MPxEmitterNode Class Reference
[OpenMayaFX - API module for effects, Proxy classes]

#include <MPxEmitterNode.h>

Inheritance diagram for MPxEmitterNode:

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Collaboration diagram for MPxEmitterNode:

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List of all members.

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Detailed Description

Base class for user defined particle emitters.

MPxEmitterNode allows the creation and manipulation of dependency graph nodes representing particle emitters.

Examples:

ownerEmitter.h, simpleEmitter.h, and sweptEmitter.h.

Public Types
enum	MEmitterType {   kDirectional = 0, kOmni, kSurface, kCurve,   kVolume }
	Types of emitters. More...
Public Member Functions
	MPxEmitterNode ()
virtual	~MPxEmitterNode ()
virtual MPxNode::Type	type () const
virtual MStatus	compute (const MPlug &plug, MDataBlock &dataBlock)
virtual void	draw (M3dView &view, const MDagPath &path, M3dView::DisplayStyle style, M3dView::DisplayStatus)
MEmitterType	getEmitterType (MDataBlock &block)
MObject	getOwnerShape ()
MTime	getCurrentTime (MDataBlock &block)
MTime	getStartTime (int plugIndex, MDataBlock &block)
MTime	getDeltaTime (int plugIndex, MDataBlock &block)
int	getRandomSeed (int plugIndex, MDataBlock &block)
void	getRandomState (int plugIndex, MDataBlock &block)
void	setRandomState (int plugIndex, MDataBlock &block)
void	resetRandomState (int plugIndex, MDataBlock &block)
double	randgen ()
double	getRate (MDataBlock &block)
double	getMinDistance (MDataBlock &block)
double	getMaxDistance (MDataBlock &block)
MPoint	getWorldPosition ()
MMatrix	getWorldMatrix ()
bool	volumePrimitiveBoundingBox (MBoundingBox &box)
bool	volumePrimitivePointInside (const MPoint &worldPoint, const MMatrix &emitterWorldMatrix)
double	volumePrimitiveDistanceFromAxis (const MPoint &worldPoint, const MMatrix &emitterWorldMatrix)
bool	hasValidEmission2dTexture (const MObject &texAttr, MStatus *status=NULL)
MStatus	evalEmission2dTexture (const MObject &texAttr, MDoubleArray &uCoords, MDoubleArray &vCoords, MVectorArray *resultColors, MDoubleArray *resultAlphas)
Static Public Attributes
static MObject	mEmitterType
	emitter type attribute
static MObject	mRate
	rate attribute
static MObject	mSpeed
	speed attribute
static MObject	mDirection
	direction attribute
static MObject	mDirectionX
	X component of mDirection.
static MObject	mDirectionY
	Y component of mDirection.
static MObject	mDirectionZ
	Z component of mDirection.
static MObject	mOwnerPosData
	owner postion attribute, multi
static MObject	mOwnerVelData
	owner velocity attribute, multi
static MObject	mOwnerCentroid
	owner centroid attribute
static MObject	mOwnerCentroidX
	X component of mOwnerCentroid.
static MObject	mOwnerCentroidY
	Y component of mOwnerCentroid.
static MObject	mOwnerCentroidZ
	Z component of mOwnerCentroid.
static MObject	mSweptGeometry
	input swept geometry attribute
static MObject	mWorldMatrix
	world matrix attribute
static MObject	mStartTime
	start time attribute
static MObject	mDeltaTime
	delta time attribute
static MObject	mIsFull
	flag for maximum count attribute
static MObject	mInheritFactor
	inherit factor attribute
static MObject	mSeed
	random seed attribute
static MObject	mRandState
	random state attribute
static MObject	mCurrentTime
	current time attribute
static MObject	mOutput
	output particle attribute, multi
static MObject	mMinDistance
	min distance attribute
static MObject	mMaxDistance
	max distance attribute

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Member Enumeration Documentation

enum MPxEmitterNode::MEmitterType

Types of emitters.

Enumerator:

kDirectional
kOmni
kSurface
kCurve
kVolume

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Constructor & Destructor Documentation

MPxEmitterNode::MPxEmitterNode

(

)

Class constructor.

MPxEmitterNode::~MPxEmitterNode

(

)

[virtual]

The class destructor.

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Member Function Documentation

MPxNode::Type MPxEmitterNode::type

(

)

const [virtual]

This method returns the type of the node. It should not be overridden by the user. It will return MPxNode::kEmitterNode.

Returns:

The type of node

Status Codes:

• MS::kSuccess The undo was successful
• MS::kFailure This method is not undoable

Reimplemented from MPxNode.

