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UsdGeomPrimvar Class Reference

Schema wrapper for UsdAttribute for authoring and introspecting attributes that are primvars. More...

Public Member Functions

USDGEOM_API UsdGeomPrimvar (const UsdAttribute &attr)
 Speculative constructor that will produce a valid UsdGeomPrimvar when attr already represents an attribute that is Primvar, and produces an invalid Primvar otherwise (i.e. More...
 
USDGEOM_API TfToken GetInterpolation () const
 Return the Primvar's interpolation, which is UsdGeomTokens->constant if unauthored. More...
 
USDGEOM_API bool SetInterpolation (const TfToken &interpolation)
 Set the Primvar's interpolation. More...
 
USDGEOM_API bool HasAuthoredInterpolation () const
 Has interpolation been explicitly authored on this Primvar? More...
 
USDGEOM_API int GetElementSize () const
 Return the "element size" for this Primvar, which is 1 if unauthored. More...
 
USDGEOM_API bool SetElementSize (int eltSize)
 Set the elementSize for this Primvar. More...
 
USDGEOM_API bool HasAuthoredElementSize () const
 Has elementSize been explicitly authored on this Primvar? More...
 
USDGEOM_API void GetDeclarationInfo (TfToken *name, SdfValueTypeName *typeName, TfToken *interpolation, int *elementSize) const
 Convenience function for fetching all information required to properly declare this Primvar. More...
 
template<>
USDGEOM_API bool Get (std::string *value, UsdTimeCode time) const
 
template<>
USDGEOM_API bool Get (VtStringArray *value, UsdTimeCode time) const
 
template<>
USDGEOM_API bool Get (VtValue *value, UsdTimeCode time) const
 
UsdAttribute API
 operator UsdAttribute const & () const
 Allow UsdGeomPrimvar to auto-convert to UsdAttribute, so you can pass a UsdGeomPrimvar to any function that accepts a UsdAttribute or const-ref thereto. More...
 
UsdAttribute const & GetAttr () const
 Explicit UsdAttribute extractor. More...
 
bool IsDefined () const
 Return true if the underlying UsdAttribute::IsDefined(), and in addition the attribute is identified as a Primvar. More...
 
bool HasValue () const
 Return true if the underlying attribute has a value, either from authored scene description or a fallback. More...
 
bool HasAuthoredValue () const
 Return true if the underlying attribute has an unblocked, authored value. More...
 
 operator bool () const
 
TfToken const & GetName () const
 
USDGEOM_API TfToken GetPrimvarName () const
 Returns the primvar's name, devoid of the "primvars:" namespace. More...
 
USDGEOM_API bool NameContainsNamespaces () const
 Does this primvar contain any namespaces other than the "primvars:" namespace? More...
 
TfToken GetBaseName () const
 
TfToken GetNamespace () const
 
std::vector< std::string > SplitName () const
 
SdfValueTypeName GetTypeName () const
 
template<typename T >
bool Get (T *value, UsdTimeCode time=UsdTimeCode::Default()) const
 Get the attribute value of the Primvar at time . More...
 
template<typename T >
bool Set (const T &value, UsdTimeCode time=UsdTimeCode::Default()) const
 Set the attribute value of the Primvar at time. More...
 
USDGEOM_API bool GetTimeSamples (std::vector< double > *times) const
 Populates a vector with authored sample times for this primvar. More...
 
USDGEOM_API bool GetTimeSamplesInInterval (const GfInterval &interval, std::vector< double > *times) const
 Populates a vector with authored sample times in interval. More...
 
USDGEOM_API bool ValueMightBeTimeVarying () const
 Return true if it is possible, but not certain, that this primvar's value changes over time, false otherwise. More...
 
Id attribute API

Often there is the need to identify a prim within a scene (e.g. a mesh on which a procedural should operate, or a shader to inherit). A string or string[] -typed primvar can be turned into an "Id Path" primvar by calling SetIdTarget() with the path of any object on the current stage. When the primvar is subsequently queried via Get(), the returned value will be the stringified value of the targeted object's path in whatever namespace is defined by the querying stage's root layer. In other words, authoring an Id primvar into a published model will return the path-to-target in the model, but when the model is referenced into a larger scene, it will return the complete scene path.

