library: libCore
#include "TBuffer3D.h"


class description - source file - inheritance tree (.pdf)

class TBuffer3D : public TObject

Inheritance Chart:
TBuffer3D(const TBuffer3D&) void Init() const TBuffer3D& operator=(const TBuffer3D&) const public:
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) virtual ~TBuffer3D() static TClass* Class() void ClearSectionsValid() static UInt_t DecCSLevel() static UInt_t GetCSLevel() UInt_t GetSections(UInt_t mask) const static void IncCSLevel() virtual TClass* IsA() const UInt_t NbPnts() const UInt_t NbPols() const UInt_t NbSegs() const Bool_t SectionsValid(UInt_t mask) const void SetAABoundingBox(const Double_t* origin, const Double_t* halfLengths) void SetLocalMasterIdentity() Bool_t SetRawSizes(UInt_t reqPnts, UInt_t reqPntsCapacity, UInt_t reqSegs, UInt_t reqSegsCapacity, UInt_t reqPols, UInt_t reqPolsCapacity) void SetSectionsValid(UInt_t mask) virtual void ShowMembers(TMemberInspector& insp, char* parent) virtual void Streamer(TBuffer& b) void StreamerNVirtual(TBuffer& b) Int_t Type() const

Data Members

const Int_t fType Primitive type - predefined ones in TBuffer3DTypes.h UInt_t fNbPnts Number of points describing the shape UInt_t fNbSegs Number of segments describing the shape UInt_t fNbPols Number of polygons describing the shape UInt_t fPntsCapacity Current capacity of fPnts space UInt_t fSegsCapacity Current capacity of fSegs space UInt_t fPolsCapacity Current capacity of fSegs space UInt_t fSections Section validity flags static UInt_t fgCSLevel public:
static const TBuffer3D::EBoolOpCode kCSUnion static const TBuffer3D::EBoolOpCode kCSIntersection static const TBuffer3D::EBoolOpCode kCSDifference static const TBuffer3D::EBoolOpCode kCSNoOp static const TBuffer3D::ESection kNone static const TBuffer3D::ESection kCore static const TBuffer3D::ESection kBoundingBox static const TBuffer3D::ESection kShapeSpecific static const TBuffer3D::ESection kRawSizes static const TBuffer3D::ESection kRaw static const TBuffer3D::ESection kAll TObject* fID ID/object generating buffer - see TVirtualViewer3D for setting Int_t fColor Color index Short_t fTransparency Percentage transparency [0,100] Bool_t fLocalFrame True = Local, False = Master reference frame Bool_t fReflection Matrix is reflection - TODO: REMOVE when OGL viewer rewokred to local frame Double_t fLocalMaster[16] Local->Master Matrix - identity if master frame Double_t fBBVertex[8][3] 8 verticies defining bounding box. Double_t* fPnts x0, y0, z0, x1, y1, z1, ..... ..... .... Int_t* fSegs c0, p0, q0, c1, p1, q1, ..... ..... .... Int_t* fPols c0, n0, s0, s1, ... sn, c1, n1, s0, ... sn

Class Description

 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.

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 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)

*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:

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:

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 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.

TBuffer3D(Int_t type, UInt_t reqPnts, UInt_t reqPntsCapacity, UInt_t reqSegs, UInt_t reqSegsCapacity, UInt_t reqPols, UInt_t reqPolsCapacity) : fType(type) // Initialise buffer
 Construct from supplied shape type and raw sizes

~TBuffer3D() // Initialise buffer

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[3], const Double_t halfLengths[3])
 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()

void IncCSLevel()

UInt_t DecCSLevel()

Inline Functions

        const TBuffer3D& operator=(const TBuffer3D&) const
               TBuffer3D 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)
                    void SetSectionsValid(UInt_t mask)
                  Bool_t SectionsValid(UInt_t mask) const
                  UInt_t GetSections(UInt_t mask) const
                  UInt_t NbPnts() const
                  UInt_t NbSegs() const
                  UInt_t NbPols() const
                   Int_t Type() const
                 TClass* Class()
                 TClass* IsA() const
                    void ShowMembers(TMemberInspector& insp, char* parent)
                    void Streamer(TBuffer& b)
                    void StreamerNVirtual(TBuffer& b)

Author: Olivier Couet 05/05/04
Last update: root/base:$Name: $:$Id: TBuffer3D.cxx,v 1.00
Copyright (C) 1995-2004, Rene Brun and Fons Rademakers. *

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