Computation Registrations

Computation registrations initiate the process of defining computations. More...

Collaboration diagram for Computation Registrations:

Functions
EXEC_API Exec_PrimComputationBuilder	PrimComputation (const TfToken &computationName)
	Registers a prim computation named computationName.
EXEC_API Exec_AttributeComputationBuilder	AttributeComputation (const TfToken &attributeName, const TfToken &computationName)
	Registers an attribute computation named computationName on attributes named attributeName.
template<class... DispatchedOntoSchemaTypes>
Exec_PrimComputationBuilder	DispatchedPrimComputation (const TfToken &computationName, DispatchedOntoSchemaTypes &&...schemaTypes)
	Registers a dispatched prim computation named computationName.
EXEC_API Exec_PrimComputationBuilder	DispatchedPrimComputation (const TfToken &computationName, ExecDispatchesOntoSchemas &&ontoSchemas)
template<class... DispatchedOntoSchemaTypes>
Exec_AttributeComputationBuilder	DispatchedAttributeComputation (const TfToken &computationName, DispatchedOntoSchemaTypes &&...schemaTypes)
	Registers a dispatched attribute computation named computationName.
EXEC_API Exec_AttributeComputationBuilder	DispatchedAttributeComputation (const TfToken &computationName, ExecDispatchesOntoSchemas &&ontoSchemas)
template<typename ResultType = _UnspecifiedType, typename ReturnType = _UnspecifiedType>
Derived &	Callback (ReturnType(*callback)(const VdfContext &))
	Registers a callback function that implements the evaluation logic for a computation.
template<typename... Args>
Exec_PrimComputationBuilder &	Inputs (Args &&... args)
	Takes one or more input registrations that specify how to source input values for a prim computation.
template<typename... Args>
Exec_AttributeComputationBuilder &	Inputs (Args &&... args)
	Takes one or more input registrations that specify how to source input values for an attribute computation.

Detailed Description

Computation registrations initiate the process of defining computations.

The object returned by a computation registration has methods that are used to specify the callback that implements the computation and the inputs that are provided to the callback at evaluation time.

Function Documentation

AttributeComputation()

EXEC_API Exec_AttributeComputationBuilder AttributeComputation	(	const TfToken &	attributeName,
		const TfToken &	computationName
	)

Registers an attribute computation named computationName on attributes named attributeName.

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register a trivial attribute computation.
    self.AttributeComputation(
        _tokens->attr,   // attributeName
        _tokens->eleven) // computationName
        .Callback<double>(+[](const VdfContext &) { return 11.0; })
}

Callback()

Derived & Callback

(

ReturnType(*)(const VdfContext &)

callback

)

Registers a callback function that implements the evaluation logic for a computation.

This registration must follow a computation registration.

Callback functions must be function pointers where the signature is ReturnType (*)(const VdfContext &) and ReturnType can be any of the following:

• The result type of the computation, in which case ResultType can be deduced from the callback type.
• A type that is convertible to the result type of the computaion, in which case ResultType must be explicitly specified as a template parameter.
• void in which case ResultType must be explicitly specified as a template parameter and the callback must call VdfContext::SetOutput to provide the output value.

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register a prim computation with a callback where the result type
    // is deduced to be `float`.
    self.PrimComputation(_tokens->doubleValuedComputation)
        .Callback(
            +[](const VdfContext &) { return 11.0f; });
 
    // Register a prim computation with a callback where the explicit
    // result type is `std::string`.
    self.PrimComputation(_tokens->stringValuedComputation)
        .Callback<std::string>(
            +[](const VdfContext &) { return "a string value"; });
 
    // Register a prim computation with a callback that explicitly calls
    // SetValue.
    self.PrimComputation(_tokens->stringValuedComputation)
        .Callback<int>(
            +[](const VdfContext &) { ctx.SetValue(42); });
}

Definition at line 1655 of file computationBuilders.h.

DispatchedAttributeComputation()

Exec_AttributeComputationBuilder DispatchedAttributeComputation	(	const TfToken &	computationName,
		DispatchedOntoSchemaTypes &&...	schemaTypes
	)

Registers a dispatched attribute computation named computationName.

See also

DispatchedPrimComputation

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register a dispatched attribute computation that can be found on
    // attributes on scopes.
    const TfType scopeType = TfType::FindByName("UsdGeomScope");
    self.DispatchedAttributeComputation(_tokens->eleven, scopeType)
        .Callback<double>(+[](const VdfContext &) { return 11.0; })
 
    // Register a prim computation that requests the above dispatched
    // computation on an attribute on the owning prim named 'attr'.
    self.PrimComputation(_tokens->myComputation)
        .Callback<double>(+[](const VdfContext &ctx) {
            const double *const valuePtr =
                ctx.GetInputValuePtr<double>(_tokens->eleven);
            return valuePtr ? *valuePtr : -1.0;
        })
        .Inputs(
 
            // This input opts-in to finding dispatched computations.
            Attribute(_tokens->attr)
                .Computation<double>(_tokens->eleven)
                .FallsBackToDispatched())
}

Definition at line 1759 of file computationBuilders.h.

DispatchedPrimComputation()

Exec_PrimComputationBuilder DispatchedPrimComputation	(	const TfToken &	computationName,
		DispatchedOntoSchemaTypes &&...	schemaTypes
	)

Registers a dispatched prim computation named computationName.

A dispatched prim computation is only visible to computations on the prim that does the dispatching. I.e., the computation registrations for a schema can include dispatched computations and inputs to computations registered on the same schema can request the dispatched computations, using the input option FallsBackToDispatched(), from other provider prims and find them there. Other schema computation registrations will not be able to find the dispatched computations, however.

Dispatched computations can be restricted as to which prims they can dispatch onto, based on the typed and applied schemas of a given target prim. The second parameter to the DispatchedPrimComputation registration function can be used to specify zero or more schema types (as TfTypes). If any types are given, the dispatched computation will only be found on a target prim if that prim's typed schema type (or one of its base type) is among the given schema types or if the fully expanded list of API schemas applied to the prim includes a schema that is among the given schema types.

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register a dispatched prim computation that can be found on
    // scopes.
    const TfType scopeType = TfType::FindByName("UsdGeomScope");
    self.DispatchedPrimComputation(_tokens->eleven, scopeType)
        .Callback<double>(+[](const VdfContext &) { return 11.0; })
 
    // Register a prim computation that requests the above dispatched
    // computation via uses relationship targets. Any targeted prim
    // whose type is UsdGeomScope will find the requested computation.
    self.PrimComputation(_tokens->myComputation)
        .Callback<double>(+[](const VdfContext &ctx) {
            const double *const valuePtr =
                ctx.GetInputValuePtr<double>(_tokens->eleven);
            return valuePtr ? *valuePtr : -1.0;
        })
        .Inputs(
 
            // This input opts-in to finding dispatched computations.
            Relationship(_tokens->myRelationship)
                .TargetedObjects<double>(_tokens->eleven)
                .FallsBackToDispatched())
}

Definition at line 1744 of file computationBuilders.h.

Inputs() [1/2]

Exec_PrimComputationBuilder & Inputs

(

Args &&...

args

)

Takes one or more input registrations that specify how to source input values for a prim computation.

This registration must follow a computation registration.

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register a prim computation that reads from two inputs.
    self.PrimComputation(_tokens->myPrimComputation)
        .Callback<int>(&_MyCallbackFn)
        .Inputs(
            AttributeValue<int>(_tokens->myAttribute),
            NamespaceAncestor<double>(_tokens->anotherPrimComputation));
}

Definition at line 1706 of file computationBuilders.h.

Inputs() [2/2]

Exec_AttributeComputationBuilder & Inputs

(

Args &&...

args

)

Takes one or more input registrations that specify how to source input values for an attribute computation.

This registration must follow a computation registration.

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register an attribute computation that reads from two inputs.
    self.AttributeComputation(
        _tokens->attr,
        _tokens->myPrimComputation)
        .Callback<int>(&_MyCallbackFn)
        .Inputs(
            NamespaceAncestor<double>(_tokens->anotherPrimComputation));
}

Definition at line 1725 of file computationBuilders.h.

PrimComputation()

EXEC_API Exec_PrimComputationBuilder PrimComputation

(

const TfToken &

computationName

)

Registers a prim computation named computationName.

Example

EXEC_REGISTER_COMPUTATIONS_FOR_SCHEMA(MySchemaType)
{
    // Register a trivial prim computation.
    self.PrimComputation(_tokens->eleven)
        .Callback<double>(+[](const VdfContext &) { return 11.0; })
}