#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())

	UsdLuxLightListAPI (const UsdSchemaBase &schemaObj)

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

USDLUX_API UsdAttribute	GetLightListCacheBehaviorAttr () const

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

USDLUX_API UsdRelationship	GetLightListRel () const

USDLUX_API UsdRelationship	CreateLightListRel () const

USDLUX_API SdfPathSet	ComputeLightList (ComputeMode mode) const

USDLUX_API void	StoreLightList (const SdfPathSet &) const

USDLUX_API void	InvalidateLightList () const

Public Member Functions inherited from UsdAPISchemaBase
	UsdAPISchemaBase (const UsdPrim &prim=UsdPrim())

	UsdAPISchemaBase (const UsdSchemaBase &schemaObj)

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

Public Member Functions inherited from UsdSchemaBase
bool	IsConcrete () const

bool	IsTyped () const

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

bool	IsAppliedAPISchema () const

bool	IsMultipleApplyAPISchema () const

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

Static Public Member Functions
static USDLUX_API const TfTokenVector &	GetSchemaAttributeNames (bool includeInherited=true)

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

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

static USDLUX_API UsdLuxLightListAPI	Apply (const UsdPrim &prim)

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

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

Static Public Attributes
static const UsdSchemaKind	schemaKind = UsdSchemaKind::SingleApplyAPI

Static Public Attributes inherited from UsdAPISchemaBase
static const UsdSchemaKind	schemaKind = UsdSchemaKind::AbstractBase

Static Public Attributes inherited from UsdSchemaBase
static const UsdSchemaKind	schemaKind = UsdSchemaKind::AbstractBase

Protected Member Functions
USDLUX_API UsdSchemaKind	_GetSchemaKind () const override

Protected Member Functions inherited from UsdAPISchemaBase
	UsdAPISchemaBase (const UsdPrim &prim, const TfToken &instanceName)

	UsdAPISchemaBase (const UsdSchemaBase &schemaObj, const TfToken &instanceName)

const TfToken &	_GetInstanceName () const

USD_API bool	_IsCompatible () const override

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)

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:

// Load everything on the stage so we can find all lights,
// including those inside payloads
stage->Load();

// Traverse all prims, checking if they have an applied UsdLuxLightAPI
// (Note: ignoring instancing and a few other things for simplicity)
SdfPathVector lights;
for (UsdPrim prim: stage->Traverse()) {
    if (prim.HasAPI<UsdLuxLightAPI>()) {
        lights.push_back(i->GetPath());
    }
}

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:

def Xform "BigSetWithLights" (
    kind = "assembly"
    payload = @BigSetWithLights.usd@   // Heavy payload
) {
    // Pre-computed, cached list of lights inside payload
    rel lightList = [
        <./Lights/light_1>,
        <./Lights/light_2>,
        ...
    ]
    token lightList:cacheBehavior = "consumeAndContinue";
}

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):

// Find and load all lights, using lightList cache where available
UsdLuxLightListAPI list(stage->GetPseudoRoot());
SdfPathSet lights = list.ComputeLightList(
    UsdLuxLightListAPI::ComputeModeConsultModelHierarchyCache);
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 180 of file lightListAPI.h.

Member Enumeration Documentation

enum UsdLuxLightListAPI::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 lightListAPI.h.

Constructor & Destructor Documentation

UsdLuxLightListAPI::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 192 of file lightListAPI.h.

UsdLuxLightListAPI::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 200 of file lightListAPI.h.

virtual USDLUX_API UsdLuxLightListAPI::~UsdLuxLightListAPI ( )

virtual

Destructor.

Member Function Documentation

USDLUX_API UsdSchemaKind UsdLuxLightListAPI::_GetSchemaKind ( ) const

overrideprotectedvirtual

Returns the kind of schema this class belongs to.

See Also: UsdSchemaKind

Reimplemented from UsdAPISchemaBase.

static USDLUX_API UsdLuxLightListAPI 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()

static USDLUX_API bool UsdLuxLightListAPI::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 UsdLuxLightListAPI::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.

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

See GetLightListCacheBehaviorAttr(), and also Usd_Create_Or_Get_Property 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 UsdLuxLightListAPI::CreateLightListRel ( ) const

See GetLightListRel(), and also Usd_Create_Or_Get_Property for when to use Get vs Create

static USDLUX_API UsdLuxLightListAPI 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));

USDLUX_API UsdAttribute UsdLuxLightListAPI::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 UsdLuxLightListAPI::GetLightListRel ( ) const

Relationship to lights in the scene.

static USDLUX_API const TfTokenVector& UsdLuxLightListAPI::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 UsdLuxLightListAPI::InvalidateLightList ( ) const

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

USDLUX_API void UsdLuxLightListAPI::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

friend class UsdSchemaRegistry

friend

Definition at line 278 of file lightListAPI.h.

Member Data Documentation

const UsdSchemaKind UsdLuxLightListAPI::schemaKind = UsdSchemaKind::SingleApplyAPI

static

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

See Also: UsdSchemaKind

Definition at line 186 of file lightListAPI.h.

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

pxr/usd/usdLux/lightListAPI.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

Friends And Related Function Documentation

Member Data Documentation