API schema to support discovery and publishing of lights in a scene. More...

Inheritance diagram for UsdLuxListAPI:

Public Types
enum	ComputeMode { ComputeModeConsultModelHierarchyCache, ComputeModeIgnoreCache }
	Runtime control over whether to consult stored lightList caches. More...

Public Member Functions
	UsdLuxListAPI (const UsdPrim &prim=UsdPrim())
	Construct a UsdLuxListAPI on UsdPrim `prim` . More...

	UsdLuxListAPI (const UsdSchemaBase &schemaObj)
	Construct a UsdLuxListAPI on the prim held by `schemaObj` . More...

virtual USDLUX_API	~UsdLuxListAPI ()
	Destructor. More...

USDLUX_API UsdAttribute	GetLightListCacheBehaviorAttr () const
	Controls how the lightList should be interpreted. More...

USDLUX_API UsdAttribute	CreateLightListCacheBehaviorAttr (VtValue const &defaultValue=VtValue(), bool writeSparsely=false) const
	See GetLightListCacheBehaviorAttr(), and also Create vs Get Property Methods for when to use Get vs Create. More...

USDLUX_API UsdRelationship	GetLightListRel () const
	Relationship to lights in the scene. More...

USDLUX_API UsdRelationship	CreateLightListRel () const
	See GetLightListRel(), and also Create vs Get Property Methods for when to use Get vs Create. More...

USDLUX_API SdfPathSet	ComputeLightList (ComputeMode mode) const
	Computes and returns the list of lights and light filters in the stage, optionally consulting a cached result. More...

USDLUX_API void	StoreLightList (const SdfPathSet &) const
	Store the given paths as the lightlist for this prim. More...

USDLUX_API void	InvalidateLightList () const
	Mark any stored lightlist as invalid, by setting the lightList:cacheBehavior attribute to ignore. More...

Public Member Functions inherited from UsdAPISchemaBase
	UsdAPISchemaBase (const UsdPrim &prim=UsdPrim())
	Construct a UsdAPISchemaBase on UsdPrim `prim` . More...

	UsdAPISchemaBase (const UsdSchemaBase &schemaObj)
	Construct a UsdAPISchemaBase on the prim held by `schemaObj` . More...

virtual USD_API	~UsdAPISchemaBase ()=0
	Destructor. More...

Public Member Functions inherited from UsdSchemaBase
bool	IsConcrete () const
	Returns whether or not this class corresponds to a concrete instantiable prim type in scene description. More...

bool	IsTyped () const
	Returns whether or not this class inherits from UsdTyped. More...

bool	IsAPISchema () const
	Returns whether this is an API schema or not. More...

bool	IsAppliedAPISchema () const
	Returns whether this is an applied API schema or not. More...

bool	IsMultipleApplyAPISchema () const
	Returns whether this is an applied API schema or not. More...

UsdSchemaKind	GetSchemaKind () const
	Returns the kind of schema this class is. More...

USD_API	UsdSchemaBase (const UsdPrim &prim=UsdPrim())
	Construct and store `prim` as the held prim. More...

USD_API	UsdSchemaBase (const UsdSchemaBase &otherSchema)
	Construct and store for the same prim held by `otherSchema`. More...

virtual USD_API	~UsdSchemaBase ()
	Destructor. More...

USD_API	operator bool () const

UsdPrim	GetPrim () const
	Return this schema object's held prim. More...

SdfPath	GetPath () const
	Shorthand for GetPrim()->GetPath(). More...

USD_API const UsdPrimDefinition *	GetSchemaClassPrimDefinition () const
	Return the prim definition associated with this schema instance if one exists, otherwise return null. More...

Static Public Member Functions
static USDLUX_API const TfTokenVector &	GetSchemaAttributeNames (bool includeInherited=true)
	Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes. More...

static USDLUX_API UsdLuxListAPI	Get (const UsdStagePtr &stage, const SdfPath &path)
	Return a UsdLuxListAPI holding the prim adhering to this schema at `path` on `stage`. More...

static USDLUX_API bool	CanApply (const UsdPrim &prim, std::string *whyNot=nullptr)
	Returns true if this single-apply API schema can be applied to the given `prim`. More...

static USDLUX_API UsdLuxListAPI	Apply (const UsdPrim &prim)
	Applies this single-apply API schema to the given `prim`. More...

Static Public Member Functions inherited from UsdAPISchemaBase
static USD_API const TfTokenVector &	GetSchemaAttributeNames (bool includeInherited=true)
	Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes. More...

