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UsdGeomXformable Class Reference

Base class for all transformable prims, which allows arbitrary sequences of component affine transformations to be encoded. More...

+ Inheritance diagram for UsdGeomXformable:

Classes

class  XformQuery
 Helper class that caches the ordered vector of UsGeomXformOps that contribute to the local transformation of an xformable prim. More...
 

Public Member Functions

 UsdGeomXformable (const UsdPrim &prim=UsdPrim())
 Construct a UsdGeomXformable on UsdPrim prim . More...
 
 UsdGeomXformable (const UsdSchemaBase &schemaObj)
 Construct a UsdGeomXformable on the prim held by schemaObj . More...
 
virtual USDGEOM_API ~UsdGeomXformable ()
 Destructor. More...
 
USDGEOM_API UsdAttribute GetXformOpOrderAttr () const
 Encodes the sequence of transformation operations in the order in which they should be pushed onto a transform stack while visiting a UsdStage's prims in a graph traversal that will effect the desired positioning for this prim and its descendant prims. More...
 
USDGEOM_API UsdAttribute CreateXformOpOrderAttr (VtValue const &defaultValue=VtValue(), bool writeSparsely=false) const
 See GetXformOpOrderAttr(), and also Create vs Get Property Methods for when to use Get vs Create. More...
 
USDGEOM_API UsdGeomXformOp AddXformOp (UsdGeomXformOp::Type const opType, UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionDouble, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add an affine transformation to the local stack represented by this Xformable. More...
 
USDGEOM_API UsdGeomXformOp AddTranslateOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionDouble, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a translate operation to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddScaleOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a scale operation to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateXOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation about the X-axis to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateYOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation about the YX-axis to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateZOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation about the Z-axis to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateXYZOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation op with XYZ rotation order to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateXZYOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation op with XZY rotation order to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateYXZOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation op with YXZ rotation order to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateYZXOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation op with YZX rotation order to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateZXYOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation op with ZXY rotation order to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddRotateZYXOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a rotation op with ZYX rotation order to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddOrientOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionFloat, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a orient op (arbitrary axis/angle rotation) to the local stack represented by this xformable. More...
 
USDGEOM_API UsdGeomXformOp AddTransformOp (UsdGeomXformOp::Precision const precision=UsdGeomXformOp::PrecisionDouble, TfToken const &opSuffix=TfToken(), bool isInverseOp=false) const
 Add a tranform op (4x4 matrix transformation) to the local stack represented by this xformable. More...
 
USDGEOM_API bool SetResetXformStack (bool resetXform) const
 Specify whether this prim's transform should reset the transformation stack inherited from its parent prim. More...
 
USDGEOM_API bool GetResetXformStack () const
 Does this prim reset its parent's inherited transformation? More...
 
USDGEOM_API bool SetXformOpOrder (std::vector< UsdGeomXformOp > const &orderedXformOps, bool resetXformStack=false) const
 Reorder the already-existing transform ops on this prim. More...
 
USDGEOM_API std::vector
< UsdGeomXformOp
GetOrderedXformOps (bool *resetsXformStack) const
 Return the ordered list of transform operations to be applied to this prim, in least-to-most-local order. More...
 
USDGEOM_API bool ClearXformOpOrder () const
 Clears the local transform stack. More...
 
USDGEOM_API UsdGeomXformOp MakeMatrixXform () const
 Clears the existing local transform stack and creates a new xform op of type 'transform'. More...
 
USDGEOM_API bool TransformMightBeTimeVarying () const
 Determine whether there is any possibility that this prim's local transformation may vary over time. More...
 
USDGEOM_API bool TransformMightBeTimeVarying (const std::vector< UsdGeomXformOp > &ops) const
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Determine whether there is any possibility that this prim's local transformation may vary over time, using a pre-fetched (cached) list of ordered xform ops supplied by the client. More...
 
USDGEOM_API bool GetTimeSamples (std::vector< double > *times) const
 Sets times to the union of all the timesamples at which xformOps that are included in the xformOpOrder attribute are authored. More...
 
USDGEOM_API bool GetTimeSamplesInInterval (const GfInterval &interval, std::vector< double > *times) const
 Sets times to the union of all the timesamples in the interval, interval, at which xformOps that are included in the xformOpOrder attribute are authored. More...
 
USDGEOM_API bool GetLocalTransformation (GfMatrix4d *transform, bool *resetsXformStack, const UsdTimeCode time=UsdTimeCode::Default()) const
 Computes the fully-combined, local-to-parent transformation for this prim. More...
 
USDGEOM_API bool GetLocalTransformation (GfMatrix4d *transform, bool *resetsXformStack, const std::vector< UsdGeomXformOp > &ops, const 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 fully-combined, local-to-parent transformation for this prim as efficiently as possible, using a pre-fetched (cached) list of ordered xform ops supplied by the client. More...
 
