OpenSceneGraph  3.0.1
Classes | Public Member Functions | Protected Types | Protected Member Functions | Protected Attributes
osgShadow::ViewDependentShadowTechnique Class Reference

ViewDependentShadowTechnique is a base class for all View Dependent Shadow techniques. More...

Inheritance diagram for osgShadow::ViewDependentShadowTechnique:
Inheritance graph
[legend]

List of all members.

Classes

struct  ViewData
 Base container class for view dependent shadow resources. More...

Public Member Functions

 ViewDependentShadowTechnique (void)
 osgShadow::ShadowTechnique equivalent methods for view dependent techniques
 ViewDependentShadowTechnique (const ViewDependentShadowTechnique &vdst, const osg::CopyOp &copyop=osg::CopyOp::SHALLOW_COPY)
 Classic OSG cloning constructor.
 META_Object (osgShadow, ViewDependentShadowTechnique)
 Declaration of standard OSG object methods.
virtual void dirty ()
 Dirty view data bits and force update of view data resources.
virtual void init ()
 Initialize the ShadowedScene and some data structures.
virtual void update (osg::NodeVisitor &nv)
 Run the update traversal of the ShadowedScene and update any local cached data structures.
virtual void cull (osgUtil::CullVisitor &cv)
 Run the cull traversal of the ShadowedScene and set up the rendering for this ShadowTechnique.
virtual void cleanSceneGraph ()
 Clean scene graph from any shadow technique specific nodes, state and drawables.
virtual void traverse (osg::NodeVisitor &nv)
 Traverse shadow scene graph.

Protected Types

typedef std::map< osg::ref_ptr
< osgUtil::CullVisitor >
, osg::ref_ptr< ViewData > > 
ViewDataMap
 Map of view dependent data per view cull visitor (CVs are used as indices) ViewDependentShadowTechnique uses this map to find VieData for each cull vitior.

Protected Member Functions

 ~ViewDependentShadowTechnique (void)
 Classic protected OSG destructor.
virtual
ViewDependentShadowTechnique::ViewData
getViewDependentData (osgUtil::CullVisitor *cv)
 Return view dependent data for the cull visitor.
virtual void setViewDependentData (osgUtil::CullVisitor *cv, ViewDependentShadowTechnique::ViewData *data)
 Define view dependent data for the cull visitor.

Protected Attributes

ViewDataMap _viewDataMap
OpenThreads::Mutex _viewDataMapMutex
 Mutex used to serialize accesses to ViewDataMap.

Detailed Description

ViewDependentShadowTechnique is a base class for all View Dependent Shadow techniques.

It defines fundamental object structure and methods to manage separate shadow resources for each view of the scene. By view we understand osg::View or SceneView instance and their associated Camera. Typical osg application has one or more such views. View Dependent Shadow techniques manage shadow generation for them.

View Dependent Shadow techniques are used to optimize shadow algorithms for part of the scene seen on the view. If rest of the scene is behind view frustum, there is no sense in computing shadows for it. Since in practice we often use 3d databases extending far beyond current camera frustum View Dependent Shadow approach may produce much better shadows.

The other goal is to provide framework for thread safe rendering of the shadows. It allows to use shadows with different OSG threading models.

Conceptually ViewDependentShadowTechnique is similar to osgSim::OverlayNode. Its a container class for number of ViewData (or ViewData derived) objects doing actual shadow work for each of the scene views.

But ViewDependentShadowTechnique is intended as foundation layer for all derived classes so in some way it extends osgSim::OverlayNode approach a bit.

HOW IT WORKS:

ViewDependendentShadowTechnique is derived from osgShadow::ShadowTechnique and as such overrides virtual methods of osgShadow::ShadowTechnique. But most of the shadow dirty work is done by ViewData objects, ViewDependendentShadowTechnique::cull is the only osgShadow::ShadowTechnique method where ViewDependendentShadowTechnique does something significant:

What ViewDependentShadowTechnique::cull( CullVisitor & cv ) does ? It identifies View. CullVisitor ptr is used as View identificator. In practice we do not check and interpret what are actual Views and SceneViews set up by application. We focus on Camera and CullVisitors as a identificators of views. We can safely do this because each such view will have associated unique CullVisitor used to cull the scene in every frame.