Static Public Member Functions inherited from UsdSchemaBase
static const TfTokenVector &	GetSchemaAttributeNames (bool includeInherited=true)

Static Public Attributes
static const UsdSchemaKind	schemaKind = UsdSchemaKind::SingleApplyAPI
	Compile time constant representing what kind of schema this class is. More...

Static Public Attributes inherited from UsdAPISchemaBase
static const UsdSchemaKind	schemaKind = UsdSchemaKind::AbstractBase
	Compile time constant representing what kind of schema this class is. More...

Static Public Attributes inherited from UsdSchemaBase
static const UsdSchemaKind	schemaKind = UsdSchemaKind::AbstractBase
	Compile time constant representing what kind of schema this class is. More...

Protected Member Functions
USDLUX_API UsdSchemaKind	_GetSchemaKind () const override
	Returns the kind of schema this class belongs to. More...

Protected Member Functions inherited from UsdAPISchemaBase
	UsdAPISchemaBase (const UsdPrim &prim, const TfToken &instanceName)
	Construct a multiple-apply UsdAPISchemaBase on UsdPrim `prim` with the specified `instanceName`. More...

	UsdAPISchemaBase (const UsdSchemaBase &schemaObj, const TfToken &instanceName)
	Construct a multiple-apply UsdAPISchemaBase on the prim held by `schemaObj` with the given `instanceName`. More...

const TfToken &	_GetInstanceName () const
	Returns the instance name of the API schema object belonging to a multiple-apply API schema. More...

USD_API bool	_IsCompatible () const override
	Check whether this APISchema object is valid for the currently held prim. More...

Protected Member Functions inherited from UsdSchemaBase
virtual UsdSchemaKind	_GetSchemaType () const

const TfType &	_GetType () const

USD_API UsdAttribute	_CreateAttr (TfToken const &attrName, SdfValueTypeName const &typeName, bool custom, SdfVariability variability, VtValue const &defaultValue, bool writeSparsely) const

Friends
class	UsdSchemaRegistry

Additional Inherited Members
Static Protected Member Functions inherited from UsdAPISchemaBase
template<typename APISchemaType >
static APISchemaType	_ApplyAPISchema (const UsdPrim &prim, const TfToken &apiSchemaName)
	Helper method to apply a single-apply API schema with the given schema name `apiSchemaName'` and C++ type 'APISchemaType'. More...

template<typename APISchemaType >
static APISchemaType	_MultipleApplyAPISchema (const UsdPrim &prim, const TfToken &apiSchemaName, const TfToken &instanceName)
	Helper method to apply a multiple-apply API schema with the given schema name `apiSchemaName'`, C++ type 'APISchemaType' and instance name `instanceName`. More...

Detailed Description

API schema to support discovery and publishing of lights in a scene.

Discovering Lights via Traversal

To motivate this API, consider what is required to discover all lights in a scene. We must load all payloads and traverse all prims:

*  01  // Load everything on the stage so we can find all lights,
*  02  // including those inside payloads
*  03  stage->Load();
*  04  
*  05  // Traverse all prims, checking if they are of type UsdLuxLight
*  06  // (Note: ignoring instancing and a few other things for simplicity)
*  07  SdfPathVector lights;
*  08  for (UsdPrim prim: stage->Traverse()) {
*  09      if (prim.IsA<UsdLuxLight>()) {
*  10          lights.push_back(i->GetPath());
*  11      }
*  12  }
*  

This traversal – suitably elaborated to handle certain details – is the first and simplest thing UsdLuxListAPI provides. UsdLuxListAPI::ComputeLightList() performs this traversal and returns all lights in the scene:

*  01  UsdLuxListAPI listAPI(stage->GetPseudoRoot());
*  02  SdfPathVector lights = listAPI.ComputeLightList();
*  

Publishing a Cached Light List

Consider a USD client that needs to quickly discover lights but wants to defer loading payloads and traversing the entire scene where possible, and is willing to do up-front computation and caching to achieve that.

UsdLuxListAPI provides a way to cache the computed light list, by publishing the list of lights onto prims in the model hierarchy. Consider a big set that contains lights:

*  01  def Xform "BigSetWithLights" (
*  02      kind = "assembly"
*  03      payload = @BigSetWithLights.usd@   // Heavy payload
*  04  ) {
*  05      // Pre-computed, cached list of lights inside payload
*  06      rel lightList = [
*  07          <./Lights/light_1>,
*  08          <./Lights/light_2>,
*  09          ...
*  10      ]
*  11      token lightList:cacheBehavior = "consumeAndContinue";
*  12  }
*  

The lightList relationship encodes a set of lights, and the lightList:cacheBehavior property provides fine-grained control over how to use that cache. (See details below.)

