usg::GeomSceneContext Class Reference

#include <GeomSceneContext.h>

Public Member Functions
	GeomSceneContext ()
	Default ctor creates a single default TimeValue to process.
	GeomSceneContext (const usg::StageRef &stage, const fdk::TimeValueSet &times, const ArgSet &scope_vars=ArgSet())
	Build the context for a stage and set the process times and scope vars.
	GeomSceneContext (const GeomSceneContext &b, const usg::StageRef &new_stage)
	Copies the second context while updating the StageRef.
	GeomSceneContext (const GeomSceneContext &b, const fdk::TimeValueSet &times, bool append_times=false)
const ArgSet &	requestScopeVars () const
	Additional request context scope vars for upstream GeomEngines to use.
void	setRequestScopeVars (const ArgSet &vars)
	Overwrites the current request context scope vars.
const usg::StageRef &	stage () const
EngineMode	processMode () const
bool	doGeometryProcessing () const
	Should the engine make any changes to layer/prim/property contents.
bool	doGeometryInitialization () const
	Should the engine define or initialize layer/prim/property contents.
bool	doModifyPropertyValues () const
	Should the engine add values to properties.
bool	defineGeometry () const
	Should the engine define Layer contents.
bool	initializeProperties () const
bool	modifyProperties () const
bool	editStageState () const
const fdk::TimeValueSet &	processTimes () const
size_t	numProcessTimes () const
	Returns the minimum number of times to process, requested by downstream consumers.

Protected Attributes
usg::StageRef	_stage
	The stage we're building.
EngineMode	_processMode
	Nominal engine processing mode to use.
fdk::TimeValueSet	_processTimes
	Times to process the scene at.
ArgSet	_requestScopeVars
	Provides additional context for upstream GeomEngines.

Friends
class	GeomEngine
USG_ENGINE_API std::ostream &	operator<< (std::ostream &, const GeomSceneContext &)

Detailed Description

Context for GeomEngine getScenegraph(), processScenegraph() to fill in the scenegraph Stage the scene consumer wants.

A GeomEngine

This class also contains an arbitrary set of scene-global key/value attributes that can help guide or define behaviors. Some are scoping parameters set by downstream GeomEngines to be passed upstream to guide the creation of prims or materials.

Constructor & Destructor Documentation

GeomSceneContext()

usg::GeomSceneContext::GeomSceneContext	(	const GeomSceneContext &	b,
		const fdk::TimeValueSet &	times,
		bool	append_times = false
	)

Copies stage and mode from a second context and either replaces or adds to the process times. Note this does not copy the scope vars.

Member Function Documentation

stage()

const usg::StageRef & usg::GeomSceneContext::stage ( ) const

inline

The current usg::Stage being built. If processMode() is DefineGeometry then the Stage will be composed at some point in the engine graph, usually the bottom.

processMode()

EngineMode usg::GeomSceneContext::processMode ( ) const

inline

The nominal processing mode the engine should handle in processScenegraph(). This is determined by the current engine dirty state flags and what state targets the engine has declared it wants to handle.

If there are multiple enabled dirty flags the highest priority mode is used. For example if define-geometry and modify-values are both true then the mode will be EngineMode::DefineGeometry.

An engine can further examine its dirty states if more processing context is needed.

initializeProperties()

bool usg::GeomSceneContext::initializeProperties ( ) const

inline

Should the engine just initialize property defaults. This should happen after properties are defined or the properties have been cleared due to a parameter change.

An engine must be prepared to re-assign these property defaults whenever the engine modify-values state becomes dirty as the contents of all properties get cleared.

modifyProperties()

bool usg::GeomSceneContext::modifyProperties ( ) const

inline

Should the engine just modify property contents, typically because more time samples have been requested. If the engine does not create time samples this mode can be ignored.

editStageState()

bool usg::GeomSceneContext::editStageState ( ) const

inline

Should the engine affect the composed Stage dynamically - ie apply stage edits. These changes are intended to be transitory/temporary and not exported to a .usd file.

An example of this would be for extra stage metadata used internally to affect the Hydra delegates, etc, or to manipulate any non-Stage data in the GeomSceneOutput.

This is effectively the same as checking mayEditStage() since even after the first processing pass we want to know if the engine -intends- to edit stage values on each subsequent process pass.

processTimes()

const fdk::TimeValueSet & usg::GeomSceneContext::processTimes ( ) const

inline

The set of time values the engine should process at, typically to add new time samples to any animating properties. If the engine does not produce any time samples this can be ignored.

The engine is not restricted to processing and creating just these times, however if the engine is creating time-sampled properties then at a minimum it should create them for these times.

Important note - an engine can be repeatedly called by downstream consumers to process additional times in any random order, so engines should determine if a) do they need to create property time samples, and b) do so in an efficient way so handling additional times is as cheap as possible. For example an engine should avoid calculating the topology of a mesh for every process time request, especially if the mesh is not animating.