openscenegraph
Public Types | Public Member Functions | Protected Member Functions | Protected Attributes | List of all members
osgSim::Impostor Class Reference
Inheritance diagram for osgSim::Impostor:
osg::LOD osg::Group osg::Node osg::Object osg::Referenced

Public Types

typedef std::vector
< osg::ref_ptr< ImpostorSprite > > 		ImpostorSpriteList
- Public Types inherited from osg::LOD
enum  CenterMode { USE_BOUNDING_SPHERE_CENTER, USER_DEFINED_CENTER }
enum  RangeMode { DISTANCE_FROM_EYE_POINT, PIXEL_SIZE_ON_SCREEN }
typedef
osg::BoundingSphere::vec_type 		vec_type
typedef
osg::BoundingSphere::value_type 		value_type
typedef std::pair< float, float > MinMaxPair
typedef std::vector< MinMaxPair > RangeList

Public Member Functions

 Impostor ()
 Impostor (const Impostor &es, const osg::CopyOp &copyop=osg::CopyOp::SHALLOW_COPY)
 META_Node (osgSim, Impostor)
virtual void traverse (osg::NodeVisitor &nv)
void setImpostorThreshold (float distance)
float getImpostorThreshold () const
void setImpostorThresholdToBound (float ratio=1.0f)
ImpostorSprite * findBestImpostorSprite (unsigned int contextID, const osg::Vec3 &currLocalEyePoint) const
void addImpostorSprite (unsigned int contextID, ImpostorSprite *is)
ImpostorSpriteList & getImpostorSpriteList (unsigned int contexID)
const ImpostorSpriteList & getImpostorSpriteList (unsigned int contexID) const
virtual osg::BoundingSphere computeBound () const
- Public Member Functions inherited from osg::LOD
 LOD ()
 LOD (const LOD &, const CopyOp &copyop=CopyOp::SHALLOW_COPY)
 META_Node (osg, LOD)
virtual bool addChild (Node *child)
virtual bool addChild (Node *child, float min, float max)
virtual bool removeChildren (unsigned int pos, unsigned int numChildrenToRemove=1)
void setCenterMode (CenterMode mode)
CenterMode getCenterMode () const
void setCenter (const vec_type &center)
const vec_type & getCenter () const
void setRadius (value_type radius)
value_type getRadius () const
void setRangeMode (RangeMode mode)
RangeMode getRangeMode () const
void setRange (unsigned int childNo, float min, float max)
float getMinRange (unsigned int childNo) const
float getMaxRange (unsigned int childNo) const
unsigned int getNumRanges () const
void setRangeList (const RangeList &rangeList)
const RangeList & getRangeList () const
- Public Member Functions inherited from osg::Group
 Group ()
 Group (const Group &, const CopyOp &copyop=CopyOp::SHALLOW_COPY)
 META_Node (osg, Group)
virtual Group * asGroup ()
virtual const Group * asGroup () const
virtual bool insertChild (unsigned int index, Node *child)
bool removeChild (Node *child)
bool removeChild (unsigned int pos, unsigned int numChildrenToRemove=1)
virtual bool replaceChild (Node *origChild, Node *newChild)
unsigned int getNumChildren () const
virtual bool setChild (unsigned int i, Node *node)
Node * getChild (unsigned int i)
const Node * getChild (unsigned int i) const
bool containsNode (const Node *node) const
unsigned int getChildIndex (const Node *node) const
virtual void setThreadSafeRefUnref (bool threadSafe)
virtual void resizeGLObjectBuffers (unsigned int maxSize)
virtual void releaseGLObjects (osg::State *=0) const
- Public Member Functions inherited from osg::Node
 Node ()
 Node (const Node &, const CopyOp &copyop=CopyOp::SHALLOW_COPY)
virtual Object * cloneType () const
virtual Object * clone (const CopyOp &copyop) const
virtual bool isSameKindAs (const Object *obj) const
virtual const char * libraryName () const
virtual const char * className () const
virtual Transform * asTransform ()
virtual const Transform * asTransform () const
virtual Switch * asSwitch ()
virtual const Switch * asSwitch () const
virtual Geode * asGeode ()
virtual const Geode * asGeode () const
virtual osgTerrain::Terrain * asTerrain ()
virtual const osgTerrain::Terrain * asTerrain () const
virtual void accept (NodeVisitor &nv)
virtual void ascend (NodeVisitor &nv)
const ParentList & getParents () const
ParentList getParents ()
Group * getParent (unsigned int i)
const Group * getParent (unsigned int i) const
unsigned int getNumParents () const
NodePathList getParentalNodePaths (osg::Node *haltTraversalAtNode=0) const
MatrixList getWorldMatrices (const osg::Node *haltTraversalAtNode=0) const
void setUpdateCallback (NodeCallback *nc)
NodeCallback * getUpdateCallback ()
const NodeCallback * getUpdateCallback () const
void addUpdateCallback (NodeCallback *nc)
void removeUpdateCallback (NodeCallback *nc)
unsigned int getNumChildrenRequiringUpdateTraversal () const
void setEventCallback (NodeCallback *nc)
NodeCallback * getEventCallback ()
const NodeCallback * getEventCallback () const
void addEventCallback (NodeCallback *nc)
void removeEventCallback (NodeCallback *nc)
unsigned int getNumChildrenRequiringEventTraversal () const
void setCullCallback (NodeCallback *nc)
NodeCallback * getCullCallback ()
const NodeCallback * getCullCallback () const
void addCullCallback (NodeCallback *nc)
void removeCullCallback (NodeCallback *nc)
void setCullingActive (bool active)
bool getCullingActive () const
unsigned int getNumChildrenWithCullingDisabled () const
bool isCullingActive () const
unsigned int getNumChildrenWithOccluderNodes () const
bool containsOccluderNodes () const
void setNodeMask (NodeMask nm)
NodeMask getNodeMask () const
void setStateSet (osg::StateSet *stateset)
osg::StateSet * getOrCreateStateSet ()
osg::StateSet * getStateSet ()
const osg::StateSet * getStateSet () const
void setDescriptions (const DescriptionList &descriptions)
DescriptionList & getDescriptions ()
const DescriptionList & getDescriptions () const
const std::string & getDescription (unsigned int i) const
std::string & getDescription (unsigned int i)
unsigned int getNumDescriptions () const
void addDescription (const std::string &desc)
void setInitialBound (const osg::BoundingSphere &bsphere)
const BoundingSphere & getInitialBound () const
void dirtyBound ()
const BoundingSphere & getBound () const
void setComputeBoundingSphereCallback (ComputeBoundingSphereCallback *callback)
ComputeBoundingSphereCallback * getComputeBoundingSphereCallback ()
const
ComputeBoundingSphereCallback * 		getComputeBoundingSphereCallback () const
- Public Member Functions inherited from osg::Object
 Object ()
 Object (bool threadSafeRefUnref)
 Object (const Object &, const CopyOp &copyop=CopyOp::SHALLOW_COPY)
virtual void setName (const std::string &name)
void setName (const char *name)
const std::string & getName () const
void setDataVariance (DataVariance dv)
DataVariance getDataVariance () const
virtual void computeDataVariance ()
void setUserDataContainer (osg::UserDataContainer *udc)
osg::UserDataContainer * getUserDataContainer ()
const osg::UserDataContainer * getUserDataContainer () const
osg::UserDataContainer * getOrCreateUserDataContainer ()
virtual void setUserData (Referenced *obj)
virtual Referenced * getUserData ()
virtual const Referenced * getUserData () const
template<typename T >
bool getUserValue (const std::string &name, T &value) const
template<typename T >
void setUserValue (const std::string &name, const T &value)
- Public Member Functions inherited from osg::Referenced
 Referenced ()
 Referenced (bool threadSafeRefUnref)
 Referenced (const Referenced &)
Referenced & operator= (const Referenced &)
bool getThreadSafeRefUnref () const
OpenThreads::Mutex * getRefMutex () const
int ref () const
int unref () const
int unref_nodelete () const
int referenceCount () const
ObserverSet * getObserverSet () const
ObserverSet * getOrCreateObserverSet () const
void addObserver (Observer *observer) const
void removeObserver (Observer *observer) const

Protected Member Functions

virtual ~Impostor ()
ImpostorSprite * createImpostorSprite (osgUtil::CullVisitor *cv)
- Protected Member Functions inherited from osg::LOD
virtual ~LOD ()
- Protected Member Functions inherited from osg::Group
virtual ~Group ()
virtual void childRemoved (unsigned int, unsigned int)
virtual void childInserted (unsigned int)
- Protected Member Functions inherited from osg::Node
virtual ~Node ()
void addParent (osg::Group *node)
void removeParent (osg::Group *node)
void setNumChildrenRequiringUpdateTraversal (unsigned int num)
void setNumChildrenRequiringEventTraversal (unsigned int num)
void setNumChildrenWithCullingDisabled (unsigned int num)
void setNumChildrenWithOccluderNodes (unsigned int num)
- Protected Member Functions inherited from osg::Object
virtual ~Object ()
- Protected Member Functions inherited from osg::Referenced
virtual ~Referenced ()
void signalObserversAndDelete (bool signalDelete, bool doDelete) const
void deleteUsingDeleteHandler () const

Protected Attributes

osg::buffered_object
< ImpostorSpriteList > 		_impostorSpriteListBuffer
float _impostorThreshold
- Protected Attributes inherited from osg::LOD
CenterMode _centerMode
vec_type _userDefinedCenter
value_type _radius
RangeMode _rangeMode
RangeList _rangeList
- Protected Attributes inherited from osg::Group
NodeList _children
- Protected Attributes inherited from osg::Node
BoundingSphere _initialBound
ref_ptr
< ComputeBoundingSphereCallback > 		_computeBoundCallback
BoundingSphere _boundingSphere
bool _boundingSphereComputed
ParentList _parents
ref_ptr< NodeCallback > _updateCallback
unsigned int _numChildrenRequiringUpdateTraversal
ref_ptr< NodeCallback > _eventCallback
unsigned int _numChildrenRequiringEventTraversal
ref_ptr< NodeCallback > _cullCallback
bool _cullingActive
unsigned int _numChildrenWithCullingDisabled
unsigned int _numChildrenWithOccluderNodes
NodeMask _nodeMask
ref_ptr< StateSet > _stateset
- Protected Attributes inherited from osg::Object
std::string _name
DataVariance _dataVariance
osg::UserDataContainer * _userDataContainer
- Protected Attributes inherited from osg::Referenced
OpenThreads::AtomicPtr _observerSet
OpenThreads::Atomic _refCount