The cache can be created by first invoking ComputeLightList(ComputeModeIgnoreCache) to pre-compute the list and then storing the result with UsdLuxListAPI::StoreLightList().

To enable efficient retrieval of the cache, it should be stored on a model hierarchy prim. Furthermore, note that while you can use a UsdLuxListAPI bound to the pseudo-root prim to query the lights (as in the example above) because it will perform a traversal over descendants, you cannot store the cache back to the pseduo-root prim.

To consult the cached list, we invoke ComputeLightList(ComputeModeConsultModelHierarchyCache):

*  01  // Find and load all lights, using lightList cache where available
*  02  UsdLuxListAPI list(stage->GetPseudoRoot());
*  03  SdfPathSet lights = list.ComputeLightList(
*  04      UsdLuxListAPI::ComputeModeConsultModelHierarchyCache);
*  05  stage.LoadAndUnload(lights, SdfPathSet());
*  

In this mode, ComputeLightList() will traverse the model hierarchy, accumulating cached light lists.

Controlling Cache Behavior

The lightList:cacheBehavior property gives additional fine-grained control over cache behavior:

The fallback value, "ignore", indicates that the lightList should be disregarded. This provides a way to invalidate cache entries. Note that unless "ignore" is specified, a lightList with an empty list of targets is considered a cache indicating that no lights are present.

The value "consumeAndContinue" indicates that the cache should be consulted to contribute lights to the scene, and that recursion should continue down the model hierarchy in case additional lights are added as descedants. This is the default value established when StoreLightList() is invoked. This behavior allows the lights within a large model, such as the BigSetWithLights example above, to be published outside the payload, while also allowing referencing and layering to add additional lights over that set.

The value "consumeAndHalt" provides a way to terminate recursive traversal of the scene for light discovery. The cache will be consulted but no descendant prims will be examined.

Instancing

Where instances are present, UsdLuxListAPI::ComputeLightList() will return the instance-unique paths to any lights discovered within those instances. Lights within a UsdGeomPointInstancer will not be returned, however, since they cannot be referred to solely via paths.

For any described attribute Fallback Value or Allowed Values below that are text/tokens, the actual token is published and defined in UsdLuxTokens. So to set an attribute to the value "rightHanded", use UsdLuxTokens->rightHanded as the value.

Definition at line 180 of file listAPI.h.

Member Enumeration Documentation

enum ComputeMode

Runtime control over whether to consult stored lightList caches.

Enumerator

ComputeModeConsultModelHierarchyCache

Consult any caches found on the model hierarchy.

Do not traverse beneath the model hierarchy.

ComputeModeIgnoreCache

Ignore any caches found, and do a full prim traversal.

Definition at line 350 of file listAPI.h.

Constructor & Destructor Documentation

UsdLuxListAPI ( const UsdPrim & prim = UsdPrim() )

inlineexplicit

Construct a UsdLuxListAPI on UsdPrim prim .

Equivalent to UsdLuxListAPI::Get(prim.GetStage(), prim.GetPath()) for a valid prim, but will not immediately throw an error for an invalid prim

Definition at line 192 of file listAPI.h.

UsdLuxListAPI ( const UsdSchemaBase & schemaObj )

inlineexplicit

Construct a UsdLuxListAPI on the prim held by schemaObj .

Should be preferred over UsdLuxListAPI(schemaObj.GetPrim()), as it preserves SchemaBase state.

Definition at line 200 of file listAPI.h.

virtual USDLUX_API ~UsdLuxListAPI ( )

virtual

Destructor.

Member Function Documentation

USDLUX_API UsdSchemaKind _GetSchemaKind ( ) const

overrideprotectedvirtual

Returns the kind of schema this class belongs to.

See Also: UsdSchemaKind

Reimplemented from UsdAPISchemaBase.

static USDLUX_API UsdLuxListAPI Apply ( const UsdPrim & prim )

static

Applies this single-apply API schema to the given prim.

This information is stored by adding "ListAPI" to the token-valued, listOp metadata apiSchemas on the prim.

Returns: A valid UsdLuxListAPI object is returned upon success. An invalid (or empty) UsdLuxListAPI object is returned upon failure. See UsdPrim::ApplyAPI() for conditions resulting in failure.

