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# MPxNode Class Reference
OpenMaya - API module for common classes | Proxy classes

This reference page is linked to from the following overview topics: Autodesk Maya 2014, Command Plug-ins, Dependency Graph Plug-in Basics, The Dependency Graph, Dependency Graph Plug-ins, Example: Creating a Depth Shader, Example: Using Time to Animate a Cube Mesh, Example: Voxelizer Node, Parent class descriptions, The basics, Dependency Graph (DG) nodes, MPxNode and its derived classes, Manipulator Containers, Shapes in Maya, Writing a shape, File IO, Writing a shading node plug-in, Anatomy of a shading node plug-in, Overview of custom transforms, Implementing a Deformer Node, Scene Overrides, Transition Guide, splitUVCmd example, Using the Maya Python API, Removal of MStatus return codes from .NET API, Using .NET assembly attributes, Threading and Maya API, Overview of example plug-ins, Example C++ plug-in descriptions, Appendix C: Frequently asked questions.

Search for all occurrences

## Detailed Description

Base class for user defined dependency nodes.

MPxNode is the the parent class for user defined dependency nodes. A dependency node is an object that resides in the dependency graph. It computes output attributes based on a set of input attributes. When an input changes, the compute method is called for each dependent output.

The dependency graph is made up of nodes that have connections between their attributes. When an attribute changes, recomputation propagates through the graph until all affected values have been updated.

When writing a dependency node, there is a very basic rule that should be observed. The outputs should be calculated only using the values of the inputs. All information about the world outside the node should come from input attributes. If this rule is not observed, then the results may be unpredictable.

All dependency nodes have four basic attributes. Documentation for them may be found with the documentation for the dependency nodes in Maya. Only one attribute requires special attention by node developers. Developers must decide whether to support the HasNoEffect setting of the state attribute. {HasNoEffect} means that a node should pass through all data without performing computations on it. For example, a deformer node will pass geometry through unmodified when state is set to HasNoEffect. It is up the the plug-in writer to observe the HasNoEffect mode if it is relevant to the type of node.

Examples:

  affectsNode.cpp, animCubeNode.cpp, anisotropicShader.cpp, apiMeshCreator.h, arcLenNode.cpp, backfillShader.cpp, blindDataMesh.h, brickShader.cpp, buildRotationNode.cpp, cellShader.cpp, cgfxShaderNode.cpp, cgfxShaderNode.h, cgfxVector.h, checkerShader.cpp, circleNode.cpp, clearcoat.cpp, closestPointOnCurveNode.h, compositingShader.cpp, contrastShader.cpp, cvColorShader.cpp, depthShader.cpp, displacementShader.cpp, exampleMRampAttribute.cpp, flameShader.cpp, fullLoftNode.cpp, gammaShader.cpp, genericAttributeNode.cpp, geomShader.cpp, hlslShader.cpp, hlslShader.h, interpShader.cpp, jitterNode.cpp, lambertShader.cpp, latticeNoise.h, lavaShader.cpp, lightShader.cpp, mixtureShader.cpp, multiCurveNode.cpp, noiseShader.cpp, phongShader.cpp, pointOnMeshInfoNode.h, pointOnSubdNode.h, polyModifierNode.h, renderAccessNode.cpp, shadowMatteShader.cpp, shellNode.cpp, shiftNode.cpp, simpleLoftNode.cpp, sineNode.cpp, slopeShaderNode.h, solidCheckerShader.cpp, stringFormatNode.cpp, testNobjectNode.h, testNucleusNode.h, transCircleNode.cpp, volumeShader.cpp, and weightListNode.cpp.

`#include <MPxNode.h>`

Inheritance diagram for MPxNode:
[legend]

List of all members.

## Public Types
enum | Type { kDependNode, kLocatorNode, kDeformerNode, kManipContainer, kSurfaceShape, kFieldNode, kEmitterNode, kSpringNode, kIkSolverNode, kHardwareShader, kHwShaderNode, kTransformNode, kObjectSet, kFluidEmitterNode, kImagePlaneNode, kParticleAttributeMapperNode, kCameraSetNode, kConstraintNode, kManipulatorNode, kClientDeviceNode, kThreadedDeviceNode, kAssembly, kLast }
| Defines the type of node. More...
## Public Member Functions
| MPxNode ()
| Constructor.
virtual | ~MPxNode ()
| Destructor.
virtual void | postConstructor ()
| Post constructor.
virtual MStatus | compute (const MPlug &plug, MDataBlock &dataBlock)
| This method should be overridden in user defined nodes.
virtual bool | getInternalValueInContext (const MPlug &plug, MDataHandle &dataHandle, MDGContext &ctx)
| This method is overriden by nodes that store attribute data in some internal format.
virtual bool | setInternalValueInContext (const MPlug &plug, const MDataHandle &dataHandle, MDGContext &ctx)
| This method is overriden by nodes that store attribute data in some internal format.
virtual bool | getInternalValue (const MPlug &plug, MDataHandle &dataHandle)
| This method is obsolete.
virtual bool | setInternalValue (const MPlug &plug, const MDataHandle &dataHandle)
| This method is obsolete.
virtual int | internalArrayCount (const MPlug &plug, const MDGContext &ctx) const
| This method is overriden by nodes that have internal array attributes which are not stored in Maya's datablock.
virtual void | copyInternalData (MPxNode *)
| This method is overriden by nodes that store attribute data in some internal format.
virtual MStatus | legalConnection (const MPlug &plug, const MPlug &otherPlug, bool asSrc, bool &isLegal) const
| This method allows you to check for legal connections being made to attributes of this node.
virtual MStatus | legalDisconnection (const MPlug &plug, const MPlug &otherPlug, bool asSrc, bool &isLegal) const
| This method allows you to check for legal disconnections being made to attributes of this node.
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.
virtual MStatus | connectionMade (const MPlug &plug, const MPlug &otherPlug, bool asSrc)
| This method gets called when connections are made to attributes of this node.
virtual MStatus | connectionBroken (const MPlug &plug, const MPlug &otherPlug, bool asSrc)
| This method gets called when connections are broken with attributes of this node.
virtual bool | isPassiveOutput (const MPlug &plug) 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.
virtual MStatus | shouldSave (const MPlug &plug, bool &isSaving)
| This method may be overridden by the user defined node.
virtual MPlug | passThroughToOne (const MPlug &plug) const
| This method may be overriden by nodes that have a one-to-one relationship between an input attribute and a corresponding output attribute.
virtual bool | passThroughToMany (const MPlug &plug, MPlugArray &plugArray) const
| This method is overriden 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.
virtual Type | type () const
| Returns the type of node that this is.
virtual bool | isAbstractClass () const
| Override this class to return true if this node is an abstract node.
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.
virtual MTypeId | typeId () const
| Returns the TYPEID of this node.
virtual MString | typeName () const
| Returns the type name of this node.
virtual MString | name () const
| Returns the name of this particular instance of this class.
virtual MObject | thisMObject () const
| Returns the MObject associated with this user defined node.
virtual MStatus | setExistWithoutInConnections (bool flag)
| This method specifies whether or not the node can exist without input connections.
virtual bool | existWithoutInConnections (MStatus *ReturnStatus=NULL) const
| Determines whether or not this node can exist without input connections.
virtual MStatus | setExistWithoutOutConnections (bool flag)
| This method specifies whether or not the node can exist without output connections.
virtual bool | existWithoutOutConnections (MStatus *ReturnStatus=NULL) const
| Determines whether or not this node can exist without output connections.
## Static Public Member Functions
static MStatus | addAttribute (const MObject &attr)
| This method adds a new attribute to a user defined node type during the type's initialization.
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.
static MStatus | attributeAffects (const MObject &whenChanges, const MObject &isAffected)
| This method specifies that a particular input attribute affects a specific output attribute.
static const char * | className ()
| Returns the name of this class.
## Static Public Attributes
static MObject | message
| message attribute Search for all occurrences
static MObject | isHistoricallyInteresting
| is historically interesting attribute Search for all occurrences
static MObject | caching
| caching attribute Search for all occurrences
static MObject | state
| state attribute
## Protected Member Functions
virtual MDataBlock | forceCache (MDGContext &ctx=MDGContext::fsNormal)
| USE _forceCache() IN SCRIPT.
virtual void | setMPSafe (bool flag)
| USE _setMPSafe() IN SCRIPT.
virtual MStatus | setDoNotWrite (bool flag)
| USE _setDoNotWrite() IN SCRIPT.
virtual bool | doNotWrite (MStatus *ReturnStatus=NULL) const
| USE _doNotWrite() IN SCRIPT. Search for all occurrences

## Member Enumeration Documentation

enum Type

Search for all occurrences

Defines the type of node.

Enumerator:

  kDependNode | Custom node derived from MPxNode. Search for all occurrences
  kLocatorNode | Custom locator derived from MPxLocatorNode. Search for all occurrences
  kDeformerNode | Custom deformer derived from MPxDeformerNode. Search for all occurrences
  kManipContainer | Custom container derived from MPxManipContainer. Search for all occurrences
  kSurfaceShape | Custom shape derived from MPxSurfaceShape. Search for all occurrences
  kFieldNode | Custom field derived from MPxFieldNode. Search for all occurrences
  kEmitterNode | Custom emitter derived from MPxEmitterNode. Search for all occurrences
  kSpringNode | Custom spring derived from MPxSpringNode. Search for all occurrences
  kIkSolverNode | Custom IK solver derived from MPxIkSolverNode. Search for all occurrences
  kHardwareShader | Custom shader derived from MPxHardwareShader. Search for all occurrences
  kHwShaderNode | Custom shader derived from MPxHwShaderNode. Search for all occurrences
  kTransformNode | Custom transform derived from MPxTransform. Search for all occurrences
  kObjectSet | Custom set derived from MPxObjectSet. Search for all occurrences
  kFluidEmitterNode | Custom fluid emitter derived from MpxFluidEmitterNode. Search for all occurrences
  kImagePlaneNode | Custom image plane derived from MPxImagePlane. Search for all occurrences
  kParticleAttributeMapperNode | Custom particle attribute mapper derived from MPxParticleAttributeMapperNode. Search for all occurrences
  kCameraSetNode | Custom director derived from MPxCameraSet. Search for all occurrences
  kConstraintNode | Custom constraint derived from MPxConstraint. Search for all occurrences
  kManipulatorNode | Custom manipulator derived from MPxManipulatorNode. Search for all occurrences
  kClientDeviceNode | Custom threaded device derived from MPxThreadedDeviceNode. Search for all occurrences
  kThreadedDeviceNode | Custom threaded device node. Search for all occurrences
  kAssembly | Custom assembly derived from MPxAssembly. Search for all occurrences
  kLast | Last value, used for counting. Search for all occurrences

## Constructor & Destructor Documentation

MPxNode | ( |  | ) |

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.

## Member Function Documentation

void postConstructor | ( |  | ) | `[virtual]`

Search for all occurrences

Post constructor.

Internally maya creates two objects when a user defined node is created, the internal MObject and the user derived object. The association between the these two objects is not made until after the MPxNode constructor is called. This implies that no MPxNode member function can be called from the MPxNode constructor. The postConstructor will get called immediately after the constructor when it is safe to call any MPxNode member function.

Reimplemented in MPxPolyTrg, and MPxTransform.

Examples:
  anisotropicShader.cpp, apiMeshShape.h, backfillShader.cpp, brickShader.cpp, cellShader.cpp, cgfxShaderNode.h, checkerShader.cpp, clearcoat.cpp, compositingShader.cpp, contrastShader.cpp, curvedArrowsNode.cpp, cvColorShader.cpp, depthShader.cpp, displacementShader.cpp, flameShader.cpp, gammaShader.cpp, geometrySurfaceConstraint.h, geomShader.cpp, hlslShader.h, hwAnisotropicShader_NV20.h, hwColorPerVertexShader.cpp, hwDecalBumpShader_NV20.h, hwManagedTextureShader.cpp, hwPhongShader.h, hwReflectBumpShader_NV20.h, hwRefractReflectShader_NV20.h, hwToonShader_NV20.h, hwUnlitShader.h, interpShader.cpp, lambertShader.cpp, lavaShader.cpp, lightShader.cpp, mixtureShader.cpp, noiseShader.cpp, phongShader.cpp, quadricShape.cpp, renderAccessNode.cpp, shadowMatteShader.cpp, slopeShaderNode.h, solidCheckerShader.cpp, squareScaleManipContext.h, and volumeShader.cpp.

MStatus compute | ( | const MPlug & | plug,
|  | MDataBlock & | block
| ) |  | `[virtual]`

Search for all occurrences

This method should be overridden in user defined nodes.

Recompute the given output based on the nodes inputs. The plug represents the data value that needs to be recomputed, and the data block holds the storage for all of the node's attributes.

The MDataBlock will provide smart handles for reading and writing this node's attribute values. Only these values should be used when performing computations.

When evaluating the dependency graph, Maya will first call the compute method for this node. If the plug that is provided to the compute indicates that that the attribute was defined by the Maya parent node, the compute method should return MS::kUnknownParameter. When this occurs, Maya will call the internal Maya node from which the user-defined node is derived to compute the plug's value.

This means that a user defined node does not need to be concerned with computing inherited output attributes. However, if desired, these can be safely recomputed by this method to change the behaviour of the node.

Parameters:

  [in] | plug | plug representing the attribute that needs to be recomputed
  [in] | block | data block containing storage for the node's attributes

Returns:
  Status code

Status Codes:
  - MS::kSuccess Compute was successful
  - MS::kFailure Compute failed

Reimplemented in MPxEmitterNode, MPxFieldNode, MPxFluidEmitterNode, MPxParticleAttributeMapperNode, MPxPolyTrg, and MPxTransform.

Examples:
  affectsNode.cpp, animCubeNode.cpp, anisotropicShader.cpp, apiMeshCreator.h, apiMeshShape.h, arcLenNode.cpp, backfillShader.cpp, blindDataMesh.h, blindDataShader.h, brickShader.cpp, buildRotationNode.cpp, cellShader.cpp, cgfxShaderNode.h, cgfxVector.h, checkerShader.cpp, circleNode.cpp, clearcoat.cpp, closestPointOnCurveNode.h, compositingShader.cpp, contrastShader.cpp, curvedArrowsNode.cpp, cvColorNode.cpp, cvColorShader.cpp, depthShader.cpp, displacementShader.cpp, exampleMRampAttribute.cpp, flameShader.cpp, footPrintManip.cpp, footPrintNode.cpp, fullLoftNode.cpp, gammaShader.cpp, genericAttributeNode.cpp, geometrySurfaceConstraint.h, geomShader.cpp, hwColorPerVertexShader.cpp, hwDecalBumpShader_NV20.h, hwPhongShader.h, hwReflectBumpShader_NV20.h, hwRefractReflectShader_NV20.h, hwToonShader_NV20.h, hwUnlitShader.h, interpShader.cpp, jitterNode.cpp, lambertShader.cpp, latticeNoise.h, lavaShader.cpp, lightShader.cpp, mixtureShader.cpp, multiCurveNode.cpp, noiseShader.cpp, phongShader.cpp, pointOnMeshInfoNode.h, pointOnSubdNode.h, quadricShape.cpp, renderAccessNode.cpp, shadowMatteShader.cpp, shellNode.cpp, shiftNode.cpp, simpleLoftNode.cpp, simpleSpring.h, sineNode.cpp, slopeShaderNode.h, solidCheckerShader.cpp, stringFormatNode.cpp, swissArmyManip.cpp, testNobjectNode.h, testNucleusNode.h, transCircleNode.cpp, volumeShader.cpp, and weightListNode.cpp.

bool getInternalValueInContext | ( | const MPlug & | plug,
|  | MDataHandle & | dataHandle,
|  | MDGContext & | ctx
| ) |  | `[virtual]`

Search for all occurrences

This method is overriden by nodes that store attribute data in some internal format.

The internal state of attributes can be set or queried using the setInternal and internal methods of MFnAttribute.

When internal attribute values are queried via getAttr or MPlug::getValue this method is called.

NOTE: the default behaviour of this method is to call MPxNode::getInternalValue( const MPlug&, const MDataHandle& ) if the context is normal.

Parameters:

  [in] | plug | the attribute that is being queried
  [out] | dataHandle | the dataHandle to store the attribute value
  [in] | ctx | the context the method is being evaluated in

Returns:
  - true the attribute was place on the datablock
  - false could not handle the specified attribute, pass this request to the default handler

Examples:
  cgfxShaderNode.h, customImagePlane.cpp, hlslShader.h, hwColorPerVertexShader.cpp, and hwPhongShader.h.

bool setInternalValueInContext | ( | const MPlug & | plug,
|  | const MDataHandle & | dataHandle,
|  | MDGContext & | ctx
| ) |  | `[virtual]`

Search for all occurrences

This method is overriden by nodes that store attribute data in some internal format.

The internal state of attributes can be set or queried using the setInternal and internal methods of MFnAttribute.

When internal attribute values are set via setAttr or MPlug::setValue this method is called.

Another use for this method is to impose attribute limits.

NOTE: the default behaviour of this method is to call MPxNode::setInternalValue( const MPlug&, const MDataHandle& ) if the context is normal.

Parameters:

  [in] | plug | the attribute that is being set
  [in] | dataHandle | the dataHandle containing the value to set
  [in] | ctx | the context the method is being evaluated in

Returns:
  - true the attribute was set
  - false could not handle the specified attribute, pass this request to the default handler

Examples:
  cgfxShaderNode.h, customImagePlane.cpp, hlslShader.h, hwColorPerVertexShader.cpp, and hwPhongShader.h.

bool getInternalValue | ( | const MPlug & | plug,
|  | MDataHandle & | dataHandle
| ) |  | `[virtual]`

Search for all occurrences

This method is obsolete.

Deprecated:
  Use the method MPxNode::getInternalValueInContext instead.

Parameters:

  [in] | plug |
  [out] | dataHandle |

Examples:
  apiMeshShape.cpp, apiMeshShape.h, cgfxShaderNode.cpp, hlslShader.cpp, pnTrianglesNode.h, and quadricShape.cpp.

bool setInternalValue | ( | const MPlug & | plug,
|  | const MDataHandle & | dataHandle
| ) |  | `[virtual]`

Search for all occurrences

This method is obsolete.

Deprecated:
  Use the method MPxNode::setInternalValueInContext instead.

Parameters:

  [in] | plug |
  [in] | dataHandle |

Examples:
  apiMeshShape.cpp, apiMeshShape.h, cgfxShaderNode.cpp, hlslShader.cpp, pnTrianglesNode.h, and quadricShape.cpp.

int internalArrayCount | ( | const MPlug & | plug,
|  | const MDGContext & | ctx
| ) |  | const`[virtual]`

Search for all occurrences

This method is overriden by nodes that have internal array attributes which are not stored in Maya's datablock.

This method is used by Maya to determine the non-sparse count of array elements during file io. If the internal array is stored sparsely, you should return the maximum index of the array plus one. If the internal array is non-sparse then return the length of the array.

This method does not need to be implemented for attributes that are stored in the datablock since Maya will use the datablock size.

If this method is overriden, it should return -1 for attributes which it does not handle. Maya will use the datablock size to determine the array length when -1 is returned.

Parameters:

  [in] | plug | the array plug
  [in] | ctx | the context

void copyInternalData | ( | MPxNode * | node | ) | `[virtual]`

Search for all occurrences

This method is overriden by nodes that store attribute data in some internal format.

On duplication this method is called on the duplicated node with the node being duplicated passed as the parameter. Overriding this method gives your node a chance to duplicate any internal data you've been storing and manipulating outside of normal attribute data.

Parameters:

  [in] | node | the node that is being duplicated

Reimplemented in MPxTransform.

Examples:
  cgfxShaderNode.h, and hlslShader.h.

MStatus legalConnection | ( | const MPlug & | plug,
|  | const MPlug & | otherPlug,
|  | bool | asSrc,
|  | bool & | isLegal
| ) |  | const`[virtual]`

Search for all occurrences

This method allows you to check for legal connections being made to attributes of this node.

You should return kUnknownParameter to specify that maya should handle this connection if you are unable to determine if it is legal.

Parameters:

  [in] | plug | attribute on this node
  [in] | otherPlug | attribute on other node
  [in] | asSrc | is this plug a source of the connection
  [in] | isLegal | set this to true if the connection is legal, false otherwise

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kUnknownParameter Unknown attribute

MStatus legalDisconnection | ( | const MPlug & | plug,
|  | const MPlug & | otherPlug,
|  | bool | asSrc,
|  | bool & | isLegal
| ) |  | const`[virtual]`

Search for all occurrences

This method allows you to check for legal disconnections being made to attributes of this node.

You should return kUnknownParameter to specify that maya should handle this disconnection if you are unable to determine if it is legal.

Parameters:

  [in] | plug | attribute on this node
  [in] | otherPlug | attribute on other node
  [in] | asSrc | is this plug a source of the connection
  [out] | isLegal | set this to true if the disconnection is legal, false otherwise

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kUnknownParameter Unknown attribute

MStatus setDependentsDirty | ( | const MPlug & | plugBeingDirtied,
|  | MPlugArray & | affectedPlugs
| ) |  | `[virtual]`

Search for all occurrences

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.

The list of plugs for Maya to mark dirty is returned by the plug array {affectedPlugs}. This method handles both dynamic as well as non-dynamic plugs and is useful in the following ways:

- Allows attributeAffects-style relationships to be handled for dynamically-added attributes. Since MPxNode::attributeAffects can only be used with non-dynamic attributes, use of this method allows a way for all attributes of a node to affect one another, both dynamic and non-dynamic.

- Provides more flexible relationships than what is available with MPxNode::attributeAffects. For example, you may wish to not dirty plugs when the current frame is one. However, as the routine is called during dirty propagation, there are restrictions on what can be done within the routine, most importantly you must not cause any dependency graph computation. For details, see the IMPORTANT NOTE below.

This method is designed to work harmoniously with MPxNode::attributeAffects on the same node. Alternately, you can do all affects relationships within a yourNode::setDependentsDirty() implementation.

The body of a user-implemented setDependentsDirty() implementation might look like the following example, which causes the plug called "B" to be set dirty whever plug "A" is changed, i.e. A affects B.

        const   MString exampleNode::A( "A" );  // Dynamic attribute "A"
        MObject exampleNode::attrB;     // Non-dynamic attribute "B"

        MStatus exampleNode::setDependentsDirty(
                const MPlug &plugBeingDirtied,
                MPlugArray &affectedPlugs )
        {
            // This example shows a dynamic attribute (A) affecting a
            // non-dynamic attribute (B). For an example of a dynamic
            // affecting a dynamic, please the the developer's toolkit
            // example plug-in, affectsNode.cpp.
            //
            if ( plugBeingDirtied.partialName() == A ) {
                // "A" is being dirtied. We want "A" to affect "B", so we
                // add "B" to the list of plugs for Maya to dirty. Once again,
                // please see the IMPORTANT NOTE about what you can and
                // cannot do within a setDependentsDirty() routine.
                //
                MObject thisNode = thisMObject();
                MPlug pB( thisNode, exampleNode::attrB );
                affectedPlugs.append( pB );
            }
            return( MS::kSuccess );
        }

In the above example, whenever plugBeingDirtied is A, we add B to affectedPlugs so that Maya will dirty B and also any plugs which depend upon B.

For cases where multi compound attributes are dirtied, it is the programmer's responsibility to define ALL affects relationships. Dirtying the parent plug of a multi does not imply that all of its children will be marked dirty. Likewise, dirtying a child attribute does not imply the parent of the multi is dirty. This must be explicitly defined using the affected plug array. The following example demonstrates how one would dirty both the element affected and the parent plug.

        MObject exampleNode::inputAttr;     // Non-dynamic multi-input attribute.
        MObject exampleNode::outputAttr;    // Non-dynamic multi-output attribute.
        MStatus exampleNode::setDependentsDirty(MPlug const & inPlug,
                                                MPlugArray  & affectedPlugs)
        {
            if ( inPlug.attribute() != inputAttr ) {
                return MS::kSuccess;
            }

            MPlug outArrayPlug(thisMObject(),outputAttr);

            if (inPlug.isElement()) {
                // First dirty the output output element first.
                // Of course, dirty output element itself
                MPlug elemPlug = outArrayPlug.elementByLogicalIndex(
                                                    inPlug.logicalIndex());
                affectedPlugs.append(elemPlug);

                // We also need to dirty the parent.
                //
                affectedPlugs.append(outArrayPlug);
            } else {
                // Mark the parent output plug as dirty.
                //
                affectedPlugs.append(outArrayPlug);

                // Also visit each element.
                //
                unsigned int i,n = outArrayPlug.numElements();
                for (i = 0; i < n; i++) {
                    MPlug elemPlug = outArrayPlug.elementByPhysicalIndex(i);
                    affectedPlugs.append(elemPlug);
                }
            }
            return MS::kSuccess;
        }

IMPORTANT NOTE: since the setDependentsDirty() method is called during dirty propagation, you must be careful not to perform any dependency graph computations from within the routine. Instead, if you want to know the value of a plug, use MDataBlock::outputValue() because it will not result in computation (and thus recursion). In general, the majority of {setDependentsDirty()} methods which users will implement should involve only fixed relationships. In the rare occurence where you need to look at plug values, please heed the warning with {MDataBlock::outputValue()} and use plugs which contain values which you know to be up to date prior to the start of dirty propagation.

Parameters:

  [in] | plugBeingDirtied | plug which is being set dirty by Maya
  [in] | affectedPlugs | the programmer should add any plugs which they want to set dirty to this list.

Returns:
  Status code

Status Codes:
  - MS::kSuccess Dirtying was successful
  - MS::kFailure Dirtying failed

Examples:
  affectsNode.cpp, and apiMeshShape.h.

MStatus connectionMade | ( | const MPlug & | plug,
|  | const MPlug & | otherPlug,
|  | bool | asSrc
| ) |  | `[virtual]`

Search for all occurrences

This method gets called when connections are made to attributes of this node.

You should return kUnknownParameter to specify that maya should handle this connection or if you want maya to process the connection as well.

Parameters:

  [in] | plug | attribute on this node
  [in] | otherPlug | attribute on other node
  [in] | asSrc | is this plug a source of the connection

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kUnknownParameter Unknown attribute

Examples:
  apiMeshShape.cpp, and apiMeshShape.h.

MStatus connectionBroken | ( | const MPlug & | plug,
|  | const MPlug & | otherPlug,
|  | bool | asSrc
| ) |  | `[virtual]`

Search for all occurrences

This method gets called when connections are broken with attributes of this node.

You should return kUnknownParameter to specify that maya should handle this connection or if you want maya to process the connection as well.

Parameters:

  [in] | plug | attribute on this node
  [in] | otherPlug | attribute on other node
  [in] | asSrc | is this plug a source of the connection

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kUnknownParameter Unknown attribute

Examples:
  apiMeshShape.cpp, and apiMeshShape.h.

bool isPassiveOutput | ( | const MPlug & | plug | ) | const`[virtual]`

Search for all occurrences

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.

For example, output plugs on animation curve nodes are passive. This allows the attributes driven by the animation curves to be set to new values by the user.

Parameters:

  [in] | plug | plug representing output in question

Returns:
  true indicates passive

MStatus shouldSave | ( | const MPlug & | plug,
|  | bool & | isSaving
| ) |  | `[virtual]`

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This method may be overridden by the user defined node.

It should only be required to override this on rare occasions.

This method determines whether a specific attribute of this node should be written out during a file save. The default behavior is to only write the value if it differs from the default and is not being supplied by a connection. This behavior should be sufficient in most cases. This method is not called for ramp attributes since they should always be written.

Parameters:

  [in] | plug | plug representing the attribute to be saved
  [in] | isSaving | boolean telling whether to save or not

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kUnknownParameter Unknown attribute

Examples:
  apiMeshShape.cpp, apiMeshShape.h, cgfxShaderNode.cpp, and cgfxShaderNode.h.

MPlug passThroughToOne | ( | const MPlug & | plug | ) | const`[virtual]`

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This method may be overriden by nodes that have a one-to-one relationship between an input attribute and a corresponding output attribute.

This method is used by Maya to perform the following capabilities:

- When this node is deleted, the delete command will rewire the source of the input attribute to the destination of the output attribute if the source and destination are connected to nodes that are not deleted.
- History traversal algorithms such as the bakePartialHistory command use this method to direct its traversal through a shape's construction history.
- The base class Maya implementation of passThroughToAll will call this method if passThroughToAll returns false.

Parameters:

  [in] | plug | the plug

Returns:
  The corresponding plug, or an empty plug if no corresponding plug exists

bool passThroughToMany | ( | const MPlug & | plug,
|  | MPlugArray & | plugArray
| ) |  | const`[virtual]`

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This method is overriden 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.

In particular, the Artisan paint code uses this method when searching for paintable nodes, and the disk cache code uses this method when searching for upstream cacheFile nodes.

If this method is not implemented or returns false, the base class Maya implementation of this method calls passThroughToOne and returns the results of that call.

Parameters:

  [in] | plug | the plug
  [in] | plugArray | the corresponding plugs

Returns:
  true if plug was handled, false to invoke base class implementation

MPxNode::Type type | ( |  | ) | const`[virtual]`

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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 in MPxAssembly, MPxCameraSet, MPxClientDeviceNode, MPxDeformerNode, MPxEmitterNode, MPxFieldNode, MPxFluidEmitterNode, MPxHardwareShader, MPxHwShaderNode, MPxIkSolverNode, MPxImagePlane, MPxLocatorNode, MPxManipContainer, MPxObjectSet, MPxParticleAttributeMapperNode, MPxSpringNode, MPxSurfaceShape, MPxThreadedDeviceNode, and MPxTransform.

bool isAbstractClass | ( |  | ) | const`[virtual]`

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Override this class to return true if this node is an abstract node.

An abstract node can only be used as a base class. It cannot be created using the 'createNode' command.

It is not necessary to override this method.

Returns:
  true if the node is abstract.

Reimplemented in MPxPolyTrg.

MStatus addAttribute | ( | const MObject & | attr | ) | `[static]`

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This method adds a new attribute to a user defined node type during the type's initialization.

This method will only work during the static initialization method of the user defined node class. The initialization method is the one that is passed into MFnPlugin::registerNode. The attributes must first be created using one of the MFnAttribute classes, and can then be added using this method.

For compound attributes, the proper way to use this method is by calling it with the parent attribute. If a compound attribute is passed, this method will add all of its children. NOTE: A failure will occur if you attempt to call addAttribute() on the children of a compound attribute.

Parameters:

  [in] | attr | new attribute to add

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kInvalidParameter Attribute is invalid or already added or child of a compound attribute is being added before the parent
  - MS::kFailure Method was not called during the node's initialize routine

MStatus inheritAttributesFrom | ( | const MString & | parentClassName | ) | `[static]`

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This method allows a class of plugin node to inherit all of the attributes of a second class of plugin node.

This method will only work during the static initialization method of the user defined node class and must be called before any other attributes have been added. The initialization method is the one that is passed into MFnPlugin::registerNode.

A plugin node may only inherit attributes from one other class of plugin node. Attempting to call this method multiple times within a node's initialization method will result in an error.

Both node classes must be registered using the same MPxNode::Type.

Parameters:

  [in] | parentClassName | class of node to inherit attributes from

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kInvalidParameter Class name is invalid or was registered with a different MPxNode::Type.
  - MS::kFailure Method was called outside of the node's initialize routine, or was called multiple times, or was called after attributes had already been added.

MStatus attributeAffects | ( | const MObject & | whenChanges,
|  | const MObject & | isAffected
| ) |  | `[static]`

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This method specifies that a particular input attribute affects a specific output attribute.

This is required to make evaluation efficient. When an input changes, only the affected outputs will be computed. Output attributes cannot be keyable - if they are keyable, this method will fail.

This method must be called for every attribute dependency when initializing the node's attributes. The attributes must first be added using the MPxNode::addAttribute method. Failing to call this method will cause the node not to update when its inputs change. If there are no calls to this method in a node's initialization, then the compute method will never be called.

This method will only work during the static initialization method of the user defined node class. The initialization method is the one that is passed into MFnPlugin::registerNode. As a result, it does not work with dynamic attributes. For an alternate solution which handles dynamic as well as non-dynamic attributes refer to MPxNode::setDependentsDirty.

Parameters:

  [in] | whenChanges | input attribute - MObject that points to an input attribute that has already been added
  [in] | isAffected | affected output attribute - MObject that points to an output attribute that has already been added

Returns:
  Status code

Status Codes:
  - MS::kSuccess Operation successful
  - MS::kInvalidParameter At least one of the attributes is invalid or has not been added to this node using the addAttribute routine
  - MS::kFailure Method was not called during the node's initialize routine

MStringArray getFilesToArchive | ( | bool | shortName = `false`,
|  | bool | unresolvedName = `false`,
|  | bool | markCouldBeImageSequence = `false`
| ) |  | const`[virtual]`

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Use this method to return all external files used by this node.

This file list will be used by the File > Archive zip feature, maya.exe -archive and the `file -q -list` mel command.

Only include files that exist.

If shortName is true, return just the filename portion of the path (can be obtained with MString::baseName()). Otherwise, return a full path.

If unresolvedName is true, return the path before any resolution has been done (i.e leave it as a relative path, include unexpanded environment variables, tildes, ".."s etc). Otherwise, resolve the file path and return an absolute path (to resolve with standard Maya path resolution, use MFileObject::resolvedFullName()).

Parameters:

  [in] | shortName | If true, only add the filename of the path
  [in] | unresolvedName | If true, add paths before any resolution, rather than absolute paths.
  [in] | markCouldBeImageSequence | If true, append an asterisk after any file path that could be an image sequence (note: only used by maya.exe -archive)

Returns:
  Array of file paths

const char * className | ( |  | ) | `[static]`

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Returns the name of this class.

Returns:
  The name of this class.

Reimplemented in MPxAssembly, MPxCameraSet, MPxClientDeviceNode, MPxConstraint, MPxDeformerNode, MPxEmitterNode, MPxFieldNode, MPxFluidEmitterNode, MPxHardwareShader, MPxHwShaderNode, MPxIkSolverNode, MPxImagePlane, MPxLocatorNode, MPxManipContainer, MPxManipulatorNode, MPxObjectSet, MPxParticleAttributeMapperNode, MPxSpringNode, MPxSurfaceShape, MPxThreadedDeviceNode, and MPxTransform.

MTypeId typeId | ( |  | ) | const`[virtual]`

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Returns the TYPEID of this node.

The TYPEID is a four byte identifier that uniquely identifies this type of node to the binary file format.

It is not necessary to override this method.

Returns:
  Type id of the node

Reimplemented in MPxAssembly.

MString typeName | ( |  | ) | const`[virtual]`

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Returns the type name of this node.

The type name identifies the node type to the ASCII file format. It may also be used with the MEL command "createNode" to create a new node of this type.

It is not necessary to override this method.

Returns:
  Type name of the node

Reimplemented in MPxAssembly.

MString name | ( |  | ) | const`[virtual]`

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Returns the name of this particular instance of this class.

Each object in the dependency graph has a name. This name will be used by the UI and by MEL.

It is not necessary to override this method.

Returns:
  Type id of the node

Reimplemented in MPxAssembly.

MObject thisMObject | ( |  | ) | const`[virtual]`

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Returns the MObject associated with this user defined node.

This makes it possible to use MFnDependencyNode or to construct plugs to this node's attributes.

It is not necessary to override this method.

Returns:
  MObject handle for this node

Reimplemented in MPxAssembly.

MStatus setExistWithoutInConnections | ( | bool | flag | ) | `[virtual]`

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This method specifies whether or not the node can exist without input connections.

If a node connected to this node is deleted resulting in no more input connections and if this flag is false, then this node will be deleted.

Parameters:

  [in] | flag | true if this node can exist without input connections, false otherwise

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.

Reimplemented in MPxAssembly.

bool existWithoutInConnections | ( | MStatus * | ReturnStatus = `NULL` | ) | const`[virtual]`

Search for all occurrences

Determines whether or not this node can exist without input connections.

If a node connected to this node is deleted resulting in no more input connections and if this flag is false, then this node will be deleted.

Parameters:

  [out] | ReturnStatus | Status code.

Returns:
  true is this node can exist without input connections, false otherwise

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.

Reimplemented in MPxAssembly.

MStatus setExistWithoutOutConnections | ( | bool | flag | ) | `[virtual]`

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This method specifies whether or not the node can exist without output connections.

If a node connected to this node is deleted resulting in no more output connections and if this flag is false, then this node will be deleted.

Parameters:

  [in] | flag | true if this node can exist without output connections, false otherwise

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.

Reimplemented in MPxAssembly.

bool existWithoutOutConnections | ( | MStatus * | ReturnStatus = `NULL` | ) | const`[virtual]`

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Determines whether or not this node can exist without output connections.

If a node connected to this node is deleted resulting in no more output connections and if this flag is false, then this node will be deleted.

Parameters:

  [out] | ReturnStatus | Status code.

Returns:
  true is this node can exist without output connections, false otherwise

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.

Reimplemented in MPxAssembly.

MDataBlock forceCache | ( | MDGContext & | context = `MDGContext::fsNormal` | ) | `[protected, virtual]`

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USE _forceCache() IN SCRIPT.

Get the datablock for this node.

If there is no datablock then one will be created. NOTE: This should be used only in places where fast access to the datablock outside of a compute is critical such as the transformUsing method of MPxSurfaceShape.

Parameters:

  [in] | context | The context in which the node will evaluate.

Returns:
  The datablock

Reimplemented in MPxAssembly.

void setMPSafe | ( | bool | flag | ) | `[protected, virtual]`

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USE _setMPSafe() IN SCRIPT.

Set a flag to specify if a user defined shading node is safe for multi-processor rendering.

For a shading node to be MP safe, it cannot access any shared global data and should only use attributes in the datablock to get input data and store output data.

This flag does NOT mark a node thread safe for parallel DG evaluation in Viewport 2.0. To mark a node thread safe for parallel DG evaluation see the setNodeTypeFlag mel command.

NOTE: This should be called from the postConstructor() method for shading node plug-ins only. If a shading node is non-safe, then it will only be useful during single processor rendering.

Parameters:

  [in] | flag | True if user node is safe, false if non-safe.

Reimplemented in MPxAssembly.

MStatus setDoNotWrite | ( | bool | flag | ) | `[protected, virtual]`

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USE _setDoNotWrite() IN SCRIPT.

Use this method to mark the "do not write" state of this proxy node.

If set, this node will not be saved when the Maya model is written out.

NOTES: 1. Plug-in "requires" information will be written out with the model when saved. But a subsequent reload and resave of the file will cause these to go away. 2. If this node is a DAG and has a parent or children, the "do not write" flag of the parent or children will not be set. It is the developer�s responsibility to ensure that the resulting scene file is capable of being read in without errors due to unwritten nodes.

Parameters:

  [in] | flag | True if the user node should not be saved.

Reimplemented in MPxAssembly.

bool doNotWrite | ( | MStatus * | ReturnStatus = `NULL` | ) | const`[protected, virtual]`

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USE _doNotWrite() IN SCRIPT.

Use this method to query the "do not write" state of this proxy node.

True is returned if this node will not be saved when the Maya model is written out.

Parameters:

  [out] | ReturnStatus |

Reimplemented in MPxAssembly.

MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode
MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode MPxNode