Additional Inherited Members

- Static Public Member Functions inherited from osg::Referenced
static OpenThreads::Mutex * getGlobalReferencedMutex ()
static void setThreadSafeReferenceCounting (bool enableThreadSafeReferenceCounting)
static bool getThreadSafeReferenceCounting ()
static void setDeleteHandler (DeleteHandler *handler)
static DeleteHandler * getDeleteHandler ()

Detailed Description

Impostor - is a form of Level Of Detail group node which allows both switching between children depending on distance from eye point and image caching.

The principle behind Imposters is that they cache an image of real geometry and then the image is drawn in subsequent frames instead of the real geometry. It's a bit like a Billboard but is updated at runtime and w.r.t view point. By drawing just the texture mapped quad you can cut down scene complexity and improve performance.

For more details have a look at:

http://grail.cs.washington.edu/projects/hic/

The OSG doesn't implement exactly the same technique as above, but its should be a good starting place. The OSG's impostors are much less intrusive since you don't need to restructure your whole scene to use them.

All you need to do to use Impostors is to set up the visible range values for each LOD child of the Impostor, as per osg::LOD, and set an Impostor threshold to tell the renderer at what distance the Impostor's image caching should cut in. The osg::CullVisitor automatically handles all the setting of pre-rendering stages to calculate the required ImpostorSprites (which encapsulates the image cache and quad), and updates them as the view point changes. If you use osg::SceneView/CullVisitor all the complexity of supporting Impostor will be nicely hidden away.

TODO: Various improvements are planned for the Impostor- 1) Estimation of how many frames an ImpostorSprite will be reused, if it won't be used more often than a minimum threshold then do not create ImpostorSprite - use the real geometry. 2) Sharing of texture memory between ImpostorSprites. 3) Simple 3D geometry for ImpostorSprite's rather than Billboarding. 4) Shrinking of the ImpostorSprite size to more closely fit the underlying geometry.

Member Typedef Documentation

typedef std::vector< osg::ref_ptr<ImpostorSprite> > osgSim::Impostor::ImpostorSpriteList

Constructor & Destructor Documentation

osgSim::Impostor::Impostor ( )
osgSim::Impostor::Impostor ( const Impostor &  es,
const osg::CopyOp &  copyop = osg::CopyOp::SHALLOW_COPY 
)
inline
virtual osgSim::Impostor::~Impostor ( )
inlineprotectedvirtual

Member Function Documentation

void osgSim::Impostor::addImpostorSprite ( unsigned int  contextID,
ImpostorSprite *  is 
)

Add an ImpostorSprite to the Impostor.

virtual osg::BoundingSphere osgSim::Impostor::computeBound ( ) const
virtual

Compute the bounding sphere around Node's geometry or children. This method is automatically called by getBound() when the bounding sphere has been marked dirty via dirtyBound().

Reimplemented from osg::LOD.

ImpostorSprite* osgSim::Impostor::createImpostorSprite ( osgUtil::CullVisitor *  cv)
protected
ImpostorSprite* osgSim::Impostor::findBestImpostorSprite ( unsigned int  contextID,
const osg::Vec3 &  currLocalEyePoint 
) const

Find the ImposterSprite which fits the current eye point best.

ImpostorSpriteList& osgSim::Impostor::getImpostorSpriteList ( unsigned int  contexID)
inline

Get the list of ImpostorSprites attached to this Impostor.

const ImpostorSpriteList& osgSim::Impostor::getImpostorSpriteList ( unsigned int  contexID) const
inline

Get a const list of ImpostorSprites attached to this const Impostor.

float osgSim::Impostor::getImpostorThreshold ( ) const
inline
osgSim::Impostor::META_Node ( osgSim  ,
Impostor   
)
void osgSim::Impostor::setImpostorThreshold ( float  distance)
inline

Set the Impostor threshold distance. For eye points further than this threshold the Imposter is used if appropriate, otherwise the LOD children as chosen as per a standard LOD node.

void osgSim::Impostor::setImpostorThresholdToBound ( float  ratio = 1.0f)
inline

Set the Impostor threshold distance relative to the node's bounding sphere's radius.

virtual void osgSim::Impostor::traverse ( osg::NodeVisitor &  )
virtual

Traverse downwards : calls children's accept method with NodeVisitor.

Reimplemented from osg::LOD.

Member Data Documentation

osg::buffered_object<ImpostorSpriteList> osgSim::Impostor::_impostorSpriteListBuffer
mutableprotected
float osgSim::Impostor::_impostorThreshold
protected
The documentation for this class was generated from the following file:
Generated on Thu Nov 22 2012 15:10:02 for openscenegraph by   doxygen 1.8.1.2