Based on CullVisitor ptr passed to cull method, associated Technique::ViewData object is created (if neccessary) and then seleced. Then control is passed to this ViewData object. So, each view has its associated unique ViewData (or derived) object performing dirty work of shadow resources management and shadow generation for the view.

To support creation of classes derived from ViewDependentShadowTechnique it was neccessary to provide mechanism to override ViewData and allow for initialization of new derived ViewData objects. Creation and initialization is performed when ViewDependendentShadowTechnique::cull gets called with CullVistor ptr which does not yet have associated ViewData object. When it happens, virtual initViewDependentData method is called to give derived techniques a chance to allocate and iniitalize its specific resources as new ViewData derived instance. In practice initViewDependentData in derived techniques should look the same as in base class so as a convenience it was defined as META_ViewDependentShadowTechnique macro. Derived techniques use this macro to override initViewDependentData method for their usage.

After ViewData derived object is construted and selected, control is passed to this object by call to virtual ViewData::cull method. The rest of work is the done by this object. ViewDependentShadowTechnique::ViewData is intended as a base class so it does nothing. In practice the rest of dirty work will do new ViewData classes implemented in derived techniques.


Member Typedef Documentation

Map of view dependent data per view cull visitor (CVs are used as indices) ViewDependentShadowTechnique uses this map to find VieData for each cull vitior.


Constructor & Destructor Documentation

osgShadow::ViewDependentShadowTechnique::ViewDependentShadowTechnique ( void  )

osgShadow::ShadowTechnique equivalent methods for view dependent techniques

Classic OSG constructor

osgShadow::ViewDependentShadowTechnique::ViewDependentShadowTechnique ( const ViewDependentShadowTechnique vdst,
const osg::CopyOp copyop = osg::CopyOp::SHALLOW_COPY 
)

Classic OSG cloning constructor.

osgShadow::ViewDependentShadowTechnique::~ViewDependentShadowTechnique ( void  ) [protected]

Classic protected OSG destructor.


Member Function Documentation

virtual void osgShadow::ViewDependentShadowTechnique::cleanSceneGraph ( ) [virtual]

Clean scene graph from any shadow technique specific nodes, state and drawables.

Reimplemented from osgShadow::ShadowTechnique.

virtual void osgShadow::ViewDependentShadowTechnique::cull ( osgUtil::CullVisitor cv) [virtual]

Run the cull traversal of the ShadowedScene and set up the rendering for this ShadowTechnique.

Reimplemented from osgShadow::ShadowTechnique.

virtual void osgShadow::ViewDependentShadowTechnique::dirty ( ) [virtual]

Dirty view data bits and force update of view data resources.

Reimplemented from osgShadow::ShadowTechnique.

virtual ViewDependentShadowTechnique::ViewData* osgShadow::ViewDependentShadowTechnique::getViewDependentData ( osgUtil::CullVisitor cv) [protected, virtual]

Return view dependent data for the cull visitor.

virtual void osgShadow::ViewDependentShadowTechnique::init ( ) [virtual]

Initialize the ShadowedScene and some data structures.

Reimplemented from osgShadow::ShadowTechnique.

osgShadow::ViewDependentShadowTechnique::META_Object ( osgShadow  ,
ViewDependentShadowTechnique   
)

Declaration of standard OSG object methods.

virtual void osgShadow::ViewDependentShadowTechnique::setViewDependentData ( osgUtil::CullVisitor cv,
ViewDependentShadowTechnique::ViewData data 
) [protected, virtual]

Define view dependent data for the cull visitor.

virtual void osgShadow::ViewDependentShadowTechnique::traverse ( osg::NodeVisitor nv) [virtual]

Traverse shadow scene graph.

Reimplemented from osgShadow::ShadowTechnique.

virtual void osgShadow::ViewDependentShadowTechnique::update ( osg::NodeVisitor nv) [virtual]

Run the update traversal of the ShadowedScene and update any local cached data structures.

Reimplemented from osgShadow::ShadowTechnique.


Member Data Documentation

Mutex used to serialize accesses to ViewDataMap.


The documentation for this class was generated from the following file:

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