virtual TObject*TObject::Clone(const char* newname = "") const
virtual Int_tTObject::Compare(const TObject* obj) const
virtual voidTObject::Copy(TObject& object) const
static UInt_tDecCSLevel()
virtual voidTObject::Delete(Option_t* option = "")MENU
virtual Int_tTObject::DistancetoPrimitive(Int_t px, Int_t py)
virtual voidTObject::Draw(Option_t* option = "")
virtual voidTObject::DrawClass() constMENU
virtual TObject*TObject::DrawClone(Option_t* option = "") constMENU
virtual voidTObject::Dump() constMENU
virtual voidTObject::Error(const char* method, const char* msgfmt) const
virtual voidTObject::Execute(const char* method, const char* params, Int_t* error = 0)
virtual voidTObject::Execute(TMethod* method, TObjArray* params, Int_t* error = 0)
virtual voidTObject::ExecuteEvent(Int_t event, Int_t px, Int_t py)
virtual voidTObject::Fatal(const char* method, const char* msgfmt) const
virtual TObject*TObject::FindObject(const char* name) const
virtual TObject*TObject::FindObject(const TObject* obj) const
static UInt_tGetCSLevel()
virtual Option_t*TObject::GetDrawOption() const
static Long_tTObject::GetDtorOnly()
virtual const char*TObject::GetIconName() const
virtual const char*TObject::GetName() const
virtual char*TObject::GetObjectInfo(Int_t px, Int_t py) const
static Bool_tTObject::GetObjectStat()
virtual Option_t*TObject::GetOption() const
UInt_tGetSections(UInt_t mask) const
virtual const char*TObject::GetTitle() const
virtual UInt_tTObject::GetUniqueID() const
virtual Bool_tTObject::HandleTimer(TTimer* timer)
virtual ULong_tTObject::Hash() const
static voidIncCSLevel()
virtual voidTObject::Info(const char* method, const char* msgfmt) const
virtual Bool_tTObject::InheritsFrom(const char* classname) const
virtual Bool_tTObject::InheritsFrom(const TClass* cl) const
virtual voidTObject::Inspect() constMENU
voidTObject::InvertBit(UInt_t f)
virtual TClass*IsA() const
virtual Bool_tTObject::IsEqual(const TObject* obj) const
virtual Bool_tTObject::IsFolder() const
Bool_tTObject::IsOnHeap() const
virtual Bool_tTObject::IsSortable() const
Bool_tTObject::IsZombie() const
virtual voidTObject::ls(Option_t* option = "") const
voidTObject::MayNotUse(const char* method) const
UInt_tNbPnts() const
UInt_tNbPols() const
UInt_tNbSegs() const
virtual Bool_tTObject::Notify()
voidTObject::Obsolete(const char* method, const char* asOfVers, const char* removedFromVers) const
static voidTObject::operator delete(void* ptr)
static voidTObject::operator delete(void* ptr, void* vp)
static voidTObject::operator delete[](void* ptr)
static voidTObject::operator delete[](void* ptr, void* vp)
void*TObject::operator new(size_t sz)
void*TObject::operator new(size_t sz, void* vp)
void*TObject::operator new[](size_t sz)
void*TObject::operator new[](size_t sz, void* vp)
virtual voidTObject::Paint(Option_t* option = "")
virtual voidTObject::Pop()
virtual voidTObject::Print(Option_t* option = "") const
virtual Int_tTObject::Read(const char* name)
virtual voidTObject::RecursiveRemove(TObject* obj)
voidTObject::ResetBit(UInt_t f)
virtual voidTObject::SaveAs(const char* filename = "", Option_t* option = "") constMENU
virtual voidTObject::SavePrimitive(ostream& out, Option_t* option = "")
Bool_tSectionsValid(UInt_t mask) const
voidSetAABoundingBox(const Double_t* origin, const Double_t* halfLengths)
voidTObject::SetBit(UInt_t f)
voidTObject::SetBit(UInt_t f, Bool_t set)
virtual voidTObject::SetDrawOption(Option_t* option = "")MENU
static voidTObject::SetDtorOnly(void* obj)
static voidTObject::SetObjectStat(Bool_t stat)
Bool_tSetRawSizes(UInt_t reqPnts, UInt_t reqPntsCapacity, UInt_t reqSegs, UInt_t reqSegsCapacity, UInt_t reqPols, UInt_t reqPolsCapacity)
voidSetSectionsValid(UInt_t mask)
virtual voidTObject::SetUniqueID(UInt_t uid)
virtual voidShowMembers(TMemberInspector& insp)
virtual voidStreamer(TBuffer& b)
voidStreamerNVirtual(TBuffer& b)
virtual voidTObject::SysError(const char* method, const char* msgfmt) const
Bool_tTObject::TestBit(UInt_t f) const
Int_tTObject::TestBits(UInt_t f) const
Int_tType() const
virtual voidTObject::UseCurrentStyle()
virtual voidTObject::Warning(const char* method, const char* msgfmt) const
virtual Int_tTObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0)
virtual Int_tTObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0) const
virtual voidTObject::DoError(int level, const char* location, const char* fmt, va_list va) const
TBuffer3D(const TBuffer3D&)
const TBuffer3D&operator=(const TBuffer3D&)

Data Members

enum EBoolOpCode { kCSUnion
enum ESection { kNone
enum TObject::EStatusBits { kCanDelete
enum TObject::[unnamed] { kIsOnHeap
Double_tfBBVertex[8][3]8 verticies defining bounding box.
Int_tfColorColor index
TObject*fIDID/object generating buffer - see TVirtualViewer3D for setting
Bool_tfLocalFrameTrue = Local, False = Master reference frame
Double_tfLocalMaster[16]Local->Master Matrix - identity if master frame
UInt_tfPhysicalIDUnique replica ID.
Double_t*fPntsx0, y0, z0, x1, y1, z1, ..... ..... ....
Int_t*fPolsc0, n0, s0, s1, ... sn, c1, n1, s0, ... sn
Bool_tfReflectionMatrix is reflection - TODO: REMOVE when OGL viewer rewokred to local frame
Int_t*fSegsc0, p0, q0, c1, p1, q1, ..... ..... ....
Short_tfTransparencyPercentage transparency [0,100]
UInt_tfNbPntsNumber of points describing the shape
UInt_tfNbPolsNumber of polygons describing the shape
UInt_tfNbSegsNumber of segments describing the shape
UInt_tfPntsCapacityCurrent capacity of fPnts space
UInt_tfPolsCapacityCurrent capacity of fSegs space
UInt_tfSectionsSection validity flags
UInt_tfSegsCapacityCurrent capacity of fSegs space
const Int_tfTypePrimitive type - predefined ones in TBuffer3DTypes.h
static UInt_tfgCSLevel

Class Charts

Inheritance Inherited Members Includes Libraries
Class Charts

Function documentation

TBuffer3D(Int_t type, UInt_t reqPnts = 0, UInt_t reqPntsCapacity = 0, UInt_t reqSegs = 0, UInt_t reqSegsCapacity = 0, UInt_t reqPols = 0, UInt_t reqPolsCapacity = 0)
 Construct from supplied shape type and raw sizes
void Init()
 Initialise buffer
void ClearSectionsValid()
 Clear any sections marked valid
void SetLocalMasterIdentity()
 Set kRaw tesselation section of buffer with supplied sizes
 Set fLocalMaster in section kCore to identity
void SetAABoundingBox(const Double_t* origin, const Double_t* halfLengths)
 Set fBBVertex in kBoundingBox section to a axis aligned (local) BB
 using supplied origin and box half lengths

  /|      /|
 3-------2 |
 | 4-----|-5
 |/      |

Bool_t SetRawSizes(UInt_t reqPnts, UInt_t reqPntsCapacity, UInt_t reqSegs, UInt_t reqSegsCapacity, UInt_t reqPols, UInt_t reqPolsCapacity)
 Set kRaw tesselation section of buffer with supplied sizes
UInt_t GetCSLevel()
return CS level
void IncCSLevel()
increment CS level
UInt_t DecCSLevel()
decrement CS level
TBuffer3D(const TBuffer3D& )
 Non-copyable class
const TBuffer3D & operator=(const TBuffer3D& )
void SetSectionsValid(UInt_t mask)
 Section validity flags
{ fSections |= mask & kAll; }
Bool_t SectionsValid(UInt_t mask) const
{ return (Bool_t) (GetSections(mask) == mask); }
UInt_t GetSections(UInt_t mask) const
{ return (UInt_t) (fSections & mask); }
UInt_t NbPnts() const
{ return fNbPnts; }
UInt_t NbSegs() const
{ return fNbSegs; }
UInt_t NbPols() const
{ return fNbPols; }
Int_t Type() const
{ return fType; }