| Ar module — pxr-usd-api 105.1 documentation | |
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| Ar module | |
| # Ar module | |
| Summary: The Ar (Asset Resolution) library is responsible for querying, reading, and writing asset data. | |
| Classes: | |
| DefaultResolver | |
| Default asset resolution implementation used when no plugin implementation is provided. | |
| DefaultResolverContext | |
| Resolver context object that specifies a search path to use during asset resolution. | |
| Notice | |
| ResolvedPath | |
| Represents a resolved asset path. | |
| Resolver | |
| Interface for the asset resolution system. | |
| ResolverContext | |
| An asset resolver context allows clients to provide additional data to the resolver for use during resolution. | |
| ResolverContextBinder | |
| Helper object for managing the binding and unbinding of ArResolverContext objects with the asset resolver. | |
| ResolverScopedCache | |
| Helper object for managing asset resolver cache scopes. | |
| Timestamp | |
| Represents a timestamp for an asset. | |
| class pxr.Ar.DefaultResolver | |
| Default asset resolution implementation used when no plugin | |
| implementation is provided. | |
| In order to resolve assets specified by relative paths, this resolver | |
| implements a simple”search path”scheme. The resolver will anchor the | |
| relative path to a series of directories and return the first absolute | |
| path where the asset exists. | |
| The first directory will always be the current working directory. The | |
| resolver will then examine the directories specified via the following | |
| mechanisms (in order): | |
| The currently-bound ArDefaultResolverContext for the calling | |
| thread | |
| ArDefaultResolver::SetDefaultSearchPath | |
| The environment variable PXR_AR_DEFAULT_SEARCH_PATH. This is | |
| expected to be a list of directories delimited by the platform’s | |
| standard path separator. | |
| ArDefaultResolver supports creating an ArDefaultResolverContext via | |
| ArResolver::CreateContextFromString by passing a list of directories | |
| delimited by the platform’s standard path separator. | |
| Methods: | |
| SetDefaultSearchPath | |
| classmethod SetDefaultSearchPath(searchPath) -> None | |
| static SetDefaultSearchPath() | |
| classmethod SetDefaultSearchPath(searchPath) -> None | |
| Set the default search path that will be used during asset resolution. | |
| This must be called before the first call to ArGetResolver. The | |
| specified paths will be searched in addition to, and before paths | |
| specified via the environment variable PXR_AR_DEFAULT_SEARCH_PATH | |
| Parameters | |
| searchPath (list[str]) – | |
| class pxr.Ar.DefaultResolverContext | |
| Resolver context object that specifies a search path to use during | |
| asset resolution. This object is intended for use with the default | |
| ArDefaultResolver asset resolution implementation; see documentation | |
| for that class for more details on the search path resolution | |
| algorithm. | |
| Example usage: | |
| ArDefaultResolverContext ctx({"/Local/Models", "/Installed/Models"}); | |
| { | |
| // Bind the context object: | |
| ArResolverContextBinder binder(ctx); | |
| // While the context is bound, all calls to ArResolver::Resolve | |
| // (assuming ArDefaultResolver is the underlying implementation being | |
| // used) will include the specified paths during resolution. | |
| std::string resolvedPath = resolver.Resolve("ModelName/File.txt") | |
| } | |
| // Once the context is no longer bound (due to the ArResolverContextBinder | |
| // going out of scope), its search path no longer factors into asset | |
| // resolution. | |
| Methods: | |
| GetSearchPath() | |
| Return this context's search path. | |
| GetSearchPath() → list[str] | |
| Return this context’s search path. | |
| class pxr.Ar.Notice | |
| Classes: | |
| ResolverChanged | |
| ResolverNotice | |
| class ResolverChanged | |
| Methods: | |
| AffectsContext | |
| AffectsContext() | |
| class ResolverNotice | |
| class pxr.Ar.ResolvedPath | |
| Represents a resolved asset path. | |
| Methods: | |
| GetPathString() | |
| Return the resolved path held by this object as a string. | |
| GetPathString() → str | |
| Return the resolved path held by this object as a string. | |
| class pxr.Ar.Resolver | |
| Interface for the asset resolution system. An asset resolver is | |
| responsible for resolving asset information (including the asset’s | |
| physical path) from a logical path. | |
| See ar_implementing_resolver for information on how to customize asset | |
| resolution behavior by implementing a subclass of ArResolver. Clients | |
| may use ArGetResolver to access the configured asset resolver. | |
| Methods: | |
| CanWriteAssetToPath(resolvedPath, whyNot) | |
| Returns true if an asset may be written to the given resolvedPath , false otherwise. | |
| CreateContextFromString(contextStr) | |
| Return an ArResolverContext created from the primary ArResolver implementation using the given contextStr . | |
| CreateContextFromStrings(contextStrs) | |
| Return an ArResolverContext created by combining the ArResolverContext objects created from the given contextStrs . | |
| CreateDefaultContext() | |
| Return an ArResolverContext that may be bound to this resolver to resolve assets when no other context is explicitly specified. | |
| CreateDefaultContextForAsset(assetPath) | |
| Return an ArResolverContext that may be bound to this resolver to resolve the asset located at assetPath or referenced by that asset when no other context is explicitly specified. | |
| CreateIdentifier(assetPath, anchorAssetPath) | |
| Returns an identifier for the asset specified by assetPath . | |
| CreateIdentifierForNewAsset(assetPath, ...) | |
| Returns an identifier for a new asset specified by assetPath . | |
| GetAssetInfo(assetPath, resolvedPath) | |
| Returns an ArAssetInfo populated with additional metadata (if any) about the asset at the given assetPath . | |
| GetCurrentContext() | |
| Returns the asset resolver context currently bound in this thread. | |
| GetExtension(assetPath) | |
| Returns the file extension for the given assetPath . | |
| GetModificationTimestamp(assetPath, resolvedPath) | |
| Returns an ArTimestamp representing the last time the asset at assetPath was modified. | |
| IsContextDependentPath(assetPath) | |
| Returns true if assetPath is a context-dependent path, false otherwise. | |
| RefreshContext(context) | |
| Refresh any caches associated with the given context. | |
| Resolve(assetPath) | |
| Returns the resolved path for the asset identified by the given assetPath if it exists. | |
| ResolveForNewAsset(assetPath) | |
| Returns the resolved path for the given assetPath that may be used to create a new asset. | |
| CanWriteAssetToPath(resolvedPath, whyNot) → bool | |
| Returns true if an asset may be written to the given resolvedPath | |
| , false otherwise. | |
| If this function returns false and whyNot is not nullptr , it | |
| may be filled with an explanation. | |
| Parameters | |
| resolvedPath (ResolvedPath) – | |
| whyNot (str) – | |
| CreateContextFromString(contextStr) → ResolverContext | |
| Return an ArResolverContext created from the primary ArResolver | |
| implementation using the given contextStr . | |
| Parameters | |
| contextStr (str) – | |
| CreateContextFromString(uriScheme, contextStr) -> ResolverContext | |
| Return an ArResolverContext created from the ArResolver registered for | |
| the given uriScheme using the given contextStr . | |
| An empty uriScheme indicates the primary resolver and is | |
| equivalent to CreateContextFromString(string). | |
| If no resolver is registered for uriScheme , returns an empty | |
| ArResolverContext. | |
| Parameters | |
| uriScheme (str) – | |
| contextStr (str) – | |
| CreateContextFromStrings(contextStrs) → ResolverContext | |
| Return an ArResolverContext created by combining the ArResolverContext | |
| objects created from the given contextStrs . | |
| contextStrs is a list of pairs of strings. The first element in | |
| the pair is the URI scheme for the ArResolver that will be used to | |
| create the ArResolverContext from the second element in the pair. An | |
| empty URI scheme indicates the primary resolver. | |
| For example: | |
| ArResolverContext ctx = ArGetResolver().CreateContextFromStrings( | |
| { {"", "context str 1"}, | |
| {"my_scheme", "context str 2"} }); | |
| This will use the primary resolver to create an ArResolverContext | |
| using the string”context str 1”and use the resolver registered for | |
| the”my_scheme”URI scheme to create an ArResolverContext using”context | |
| str 2”. These contexts will be combined into a single | |
| ArResolverContext and returned. | |
| If no resolver is registered for a URI scheme in an entry in | |
| contextStrs , that entry will be ignored. | |
| Parameters | |
| contextStrs (list[tuple[str, str]]) – | |
| CreateDefaultContext() → ResolverContext | |
| Return an ArResolverContext that may be bound to this resolver to | |
| resolve assets when no other context is explicitly specified. | |
| The returned ArResolverContext will contain the default context | |
| returned by the primary resolver and all URI resolvers. | |
| CreateDefaultContextForAsset(assetPath) → ResolverContext | |
| Return an ArResolverContext that may be bound to this resolver to | |
| resolve the asset located at assetPath or referenced by that asset | |
| when no other context is explicitly specified. | |
| The returned ArResolverContext will contain the default context for | |
| assetPath returned by the primary resolver and all URI resolvers. | |
| Parameters | |
| assetPath (str) – | |
| CreateIdentifier(assetPath, anchorAssetPath) → str | |
| Returns an identifier for the asset specified by assetPath . | |
| If anchorAssetPath is not empty, it is the resolved asset path | |
| that assetPath should be anchored to if it is a relative path. | |
| Parameters | |
| assetPath (str) – | |
| anchorAssetPath (ResolvedPath) – | |
| CreateIdentifierForNewAsset(assetPath, anchorAssetPath) → str | |
| Returns an identifier for a new asset specified by assetPath . | |
| If anchorAssetPath is not empty, it is the resolved asset path | |
| that assetPath should be anchored to if it is a relative path. | |
| Parameters | |
| assetPath (str) – | |
| anchorAssetPath (ResolvedPath) – | |
| GetAssetInfo(assetPath, resolvedPath) → ArAssetInfo | |
| Returns an ArAssetInfo populated with additional metadata (if any) | |
| about the asset at the given assetPath . | |
| resolvedPath is the resolved path computed for the given | |
| assetPath . | |
| Parameters | |
| assetPath (str) – | |
| resolvedPath (ResolvedPath) – | |
| GetCurrentContext() → ResolverContext | |
| Returns the asset resolver context currently bound in this thread. | |
| ArResolver::BindContext, ArResolver::UnbindContext | |
| GetExtension(assetPath) → str | |
| Returns the file extension for the given assetPath . | |
| The returned extension does not include a”.”at the beginning. | |
| Parameters | |
| assetPath (str) – | |
| GetModificationTimestamp(assetPath, resolvedPath) → Timestamp | |
| Returns an ArTimestamp representing the last time the asset at | |
| assetPath was modified. | |
| resolvedPath is the resolved path computed for the given | |
| assetPath . If a timestamp cannot be retrieved, return an invalid | |
| ArTimestamp. | |
| Parameters | |
| assetPath (str) – | |
| resolvedPath (ResolvedPath) – | |
| IsContextDependentPath(assetPath) → bool | |
| Returns true if assetPath is a context-dependent path, false | |
| otherwise. | |
| A context-dependent path may result in different resolved paths | |
| depending on what asset resolver context is bound when Resolve is | |
| called. Assets located at the same context-dependent path may not be | |
| the same since those assets may have been loaded from different | |
| resolved paths. In this case, the assets’resolved paths must be | |
| consulted to determine if they are the same. | |
| Parameters | |
| assetPath (str) – | |
| RefreshContext(context) → None | |
| Refresh any caches associated with the given context. | |
| If doing so would invalidate asset paths that had previously been | |
| resolved, an ArNotice::ResolverChanged notice will be sent to inform | |
| clients of this. | |
| Parameters | |
| context (ResolverContext) – | |
| Resolve(assetPath) → ResolvedPath | |
| Returns the resolved path for the asset identified by the given | |
| assetPath if it exists. | |
| If the asset does not exist, returns an empty ArResolvedPath. | |
| Parameters | |
| assetPath (str) – | |
| ResolveForNewAsset(assetPath) → ResolvedPath | |
| Returns the resolved path for the given assetPath that may be used | |
| to create a new asset. | |
| If such a path cannot be computed for assetPath , returns an empty | |
| ArResolvedPath. | |
| Note that an asset might or might not already exist at the returned | |
| resolved path. | |
| Parameters | |
| assetPath (str) – | |
| class pxr.Ar.ResolverContext | |
| An asset resolver context allows clients to provide additional data to | |
| the resolver for use during resolution. Clients may provide this data | |
| via context objects of their own (subject to restrictions below). An | |
| ArResolverContext is simply a wrapper around these objects that allows | |
| it to be treated as a single type. Note that an ArResolverContext may | |
| not hold multiple context objects with the same type. | |
| A client-defined context object must provide the following: | |
| Default and copy constructors | |
| operator< | |
| operator== | |
| An overload for size_t hash_value(const T&) | |
| Note that the user may define a free function: | |
| std::string ArGetDebugString(const Context & ctx); (Where Context is | |
| the type of the user’s path resolver context.) | |
| This is optional; a default generic implementation has been | |
| predefined. This function should return a string representation of the | |
| context to be utilized for debugging purposes(such as in TF_DEBUG | |
| statements). | |
| The ArIsContextObject template must also be specialized for this | |
| object to declare that it can be used as a context object. This is to | |
| avoid accidental use of an unexpected object as a context object. The | |
| AR_DECLARE_RESOLVER_CONTEXT macro can be used to do this as a | |
| convenience. | |
| AR_DECLARE_RESOLVER_CONTEXT | |
| ArResolver::BindContext | |
| ArResolver::UnbindContext | |
| ArResolverContextBinder | |
| Methods: | |
| Get() | |
| Returns pointer to the context object of the given type held in this resolver context. | |
| GetDebugString() | |
| Returns a debug string representing the contained context objects. | |
| IsEmpty() | |
| Returns whether this resolver context is empty. | |
| Get() → ContextObj | |
| Returns pointer to the context object of the given type held in this | |
| resolver context. | |
| Returns None if this resolver context is not holding an object of the | |
| requested type. | |
| GetDebugString() → str | |
| Returns a debug string representing the contained context objects. | |
| IsEmpty() → bool | |
| Returns whether this resolver context is empty. | |
| class pxr.Ar.ResolverContextBinder | |
| Helper object for managing the binding and unbinding of | |
| ArResolverContext objects with the asset resolver. | |
| Asset Resolver Context Operations | |
| class pxr.Ar.ResolverScopedCache | |
| Helper object for managing asset resolver cache scopes. | |
| A scoped resolution cache indicates to the resolver that results of | |
| calls to Resolve should be cached for a certain scope. This is | |
| important for performance and also for consistency it ensures that | |
| repeated calls to Resolve with the same parameters will return the | |
| same result. | |
| Scoped Resolution Cache | |
| class pxr.Ar.Timestamp | |
| Represents a timestamp for an asset. Timestamps are represented by | |
| Unix time, the number of seconds elapsed since 00:00:00 UTC 1/1/1970. | |
| Methods: | |
| GetTime() | |
| Return the time represented by this timestamp as a double. | |
| IsValid() | |
| Return true if this timestamp is valid, false otherwise. | |
| GetTime() → float | |
| Return the time represented by this timestamp as a double. | |
| If this timestamp is invalid, issue a coding error and return a quiet | |
| NaN value. | |
| IsValid() → bool | |
| Return true if this timestamp is valid, false otherwise. | |
| © Copyright 2019-2023, NVIDIA. | |
| Last updated on Nov 14, 2023. | |