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UsdLuxLightListAPI Class Reference

#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 UsdPrimDefinitionGetSchemaClassPrimDefinition () 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 TfTokenVectorGetSchemaAttributeNames (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
 

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(
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 180 of file lightListAPI.h.

Member Enumeration Documentation

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: