C++ API Reference
MPxThreadedDeviceNode Class Reference

Base class for threaded node creation. More...

#include <MPxThreadedDeviceNode.h>

+ Inheritance diagram for MPxThreadedDeviceNode:

Public Member Functions

 MPxThreadedDeviceNode ()
 Constructor. More...
 
 ~MPxThreadedDeviceNode () override
 Class destructor.
 
MPxNode::Type type () const override
 Returns the type of node that this is. More...
 
virtual void threadHandler ()
 This method should be overridden in user defined nodes. More...
 
virtual void threadShutdownHandler ()
 This method should be overridden in user defined nodes. More...
 
bool isLive ()
 Returns the true if the node is live.
 
bool isDone ()
 Returns the true if the node has finished running.
 
MStatus setDone (bool done)
 This method is used to set done state of the thread. More...
 
MStatus beginThreadLoop ()
 This method should be called at the beginning of the loop in the secondary thread. More...
 
MStatus endThreadLoop ()
 This method should be called at the end of the loop in the secondary thread. More...
 
MStatus createMemoryPools (int nCount, int nElements, long nSize)
 This method should be called from the post constructor to create the memory buffers required. More...
 
MStatus destroyMemoryPools ()
 This method should be called to destroy the memory pools. More...
 
MStatus acquireDataStorage (MCharBuffer &buffer)
 This method is used to acquire a pointer to a block of storage that was allocated by the createMemoryPools() method. More...
 
MStatus pushThreadData (MCharBuffer &buffer)
 This method is used to push the block of storage onto the internal queue. More...
 
MStatus popThreadData (MCharBuffer &buffer)
 This method is used to pop the block of storage from the internal queue. More...
 
long threadDataCount ()
 This method returns the number of pieces of thread data that are currently in the node's queue. More...
 
MStatus releaseDataStorage (MCharBuffer &buffer)
 After popThreadData() is called, the pointer should be released so that it can be used again. More...
 
MStatus setRefreshOutputAttributes (const MObjectArray &attributeList)
 This method is used to set the list of output attributes which will be marked dirty by the secondary thread. More...
 
- Public Member Functions inherited from MPxNode
 MPxNode ()
 Constructor. More...
 
virtual ~MPxNode ()
 Destructor.
 
virtual void postConstructor ()
 Post constructor. More...
 
virtual MStatus compute (const MPlug &, MDataBlock &)
 This method should be overridden in user defined nodes. More...
 
virtual bool getInternalValue (const MPlug &, MDataHandle &)
 This method is overridden by nodes that store attribute data in some internal format. More...
 
virtual bool setInternalValue (const MPlug &, const MDataHandle &)
 This method is overridden by nodes that store attribute data in some internal format. More...
 
virtual int internalArrayCount (const MPlug &) const
 This method is overridden by nodes that have internal array attributes which are not stored in Maya's datablock. More...
 
virtual void copyInternalData (MPxNode *)
 This method is overridden by nodes that store attribute data in some internal format. More...
 
virtual MStatus legalConnection (const MPlug &, const MPlug &, bool asSrc, bool &isLegal) const
 This method allows you to check for legal connections being made to attributes of this node. More...
 
virtual MStatus legalDisconnection (const MPlug &, const MPlug &, bool asSrc, bool &isLegal) const
 This method allows you to check for legal disconnections being made to attributes of this node. More...
 
virtual MStatus setDependentsDirty (const MPlug &plug, MPlugArray &plugArray)
 This method can be overridden in user defined nodes to specify which plugs should be set dirty based upon an input plug {plugBeingDirtied} which Maya is marking dirty. More...
 
virtual MStatus preEvaluation (const MDGContext &context, const MEvaluationNode &evaluationNode)
 Prepare a node's internal state for threaded evaluation. More...
 
virtual MStatus postEvaluation (const MDGContext &context, const MEvaluationNode &evaluationNode, PostEvaluationType evalType)
 Clean up node's internal state after threaded evaluation. More...
 
virtual SchedulingType schedulingType () const
 When overridden this method controls the degree of parallelism supported by the node during threaded evaluation. More...
 
virtual void getCacheSetup (const MEvaluationNode &, MNodeCacheDisablingInfo &, MNodeCacheSetupInfo &, MObjectArray &) const
 Provide node-specific setup info for the Cached Playback system. More...
 
virtual void configCache (const MEvaluationNode &, MCacheSchema &) const
 Defines the node's behavior when participating in Cached Playback. More...
 
virtual MTimeRange transformInvalidationRange (const MPlug &source, const MTimeRange &input) const
 Override this method to register this node as an Invalidation-Range-Transformation kernel (IRT kernel) An IRT kernel node will change the invalidation time range for its downstream nodes For example, Dynamics-solver will transform invalidation time range [a,b] to [a,+inf) And Clip-Time-Editor will send out the invalidation range for each of the clip [a,b] to ( [t0+a,t0+b] U [t1+a,t1+b] U [t2+a,t2+b] U ... More...
 
bool hasInvalidationRangeTransformation () const
 Checks if this MPxNode derived node overrides the MPxNode::transformInvalidationRange method.
 
virtual MStatus connectionMade (const MPlug &, const MPlug &, bool asSrc)
 This method gets called when connections are made to attributes of this node. More...
 
virtual MStatus connectionBroken (const MPlug &, const MPlug &, bool asSrc)
 This method gets called when connections are broken with attributes of this node. More...
 
virtual MStatus dependsOn (const MPlug &, const MPlug &, bool &depends) const
 This method may be overridden by the user defined node. More...
 
virtual bool isPassiveOutput (const MPlug &) const
 This method may be overridden by the user defined node if it wants to provide output attributes which do not prevent value modifications to the destination attribute. More...
 
virtual MStatus shouldSave (const MPlug &, bool &isSaving)
 This method may be overridden by the user defined node. More...
 
virtual MPlug passThroughToOne (const MPlug &) const
 This method may be overridden by nodes that have a one-to-one relationship between an input attribute and a corresponding output attribute. More...
 
virtual bool passThroughToMany (const MPlug &, MPlugArray &) const
 This method is overridden by nodes that want to control the traversal behavior of some Maya search algorithms which traverse the history/future of shape nodes looking for directly related nodes. More...
 
virtual bool isAbstractClass () const
 Override this class to return true if this node is an abstract node. More...
 
virtual bool isTrackingTopology () const
 Override this class to return true if this node wants to track topology. More...
 
virtual MStringArray getFilesToArchive (bool shortName=false, bool unresolvedName=false, bool markCouldBeImageSequence=false) const
 Use this method to return all external files used by this node. More...
 
virtual void getExternalContent (MExternalContentInfoTable &table) const
 Returns the external content (files) that this node depends on. More...
 
bool addExternalContentForFileAttr (MExternalContentInfoTable &, const MObject &attr) const
 Adds content info to the specified table from a file path attribute. More...
 
bool setExternalContentForFileAttr (const MObject &attr, const MExternalContentLocationTable &)
 Sets content info in the specified attribute from the table. More...
 
virtual void setExternalContent (const MExternalContentLocationTable &)
 Changes the location of external content in batch. More...
 
virtual MTypeId typeId () const
 Returns the TYPEID of this node. More...
 
virtual MString typeName () const
 Returns the type name of this node. More...
 
virtual MString name () const
 Returns the name of this particular instance of this class. More...
 
virtual MObject thisMObject () const
 Returns the MObject associated with this user defined node. More...
 
virtual MStatus setExistWithoutInConnections (bool flag)
 This method specifies whether or not the node can exist without input connections. More...
 
virtual bool existWithoutInConnections (MStatus *ReturnStatus=NULL) const
 Determines whether or not this node can exist without input connections. More...
 
virtual MStatus setExistWithoutOutConnections (bool flag)
 This method specifies whether or not the node can exist without output connections. More...
 
virtual bool existWithoutOutConnections (MStatus *ReturnStatus=NULL) const
 Determines whether or not this node can exist without output connections. More...
 
void _setMPSafe (bool isMPSafe)
 This method is obsolete. More...
 
MDataBlock _forceCache (const MDGContext &)
 This method is obsolete. More...
 
virtual bool getInternalValueInContext (const MPlug &, MDataHandle &, MDGContext &)
 This method is obsolete. More...
 
virtual bool setInternalValueInContext (const MPlug &, const MDataHandle &, MDGContext &)
 This method is obsolete. More...
 
virtual int internalArrayCount (const MPlug &, const MDGContext &) const
 This method is obsolete. More...
 

Static Public Member Functions

static const char * className ()
 Returns the name of this class. More...
 
- Static Public Member Functions inherited from MPxNode
static MStatus addAttribute (const MObject &attr)
 This method adds a new attribute to a user defined node type during the type's initialization. More...
 
static MStatus inheritAttributesFrom (const MString &parentClassName)
 This method allows a class of plugin node to inherit all of the attributes of a second class of plugin node. More...
 
static MStatus attributeAffects (const MObject &whenChanges, const MObject &isAffected)
 This method specifies that a particular input attribute affects a specific output attribute. More...
 
static MStatus attributeAffects (const MObject &whenChanges, const MObject &isAffected, bool affectsTopology)
 This method is an extension to the other version of the attributeAffects method. More...
 
static const char * className ()
 Returns the name of this class. More...
 

Static Public Attributes

static MObject output
 Output data, generic attribute.
 
static MObject live
 Makes node live, boolean attribute.
 
static MObject frameRate
 Capture frame rate, double attribute.
 
- Static Public Attributes inherited from MPxNode
static MObject message
 message attribute
 
static MObject isHistoricallyInteresting
 is historically interesting attribute
 
static MObject caching
 caching attribute
 
static MObject state
 state attribute
 
static MObject frozen
 frozen attribute
 

Additional Inherited Members

- Public Types inherited from MPxNode
enum  Type {
  kDependNode, kLocatorNode, kDeformerNode, kManipContainer,
  kSurfaceShape, kFieldNode, kEmitterNode, kSpringNode,
  kIkSolverNode, kHardwareShader, kHwShaderNode, kTransformNode,
  kObjectSet, kFluidEmitterNode, kImagePlaneNode, kParticleAttributeMapperNode,
  kCameraSetNode, kConstraintNode, kManipulatorNode, kMotionPathNode,
  kClientDeviceNode, kThreadedDeviceNode, kAssembly, kSkinCluster,
  kGeometryFilter, kBlendShape, kLast
}
 Defines the type of node. More...
 
enum  SchedulingType {
  kParallel, kSerial, kGloballySerial, kUntrusted ,
  kDefaultScheduling = kSerial, kSerialize = kSerial, kGloballySerialize = kGloballySerial
}
 Defines the degree of parallelism of a node. More...
 
- Protected Member Functions inherited from MPxNode
virtual MDataBlock forceCache ()
 USE _forceCache() IN SCRIPT. More...
 
virtual MStatus setDoNotWrite (bool flag)
 USE _setDoNotWrite() IN SCRIPT. More...
 
virtual bool doNotWrite (MStatus *ReturnStatus=NULL) const
 USE _doNotWrite() IN SCRIPT. More...
 
virtual void setMPSafe (bool isMPSafe)
 This method is obsolete. More...
 
virtual MDataBlock forceCache (const MDGContext &)
 This method is obsolete. More...
 

Detailed Description

Base class for threaded node creation.

MPxThreadedDeviceNode is the base class used for creating threaded maya device nodes.

Maya handles thread management. The plug-in needs to implement the threadHandler() and threadShutdownHandler(). Maya will call these handlers as it manages the thread.

The interface implements a memory queue system where data pointers are acquired, filled, then pushed into the node using mutex locking. This is done from a separate, secondary thread. When the data has been acquired, the thread will mark the output attribute as dirty so that the compute in the main thread will be called. The main thread will pop the oldest data buffer, process it, then release the thread data. The helper class MCharBuffer is used with the memory methods.

The "live" attribute allows finer control over the secondary thread. It can be used to stop the handling of incoming data without disconnecting the output attributes. Note that the thread continues to run even if the the live attribute is set to false.

To implement an MPxThreadedDeviceNode plug-in, you must: 1. Use the post constructor to call setRefreshOutputAttributes() and createMemoryPools() 2. Implement the destructor to destroy the memory pools 3. Implement the threadHandler() virtual. Maya will call this handler when it creates the thread. Typically the thread handler will implement a loop for collecting data. This class contains a "done" state which is accessible via the isDone() and setDone() methods. Loop while isDone() is false 4. Implement the threadShutdownHandler(). This method would be called by Maya on File -> New and Exit for example. Call setDone( true ) to stop the isDone() loop implemented in the threadHandler if the plug-in uses the done state 5. The secondary thread should call beginThreadLoop() and endThreadLoop() with the data operations happening in-between. The endThreadLoop() method will perform the throttling based on the frame rate attribute and additionally cause the output attribute to be marked dirty. This in turn will cause compute() to be called in the main thread once Maya processes the dirty message 6. The thread loop should acquireDataStorage() to get a buffer, populate the buffer with information and then call pushThreadData() 8. The compute method should popThreadData() and if it's valid, process the data and release the data pointer by calling releaseDataStorage().

The live and frameRate attributes are included in this class. Changes to these attributes will cause the thread to be shutdown and restarted so that the new settings can be in effect.

If this node is deleted then the thread will automatically be shutdown when the node is placed on the undo queue. Undoing the delete will restart the thread if it was running at the time of the delete.

NOTE: This class relies on the idle event queue to perform the node attribute updating. As a result, it will not work in Maya batch mode.

Examples:
gameInputDevice/gameInputDevice.cpp, and randomizerDevice/randomizerDevice.cpp.

Constructor & Destructor Documentation

OPENMAYA_MAJOR_NAMESPACE_OPEN MPxThreadedDeviceNode ( )

Constructor.

The constructor should never call any methods from MPxNode or make any calls that require the existence of the MObject associated with the user defined node. The postConstructor method should be used to do any initialization of this kind.

For example, the postConstructor method would be used to call: setRefreshOutputAttributes()

Member Function Documentation

MPxNode::Type type ( ) const
overridevirtual

Returns the type of node that this is.

This is used to differentiate user defined nodes that are derived off different MPx base classes.

It is not necessary to override this method.

Returns
Type of the node

Reimplemented from MPxNode.

void threadHandler ( )
virtual

This method should be overridden in user defined nodes.

Thread management( creation/destruction/shutdown ) will be handled by Maya. This method will be called when the thread has been created. In a typical implementation, the thread handler will implement a loop for reading information from an external device.

Examples:
gameInputDevice/gameInputDevice.cpp, randomizerDevice/randomizerDevice.cpp, and udpDevice/udpDevice.cpp.
void threadShutdownHandler ( )
virtual

This method should be overridden in user defined nodes.

This method is used to shutdown the loop running in the thread handler.

Examples:
gameInputDevice/gameInputDevice.cpp, randomizerDevice/randomizerDevice.cpp, and udpDevice/udpDevice.cpp.
MStatus setDone ( bool  done)

This method is used to set done state of the thread.

Parameters
[in]donebool to set
Status Codes:
  • MS::kSuccess operation successful
  • MS::kFailure this MPxNode has not been initialized properly. Make sure this method is not being called from the constructor.
MStatus beginThreadLoop ( )

This method should be called at the beginning of the loop in the secondary thread.

Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly.
MStatus endThreadLoop ( )

This method should be called at the end of the loop in the secondary thread.

This method will throttle the thread loop based on the frame rate attribute value. For example, if you set the frameTime attribute to 1 and the processing of your thread loop body takes .25 seconds, then this method will cause a delay of .75 seconds before the thread loop restarts. This method will also mark the refresh output attribute as dirty which will make compute() be called in the main thread.

Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or this method is not being called in the same thread as beginThreadLoop()
MStatus createMemoryPools ( int  nCount,
int  nElements,
long  nSize 
)

This method should be called from the post constructor to create the memory buffers required.

Parameters
[in]nCountthe number of pools to create
[in]nElementsthe number of elements in each pool
[in]nSizethe size of each elememt
Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or the creation of the memory pool failed
MStatus destroyMemoryPools ( )

This method should be called to destroy the memory pools.

This can be done in the destructor.

Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or the destruction of the memory pool failed
MStatus acquireDataStorage ( MCharBuffer buffer)

This method is used to acquire a pointer to a block of storage that was allocated by the createMemoryPools() method.

Parameters
[out]buffercontains a pointer to the buffer that should be written into
Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or there are no blocks of storage available
MStatus pushThreadData ( MCharBuffer buffer)

This method is used to push the block of storage onto the internal queue.

This is usually done by a secondary thread.

NOTE: the buffer parameter will be cleared upon the successful return of this method. This is to avoid reusing the pointer.

Parameters
[in,out]buffercontains a pointer to the buffer that should be put onto the internal queue
Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or the push failed or the buffer size was 0 or the buffer pointer was NULL
MStatus popThreadData ( MCharBuffer buffer)

This method is used to pop the block of storage from the internal queue.

This is usually done in the main thread's compute() method.

Parameters
[out]buffercontains a pointer to the buffer that should be processed
Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or the pop failed
long threadDataCount ( )

This method returns the number of pieces of thread data that are currently in the node's queue.

For example if you called pushThreadData() 10 times but only called popThreadData() 3 times, you would have a thread data count of 7.

Returns
thread data count
MStatus releaseDataStorage ( MCharBuffer buffer)

After popThreadData() is called, the pointer should be released so that it can be used again.

This is usually done in the main thread's compute() method. NOTE: the buffer pointer will be reset to NULL if this method succeeds.

Parameters
[in,out]buffercontains a pointer to the buffer that has been processed and should now be released
Returns
Status code
Status Codes:
  • MS::kSuccess Operation successful
  • MS::kFailure this MPxNode has not been initialized properly or the release of the memory buffer failed or the buffer pointer is NULL
MStatus setRefreshOutputAttributes ( const MObjectArray attributeList)

This method is used to set the list of output attributes which will be marked dirty by the secondary thread.

After the secondary thread receives data, it sends a message to dirty the attributes specified in the parameter list. This will then cause a refresh to make the object update.

Parameters
[in]attributeLista list of output attributes that will cause the node to refresh automatically. NOTE: Currently, only one attribute is supported
Status Codes:
  • MS::kSuccess operation successful
  • MS::kFailure this MPxNode has not been initialized properly. Make sure this method is not being called from the constructor.
const char * className ( )
static

Returns the name of this class.

Returns
The name of this class.

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