See Also: UsdPrim::GetAppliedSchemas(); UsdPrim::HasAPI(); UsdPrim::CanApplyAPI(); UsdPrim::ApplyAPI(); UsdPrim::RemoveAPI()

static USDLUX_API bool CanApply	(	const UsdPrim &	prim,
		std::string *	whyNot = `nullptr`
	)

static

Returns true if this single-apply API schema can be applied to the given prim.

If this schema can not be a applied to the prim, this returns false and, if provided, populates whyNot with the reason it can not be applied.

Note that if CanApply returns false, that does not necessarily imply that calling Apply will fail. Callers are expected to call CanApply before calling Apply if they want to ensure that it is valid to apply a schema.

See Also: UsdPrim::GetAppliedSchemas(); UsdPrim::HasAPI(); UsdPrim::CanApplyAPI(); UsdPrim::ApplyAPI(); UsdPrim::RemoveAPI()

USDLUX_API SdfPathSet ComputeLightList ( ComputeMode mode ) const

Computes and returns the list of lights and light filters in the stage, optionally consulting a cached result.

In ComputeModeIgnoreCache mode, caching is ignored, and this does a prim traversal looking for prims of type UsdLuxLight or UsdLuxLightFilter.

In ComputeModeConsultModelHierarchyCache, this does a traversal only of the model hierarchy. In this traversal, any lights that live as model hierarchy prims are accumulated, as well as any paths stored in lightList caches. The lightList:cacheBehavior attribute gives further control over the cache behavior; see the class overview for details.

When instances are present, ComputeLightList(ComputeModeIgnoreCache) will return the instance-uniqiue paths to any lights discovered within those instances. Lights within a UsdGeomPointInstancer will not be returned, however, since they cannot be referred to solely via paths.

USDLUX_API UsdAttribute CreateLightListCacheBehaviorAttr	(	VtValue const &	defaultValue = `VtValue()`,
		bool	writeSparsely = `false`
	)		const

See GetLightListCacheBehaviorAttr(), and also Create vs Get Property Methods for when to use Get vs Create.

If specified, author defaultValue as the attribute's default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false.

USDLUX_API UsdRelationship CreateLightListRel ( ) const

See GetLightListRel(), and also Create vs Get Property Methods for when to use Get vs Create.

static USDLUX_API UsdLuxListAPI Get	(	const UsdStagePtr &	stage,
		const SdfPath &	path
	)

static

Return a UsdLuxListAPI holding the prim adhering to this schema at path on stage.

If no prim exists at path on stage, or if the prim at that path does not adhere to this schema, return an invalid schema object. This is shorthand for the following:

* UsdLuxListAPI(stage->GetPrimAtPath(path));

*

USDLUX_API UsdAttribute GetLightListCacheBehaviorAttr ( ) const

Controls how the lightList should be interpreted.

Valid values are:

consumeAndHalt: The lightList should be consulted, and if it exists, treated as a final authoritative statement of any lights that exist at or below this prim, halting recursive discovery of lights.
consumeAndContinue: The lightList should be consulted, but recursive traversal over nameChildren should continue in case additional lights are added by descendants.
ignore: The lightList should be entirely ignored. This provides a simple way to temporarily invalidate an existing cache. This is the fallback behavior.


Declaration	`token lightList:cacheBehavior`
C++ Type	TfToken
Usd Type	SdfValueTypeNames->Token
Allowed Values	consumeAndHalt, consumeAndContinue, ignore

USDLUX_API UsdRelationship GetLightListRel ( ) const

Relationship to lights in the scene.

static USDLUX_API const TfTokenVector& GetSchemaAttributeNames ( bool includeInherited = true )

static

Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes.

Does not include attributes that may be authored by custom/extended methods of the schemas involved.

USDLUX_API void InvalidateLightList ( ) const

Mark any stored lightlist as invalid, by setting the lightList:cacheBehavior attribute to ignore.

USDLUX_API void StoreLightList ( const SdfPathSet & ) const

Store the given paths as the lightlist for this prim.

Paths that do not have this prim's path as a prefix will be silently ignored. This will set the listList:cacheBehavior to "consumeAndContinue".

Member Data Documentation

const UsdSchemaKind schemaKind = UsdSchemaKind::SingleApplyAPI

static

Compile time constant representing what kind of schema this class is.

See Also: UsdSchemaKind

Definition at line 186 of file listAPI.h.

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

pxr/usd/usdLux/listAPI.h

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Friends

Additional Inherited Members

Detailed Description

Discovering Lights via Traversal

Publishing a Cached Light List

Controlling Cache Behavior

Instancing

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation