Pcp.md

Pcp module — pxr-usd-api 105.1 documentation

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Pcp module

 

# Pcp module

Summary: The PrimCache Population module implements core scenegraph composition semantics - behaviors informally referred to as Layering & Referencing.

Classes:

ArcType

Cache
PcpCache is the context required to make requests of the Pcp composition algorithm and cache the results.

Dependency
Description of a dependency.

DependencyType

DynamicFileFormatDependencyData
Contains the necessary information for storing a prim index's dependency on dynamic file format arguments and determining if a field change affects the prim index.

ErrorArcCycle
Arcs between PcpNodes that form a cycle.

ErrorArcPermissionDenied
Arcs that were not made between PcpNodes because of permission restrictions.

ErrorBase
Base class for all error types.

ErrorCapacityExceeded
Exceeded the capacity for composition arcs at a single site.

ErrorInconsistentAttributeType
Attributes that have specs with conflicting definitions.

ErrorInconsistentAttributeVariability
Attributes that have specs with conflicting variability.

ErrorInconsistentPropertyType
Properties that have specs with conflicting definitions.

ErrorInvalidAssetPath
Invalid asset paths used by references or payloads.

ErrorInvalidAssetPathBase

ErrorInvalidExternalTargetPath
Invalid target or connection path in some scope that points to an object outside of that scope.

ErrorInvalidInstanceTargetPath
Invalid target or connection path authored in an inherited class that points to an instance of that class.

ErrorInvalidPrimPath
Invalid prim paths used by references or payloads.

ErrorInvalidReferenceOffset
References or payloads that use invalid layer offsets.

ErrorInvalidSublayerOffset
Sublayers that use invalid layer offsets.

ErrorInvalidSublayerOwnership
Sibling layers that have the same owner.

ErrorInvalidSublayerPath
Asset paths that could not be both resolved and loaded.

ErrorInvalidTargetPath
Invalid target or connection path.

ErrorMutedAssetPath
Muted asset paths used by references or payloads.

ErrorOpinionAtRelocationSource
Opinions were found at a relocation source path.

ErrorPrimPermissionDenied
Layers with illegal opinions about private prims.

ErrorPropertyPermissionDenied
Layers with illegal opinions about private properties.

ErrorSublayerCycle
Layers that recursively sublayer themselves.

ErrorTargetPathBase
Base class for composition errors related to target or connection paths.

ErrorTargetPermissionDenied
Paths with illegal opinions about private targets.

ErrorType

ErrorUnresolvedPrimPath
Asset paths that could not be both resolved and loaded.

InstanceKey
A PcpInstanceKey identifies instanceable prim indexes that share the same set of opinions.

LayerStack
Represents a stack of layers that contribute opinions to composition.

LayerStackIdentifier
Arguments used to identify a layer stack.

LayerStackSite
A site specifies a path in a layer stack of scene description.

MapExpression
An expression that yields a PcpMapFunction value.

MapFunction
A function that maps values from one namespace (and time domain) to another.

NodeRef
PcpNode represents a node in an expression tree for compositing scene description.

PrimIndex
PcpPrimIndex is an index of the all sites of scene description that contribute opinions to a specific prim, under composition semantics.

PropertyIndex
PcpPropertyIndex is an index of all sites in scene description that contribute opinions to a specific property, under composition semantics.

Site
A site specifies a path in a layer stack of scene description.

class pxr.Pcp.ArcType
Methods:

GetValueFromName

Attributes:

allValues

static GetValueFromName()

allValues = (Pcp.ArcTypeRoot, Pcp.ArcTypeInherit, Pcp.ArcTypeRelocate, Pcp.ArcTypeVariant, Pcp.ArcTypeReference, Pcp.ArcTypePayload, Pcp.ArcTypeSpecialize)

class pxr.Pcp.Cache
PcpCache is the context required to make requests of the Pcp
composition algorithm and cache the results.
Because the algorithms are recursive  making a request typically makes
other internal requests to solve subproblems  caching subproblem
results is required for reasonable performance, and so this cache is
the only entrypoint to the algorithms.
There is a set of parameters that affect the composition results:

variant fallbacks: per named variant set, an ordered list of
fallback values to use when composing a prim that defines a variant
set but does not specify a selection
payload inclusion set: an SdfPath set used to identify which
prims should have their payloads included during composition; this is
the basis for explicit control over the”working set”of composition
file format target: the file format target that Pcp will request
when opening scene description layers
“USD mode”configures the Pcp composition algorithm to provide
only a custom, lighter subset of the full feature set, as needed by
the Universal Scene Description system
There are a number of different computations that can be requested.
These include computing a layer stack from a PcpLayerStackIdentifier,
computing a prim index or prim stack, and computing a property index.

Methods:

ComputeAttributeConnectionPaths(...)
Compute the attribute connection paths for the attribute at attributePath into paths .

ComputeLayerStack(identifier, allErrors)
Returns the layer stack for identifier if it exists, otherwise creates a new layer stack for identifier .

ComputePrimIndex(primPath, allErrors)
Compute and return a reference to the cached result for the prim index for the given path.

ComputePropertyIndex(propPath, allErrors)
Compute and return a reference to the cached result for the property index for the given path.

ComputeRelationshipTargetPaths(...)
Compute the relationship target paths for the relationship at relationshipPath into paths .

FindAllLayerStacksUsingLayer(layer)
Returns every computed & cached layer stack that includes layer .

FindPrimIndex(primPath)
Returns a pointer to the cached computed prim index for the given path, or None if it has not been computed.

FindPropertyIndex(propPath)
Returns a pointer to the cached computed property index for the given path, or None if it has not been computed.

FindSiteDependencies(siteLayerStack, ...)
Returns dependencies on the given site of scene description, as discovered by the cached index computations.

GetDynamicFileFormatArgumentDependencyData(...)
Returns the dynamic file format dependency data object for the prim index with the given primIndexPath .

GetLayerStackIdentifier()
Get the identifier of the layerStack used for composition.

GetMutedLayers()
Returns the list of canonical identifiers for muted layers in this cache.

GetUsedLayers()
Returns set of all layers used by this cache.

GetUsedLayersRevision()
Return a number that can be used to determine whether or not the set of layers used by this cache may have changed or not.

GetVariantFallbacks()
Get the list of fallbacks to attempt to use when evaluating variant sets that lack an authored selection.

HasAnyDynamicFileFormatArgumentDependencies()
Returns true if any prim index in this cache has a dependency on a dynamic file format argument field.

HasRootLayerStack(layerStack)
Return true if this cache's root layer stack is layerStack , false otherwise.

IsInvalidAssetPath(resolvedAssetPath)
Returns true if resolvedAssetPath was used by a prim (e.g.

IsInvalidSublayerIdentifier(identifier)
Returns true if identifier was used as a sublayer path in a layer stack but did not identify a valid layer.

IsLayerMuted(layerIdentifier)
Returns true if the layer specified by layerIdentifier is muted in this cache, false otherwise.

IsPayloadIncluded(path)
Return true if the payload is included for the given path.

IsPossibleDynamicFileFormatArgumentField(field)
Returns true if the given field is the name of a field that was composed while generating dynamic file format arguments for any prim index in this cache.

PrintStatistics()
Prints various statistics about the data stored in this cache.

Reload(changes)
Reload the layers of the layer stack, except session layers and sublayers of session layers.

RequestLayerMuting(layersToMute, ...)
Request layers to be muted or unmuted in this cache.

RequestPayloads(pathsToInclude, ...)
Request payloads to be included or excluded from composition.

SetVariantFallbacks(map, changes)
Set the list of fallbacks to attempt to use when evaluating variant sets that lack an authored selection.

UsesLayerStack(layerStack)
Return true if layerStack is used by this cache in its composition, false otherwise.

Attributes:

fileFormatTarget
str

layerStack
LayerStack

ComputeAttributeConnectionPaths(attributePath, paths, localOnly, stopProperty, includeStopProperty, deletedPaths, allErrors) → None
Compute the attribute connection paths for the attribute at
attributePath into paths .
If localOnly is true then this will compose attribute
connections from local nodes only. If stopProperty is not None
then this will stop composing attribute connections at
stopProperty , including stopProperty iff
includeStopProperty is true . If not None ,
deletedPaths will be populated with connection paths whose
deletion contributed to the computed result. allErrors will
contain any errors encountered while performing this operation.

Parameters

attributePath (Path) – 
paths (list[SdfPath]) – 
localOnly (bool) – 
stopProperty (Spec) – 
includeStopProperty (bool) – 
deletedPaths (list[SdfPath]) – 
allErrors (list[PcpError]) – 

ComputeLayerStack(identifier, allErrors) → LayerStack
Returns the layer stack for identifier if it exists, otherwise
creates a new layer stack for identifier .
This returns None if identifier is invalid (i.e. its root
layer is None ). allErrors will contain any errors encountered
while creating a new layer stack. It’ll be unchanged if the layer
stack already existed.

Parameters

identifier (LayerStackIdentifier) – 
allErrors (list[PcpError]) – 

ComputePrimIndex(primPath, allErrors) → PrimIndex
Compute and return a reference to the cached result for the prim index
for the given path.
allErrors will contain any errors encountered while performing
this operation.

Parameters

primPath (Path) – 
allErrors (list[PcpError]) – 

ComputePropertyIndex(propPath, allErrors) → PropertyIndex
Compute and return a reference to the cached result for the property
index for the given path.
allErrors will contain any errors encountered while performing
this operation.

Parameters

propPath (Path) – 
allErrors (list[PcpError]) – 

ComputeRelationshipTargetPaths(relationshipPath, paths, localOnly, stopProperty, includeStopProperty, deletedPaths, allErrors) → None
Compute the relationship target paths for the relationship at
relationshipPath into paths .
If localOnly is true then this will compose relationship
targets from local nodes only. If stopProperty is not None
then this will stop composing relationship targets at stopProperty
, including stopProperty iff includeStopProperty is true .
If not None , deletedPaths will be populated with target paths
whose deletion contributed to the computed result. allErrors will
contain any errors encountered while performing this operation.

Parameters

relationshipPath (Path) – 
paths (list[SdfPath]) – 
localOnly (bool) – 
stopProperty (Spec) – 
includeStopProperty (bool) – 
deletedPaths (list[SdfPath]) – 
allErrors (list[PcpError]) – 

FindAllLayerStacksUsingLayer(layer) → list[PcpLayerStackPtr]
Returns every computed & cached layer stack that includes layer .

Parameters
layer (Layer) – 

FindPrimIndex(primPath) → PrimIndex
Returns a pointer to the cached computed prim index for the given
path, or None if it has not been computed.

Parameters
primPath (Path) – 

FindPropertyIndex(propPath) → PropertyIndex
Returns a pointer to the cached computed property index for the given
path, or None if it has not been computed.

Parameters
propPath (Path) – 

FindSiteDependencies(siteLayerStack, sitePath, depMask, recurseOnSite, recurseOnIndex, filterForExistingCachesOnly) → list[PcpDependency]
Returns dependencies on the given site of scene description, as
discovered by the cached index computations.
depMask
specifies what classes of dependency to include; see
PcpDependencyFlags for details recurseOnSite
includes incoming dependencies on children of sitePath recurseOnIndex
extends the result to include all PcpCache child indexes below
discovered results filterForExistingCachesOnly
filters the results to only paths representing computed prim and
property index caches; otherwise a recursively-expanded result can
include un-computed paths that are expected to depend on the site

Parameters

siteLayerStack (LayerStack) – 
sitePath (Path) – 
depMask (PcpDependencyFlags) – 
recurseOnSite (bool) – 
recurseOnIndex (bool) – 
filterForExistingCachesOnly (bool) – 

FindSiteDependencies(siteLayer, sitePath, depMask, recurseOnSite, recurseOnIndex, filterForExistingCachesOnly) -> list[PcpDependency]
Returns dependencies on the given site of scene description, as
discovered by the cached index computations.
This method overload takes a site layer rather than a layer stack. It
will check every layer stack using that layer, and apply any relevant
sublayer offsets to the map functions in the returned
PcpDependencyVector.
See the other method for parameter details.

Parameters

siteLayer (Layer) – 
sitePath (Path) – 
depMask (PcpDependencyFlags) – 
recurseOnSite (bool) – 
recurseOnIndex (bool) – 
filterForExistingCachesOnly (bool) – 

GetDynamicFileFormatArgumentDependencyData(primIndexPath) → DynamicFileFormatDependencyData
Returns the dynamic file format dependency data object for the prim
index with the given primIndexPath .
This will return an empty dependency data if either there is no cache
prim index for the path or if the prim index has no dynamic file
formats that it depends on.

Parameters
primIndexPath (Path) – 

GetLayerStackIdentifier() → LayerStackIdentifier
Get the identifier of the layerStack used for composition.

GetMutedLayers() → list[str]
Returns the list of canonical identifiers for muted layers in this
cache.
See documentation on RequestLayerMuting for more details.

GetUsedLayers() → SdfLayerHandleSet
Returns set of all layers used by this cache.

GetUsedLayersRevision() → int
Return a number that can be used to determine whether or not the set
of layers used by this cache may have changed or not.
For example, if one calls GetUsedLayers() and saves the
GetUsedLayersRevision() , and then later calls GetUsedLayersRevision()
again, if the number is unchanged, then GetUsedLayers() is guaranteed
to be unchanged as well.

GetVariantFallbacks() → PcpVariantFallbackMap
Get the list of fallbacks to attempt to use when evaluating variant
sets that lack an authored selection.

HasAnyDynamicFileFormatArgumentDependencies() → bool
Returns true if any prim index in this cache has a dependency on a
dynamic file format argument field.

HasRootLayerStack(layerStack) → bool
Return true if this cache’s root layer stack is layerStack , false
otherwise.
This is functionally equivalent to comparing against the result of
GetLayerStack() , but does not require constructing a TfWeakPtr or any
refcount operations.

Parameters
layerStack (LayerStack) – 

HasRootLayerStack(layerStack) -> bool
This is an overloaded member function, provided for convenience. It
differs from the above function only in what argument(s) it accepts.

Parameters
layerStack (LayerStack) – 

IsInvalidAssetPath(resolvedAssetPath) → bool
Returns true if resolvedAssetPath was used by a prim (e.g.
in a reference) but did not resolve to a valid asset. This is
functionally equivalent to examining the values in the map returned by
GetInvalidAssetPaths, but more efficient.

Parameters
resolvedAssetPath (str) – 

IsInvalidSublayerIdentifier(identifier) → bool
Returns true if identifier was used as a sublayer path in a layer
stack but did not identify a valid layer.
This is functionally equivalent to examining the values in the vector
returned by GetInvalidSublayerIdentifiers, but more efficient.

Parameters
identifier (str) – 

IsLayerMuted(layerIdentifier) → bool
Returns true if the layer specified by layerIdentifier is muted in
this cache, false otherwise.
If layerIdentifier is relative, it is assumed to be relative to
this cache’s root layer. See documentation on RequestLayerMuting for
more details.

Parameters
layerIdentifier (str) – 

IsLayerMuted(anchorLayer, layerIdentifier, canonicalMutedLayerIdentifier) -> bool
Returns true if the layer specified by layerIdentifier is muted in
this cache, false otherwise.
If layerIdentifier is relative, it is assumed to be relative to
anchorLayer . If canonicalMutedLayerIdentifier is supplied, it
will be populated with the canonical identifier of the muted layer if
this function returns true. See documentation on RequestLayerMuting
for more details.

Parameters

anchorLayer (Layer) – 
layerIdentifier (str) – 
canonicalMutedLayerIdentifier (str) – 

IsPayloadIncluded(path) → bool
Return true if the payload is included for the given path.

Parameters
path (Path) – 

IsPossibleDynamicFileFormatArgumentField(field) → bool
Returns true if the given field is the name of a field that was
composed while generating dynamic file format arguments for any prim
index in this cache.

Parameters
field (str) – 

PrintStatistics() → None
Prints various statistics about the data stored in this cache.

Reload(changes) → None
Reload the layers of the layer stack, except session layers and
sublayers of session layers.
This will also try to load sublayers in this cache’s layer stack that
could not be loaded previously. It will also try to load any
referenced or payloaded layer that could not be loaded previously.
Clients should subsequently Apply() changes to use any now-
valid layers.

Parameters
changes (PcpChanges) – 

RequestLayerMuting(layersToMute, layersToUnmute, changes, newLayersMuted, newLayersUnmuted) → None
Request layers to be muted or unmuted in this cache.
Muted layers are ignored during composition and do not appear in any
layer stacks. The root layer of this stage may not be muted;
attempting to do so will generate a coding error. If the root layer of
a reference or payload layer stack is muted, the behavior is as if the
muted layer did not exist, which means a composition error will be
generated.
A canonical identifier for each layer in layersToMute will be
computed using ArResolver::CreateIdentifier using the cache’s root
layer as the anchoring asset. Any layer encountered during composition
with the same identifier will be considered muted and ignored.
Note that muting a layer will cause this cache to release all
references to that layer. If no other client is holding on to
references to that layer, it will be unloaded. In this case, if there
are unsaved edits to the muted layer, those edits are lost.  Since
anonymous layers are not serialized, muting an anonymous layer will
cause that layer and its contents to be lost in this case.
If changes is not nullptr , it is adjusted to reflect the
changes necessary to see the change in muted layers. Otherwise, those
changes are applied immediately.
newLayersMuted and newLayersUnmuted contains the pruned vector
of layers which are muted or unmuted by this call to
RequestLayerMuting.

Parameters

layersToMute (list[str]) – 
layersToUnmute (list[str]) – 
changes (PcpChanges) – 
newLayersMuted (list[str]) – 
newLayersUnmuted (list[str]) – 

RequestPayloads(pathsToInclude, pathsToExclude, changes) → None
Request payloads to be included or excluded from composition.
pathsToInclude
is a set of paths to add to the set for payload inclusion.
pathsToExclude
is a set of paths to remove from the set for payload inclusion.
changes
if not None , is adjusted to reflect the changes necessary to see
the change in payloads; otherwise those changes are applied
immediately.
If a path is listed in both pathsToInclude and pathsToExclude, it will
be treated as an inclusion only.

Parameters

pathsToInclude (SdfPathSet) – 
pathsToExclude (SdfPathSet) – 
changes (PcpChanges) – 

SetVariantFallbacks(map, changes) → None
Set the list of fallbacks to attempt to use when evaluating variant
sets that lack an authored selection.
If changes is not None then it’s adjusted to reflect the
changes necessary to see the change in standin preferences, otherwise
those changes are applied immediately.

Parameters

map (PcpVariantFallbackMap) – 
changes (PcpChanges) – 

UsesLayerStack(layerStack) → bool
Return true if layerStack is used by this cache in its
composition, false otherwise.

Parameters
layerStack (LayerStack) – 

property fileFormatTarget
str
Returns the file format target this cache is configured for.

Type
type

property layerStack
LayerStack
Get the layer stack for GetLayerStackIdentifier() .
Note that this will neither compute the layer stack nor report errors.
So if the layer stack has not been computed yet this will return
None . Use ComputeLayerStack() if you need to compute the layer
stack if it hasn’t been computed already and/or get errors caused by
computing the layer stack.

Type
type

class pxr.Pcp.Dependency
Description of a dependency.
Attributes:

indexPath

mapFunc

sitePath

property indexPath

property mapFunc

property sitePath

class pxr.Pcp.DependencyType
Methods:

GetValueFromName

Attributes:

allValues

static GetValueFromName()

allValues = (Pcp.DependencyTypeNone, Pcp.DependencyTypeRoot, Pcp.DependencyTypePurelyDirect, Pcp.DependencyTypePartlyDirect, Pcp.DependencyTypeDirect, Pcp.DependencyTypeAncestral, Pcp.DependencyTypeVirtual, Pcp.DependencyTypeNonVirtual, Pcp.DependencyTypeAnyNonVirtual, Pcp.DependencyTypeAnyIncludingVirtual)

class pxr.Pcp.DynamicFileFormatDependencyData
Contains the necessary information for storing a prim index’s
dependency on dynamic file format arguments and determining if a field
change affects the prim index. This data structure does not store the
prim index or its path itself and is expected to be the data in some
other data structure that maps prim indexes to its dependencies.
Methods:

CanFieldChangeAffectFileFormatArguments(...)
Given a field name and the changed field values in oldAndNewValues this return whether this change can affect any of the file format arguments generated by any of the contexts stored in this dependency.

GetRelevantFieldNames()
Returns a list of field names that were composed for any of the dependency contexts that were added to this dependency.

IsEmpty()
Returns whether this dependency data is empty.

CanFieldChangeAffectFileFormatArguments(fieldName, oldValue, newValue) → bool
Given a field name and the changed field values in
oldAndNewValues this return whether this change can affect any of
the file format arguments generated by any of the contexts stored in
this dependency.

Parameters

fieldName (str) – 
oldValue (VtValue) – 
newValue (VtValue) – 

GetRelevantFieldNames() → str.Set
Returns a list of field names that were composed for any of the
dependency contexts that were added to this dependency.

IsEmpty() → bool
Returns whether this dependency data is empty.

class pxr.Pcp.ErrorArcCycle
Arcs between PcpNodes that form a cycle.

class pxr.Pcp.ErrorArcPermissionDenied
Arcs that were not made between PcpNodes because of permission
restrictions.

class pxr.Pcp.ErrorBase
Base class for all error types.
Attributes:

errorType

property errorType

class pxr.Pcp.ErrorCapacityExceeded
Exceeded the capacity for composition arcs at a single site.

class pxr.Pcp.ErrorInconsistentAttributeType
Attributes that have specs with conflicting definitions.

class pxr.Pcp.ErrorInconsistentAttributeVariability
Attributes that have specs with conflicting variability.

class pxr.Pcp.ErrorInconsistentPropertyType
Properties that have specs with conflicting definitions.

class pxr.Pcp.ErrorInvalidAssetPath
Invalid asset paths used by references or payloads.

class pxr.Pcp.ErrorInvalidAssetPathBase

class pxr.Pcp.ErrorInvalidExternalTargetPath
Invalid target or connection path in some scope that points to an
object outside of that scope.

class pxr.Pcp.ErrorInvalidInstanceTargetPath
Invalid target or connection path authored in an inherited class that
points to an instance of that class.

class pxr.Pcp.ErrorInvalidPrimPath
Invalid prim paths used by references or payloads.

class pxr.Pcp.ErrorInvalidReferenceOffset
References or payloads that use invalid layer offsets.

class pxr.Pcp.ErrorInvalidSublayerOffset
Sublayers that use invalid layer offsets.

class pxr.Pcp.ErrorInvalidSublayerOwnership
Sibling layers that have the same owner.

class pxr.Pcp.ErrorInvalidSublayerPath
Asset paths that could not be both resolved and loaded.

class pxr.Pcp.ErrorInvalidTargetPath
Invalid target or connection path.

class pxr.Pcp.ErrorMutedAssetPath
Muted asset paths used by references or payloads.

class pxr.Pcp.ErrorOpinionAtRelocationSource
Opinions were found at a relocation source path.

class pxr.Pcp.ErrorPrimPermissionDenied
Layers with illegal opinions about private prims.

class pxr.Pcp.ErrorPropertyPermissionDenied
Layers with illegal opinions about private properties.

class pxr.Pcp.ErrorSublayerCycle
Layers that recursively sublayer themselves.

class pxr.Pcp.ErrorTargetPathBase
Base class for composition errors related to target or connection
paths.

class pxr.Pcp.ErrorTargetPermissionDenied
Paths with illegal opinions about private targets.

class pxr.Pcp.ErrorType
Methods:

GetValueFromName

Attributes:

allValues

static GetValueFromName()

allValues = (Pcp.ErrorType_ArcCycle, Pcp.ErrorType_ArcPermissionDenied, Pcp.ErrorType_IndexCapacityExceeded, Pcp.ErrorType_ArcCapacityExceeded, Pcp.ErrorType_ArcNamespaceDepthCapacityExceeded, Pcp.ErrorType_InconsistentPropertyType, Pcp.ErrorType_InconsistentAttributeType, Pcp.ErrorType_InconsistentAttributeVariability, Pcp.ErrorType_InternalAssetPath, Pcp.ErrorType_InvalidPrimPath, Pcp.ErrorType_InvalidAssetPath, Pcp.ErrorType_InvalidInstanceTargetPath, Pcp.ErrorType_InvalidExternalTargetPath, Pcp.ErrorType_InvalidTargetPath, Pcp.ErrorType_InvalidReferenceOffset, Pcp.ErrorType_InvalidSublayerOffset, Pcp.ErrorType_InvalidSublayerOwnership, Pcp.ErrorType_InvalidSublayerPath, Pcp.ErrorType_InvalidVariantSelection, Pcp.ErrorType_OpinionAtRelocationSource, Pcp.ErrorType_PrimPermissionDenied, Pcp.ErrorType_PropertyPermissionDenied, Pcp.ErrorType_SublayerCycle, Pcp.ErrorType_TargetPermissionDenied, Pcp.ErrorType_UnresolvedPrimPath)

class pxr.Pcp.ErrorUnresolvedPrimPath
Asset paths that could not be both resolved and loaded.

class pxr.Pcp.InstanceKey
A PcpInstanceKey identifies instanceable prim indexes that share the
same set of opinions. Instanceable prim indexes with equal instance
keys are guaranteed to have the same opinions for name children and
properties beneath those name children. They are NOT guaranteed to
have the same opinions for direct properties of the prim indexes
themselves.

class pxr.Pcp.LayerStack
Represents a stack of layers that contribute opinions to composition.
Each PcpLayerStack is identified by a PcpLayerStackIdentifier. This
identifier contains all of the parameters needed to construct a layer
stack, such as the root layer, session layer, and path resolver
context.
PcpLayerStacks are constructed and managed by a
Pcp_LayerStackRegistry.
Attributes:

expired
True if this object has expired, False otherwise.

identifier
LayerStackIdentifier

incrementalRelocatesSourceToTarget
SdfRelocatesMap

incrementalRelocatesTargetToSource
SdfRelocatesMap

layerOffsets

layerTree
LayerTree

layers
list[SdfLayerRefPtr]

localErrors
list[PcpError]

mutedLayers
set[str]

pathsToPrimsWithRelocates
list[SdfPath]

relocatesSourceToTarget
SdfRelocatesMap

relocatesTargetToSource
SdfRelocatesMap

property expired
True if this object has expired, False otherwise.

property identifier
LayerStackIdentifier
Returns the identifier for this layer stack.

Type
type

property incrementalRelocatesSourceToTarget
SdfRelocatesMap
Returns incremental relocation source-to-target mapping for this layer
stack.
This map contains the individual relocation entries found across all
layers in this layer stack; it does not combine ancestral entries with
descendant entries. For instance, if this layer stack contains
relocations { /A: /B} and { /A/C: /A/D}, this map will contain { /A:
/B} and { /A/C: /A/D}.

Type
type

property incrementalRelocatesTargetToSource
SdfRelocatesMap
Returns incremental relocation target-to-source mapping for this layer
stack.
See GetIncrementalRelocatesTargetToSource for more details.

Type
type

property layerOffsets

property layerTree
LayerTree
Returns the layer tree representing the structure of this layer stack.

Type
type

property layers
list[SdfLayerRefPtr]
Returns the layers in this layer stack in strong-to-weak order.
Note that this is only the local layer stack  it does not include
any layers brought in by references inside prims.

Type
type

property localErrors
list[PcpError]
Return the list of errors local to this layer stack.

Type
type

property mutedLayers
set[str]
Returns the set of layers that were muted in this layer stack.

Type
type

property pathsToPrimsWithRelocates
list[SdfPath]
Returns a list of paths to all prims across all layers in this layer
stack that contained relocates.

Type
type

property relocatesSourceToTarget
SdfRelocatesMap
Returns relocation source-to-target mapping for this layer stack.
This map combines the individual relocation entries found across all
layers in this layer stack; multiple entries that affect a single prim
will be combined into a single entry. For instance, if this layer
stack contains relocations { /A: /B} and { /A/C: /A/D}, this map will
contain { /A: /B} and { /B/C: /B/D}. This allows consumers to go from
unrelocated namespace to relocated namespace in a single step.

Type
type

property relocatesTargetToSource
SdfRelocatesMap
Returns relocation target-to-source mapping for this layer stack.
See GetRelocatesSourceToTarget for more details.

Type
type

class pxr.Pcp.LayerStackIdentifier
Arguments used to identify a layer stack.
Objects of this type are immutable.
Attributes:

pathResolverContext

rootLayer

sessionLayer

property pathResolverContext

property rootLayer

property sessionLayer

class pxr.Pcp.LayerStackSite
A site specifies a path in a layer stack of scene description.
Attributes:

layerStack

path

property layerStack

property path

class pxr.Pcp.MapExpression
An expression that yields a PcpMapFunction value.
Expressions comprise constant values, variables, and operators applied
to sub-expressions. Expressions cache their computed values
internally. Assigning a new value to a variable automatically
invalidates the cached values of dependent expressions. Common
(sub-)expressions are automatically detected and shared.
PcpMapExpression exists solely to support efficient incremental
handling of relocates edits. It represents a tree of the namespace
mapping operations and their inputs, so we can narrowly redo the
computation when one of the inputs changes.
Methods:

AddRootIdentity()
Return a new expression representing this expression with an added (if necessary) mapping from</>to</>.

Compose(f)
Create a new PcpMapExpression representing the application of f's value, followed by the application of this expression's value.

Constant
classmethod Constant(constValue) -> MapExpression

Evaluate()
Evaluate this expression, yielding a PcpMapFunction value.

Identity
classmethod Identity() -> MapExpression

Inverse()
Create a new PcpMapExpression representing the inverse of f.

MapSourceToTarget(path)
Map a path in the source namespace to the target.

MapTargetToSource(path)
Map a path in the target namespace to the source.

Attributes:

isIdentity
bool

isNull
bool

timeOffset
LayerOffset

AddRootIdentity() → MapExpression
Return a new expression representing this expression with an added (if
necessary) mapping from</>to</>.

Compose(f) → MapExpression
Create a new PcpMapExpression representing the application of f’s
value, followed by the application of this expression’s value.

Parameters
f (MapExpression) – 

static Constant()
classmethod Constant(constValue) -> MapExpression
Create a new constant.

Parameters
constValue (Value) – 

Evaluate() → Value
Evaluate this expression, yielding a PcpMapFunction value.
The computed result is cached. The return value is a reference to the
internal cached value. The cache is automatically invalidated as
needed.

static Identity()
classmethod Identity() -> MapExpression
Return an expression representing PcpMapFunction::Identity() .

static Inverse() → MapExpression
Create a new PcpMapExpression representing the inverse of f.

MapSourceToTarget(path) → Path
Map a path in the source namespace to the target.
If the path is not in the domain, returns an empty path.

Parameters
path (Path) – 

MapTargetToSource(path) → Path
Map a path in the target namespace to the source.
If the path is not in the co-domain, returns an empty path.

Parameters
path (Path) – 

property isIdentity
bool
Return true if the evaluated map function is the identity function.
For identity, MapSourceToTarget() always returns the path unchanged.

Type
type

property isNull
bool
Return true if this is a null expression.

Type
type

property timeOffset
LayerOffset
The time offset of the mapping.

Type
type

class pxr.Pcp.MapFunction
A function that maps values from one namespace (and time domain) to
another. It represents the transformation that an arc such as a
reference arc applies as it incorporates values across the arc.
Take the example of a reference arc, where a source path</Model>is
referenced as a target path,</Model_1>. The source path</Model>is the
source of the opinions; the target path</Model_1>is where they are
incorporated in the scene. Values in the model that refer to paths
relative to</Model>must be transformed to be relative
to</Model_1>instead. The PcpMapFunction for the arc provides this
service.
Map functions have a specific domain, or set of values they can
operate on. Any values outside the domain cannot be mapped. The domain
precisely tracks what areas of namespace can be referred to across
various forms of arcs.
Map functions can be chained to represent a series of map operations
applied in sequence. The map function represent the cumulative effect
as efficiently as possible. For example, in the case of a chained
reference from</Model>to</Model>to</Model>to</Model_1>, this is
effectively the same as a mapping directly from</Model>to</Model_1>.
Representing the cumulative effect of arcs in this way is important
for handling larger scenes efficiently.
Map functions can be inverted. Formally, map functions are
bijections (one-to-one and onto), which ensures that they can be
inverted. Put differently, no information is lost by applying a map
function to set of values within its domain; they retain their
distinct identities and can always be mapped back.
One analogy that may or may not be helpful: In the same way a
geometric transform maps a model’s points in its rest space into the
world coordinates for a particular instance, a PcpMapFunction maps
values about a referenced model into the composed scene for a
particular instance of that model. But rather than translating and
rotating points, the map function shifts the values in namespace (and
time).
Methods:

Compose(f)
Compose this map over the given map function.

ComposeOffset(newOffset)
Compose this map function over a hypothetical map function that has an identity path mapping and offset .

GetInverse()
Return the inverse of this map function.

Identity
classmethod Identity() -> MapFunction

IdentityPathMap
classmethod IdentityPathMap() -> PathMap

MapSourceToTarget(path)
Map a path in the source namespace to the target.

MapTargetToSource(path)
Map a path in the target namespace to the source.

Attributes:

isIdentity
bool

isIdentityPathMapping
bool

isNull
bool

sourceToTargetMap
PathMap

timeOffset
LayerOffset

Compose(f) → MapFunction
Compose this map over the given map function.
The result will represent the application of f followed by the
application of this function.

Parameters
f (MapFunction) – 

ComposeOffset(newOffset) → MapFunction
Compose this map function over a hypothetical map function that has an
identity path mapping and offset .
This is equivalent to building such a map function and invoking
Compose() , but is faster.

Parameters
newOffset (LayerOffset) – 

GetInverse() → MapFunction
Return the inverse of this map function.
This returns a true inverse inv: for any path p in this function’s
domain that it maps to p’, inv(p’) ->p.

static Identity()
classmethod Identity() -> MapFunction
Construct an identity map function.

static IdentityPathMap()
classmethod IdentityPathMap() -> PathMap
Returns an identity path mapping.

MapSourceToTarget(path) → Path
Map a path in the source namespace to the target.
If the path is not in the domain, returns an empty path.

Parameters
path (Path) – 

MapTargetToSource(path) → Path
Map a path in the target namespace to the source.
If the path is not in the co-domain, returns an empty path.

Parameters
path (Path) – 

property isIdentity
bool
Return true if the map function is the identity function.
The identity function has an identity path mapping and time offset.

Type
type

property isIdentityPathMapping
bool
Return true if the map function uses the identity path mapping.
If true, MapSourceToTarget() always returns the path unchanged.
However, this map function may have a non-identity time offset.

Type
type

property isNull
bool
Return true if this map function is the null function.
For a null function, MapSourceToTarget() always returns an empty path.

Type
type

property sourceToTargetMap
PathMap
The set of path mappings, from source to target.

Type
type

property timeOffset
LayerOffset
The time offset of the mapping.

Type
type

class pxr.Pcp.NodeRef
PcpNode represents a node in an expression tree for compositing scene
description.
A node represents the opinions from a particular site. In addition, it
may have child nodes, representing nested expressions that are
composited over/under this node.
Child nodes are stored and composited in strength order.
Each node holds information about the arc to its parent. This captures
both the relative strength of the sub-expression as well as any value-
mapping needed, such as to rename opinions from a model to use in a
particular instance.
Methods:

CanContributeSpecs()
Returns true if this node is allowed to contribute opinions for composition, false otherwise.

GetDepthBelowIntroduction()
Return the number of levels of namespace this node's site is below the level at which it was introduced by an arc.

GetIntroPath()
Get the path that introduced this node.

GetOriginRootNode()
Walk up to the root origin node for this node.

GetPathAtIntroduction()
Returns the path for this node's site when it was introduced.

GetRootNode()
Walk up to the root node of this expression.

IsDueToAncestor()

IsRootNode()
Returns true if this node is the root node of the prim index graph.

Attributes:

arcType
ArcType

children

hasSpecs
None

hasSymmetry
None

isCulled
bool

isInert
bool

isRestricted
bool

layerStack
LayerStack

mapToParent
MapExpression

mapToRoot
MapExpression

namespaceDepth
int

origin

parent

path
Path

permission
Permission

siblingNumAtOrigin
int

site
LayerStackSite

CanContributeSpecs() → bool
Returns true if this node is allowed to contribute opinions for
composition, false otherwise.

GetDepthBelowIntroduction() → int
Return the number of levels of namespace this node’s site is below the
level at which it was introduced by an arc.

GetIntroPath() → Path
Get the path that introduced this node.
Specifically, this is the path the parent node had at the level of
namespace where this node was added as a child. For a root node, this
returns the absolute root path. See also GetDepthBelowIntroduction() .

GetOriginRootNode() → NodeRef
Walk up to the root origin node for this node.
This is the very first node that caused this node to be added to the
graph. For instance, the root origin node of an implied inherit is the
original inherit node.

GetPathAtIntroduction() → Path
Returns the path for this node’s site when it was introduced.

GetRootNode() → NodeRef
Walk up to the root node of this expression.

IsDueToAncestor() → bool

IsRootNode() → bool
Returns true if this node is the root node of the prim index graph.

property arcType
ArcType
Returns the type of arc connecting this node to its parent node.

Type
type

property children

property hasSpecs
None
Returns true if this node has opinions authored for composition, false
otherwise.

Type
type

property hasSymmetry
None
Get/set whether this node provides any symmetry opinions, either
directly or from a namespace ancestor.

Type
type

property isCulled
bool

Type
type

property isInert
bool

Type
type

property isRestricted
bool

Type
type

property layerStack
LayerStack
Returns the layer stack for the site this node represents.

Type
type

property mapToParent
MapExpression
Returns mapping function used to translate paths and values from this
node to its parent node.

Type
type

property mapToRoot
MapExpression
Returns mapping function used to translate paths and values from this
node directly to the root node.

Type
type

property namespaceDepth
int
Returns the absolute namespace depth of the node that introduced this
node.
Note that this does not count any variant selections.

Type
type

property origin

property parent

property path
Path
Returns the path for the site this node represents.

Type
type

property permission
Permission

type : None
Get/set the permission for this node.
This indicates whether specs on this node can be accessed from other
nodes.

Type
type

property siblingNumAtOrigin
int
Returns this node’s index among siblings with the same arc type at
this node’s origin.

Type
type

property site
LayerStackSite
Get the site this node represents.

Type
type

class pxr.Pcp.PrimIndex
PcpPrimIndex is an index of the all sites of scene description that
contribute opinions to a specific prim, under composition semantics.
PcpComputePrimIndex() builds an index (“indexes”) the given prim site.
At any site there may be scene description values expressing arcs that
represent instructions to pull in further scene description.
PcpComputePrimIndex() recursively follows these arcs, building and
ordering the results.
Methods:

ComposeAuthoredVariantSelections()
Compose the authored prim variant selections.

ComputePrimChildNames(nameOrder, ...)
Compute the prim child names for the given path.

ComputePrimPropertyNames(nameOrder)
Compute the prim property names for the given path.

DumpToDotGraph(filename, ...)
Dump the prim index in dot format to the file named filename .

DumpToString(includeInheritOriginInfo, ...)
Dump the prim index contents to a string.

GetNodeProvidingSpec(primSpec)
Returns the node that brings opinions from primSpec into this prim index.

GetSelectionAppliedForVariantSet(variantSet)
Return the variant selection applied for the named variant set.

IsInstanceable()
Returns true if this prim index is instanceable.

IsValid()
Return true if this index is valid.

PrintStatistics()
Prints various statistics about this prim index.

Attributes:

hasAnyPayloads

localErrors
list[PcpError]

primStack

rootNode
NodeRef

ComposeAuthoredVariantSelections() → SdfVariantSelectionMap
Compose the authored prim variant selections.
These are the variant selections expressed in scene description. Note
that these selections may not have actually been applied, if they are
invalid.
This result is not cached, but computed each time.

ComputePrimChildNames(nameOrder, prohibitedNameSet) → None
Compute the prim child names for the given path.
errors will contain any errors encountered while performing this
operation.

Parameters

nameOrder (list[TfToken]) – 
prohibitedNameSet (PcpTokenSet) – 

ComputePrimPropertyNames(nameOrder) → None
Compute the prim property names for the given path.
errors will contain any errors encountered while performing this
operation. The nameOrder vector must not contain any duplicate
entries.

Parameters
nameOrder (list[TfToken]) – 

DumpToDotGraph(filename, includeInheritOriginInfo, includeMaps) → None
Dump the prim index in dot format to the file named filename .
See Dump(...) for information regarding arguments.

Parameters

filename (str) – 
includeInheritOriginInfo (bool) – 
includeMaps (bool) – 

DumpToString(includeInheritOriginInfo, includeMaps) → str
Dump the prim index contents to a string.
If includeInheritOriginInfo is true , output for implied
inherit nodes will include information about the originating inherit
node. If includeMaps is true , output for each node will
include the mappings to the parent and root node.

Parameters

includeInheritOriginInfo (bool) – 
includeMaps (bool) – 

GetNodeProvidingSpec(primSpec) → NodeRef
Returns the node that brings opinions from primSpec into this prim
index.
If no such node exists, returns an invalid PcpNodeRef.

Parameters
primSpec (PrimSpec) – 

GetNodeProvidingSpec(layer, path) -> NodeRef
Returns the node that brings opinions from the Sd prim spec at
layer and path into this prim index.
If no such node exists, returns an invalid PcpNodeRef.

Parameters

layer (Layer) – 
path (Path) – 

GetSelectionAppliedForVariantSet(variantSet) → str
Return the variant selection applied for the named variant set.
If none was applied, this returns an empty string. This can be
different from the authored variant selection; for example, if the
authored selection is invalid.

Parameters
variantSet (str) – 

IsInstanceable() → bool
Returns true if this prim index is instanceable.
Instanceable prim indexes with the same instance key are guaranteed to
have the same set of opinions, but may not have local opinions about
name children.
PcpInstanceKey

IsValid() → bool
Return true if this index is valid.
A default-constructed index is invalid.

PrintStatistics() → None
Prints various statistics about this prim index.

property hasAnyPayloads

property localErrors
list[PcpError]
Return the list of errors local to this prim.

Type
type

property primStack

property rootNode
NodeRef
Returns the root node of the prim index graph.

Type
type

class pxr.Pcp.PropertyIndex
PcpPropertyIndex is an index of all sites in scene description that
contribute opinions to a specific property, under composition
semantics.
Attributes:

localErrors
list[PcpError]

localPropertyStack

propertyStack

property localErrors
list[PcpError]
Return the list of errors local to this property.

Type
type

property localPropertyStack

property propertyStack

class pxr.Pcp.Site
A site specifies a path in a layer stack of scene description.
Attributes:

layerStack

path

property layerStack

property path

© Copyright 2019-2023, NVIDIA.
      Last updated on Nov 14, 2023.