UsdLuxLightListAPI Class Reference

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

#include <lightListAPI.h>

Inheritance diagram for UsdLuxLightListAPI:

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

Public Member Functions
	UsdLuxLightListAPI (const UsdPrim &prim=UsdPrim())
	Construct a UsdLuxLightListAPI on UsdPrim prim .
	UsdLuxLightListAPI (const UsdSchemaBase &schemaObj)
	Construct a UsdLuxLightListAPI on the prim held by schemaObj .
virtual USDLUX_API	~UsdLuxLightListAPI ()
	Destructor.
USDLUX_API UsdAttribute	GetLightListCacheBehaviorAttr () const
	Controls how the lightList should be interpreted.
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.
USDLUX_API UsdRelationship	GetLightListRel () const
	Relationship to lights in the scene.
USDLUX_API UsdRelationship	CreateLightListRel () const
	See GetLightListRel(), and also Create vs Get Property Methods for when to use Get vs Create.
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.
USDLUX_API void	StoreLightList (const SdfPathSet &) const
	Store the given paths as the lightlist for this prim.
USDLUX_API void	InvalidateLightList () const
	Mark any stored lightlist as invalid, by setting the lightList:cacheBehavior attribute to ignore.
Public Member Functions inherited from UsdAPISchemaBase
	UsdAPISchemaBase (const UsdPrim &prim=UsdPrim())
	Construct a UsdAPISchemaBase on UsdPrim prim .
	UsdAPISchemaBase (const UsdSchemaBase &schemaObj)
	Construct a UsdAPISchemaBase on the prim held by schemaObj .
virtual USD_API	~UsdAPISchemaBase ()=0
	Destructor.
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.
bool	IsTyped () const
	Returns whether or not this class inherits from UsdTyped.
bool	IsAPISchema () const
	Returns whether this is an API schema or not.
bool	IsAppliedAPISchema () const
	Returns whether this is an applied API schema or not.
bool	IsMultipleApplyAPISchema () const
	Returns whether this is an applied API schema or not.
UsdSchemaKind	GetSchemaKind () const
	Returns the kind of schema this class is.
USD_API	UsdSchemaBase (const UsdPrim &prim=UsdPrim())
	Construct and store prim as the held prim.
USD_API	UsdSchemaBase (const UsdSchemaBase &otherSchema)
	Construct and store for the same prim held by otherSchema.
virtual USD_API	~UsdSchemaBase ()
	Destructor.
UsdPrim	GetPrim () const
	Return this schema object's held prim.
SdfPath	GetPath () const
	Shorthand for GetPrim()->GetPath().
USD_API const UsdPrimDefinition *	GetSchemaClassPrimDefinition () const
	Return the prim definition associated with this schema instance if one exists, otherwise return null.
USD_API	operator bool () const
	Return true if this schema object is compatible with its held prim, false otherwise.

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.
static USDLUX_API UsdLuxLightListAPI	Get (const UsdStagePtr &stage, const SdfPath &path)
	Return a UsdLuxLightListAPI holding the prim adhering to this schema at path on stage.
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.
static USDLUX_API UsdLuxLightListAPI	Apply (const UsdPrim &prim)
	Applies this single-apply API schema to the given prim.
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.
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.
Static Public Attributes inherited from UsdAPISchemaBase
static const UsdSchemaKind	schemaKind = UsdSchemaKind::AbstractBase
	Compile time constant representing what kind of schema this class is.
Static Public Attributes inherited from UsdSchemaBase
static const UsdSchemaKind	schemaKind = UsdSchemaKind::AbstractBase
	Compile time constant representing what kind of schema this class is.

Protected Member Functions
USDLUX_API UsdSchemaKind	_GetSchemaKind () const override
	Returns the kind of schema this class belongs to.
Protected Member Functions inherited from UsdAPISchemaBase
USD_API UsdSchemaKind	_GetSchemaKind () const override
	Returns the kind of schema this class belongs to.
	UsdAPISchemaBase (const UsdPrim &prim, const TfToken &instanceName)
	Construct a multiple-apply UsdAPISchemaBase on UsdPrim prim with the specified instanceName.
	UsdAPISchemaBase (const UsdSchemaBase &schemaObj, const TfToken &instanceName)
	Construct a multiple-apply UsdAPISchemaBase on the prim held by schemaObj with the given instanceName.
const TfToken &	_GetInstanceName () const
	Returns the instance name of the API schema object belonging to a multiple-apply API schema.
USD_API bool	_IsCompatible () const override
	Check whether this APISchema object is valid for the currently held prim.
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
static USD_API TfTokenVector	_GetMultipleApplyInstanceNames (const UsdPrim &prim, const TfType &schemaType)
	Returns a vector of names of API schema objects belonging to a multiple-apply API schema applied to a given prim.

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 have an applied UsdLuxLightAPI
06  // (Note: ignoring instancing and a few other things for simplicity)
07  SdfPathVector lights;
08  for (UsdPrim prim: stage->Traverse()) {
09      if (prim.HasAPI<UsdLuxLightAPI>()) {
10          lights.push_back(i->GetPath());
11      }
12  }

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

01  UsdLuxLightListAPI 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.

UsdLuxLightListAPI 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 UsdLuxLightListAPI::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 UsdLuxLightListAPI 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  UsdLuxLightListAPI list(stage->GetPseudoRoot());
03  SdfPathSet lights = list.ComputeLightList(
04      UsdLuxLightListAPI::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, UsdLuxLightListAPI::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 163 of file lightListAPI.h.

Member Enumeration Documentation

ComputeMode

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 334 of file lightListAPI.h.

Constructor & Destructor Documentation

UsdLuxLightListAPI() [1/2]

UsdLuxLightListAPI ( const UsdPrim &  prim = UsdPrim() )

inlineexplicit

Construct a UsdLuxLightListAPI on UsdPrim prim .

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

Definition at line 175 of file lightListAPI.h.

UsdLuxLightListAPI() [2/2]

UsdLuxLightListAPI ( const UsdSchemaBase &  schemaObj )

inlineexplicit

Construct a UsdLuxLightListAPI on the prim held by schemaObj .

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

Definition at line 183 of file lightListAPI.h.

~UsdLuxLightListAPI()

virtual USDLUX_API ~UsdLuxLightListAPI ( )

virtual

Destructor.

Member Function Documentation

_GetSchemaKind()

USDLUX_API UsdSchemaKind _GetSchemaKind ( ) const

overrideprotectedvirtual

Returns the kind of schema this class belongs to.

See also

UsdSchemaKind

Reimplemented from UsdAPISchemaBase.

Apply()

static USDLUX_API UsdLuxLightListAPI Apply ( const UsdPrim &  prim )

static

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

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

Returns

A valid UsdLuxLightListAPI object is returned upon success. An invalid (or empty) UsdLuxLightListAPI 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()

CanApply()

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()

ComputeLightList()

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 that have a UsdLuxLightAPI or are of type 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.

CreateLightListCacheBehaviorAttr()

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.

CreateLightListRel()

USDLUX_API UsdRelationship CreateLightListRel

(

)

const

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

Get()

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

static

Return a UsdLuxLightListAPI 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:

UsdLuxLightListAPI(stage->GetPrimAtPath(path));

GetLightListCacheBehaviorAttr()

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

GetLightListRel()

USDLUX_API UsdRelationship GetLightListRel

(

)

const

Relationship to lights in the scene.

GetSchemaAttributeNames()

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.

InvalidateLightList()

USDLUX_API void InvalidateLightList

(

)

const

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

StoreLightList()

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".

Friends And Related Function Documentation

UsdSchemaRegistry

friend class UsdSchemaRegistry

friend

Definition at line 261 of file lightListAPI.h.

Member Data Documentation

schemaKind

const UsdSchemaKind schemaKind = UsdSchemaKind::SingleApplyAPI

static

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

See also

UsdSchemaKind

Definition at line 169 of file lightListAPI.h.

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

• pxr/usd/usdLux/lightListAPI.h