This works by adding a paired UsdRelationship in a ":idFrom" namespace "below" the string primvar. Get() evaluates UsdRelationship::GetForwardedTargets() to determine the id-string. Thus, this mechanism will always produce a unique identifier for every object in a scene, regardless of how many times an asset is referenced into a scene. Providing a mesh with a unique identifier primvar can be especially useful for renderers that allow plugins/shaders access to processed scene data based on user-provided string identifiers.

If an Id primvar has both an authored string value and a SetIdTarget()'d target, the target path takes precedence.

Currently Id primvars can have only a single target, so the only useful interpolation is constant.

USDGEOM_API bool IsIdTarget () const
 Returns true if the primvar is an Id primvar. More...
 
USDGEOM_API bool SetIdTarget (const SdfPath &path) const
 This primvar must be of String or StringArray type for this method to succeed. More...
 

Static Public Member Functions

static USDGEOM_API bool IsPrimvar (const UsdAttribute &attr)
 Test whether a given UsdAttribute represents valid Primvar, which implies that creating a UsdGeomPrimvar from the attribute will succeed. More...
 
static USDGEOM_API bool IsValidInterpolation (const TfToken &interpolation)
 Validate that the provided interpolation is a valid setting for interpolation as defined by Interpolation of Geometric Primitive Variables. More...
 

Friends

class UsdGeomImageable
 
class UsdGeomPrimvarsAPI
 
bool operator== (const UsdGeomPrimvar &lhs, const UsdGeomPrimvar &rhs)
 Equality comparison. More...
 
bool operator!= (const UsdGeomPrimvar &lhs, const UsdGeomPrimvar &rhs)
 Inequality comparison. More...
 
bool operator< (const UsdGeomPrimvar &lhs, const UsdGeomPrimvar &rhs)
 Less-than operator. More...
 
USDGEOM_API friend size_t hash_value (const UsdGeomPrimvar &obj)
 

Indexed primvars API

For non-constant values of interpolation, it is often the case that the same value is repeated many times in the array value of a primvar. An indexed primvar can be used in such cases to optimize for data storage if the primvar's interpolation is uniform, varying, or vertex. For faceVarying primvars, however, indexing serves a higher purpose (and should be used only for this purpose, since renderers and OpenSubdiv will assume it) of establishing a surface topology for the primvar. That is, faveVarying primvars use indexing to unambiguously define discontinuities in their functions at edges and vertices. Please see the OpenSubdiv documentation on FaceVarying Primvars for more information.

To create an indexed primvar, the value of the attribute associated with the primvar is set to an array consisting of all the unique values that appear in the primvar array. A separate namespaced "indices" attribute is set to an integer array containing indices into the array with all the unique elements. The final value of the primvar is computed using the indices array and the attribute value array.

See also Proper Client Handling of "Indexed" Primvars

USDGEOM_API bool SetIndices (const VtIntArray &indices, UsdTimeCode time=UsdTimeCode::Default()) const
 Sets the indices value of the indexed primvar at time. More...
 
USDGEOM_API bool GetIndices (VtIntArray *indices, UsdTimeCode time=UsdTimeCode::Default()) const
 Returns the value of the indices array associated with the indexed primvar at time. More...
 
USDGEOM_API void BlockIndices () const
 Block the indices that were previously set. More...
 
USDGEOM_API bool IsIndexed () const
 Returns true if the primvar is indexed, i.e., if it has an associated "indices" attribute. More...
 
USDGEOM_API UsdAttribute GetIndicesAttr () const
 Returns a valid indices attribute if the primvar is indexed. More...
 
USDGEOM_API UsdAttribute CreateIndicesAttr () const
 Returns the existing indices attribute if the primvar is indexed or creates a new one. More...
 
USDGEOM_API bool SetUnauthoredValuesIndex (int unauthoredValuesIndex) const
 Set the index that represents unauthored values in the indices array. More...
 
USDGEOM_API int GetUnauthoredValuesIndex () const
 Returns the index that represents unauthored values in the indices array. More...
 
template<typename ScalarType >
bool ComputeFlattened (VtArray< ScalarType > *value, UsdTimeCode time=UsdTimeCode::Default()) const
 Computes the flattened value of the primvar at time. More...
 
USDGEOM_API bool ComputeFlattened (VtValue *value, UsdTimeCode time=UsdTimeCode::Default()) const
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Computes the flattened value of the primvar at time as a VtValue. More...
 
static USDGEOM_API bool ComputeFlattened (VtValue *value, const VtValue &attrVal, const VtIntArray &indices, std::string *errString)
 Computes the flattened value of attrValue given indices. More...
 

Detailed Description

Schema wrapper for UsdAttribute for authoring and introspecting attributes that are primvars.

UsdGeomPrimvar provides API for authoring and retrieving the additional data required to encode an attribute as a "Primvar", which is a convenient contraction of RenderMan's "Primitive Variable" concept, which is represented in Alembic as "arbitrary geometry parameters" (arbGeomParams).

This includes the attribute's interpolation across the primitive (which RenderMan refers to as its class specifier and Alembic as its "geometry scope"); it also includes the attribute's elementSize, which states how many values in the value array must be aggregated for each element on the primitive. An attribute's TypeName also factors into the encoding of Primvar.

What is the Purpose of a Primvar?

There are three key aspects of Primvar identity:

  • Primvars define a value that can vary across the primitive on which they are defined, via prescribed interpolation rules
  • Taken collectively on a prim, its Primvars describe the "per-primitive overrides" to the material to which the prim is bound. Different renderers may communicate the variables to the shaders using different mechanisms over which Usd has no control; Primvars simply provide the classification that any renderer should use to locate potential overrides. Do please note that primvars override parameters on UsdShadeShader objects, not Interface Attributes on UsdShadeMaterial prims.
  • Primvars inherit down scene namespace. Regular USD attributes only apply to the prim on which they are specified, but primvars implicitly also apply to any child prims, unless those child prims have their own opinions about those primvars. This capability necessarily entails added cost to check for inherited values, but the benefit is that it allows concise encoding of certain opinions that broadly affect large amounts of geometry. See UsdGeomImageable::FindInheritedPrimvars().

Creating and Accessing Primvars

The UsdGeomPrimvarsAPI schema provides a complete interface for creating and querying prims for primvars.

The only way to create a new Primvar in scene description is by calling UsdGeomPrimvarsAPI::CreatePrimvar(). One cannot "enhance" or "promote" an already existing attribute into a Primvar, because doing so may require a namespace edit to rename the attribute, which cannot, in general, be done within a single UsdEditContext. Instead, create a new UsdGeomPrimvar of the desired name using UsdGeomPrimvarsAPI::CreatePrimvar(), and then copy the existing attribute onto the new UsdGeomPrimvar.

Primvar names can contain arbitrary sub-namespaces. The behavior of UsdGeomImageable::GetPrimvar(TfToken const &name) is to prepend "primvars:" onto 'name' if it is not already a prefix, and return the result, which means we do not have any ambiguity between the primvars "primvars:nsA:foo" and "primvars:nsB:foo". There are reserved keywords that may not be used as the base names of primvars, and attempting to create Primvars of these names will result in a coding error. The reserved keywords are tokens the Primvar uses internally to encode various features, such as the "indices" keyword used by Indexed Primvars.

If a client wishes to access an already-extant attribute as a Primvar, (which may or may not actually be valid Primvar), they can use the speculative constructor; typically, a primvar is only "interesting" if it additionally provides a value. This might look like:

* UsdGeomPrimvar primvar = UsdGeomPrimvar(usdAttr);
* if (primvar.HasValue()) {
* VtValue values;
* primvar.Get(&values, timeCode);
* TfToken interpolation = primvar.GetInterpolation();
* int elementSize = primvar.GetElementSize();
* ...
* }
*

or, because Get() returns true if and only if it found a value:

* UsdGeomPrimvar primvar = UsdGeomPrimvar(usdAttr);
* VtValue values;
* if (primvar.Get(&values, timeCode)) {
* TfToken interpolation = primvar.GetInterpolation();
* int elementSize = primvar.GetElementSize();
* ...
* }
*

Proper Client Handling of "Indexed" Primvars

As discussed in greater detail in Indexed Primvars, primvars can optionally contain a (possibly time-varying) indexing attribute that establishes a sharing topology for elements of the primvar. Consumers can always chose to ignore the possibility of indexed data by exclusively using the ComputeFlattened() API. If a client wishes to preserve indexing in their processing of a primvar, we suggest a pattern like the following, which accounts for the fact that a stronger layer can block a primvar's indexing from a weaker layer, via UsdGeomPrimvar::BlockIndices():

* VtValue values;
* VtIntArray indices;
*
* if (primvar.Get(&values, timeCode)){
* if (primvar.GetIndices(&indices, timeCode)){
* // primvar is indexed: validate/process values and indices together
* }
* else {
* // primvar is not indexed: validate/process values as flat array
* }
* }
*

UsdGeomPrimvar and UsdAttribute API

UsdGeomPrimvar presents a small slice of the UsdAttribute API - enough to extract the data that comprises the "Declaration info", and get/set of the attribute value. A UsdGeomPrimvar also auto-converts to UsdAttribute, so you can pass a UsdGeomPrimvar to any function that accepts a UsdAttribute or const-ref thereto.

Primvar Allowed Scene Description Types and Plurality

There are no limitations imposed on the allowable scene description types for Primvars; it is the responsibility of each consuming client to perform renderer-specific conversions, if need be (the USD distribution will include reference RenderMan conversion utilities).

A note about type plurality of Primvars: It is legitimate for a Primvar to be of scalar or array type, and again, consuming clients must be prepared to accommodate both. However, while it is not possible, in all cases, for USD to prevent one from changing the type of an attribute in different layers or variants of an asset, it is never a good idea to do so. This is relevant because, except in a few special cases, it is not possible to encode an interpolation of any value greater than constant without providing multiple (i.e. array) data values. Therefore, if there is any possibility that downstream clients might need to change a Primvar's interpolation, the Primvar-creator should encode it as an array rather than a scalar.

Why allow scalar values at all, then? First, sometimes it brings clarity to (use of) a shader's API to acknowledge that some parameters are meant to be single-valued over a shaded primitive. Second, many DCC's provide far richer affordances for editing scalars than they do array values, and we feel it is safer to let the content creator make the decision/tradeoff of which kind of flexibility is more relevant, rather than leaving it to an importer/exporter pair to interpret.

Also, like all attributes, Primvars can be time-sampled, and values can be authored and consumed just as any other attribute. There is currently no validation that the length of value arrays matches to the size required by a gprim's topology, interpolation, and elementSize.

For consumer convenience, we provide GetDeclarationInfo(), which returns all the type information (other than topology) needed to compute the required array size, which is also all the information required to prepare the Primvar's value for consumption by a renderer.

Lifetime Management and Primvar Validity

UsdGeomPrimvar has an explicit bool operator that validates that the attribute IsDefined() and thus valid for querying and authoring values and metadata. This is a fairly expensive query that we do not cache, so if client code retains UsdGeomPrimvar objects, it should manage its object validity closely, for performance. An ideal pattern is to listen for UsdNotice::StageContentsChanged notifications, and revalidate/refetch its retained UsdGeomPrimvar s only then, and otherwise use them without validity checking.

Interpolation of Geometric Primitive Variables

In the following explanation of the meaning of the various kinds/levels of Primvar interpolation, each bolded bullet gives the name of the token in UsdGeomTokens that provides the value. So to set a Primvar's interpolation to "varying", one would:

* primvar.SetInterpolation(UsdGeomTokens->varying);
*

Reprinted and adapted from the RPS documentation, which contains further details, interpolation describes how the Primvar will be interpolated over the uv parameter space of a surface primitive (or curve or pointcloud). The possible values are:

  • constant One value remains constant over the entire surface primitive.
  • uniform One value remains constant for each uv patch segment of the surface primitive (which is a face for meshes).
  • varying Four values are interpolated over each uv patch segment of the surface. Bilinear interpolation is used for interpolation between the four values.
  • vertex Values are interpolated between each vertex in the surface primitive. The basis function of the surface is used for interpolation between vertices.
  • faceVarying For polygons and subdivision surfaces, four values are interpolated over each face of the mesh. Bilinear interpolation is used for interpolation between the four values.

UsdGeomPrimvar As Example of Attribute Schema

Just as UsdSchemaBase and its subclasses provide the pattern for how to layer schema onto the generic UsdPrim object, UsdGeomPrimvar provides an example of how to layer schema onto a generic UsdAttribute object. In both cases, the schema object wraps and contains the UsdObject.

Primvar Namespace Inheritance

Constant interpolation primvar values can be inherited down namespace. That is, a primvar value set on a prim will also apply to any child prims, unless those children have their own opinions about those named primvars. For complete details on how primvars inherit, see usdGeom_PrimvarInheritance .

See Also
UsdGeomImageable::FindInheritablePrimvars().

Definition at line 260 of file primvar.h.

Constructor & Destructor Documentation

USDGEOM_API UsdGeomPrimvar ( const UsdAttribute attr)
explicit

Speculative constructor that will produce a valid UsdGeomPrimvar when attr already represents an attribute that is Primvar, and produces an invalid Primvar otherwise (i.e.

operator bool() will return false).

Calling UsdGeomPrimvar::IsPrimvar(attr) will return the same truth value as this constructor, but if you plan to subsequently use the Primvar anyways, just use this constructor, as demonstrated in the class documentation.

Member Function Documentation

USDGEOM_API void BlockIndices ( ) const

Block the indices that were previously set.

This effectively makes an indexed primvar no longer indexed. This is useful when overriding an existing primvar.

bool ComputeFlattened ( VtArray< ScalarType > *  value,
UsdTimeCode  time = UsdTimeCode::Default() 
) const

Computes the flattened value of the primvar at time.

If the primvar is not indexed or if the value type of this primvar is a scalar, this returns the authored value, which is the same as Get(). Hence, it's safe to call ComputeFlattened() on non-indexed primvars.

Definition at line 766 of file primvar.h.

USDGEOM_API bool ComputeFlattened ( VtValue value,
UsdTimeCode  time = UsdTimeCode::Default() 
) const

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Computes the flattened value of the primvar at time as a VtValue.

If the primvar is not indexed or if the value type of this primvar is a scalar, this returns the authored value, which is the same as Get(). Hence, it's safe to call ComputeFlattened() on non-indexed primvars.

static USDGEOM_API bool ComputeFlattened ( VtValue value,
const VtValue attrVal,
const VtIntArray &  indices,
std::string *  errString 
)
static

Computes the flattened value of attrValue given indices.

This method is a static convenience function that performs the main work of ComputeFlattened above without needing an instance of a UsdGeomPrimvar.

Returns false if the value contained in attrVal is not a supported type for flattening. Otherwise returns true. The output errString variable may be populated with an error string if an error is encountered during flattening.

USDGEOM_API UsdAttribute CreateIndicesAttr ( ) const

Returns the existing indices attribute if the primvar is indexed or creates a new one.

bool Get ( T *  value,
UsdTimeCode  time = UsdTimeCode::Default() 
) const
inline

Get the attribute value of the Primvar at time .

See Also
Usd_Handling_Indexed_Primvars for proper handling of indexed primvars

Definition at line 438 of file primvar.h.

UsdAttribute const& GetAttr ( ) const
inline

Explicit UsdAttribute extractor.

Definition at line 378 of file primvar.h.

TfToken GetBaseName ( ) const
inline
See Also
UsdAttribute::GetBaseName()

Definition at line 422 of file primvar.h.

USDGEOM_API void GetDeclarationInfo ( TfToken name,
SdfValueTypeName typeName,
TfToken interpolation,
int *  elementSize 
) const

Convenience function for fetching all information required to properly declare this Primvar.

The name returned is the "client name", stripped of the "primvars" namespace, i.e. equivalent to GetPrimvarName()

May also be more efficient than querying key individually.

USDGEOM_API int GetElementSize ( ) const

Return the "element size" for this Primvar, which is 1 if unauthored.

If this Primvar's type is not an array type, (e.g. "Vec3f[]"), then elementSize is irrelevant.

ElementSize does not generally encode the length of an array-type primvar, and rarely needs to be authored. ElementSize can be thought of as a way to create an "aggregate interpolatable type", by dictating how many consecutive elements in the value array should be taken as an atomic element to be interpolated over a gprim.

For example, spherical harmonics are often represented as a collection of nine floating-point coefficients, and the coefficients need to be sampled across a gprim's surface: a perfect case for primvars. However, USD has no float9 datatype. But we can communicate the aggregation of nine floats successfully to renderers by declaring a simple float-array valued primvar, and setting its elementSize to 9. To author a uniform spherical harmonic primvar on a Mesh of 42 faces, the primvar's array value would contain 9*42 = 378 float elements.

USDGEOM_API bool GetIndices ( VtIntArray *  indices,
UsdTimeCode  time = UsdTimeCode::Default() 
) const

Returns the value of the indices array associated with the indexed primvar at time.

See Also
SetIndices(), Proper Client Handling of "Indexed" Primvars
USDGEOM_API UsdAttribute GetIndicesAttr ( ) const

Returns a valid indices attribute if the primvar is indexed.

Returns an invalid attribute otherwise.

USDGEOM_API TfToken GetInterpolation ( ) const

Return the Primvar's interpolation, which is UsdGeomTokens->constant if unauthored.

Interpolation determines how the Primvar interpolates over a geometric primitive. See Interpolation of Geometric Primitive Variables

TfToken const& GetName ( ) const
inline
See Also
UsdAttribute::GetName()

Definition at line 401 of file primvar.h.

TfToken GetNamespace ( ) const
inline
See Also
UsdAttribute::GetNamespace()

Definition at line 425 of file primvar.h.

USDGEOM_API TfToken GetPrimvarName ( ) const

Returns the primvar's name, devoid of the "primvars:" namespace.

This is the name by which clients should refer to the primvar, if not by its full attribute name - i.e. they should not, in general, use GetBaseName(). In the error condition in which this Primvar object is not backed by a properly namespaced UsdAttribute, return an empty TfToken.

USDGEOM_API bool GetTimeSamples ( std::vector< double > *  times) const

Populates a vector with authored sample times for this primvar.

Returns false on error.

This considers any timeSamples authored on the associated "indices" attribute if the primvar is indexed.

See Also
UsdAttribute::GetTimeSamples
USDGEOM_API bool GetTimeSamplesInInterval ( const GfInterval interval,
std::vector< double > *  times 
) const

Populates a vector with authored sample times in interval.

This considers any timeSamples authored on the associated "indices" attribute if the primvar is indexed.

See Also
UsdAttribute::GetTimeSamplesInInterval
SdfValueTypeName GetTypeName ( ) const
inline
See Also
UsdAttribute::GetTypeName()

Definition at line 431 of file primvar.h.

USDGEOM_API int GetUnauthoredValuesIndex ( ) const

Returns the index that represents unauthored values in the indices array.

See Also
SetUnauthoredValuesIndex()
USDGEOM_API bool HasAuthoredElementSize ( ) const

Has elementSize been explicitly authored on this Primvar?

See Also
GetElementSize()
USDGEOM_API bool HasAuthoredInterpolation ( ) const

Has interpolation been explicitly authored on this Primvar?

See Also
GetInterpolationSize()
bool HasAuthoredValue ( ) const
inline

Return true if the underlying attribute has an unblocked, authored value.

Definition at line 391 of file primvar.h.

bool HasValue ( ) const
inline

Return true if the underlying attribute has a value, either from authored scene description or a fallback.

Definition at line 387 of file primvar.h.

bool IsDefined ( ) const
inline

Return true if the underlying UsdAttribute::IsDefined(), and in addition the attribute is identified as a Primvar.

Does not imply that the primvar provides a value

Definition at line 383 of file primvar.h.

USDGEOM_API bool IsIdTarget ( ) const

Returns true if the primvar is an Id primvar.

See Also
UsdGeomPrimvar_Id_primvars
USDGEOM_API bool IsIndexed ( ) const

Returns true if the primvar is indexed, i.e., if it has an associated "indices" attribute.

If you are going to query the indices anyways, prefer to simply consult the return-value of GetIndices(), which will be more efficient.

static USDGEOM_API bool IsPrimvar ( const UsdAttribute attr)
static

Test whether a given UsdAttribute represents valid Primvar, which implies that creating a UsdGeomPrimvar from the attribute will succeed.

Success implies that attr.IsDefined() is true.

static USDGEOM_API bool IsValidInterpolation ( const TfToken interpolation)
static

Validate that the provided interpolation is a valid setting for interpolation as defined by Interpolation of Geometric Primitive Variables.

USDGEOM_API bool NameContainsNamespaces ( ) const

Does this primvar contain any namespaces other than the "primvars:" namespace?

Some clients may only wish to consume primvars that have no extra namespaces in their names, for ease of translating to other systems that do not allow namespaces.

operator bool ( ) const
inlineexplicit

Return true if this Primvar is valid for querying and authoring values and metadata, which is identically equivalent to IsDefined().

Definition at line 396 of file primvar.h.

operator UsdAttribute const & ( ) const
inline

Allow UsdGeomPrimvar to auto-convert to UsdAttribute, so you can pass a UsdGeomPrimvar to any function that accepts a UsdAttribute or const-ref thereto.

Definition at line 375 of file primvar.h.

bool Set ( const T &  value,
UsdTimeCode  time = UsdTimeCode::Default() 
) const
inline

Set the attribute value of the Primvar at time.

Definition at line 444 of file primvar.h.

USDGEOM_API bool SetElementSize ( int  eltSize)

Set the elementSize for this Primvar.

Errors and returns false if eltSize less than 1.

See Also
GetElementSize()
USDGEOM_API bool SetIdTarget ( const SdfPath path) const

This primvar must be of String or StringArray type for this method to succeed.

If not, a coding error is raised.

See Also
UsdGeomPrimvar_Id_primvars
USDGEOM_API bool SetIndices ( const VtIntArray &  indices,
UsdTimeCode  time = UsdTimeCode::Default() 
) const

Sets the indices value of the indexed primvar at time.

The values in the indices array must be valid indices into the authored array returned by Get(). The element numerality of the primvar's 'interpolation' metadata applies to the "indices" array, not the attribute value array (returned by Get()).

USDGEOM_API bool SetInterpolation ( const TfToken interpolation)

Set the Primvar's interpolation.

Errors and returns false if interpolation is out of range as defined by IsValidInterpolation(). No attempt is made to validate that the Primvar's value contains the right number of elements to match its interpolation to its topology.

See Also
GetInterpolation(), Interpolation of Geometric Primitive Variables
USDGEOM_API bool SetUnauthoredValuesIndex ( int  unauthoredValuesIndex) const

Set the index that represents unauthored values in the indices array.

Some apps (like Maya) allow you to author primvars sparsely over a surface. Since most apps can't handle sparse primvars, Maya needs to provide a value even for the elements it didn't author. This metadatum provides a way to recover the information in apps that do support sparse authoring / representation of primvars.

The fallback value of unauthoredValuesIndex is -1, which indicates that there are no unauthored values.

See Also
GetUnauthoredValuesIndex()
std::vector<std::string> SplitName ( ) const
inline
See Also
UsdAttribute::SplitName()

Definition at line 428 of file primvar.h.

USDGEOM_API bool ValueMightBeTimeVarying ( ) const

Return true if it is possible, but not certain, that this primvar's value changes over time, false otherwise.

This considers time-varyingness of the associated "indices" attribute if the primvar is indexed.

See Also
UsdAttribute::ValueMightBeTimeVarying

Friends And Related Function Documentation

bool operator!= ( const UsdGeomPrimvar lhs,
const UsdGeomPrimvar rhs 
)
friend

Inequality comparison.

Return false if lhs and rhs represent the same UsdPrimvar, true otherwise.

Definition at line 664 of file primvar.h.

bool operator< ( const UsdGeomPrimvar lhs,
const UsdGeomPrimvar rhs 
)
friend

Less-than operator.

Returns true if lhs < rhs.

This simply compares the paths of the underlyingattributes.

Definition at line 671 of file primvar.h.

bool operator== ( const UsdGeomPrimvar lhs,
const UsdGeomPrimvar rhs 
)
friend

Equality comparison.

Return true if lhs and rhs represent the same UsdGeomPrimvar, false otherwise.

Definition at line 658 of file primvar.h.


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