- Public Member Functions inherited from UsdGeomImageable
 UsdGeomImageable (const UsdPrim &prim=UsdPrim())
 Construct a UsdGeomImageable on UsdPrim prim . More...
 
 UsdGeomImageable (const UsdSchemaBase &schemaObj)
 Construct a UsdGeomImageable on the prim held by schemaObj . More...
 
virtual USDGEOM_API ~UsdGeomImageable ()
 Destructor. More...
 
USDGEOM_API UsdAttribute GetVisibilityAttr () const
 Visibility is meant to be the simplest form of "pruning" visibility that is supported by most DCC apps. More...
 
USDGEOM_API UsdAttribute CreateVisibilityAttr (VtValue const &defaultValue=VtValue(), bool writeSparsely=false) const
 See GetVisibilityAttr(), and also Create vs Get Property Methods for when to use Get vs Create. More...
 
USDGEOM_API UsdAttribute GetPurposeAttr () const
 Purpose is a concept we have found useful in our pipeline for classifying geometry into categories that can each be independently included or excluded from traversals of prims on a stage, such as rendering or bounding-box computation traversals. More...
 
USDGEOM_API UsdAttribute CreatePurposeAttr (VtValue const &defaultValue=VtValue(), bool writeSparsely=false) const
 See GetPurposeAttr(), and also Create vs Get Property Methods for when to use Get vs Create. More...
 
USDGEOM_API UsdRelationship GetProxyPrimRel () const
 The proxyPrim relationship allows us to link a prim whose purpose is "render" to its (single target) purpose="proxy" prim. More...
 
USDGEOM_API UsdRelationship CreateProxyPrimRel () const
 See GetProxyPrimRel(), and also Create vs Get Property Methods for when to use Get vs Create. More...
 
USDGEOM_API void MakeVisible (const UsdTimeCode &time=UsdTimeCode::Default()) const
 Make the imageable visible if it is invisible at the given time. More...
 
USDGEOM_API void MakeInvisible (const UsdTimeCode &time=UsdTimeCode::Default()) const
 Makes the imageable invisible if it is visible at the given time. More...
 
USDGEOM_API TfToken ComputeVisibility (UsdTimeCode const &time=UsdTimeCode::Default()) const
 Calculate the effective visibility of this prim, as defined by its most ancestral authored "invisible" opinion, if any. More...
 
USDGEOM_API TfToken ComputeVisibility (const TfToken &parentVisibility, UsdTimeCode const &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. Calculates the effective visibility of this prim, given the computed visibility of its parent prim at the given time. More...
 
USDGEOM_API TfToken ComputePurpose () const
 Calculate the effective purpose of this prim, as defined by its most ancestral authored non-"default" opinion, if any. More...
 
USDGEOM_API TfToken ComputePurpose (const TfToken &parentPurpose) const
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Calculates the effective purpose of this prim, given the computed purpose of its parent prim. More...
 
USDGEOM_API UsdPrim ComputeProxyPrim (UsdPrim *renderPrim=NULL) const
 Find the prim whose purpose is proxy that serves as the proxy for this prim, as established by the GetProxyPrimRel(), or an invalid UsdPrim if this prim has no proxy. More...
 
USDGEOM_API bool SetProxyPrim (const UsdPrim &proxy) const
 Convenience function for authoring the renderProxy rel on this prim to target the given proxy prim. More...
 
USDGEOM_API bool SetProxyPrim (const UsdSchemaBase &proxy) const
 
USDGEOM_API GfBBox3d ComputeWorldBound (UsdTimeCode const &time, TfToken const &purpose1=TfToken(), TfToken const &purpose2=TfToken(), TfToken const &purpose3=TfToken(), TfToken const &purpose4=TfToken()) const
 Compute the bound of this prim in world space, at the specified time, and for the specified purposes. More...
 
USDGEOM_API GfBBox3d ComputeLocalBound (UsdTimeCode const &time, TfToken const &purpose1=TfToken(), TfToken const &purpose2=TfToken(), TfToken const &purpose3=TfToken(), TfToken const &purpose4=TfToken()) const
 Compute the bound of this prim in local space, at the specified time, and for the specified purposes. More...
 
USDGEOM_API GfBBox3d ComputeUntransformedBound (UsdTimeCode const &time, TfToken const &purpose1=TfToken(), TfToken const &purpose2=TfToken(), TfToken const &purpose3=TfToken(), TfToken const &purpose4=TfToken()) const
 Compute the untransformed bound of this prim, at the specified time, and for the specified purposes. More...
 
USDGEOM_API GfMatrix4d ComputeLocalToWorldTransform (UsdTimeCode const &time) const
 Compute the transformation matrix for this prim at the given time, including the transform authored on the Prim itself, if present. More...
 
USDGEOM_API GfMatrix4d ComputeParentToWorldTransform (UsdTimeCode const &time) const
 Compute the transformation matrix for this prim at the given time, NOT including the transform authored on the prim itself. More...
 
USDGEOM_API UsdGeomPrimvar CreatePrimvar (const TfToken &attrName, const SdfValueTypeName &typeName, const TfToken &interpolation=TfToken(), int elementSize=-1) const
 
USDGEOM_API UsdGeomPrimvar GetPrimvar (const TfToken &name) const
 
USDGEOM_API std::vector
< UsdGeomPrimvar
GetPrimvars () const
 
USDGEOM_API std::vector
< UsdGeomPrimvar
GetAuthoredPrimvars () const
 
USDGEOM_API bool HasPrimvar (const TfToken &name) const
 
- Public Member Functions inherited from UsdTyped
 UsdTyped (const UsdPrim &prim=UsdPrim())
 Construct a UsdTyped on UsdPrim prim . More...
 
 UsdTyped (const UsdSchemaBase &schemaObj)
 Construct a UsdTyped on the prim wrapped by schemaObj . More...
 
- Public Member Functions inherited from UsdSchemaBase
bool IsConcrete () const
 Returns whether or not this class corresponds to a concrete instantiable prim type in scene description. More...
 
bool IsTyped () const
 Returns whether or not this class inherits from UsdTyped. More...
 
bool IsAPISchema () const
 Returns whether this is an API schema or not. More...
 
bool IsAppliedAPISchema () const
 Returns whether this is an applied API schema or not. More...
 
bool IsMultipleApplyAPISchema () const
 Returns whether this is an applied API schema or not. More...
 
UsdSchemaType GetSchemaType () const
 
USD_API UsdSchemaBase (const UsdPrim &prim=UsdPrim())
 Construct and store prim as the held prim. More...
 
USD_API UsdSchemaBase (const UsdSchemaBase &otherSchema)
 Construct and store for the same prim held by otherSchema. More...
 
virtual USD_API ~UsdSchemaBase ()
 Destructor. More...
 
USD_API operator bool () const
 Return true if this schema object is compatible with its held prim, false otherwise. More...
 
UsdPrim GetPrim () const
 Return this schema object's held prim. More...
 
SdfPath GetPath () const
 Shorthand for GetPrim()->GetPath(). More...
 
USD_API SdfPrimSpecHandle GetSchemaClassPrimDefinition () const
 Return the prim definition associated with this schema instance if one exists, otherwise return null. More...
 

Static Public Member Functions

static USDGEOM_API const
TfTokenVector
GetSchemaAttributeNames (bool includeInherited=true)
 Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes. More...
 
static USDGEOM_API UsdGeomXformable Get (const UsdStagePtr &stage, const SdfPath &path)
 Return a UsdGeomXformable holding the prim adhering to this schema at path on stage. More...
 
static USDGEOM_API bool GetTimeSamples (std::vector< UsdGeomXformOp > const &orderedXformOps, std::vector< double > *times)
 Returns the union of all the timesamples at which the attributes belonging to the given orderedXformOps are authored. More...
 
static USDGEOM_API bool GetTimeSamplesInInterval (std::vector< UsdGeomXformOp > const &orderedXformOps, const GfInterval &interval, std::vector< double > *times)
 Returns the union of all the timesamples in the interval at which the attributes belonging to the given orderedXformOps are authored. More...
 
static USDGEOM_API bool GetLocalTransformation (GfMatrix4d *transform, std::vector< UsdGeomXformOp > const &ops, const UsdTimeCode time)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. This is a static version of the preceding function that takes a cached list of ordered xform ops. More...
 
static USDGEOM_API bool IsTransformationAffectedByAttrNamed (const TfToken &attrName)
 Returns true if the attribute named attrName could affect the local transformation of an xformable prim. More...
 
- Static Public Member Functions inherited from UsdGeomImageable
static USDGEOM_API const
TfTokenVector
GetSchemaAttributeNames (bool includeInherited=true)
 Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes. More...
 
static USDGEOM_API UsdGeomImageable Get (const UsdStagePtr &stage, const SdfPath &path)
 Return a UsdGeomImageable holding the prim adhering to this schema at path on stage. More...
 
static USDGEOM_API const
TfTokenVector
GetOrderedPurposeTokens ()
 Returns an ordered list of allowed values of the purpose attribute. More...
 
- Static Public Member Functions inherited from UsdTyped
static const TfTokenVectorGetSchemaAttributeNames (bool includeInherited=true)
 Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes. More...
 
static USD_API UsdTyped Get (const UsdStagePtr &stage, const SdfPath &path)
 Return a UsdTyped holding the prim adhering to this schema at path on stage. More...
 
- Static Public Member Functions inherited from UsdSchemaBase
static const TfTokenVectorGetSchemaAttributeNames (bool includeInherited=true)
 

Static Public Attributes

static const UsdSchemaType schemaType = UsdSchemaType::AbstractTyped
 Compile time constant representing what kind of schema this class is. More...
 
- Static Public Attributes inherited from UsdGeomImageable
static const UsdSchemaType schemaType = UsdSchemaType::AbstractTyped
 Compile time constant representing what kind of schema this class is. More...
 
- Static Public Attributes inherited from UsdTyped
static const UsdSchemaType schemaType = UsdSchemaType::AbstractBase
 Compile time constant representing what kind of schema this class is. More...
 
- Static Public Attributes inherited from UsdSchemaBase
static const UsdSchemaType schemaType = UsdSchemaType::AbstractBase
 Compile time constant representing what kind of schema this class is. More...
 

Protected Member Functions

USDGEOM_API UsdSchemaType _GetSchemaType () const override
 Returns the type of schema this class belongs to. More...
 
- Protected Member Functions inherited from UsdTyped
USD_API bool _IsCompatible () const override
 Subclasses may override _IsCompatible to do specific compatibility checking with the given prim, such as type compatibility or value compatibility. More...
 
- Protected Member Functions inherited from UsdSchemaBase
const TfType_GetType () const
 
USD_API UsdAttribute _CreateAttr (TfToken const &attrName, SdfValueTypeName const &typeName, bool custom, SdfVariability variability, VtValue const &defaultValue, bool writeSparsely) const
 

Friends

class UsdSchemaRegistry
 

Detailed Description

Base class for all transformable prims, which allows arbitrary sequences of component affine transformations to be encoded.

Note
You may find it useful to review Linear Algebra in UsdGeom while reading this class description.

Supported Component Transformation Operations

UsdGeomXformable currently supports arbitrary sequences of the following operations, each of which can be encoded in an attribute of the proper shape in any supported precision:

  • translate - 3D
  • scale - 3D
  • rotateX - 1D angle in degrees
  • rotateY - 1D angle in degrees
  • rotateZ - 1D angle in degrees
  • rotateABC - 3D where ABC can be any combination of the six principle Euler Angle sets: XYZ, XZY, YXZ, YZX, ZXY, ZYX. See note on rotation packing order
  • orient - 4D (quaternion)
  • transform - 4x4D

Creating a Component Transformation

To add components to a UsdGeomXformable prim, simply call AddXformOp() with the desired op type, as enumerated in UsdGeomXformOp::Type, and the desired precision, which is one of UsdGeomXformOp::Precision. Optionally, you can also provide an "op suffix" for the operator that disambiguates it from other components of the same type on the same prim. Application-specific transform schemas can use the suffixes to fill a role similar to that played by AbcGeom::XformOp's "Hint" enums for their own round-tripping logic.

We also provide specific "Add" API for each type, for clarity and conciseness, e.g. AddTranslateOp(), AddRotateXYZOp() etc.

AddXformOp() will return a UsdGeomXformOp object, which is a schema on a newly created UsdAttribute that provides convenience API for authoring and computing the component transformations. The UsdGeomXformOp can then be used to author any number of timesamples and default for the op.

Each successive call to AddXformOp() adds an operator that will be applied "more locally" than the preceding operator, just as if we were pushing transforms onto a transformation stack - which is precisely what should happen when the operators are consumed by a reader.

Note
If you can, please try to use the UsdGeomXformCommonAPI, which wraps the UsdGeomXformable with an interface in which Op creation is taken care of for you, and there is a much higher chance that the data you author will be importable without flattening into other DCC's, as it conforms to a fixed set of Scale-Rotate-Translate Ops.
See Also
Using the Authoring API

Data Encoding and Op Ordering

Because there is no "fixed schema" of operations, all of the attributes that encode transform operations are dynamic, and are scoped in the namespace "xformOp". The second component of an attribute's name provides the type of operation, as listed above. An "xformOp" attribute can have additional namespace components derived from the opSuffix argument to the AddXformOp() suite of methods, which provides a preferred way of naming the ops such that we can have multiple "translate" ops with unique attribute names. For example, in the attribute named "xformOp:translate:maya:pivot", "translate" is the type of operation and "maya:pivot" is the suffix.

The following ordered list of attribute declarations in usda define a basic Scale-Rotate-Translate with XYZ Euler angles, wherein the translation is double-precision, and the remainder of the ops are single, in which we will:

  1. Scale by 2.0 in each dimension
  2. Rotate about the X, Y, and Z axes by 30, 60, and 90 degrees, respectively
  3. Translate by 100 units in the Y direction
* float3 xformOp:rotateXYZ = (30, 60, 90)
* float3 xformOp:scale = (2, 2, 2)
* double3 xformOp:translate = (0, 100, 0)
* uniform token[] xformOpOrder = [ "xformOp:translate", "xformOp:rotateXYZ", "xformOp:scale" ]
*

The attributes appear in the dictionary order in which USD, by default, sorts them. To ensure the ops are recovered and evaluated in the correct order, the schema introduces the xformOpOrder attribute, which contains the names of the op attributes, in the precise sequence in which they should be pushed onto a transform stack. Note that the order is opposite to what you might expect, given the matrix algebra described in Linear Algebra in UsdGeom. This also dictates order of op creation, since each call to AddXformOp() adds a new op to the end of the xformOpOrder array, as a new "most-local" operation. See Example 2 below for C++ code that could have produced this USD.

If it were important for the prim's rotations to be independently overridable, we could equivalently (at some performance cost) encode the transformation also like so:

* float xformOp:rotateX = 30
* float xformOp:rotateY = 60
* float xformOp:rotateZ = 90
* float3 xformOp:scale = (2, 2, 2)
* double3 xformOp:translate = (0, 100, 0)
* uniform token[] xformOpOrder = [ "xformOp:translate", "xformOp:rotateZ", "xformOp:rotateY", "xformOp:rotateX", "xformOp:scale" ]
*

Again, note that although we are encoding an XYZ rotation, the three rotations appear in the xformOpOrder in the opposite order, with Z, followed, by Y, followed by X.

Were we to add a Maya-style scalePivot to the above example, it might look like the following:

* float3 xformOp:rotateXYZ = (30, 60, 90)
* float3 xformOp:scale = (2, 2, 2)
* double3 xformOp:translate = (0, 100, 0)
* double3 xformOp:translate:scalePivot
* uniform token[] xformOpOrder = [ "xformOp:translate", "xformOp:rotateXYZ", "xformOp:translate:scalePivot", "xformOp:scale" ]
*

Paired "Inverted" Ops

We have been claiming that the ordered list of ops serves as a set of instructions to a transform stack, but you may have noticed in the last example that there is a missing operation - the pivot for the scale op needs to be applied in its inverse-form as a final (most local) op! In the AbcGeom::Xform schema, we would have encoded an actual "final" translation op whose value was authored by the exporter as the negation of the pivot's value. However, doing so would be brittle in USD, given that each op can be independently overridden, and the constraint that one attribute must be maintained as the negation of the other in order for successful re-importation of the schema cannot be expressed in USD.

Our solution leverages the xformOpOrder member of the schema, which, in addition to ordering the ops, may also contain one of two special tokens that address the paired op and "stack resetting" behavior.

The "paired op" behavior is encoded as an "!invert!" prefix in xformOpOrder, as the result of an AddXformOp(isInverseOp=True) call. The xformOpOrder for the last example would look like:

* uniform token[] xformOpOrder = [ "xformOp:translate", "xformOp:rotateXYZ", "xformOp:translate:scalePivot", "xformOp:scale", "!invert!xformOp:translate:scalePivot" ]
*

When asked for its value via UsdGeomXformOp::GetOpTransform(), an "inverted" Op (i.e. the "inverted" half of a set of paired Ops) will fetch the value of its paired attribute and return its negation. This works for all op types - an error will be issued if a "transform" type op is singular and cannot be inverted. When getting the authored value of an inverted op via UsdGeomXformOp::Get(), the raw, uninverted value of the associated attribute is returned.

For the sake of robustness, setting a value on an inverted op is disallowed. Attempting to set a value on an inverted op will result in a coding error and no value being set.

Resetting the Transform Stack

The other special op/token that can appear in xformOpOrder is "!resetXformStack!", which, appearing as the first element of xformOpOrder, indicates this prim should not inherit the transformation of its namespace parent. See SetResetXformStack()

Expected Behavior for "Missing" Ops

If an importer expects Scale-Rotate-Translate operations, but a prim has only translate and rotate ops authored, the importer should assume an identity scale. This allows us to optimize the data a bit, if only a few components of a very rich schema (like Maya's) are authored in the app.

Using the C++ API

#1. Creating a simple transform matrix encoding

bool CreateMatrixWithDefault(UsdGeomXformable const &gprim, GfMatrix4d const &defValue)
{
if (UsdGeomXformOp transform = gprim.MakeMatrixXform()){
return transform.Set(defValue, UsdTimeCode::Default());
} else {
return false;
}
}

#2. Creating the simple SRT from the example above

bool CreateExampleSRT(UsdGeomXformable const &gprim)
{
// For insurance, we will make sure there aren't any ordered ops
// before we start
UsdGeomXformOp s, r, t;
if ( !(t = gprim.AddTranslateOp())){
return false;
}
if ( !(r = gprim.AddRotateXYZOp())){
return false;
}
if ( !(s = gprim.AddScaleOp())){
return false;
}
return (t.Set(GfVec3d(0, 100, 0), UsdTimeCode::Default()) &&
r.Set(GfVec3f(30, 60, 90), UsdTimeCode::Default()) &&
s.Set(GfVec3f(2, 2, 2), UsdTimeCode::Default()));
}

#3. Creating a parameterized SRT with pivot using UsdGeomXformCommonAPI

bool CreateSRTWithDefaults(UsdGeomXformable const &gprim,
GfVec3d const &defTranslate,
GfVec3f const &defRotateXYZ,
GfVec3f const &defScale,
GfVec3f const &defPivot)
{
return xform.SetXformVectors(defTranslate, defRotateXYZ, defScale,
defPivot, UsdGeomXformCommonAPI::RotationOrderXYZ,
} else {
return false;
}
}

#4. Creating a rotate-only pivot transform with animated rotation and translation

bool CreateAnimatedTransform(UsdGeomXformable const &gprim,
GfVec3d const &baseTranslate,
GfVec3f const &baseRotateXYZ,
GfVec3f const &defPivot)
{
// Only need to do this if you're overriding an existing scene
if (!gprim.ClearXformOpOrder()){
return false;
}
static const TfToken pivSuffix("pivot");
UsdGeomXformOp trans = gprim.AddTranslateOp();
pivSuffix);
UsdGeomXformOp rotate = gprim.AddRotateXYZOp();
pivSuffix,
/* isInverseOp = */ true);
// Now that we have created all the ops, set default values.
// Note that we do not need to (and cannot) set the value
// for the pivot's inverse op.
// For didactic brevity we are eliding success return value checks,
// but would absolutely have them in exporters!
trans.Set(baseTranslate, UsdTimeCode::Default());
pivot.Set(defPivot, UsdTimeCode::Default());
rotate.Set(baseRotateXYZ, UsdTimeCode::Default());
// Now animate the translation and rotation over a fixed interval with
// cheesy linear animation.
GfVec3d position(baseTranslate);
GfVec3f rotation(baseRotateXYZ);
for (double frame = 0; frame < 100.0; frame += 1.0){
trans.Set(position, frame);
rotate.Set(rotation, frame);
position[0] += 5.0;
rotation[2] += 7.0;
}
return true;
}

Definition at line 252 of file xformable.h.

Constructor & Destructor Documentation

UsdGeomXformable ( const UsdPrim prim = UsdPrim())
inlineexplicit

Construct a UsdGeomXformable on UsdPrim prim .

Equivalent to UsdGeomXformable::Get(prim.GetStage(), prim.GetPath()) for a valid prim, but will not immediately throw an error for an invalid prim

Definition at line 264 of file xformable.h.

UsdGeomXformable ( const UsdSchemaBase schemaObj)
inlineexplicit

Construct a UsdGeomXformable on the prim held by schemaObj .

Should be preferred over UsdGeomXformable(schemaObj.GetPrim()), as it preserves SchemaBase state.

Definition at line 272 of file xformable.h.

virtual USDGEOM_API ~UsdGeomXformable ( )
virtual

Destructor.

Member Function Documentation

USDGEOM_API UsdGeomXformOp AddOrientOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a orient op (arbitrary axis/angle rotation) to the local stack represented by this xformable.

See Also
AddXformOp()
USDGEOM_API UsdGeomXformOp AddRotateXOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation about the X-axis to the local stack represented by this xformable.

Set the angle value of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp()
USDGEOM_API UsdGeomXformOp AddRotateXYZOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation op with XYZ rotation order to the local stack represented by this xformable.

Set the angle value of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp(), note on angle packing order
USDGEOM_API UsdGeomXformOp AddRotateXZYOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation op with XZY rotation order to the local stack represented by this xformable.

Set the angle values of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp(), note on angle packing order
USDGEOM_API UsdGeomXformOp AddRotateYOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation about the YX-axis to the local stack represented by this xformable.

Set the angle value of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp()
USDGEOM_API UsdGeomXformOp AddRotateYXZOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation op with YXZ rotation order to the local stack represented by this xformable.

Set the angle values of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp(), note on angle packing order
USDGEOM_API UsdGeomXformOp AddRotateYZXOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation op with YZX rotation order to the local stack represented by this xformable.

Set the angle values of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp(), note on angle packing order
USDGEOM_API UsdGeomXformOp AddRotateZOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation about the Z-axis to the local stack represented by this xformable.

See Also
AddXformOp()
USDGEOM_API UsdGeomXformOp AddRotateZXYOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation op with ZXY rotation order to the local stack represented by this xformable.

Set the angle values of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp(), note on angle packing order
USDGEOM_API UsdGeomXformOp AddRotateZYXOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a rotation op with ZYX rotation order to the local stack represented by this xformable.

Set the angle values of the resulting UsdGeomXformOp in degrees

See Also
AddXformOp(), note on angle packing order
USDGEOM_API UsdGeomXformOp AddScaleOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionFloat,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a scale operation to the local stack represented by this xformable.

See Also
AddXformOp()
USDGEOM_API UsdGeomXformOp AddTransformOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionDouble,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a tranform op (4x4 matrix transformation) to the local stack represented by this xformable.

See Also
AddXformOp()

Note: This method takes a precision argument only to be consistent with the other types of xformOps. The only valid precision here is double since matrix values cannot be encoded in floating-pt precision in Sdf.

USDGEOM_API UsdGeomXformOp AddTranslateOp ( UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionDouble,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add a translate operation to the local stack represented by this xformable.

See Also
AddXformOp()
USDGEOM_API UsdGeomXformOp AddXformOp ( UsdGeomXformOp::Type const  opType,
UsdGeomXformOp::Precision const  precision = UsdGeomXformOp::PrecisionDouble,
TfToken const &  opSuffix = TfToken(),
bool  isInverseOp = false 
) const

Add an affine transformation to the local stack represented by this Xformable.

This will fail if there is already a transform operation of the same name in the ordered ops on this prim (i.e. as returned by GetOrderedXformOps()), or if an op of the same name exists at all on the prim with a different precision than that specified.

The newly created operation will become the most-locally applied transformation on the prim, and will appear last in the list returned by GetOrderedXformOps(). It is OK to begin authoring values to the returned UsdGeomXformOp immediately, interspersed with subsequent calls to AddXformOp() - just note the order of application, which can be changed at any time (and in stronger layers) via SetXformOpOrder().

Parameters
opTypeis the type of transform operation, one of UsdGeomXformOp::Type.
precisionallows you to specify the precision with which you desire to encode the data. This should be one of the values in the enum UsdGeomXformOp::Precision .
opSuffixallows you to specify the purpose/meaning of the op in the stack. When opSuffix is specified, the associated attribute's name is set to "xformOp:<opType>:<opSuffix>".
isInverseOpis used to indicate an inverse transformation operation.
Returns
a UsdGeomXformOp that can be used to author to the operation. An error is issued and the returned object will be invalid (evaluate to false) if the op being added already exists in xformOpOrder or if the arguments supplied are invalid.
Note
If the attribute associated with the op already exists, but isn't of the requested precision, a coding error is issued, but a valid xformOp is returned with the existing attribute.
USDGEOM_API bool ClearXformOpOrder ( ) const

Clears the local transform stack.

USDGEOM_API UsdAttribute CreateXformOpOrderAttr ( VtValue const &  defaultValue = VtValue(),
bool  writeSparsely = false 
) const

See GetXformOpOrderAttr(), and also Create vs Get Property Methods for when to use Get vs Create.

If specified, author defaultValue as the attribute's default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false.

static USDGEOM_API UsdGeomXformable Get ( const UsdStagePtr &  stage,
const SdfPath path 
)
static

Return a UsdGeomXformable holding the prim adhering to this schema at path on stage.

If no prim exists at path on stage, or if the prim at that path does not adhere to this schema, return an invalid schema object. This is shorthand for the following:

* UsdGeomXformable(stage->GetPrimAtPath(path));
*
USDGEOM_API bool GetLocalTransformation ( GfMatrix4d transform,
bool *  resetsXformStack,
const UsdTimeCode  time = UsdTimeCode::Default() 
) const

Computes the fully-combined, local-to-parent transformation for this prim.

If a client does not need to manipulate the individual ops themselves, and requires only the combined transform on this prim, this method will take care of all the data marshalling and linear algebra needed to combine the ops into a 4x4 affine transformation matrix, in double-precision, regardless of the precision of the op inputs.

Parameters
transformis the output parameter that will hold the local transform.
resetsXformStackis the output parameter that informs client whether they need to reset the transform stack before pushing transform.
timeis the UsdTimeCode at which to sample the ops.
Returns
true on success, false if there was an error reading data.
Note
A coding error is issued if transform or resetsXformStack is NULL.
USDGEOM_API bool GetLocalTransformation ( GfMatrix4d transform,
bool *  resetsXformStack,
const std::vector< UsdGeomXformOp > &  ops,
const 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 fully-combined, local-to-parent transformation for this prim as efficiently as possible, using a pre-fetched (cached) list of ordered xform ops supplied by the client.

Parameters
transformis the output parameter that will hold the local transform.
resetsXformStackis the output parameter that informs client whether they need to reset the transform stack before pushing transform.
opsis the ordered set of xform ops for this prim, and will be queried without any validity checking. Passing this in can save significant value-resolution costs, if the client is able to retain this data from a call to GetOrderedXformOps().
timeis the UsdTimeCode at which to sample the ops.
Returns
true on success, false if there was an error reading data.
Note
A coding error is issued if transform or resetsXformStack is NULL.
static USDGEOM_API bool GetLocalTransformation ( GfMatrix4d transform,
std::vector< UsdGeomXformOp > const &  ops,
const UsdTimeCode  time 
)
static

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. This is a static version of the preceding function that takes a cached list of ordered xform ops.

Parameters
transformis the output parameter that will hold the local transform.
opsis the ordered set of xform ops that must be combined together to compute the local transformation.
timeis the UsdTimeCode at which to sample the ops.
Returns
true on success, false if there was an error reading data.
USDGEOM_API std::vector<UsdGeomXformOp> GetOrderedXformOps ( bool *  resetsXformStack) const

Return the ordered list of transform operations to be applied to this prim, in least-to-most-local order.

This is determined by the intersection of authored op-attributes and the explicit ordering of those attributes encoded in the xformOpOrder attribute on this prim. Any entries in xformOpOrder that do not correspond to valid attributes on the xformable prim are skipped and a warning is issued.

A UsdGeomTransformable that has not had any ops added via AddXformOp() will return an empty vector.

The function also sets resetsXformStack to true if "!resetXformStack!" appears anywhere in xformOpOrder (i.e., if the prim resets its parent's inherited transformation).

Note
A coding error is issued if resetsXformStack is NULL.
See Also
GetResetXformStack()
USDGEOM_API bool GetResetXformStack ( ) const

Does this prim reset its parent's inherited transformation?

Returns true if "!resetXformStack!" appears anywhere in xformOpOrder. When this returns true, all ops upto the last "!resetXformStack!" in xformOpOrder are ignored when computing the local transformation.

static USDGEOM_API const TfTokenVector& GetSchemaAttributeNames ( bool  includeInherited = true)
static

Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes.

Does not include attributes that may be authored by custom/extended methods of the schemas involved.

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

Sets times to the union of all the timesamples at which xformOps that are included in the xformOpOrder attribute are authored.

This clears the times vector before accumulating sample times from all the xformOps.

See Also
UsdAttribute::GetTimeSamples
static USDGEOM_API bool GetTimeSamples ( std::vector< UsdGeomXformOp > const &  orderedXformOps,
std::vector< double > *  times 
)
static

Returns the union of all the timesamples at which the attributes belonging to the given orderedXformOps are authored.

This clears the times vector before accumulating sample times from orderedXformOps.

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

Sets times to the union of all the timesamples in the interval, interval, at which xformOps that are included in the xformOpOrder attribute are authored.

This clears the times vector before accumulating sample times from all the xformOps.

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

Returns the union of all the timesamples in the interval at which the attributes belonging to the given orderedXformOps are authored.

This clears the times vector before accumulating sample times from orderedXformOps.

See Also
UsdGeomXformable::GetTimeSamplesInInterval
USDGEOM_API UsdAttribute GetXformOpOrderAttr ( ) const

Encodes the sequence of transformation operations in the order in which they should be pushed onto a transform stack while visiting a UsdStage's prims in a graph traversal that will effect the desired positioning for this prim and its descendant prims.

You should rarely, if ever, need to manipulate this attribute directly. It is managed by the AddXformOp(), SetResetXformStack(), and SetXformOpOrder(), and consulted by GetOrderedXformOps() and GetLocalTransformation().


C++ Type: VtArray<TfToken>
Usd Type: SdfValueTypeNames->TokenArray
Variability: SdfVariabilityUniform
Fallback Value: No Fallback

static USDGEOM_API bool IsTransformationAffectedByAttrNamed ( const TfToken attrName)
static

Returns true if the attribute named attrName could affect the local transformation of an xformable prim.

USDGEOM_API UsdGeomXformOp MakeMatrixXform ( ) const

Clears the existing local transform stack and creates a new xform op of type 'transform'.

This API is provided for convenience since this is the most common xform authoring operation.

See Also
ClearXformOpOrder()
AddTransformOp()
USDGEOM_API bool SetResetXformStack ( bool  resetXform) const

Specify whether this prim's transform should reset the transformation stack inherited from its parent prim.

By default, parent transforms are inherited. SetResetXformStack() can be called at any time during authoring, but will always add a '!resetXformStack!' op as the first op in the ordered list, if one does not exist already. If one already exists, and resetXform is false, it will remove all ops upto and including the last "!resetXformStack!" op.

USDGEOM_API bool SetXformOpOrder ( std::vector< UsdGeomXformOp > const &  orderedXformOps,
bool  resetXformStack = false 
) const

Reorder the already-existing transform ops on this prim.

All elements in orderedXformOps must be valid and represent attributes on this prim. Note that it is not required that all the existing operations be present in orderedXformOps, so this method can be used to completely change the transformation structure applied to the prim.

If resetXformStack is set to true, then "!resetXformOp! will be set as the first op in xformOpOrder, to indicate that the prim does not inherit its parent's transformation.

Note
If you wish to re-specify a prim's transformation completely in a stronger layer, you should first call this method with an empty orderedXformOps vector. From there you can call AddXformOp() just as if you were authoring to the prim from scratch.
Returns
false if any of the elements of orderedXformOps are not extant on this prim, or if an error occurred while authoring the ordering metadata. Under either condition, no scene description is authored.
See Also
GetOrderedXformOps()
USDGEOM_API bool TransformMightBeTimeVarying ( ) const

Determine whether there is any possibility that this prim's local transformation may vary over time.

The determination is based on a snapshot of the authored state of the op attributes on the prim, and may become invalid in the face of further authoring.

USDGEOM_API bool TransformMightBeTimeVarying ( const std::vector< UsdGeomXformOp > &  ops) const

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Determine whether there is any possibility that this prim's local transformation may vary over time, using a pre-fetched (cached) list of ordered xform ops supplied by the client.

The determination is based on a snapshot of the authored state of the op attributes on the prim, and may become invalid in the face of further authoring.

Member Data Documentation

const UsdSchemaType schemaType = UsdSchemaType::AbstractTyped
static

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

See Also
UsdSchemaType

Definition at line 258 of file xformable.h.


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