Reimplemented in MPxFluidEmitterNode.

MStatus MPxEmitterNode::compute	(	const MPlug &	plug,
		MDataBlock &	dataBlock
	)			[virtual]

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]	dataBlock	data block containing storage for the node's attributes

Returns:

Status code

Status Codes:

• MS::kSuccess Compute was successful
• MS::kFailure Compute failed

Reimplemented from MPxNode.

Reimplemented in MPxFluidEmitterNode.

Examples:

ownerEmitter.h, simpleEmitter.h, and sweptEmitter.h.

void MPxEmitterNode::draw	(	M3dView &	view,
		const MDagPath &	path,
		M3dView::DisplayStyle	style,
		M3dView::DisplayStatus
	)			[virtual]

Overriding this method allows the drawing of custom geometry using standard OpenGL calls. The OpenGL state should be left in the same state that it was in previously. The OpenGL routine glPushAttrib may be used to make this easier.

When this routine is called, the following conditions may be assumed:

• the correct transform matrix will be loaded for the node, so the geometry should be drawn in local space
• the correct default color will be set for wire frame drawing given the object's state (eg active, dormant, etc.)
• the object is not invisible or hidden
• if the object has a bounding box, then the bounding box is at least partially in the frustum

As a convenience, this draw method will also be used by OpenGL's selection mechanism to determine whether this object gets selected by a particular mouse event. The user does not need to write a separate selection routine.

Parameters:

[in]	view	3D view that is being drawn into
[in]	path	to this node in the DAG
[in]	style	style to draw object in

Examples:

simpleEmitter.h.

MPxEmitterNode::MEmitterType MPxEmitterNode::getEmitterType

(

MDataBlock &

block

)

Retrieves the type of the emitter, determined by the "emitterType" attribute value. This is intended to be called from within the emitter's compute() method, in order to decide how the emitter should behave when evaluated.

Parameters:

[in]

block

data block containing storage for the node's attributes

Returns:

An MEmitterType value representing the type of emitter (directional, omni, surface, curve, or volume)

MObject MPxEmitterNode::getOwnerShape

(

)

If the emitter is a emitting from an object, this method returns the shape node for the object.

Returns:

An MObject representing the "owner" of this emitter (ie the object being emitted from, or kNullObj if the emitter is not emitting from an object.

MTime MPxEmitterNode::getCurrentTime

(

MDataBlock &

block

)

Intended to be called from within the emitter's compute() method, this method returns the time at which the emitter is currently being evaluated. This is equivalent to querying the "currentTime" attribute on the emitter.

Parameters:

[in]

block

data block containing storage for the node's attributes

Returns:

The time at which the emitter is being evaluated.

MTime MPxEmitterNode::getStartTime	(	int	plugIndex,
		MDataBlock &	block
	)

Intended to be called from within the emitter's compute() method, this method returns the start times for each particle system or fluid into which the emitter is emitting. Each of these "targets" is identified by an index value corresponding to the order in which they are connected to the emitter. The start time value gives the time at which the given target is to start receiving particles or fluid. If the current time is less than the start time for a target, then nothing should be emitted into that target in the current evaluation. This value is taken by evaluating an element of the emitter node's "startTime" array attribute.

Parameters:

[in]	plugIndex	identifies which emitter target's start time is to be evaluated.
[in]	block	data block containing storage for the node's attributes

Returns:

The start time for the specified target, ie the time at which the emitter is to start emitting into that target.

MTime MPxEmitterNode::getDeltaTime	(	int	plugIndex,
		MDataBlock &	block
	)

Intended to be called from within the emitter's compute() method, this method returns the width of the time interval represented by the current emitter evaluation. Usually emitter emission rates are given as rates per second, so by converting this deltaTime value to seconds, plugin emitters can determine how many particles or how much fluid to emit in the current evaluation. This value is taken from the emitter's "deltaTime" attribute value, and can vary between different emitter targets (particle systems or fluid shapes into which the emitter is emitting), due to potential differences in oversampling settings. The "plugIndex" parameter indicates which target's time delta is being evaluated.

Parameters:

[in]	plugIndex	identifies which emitter target's time delta is to be evaluated.
[in]	block	data block containing storage for the node's attributes

Returns:

The time delta for the current emitter evaluation on the specified target.

int MPxEmitterNode::getRandomSeed	(	int	plugIndex,
		MDataBlock &	block
	)

Intended to be called from within the emitter's compute() method, this method returns the random seed for a specified emission target (particle system or fluid shape into which the emitter is emitting). This seed value is set on the target itself, and should be used to ensure that any randomized emission behavior is repeatable when animations are played back repeatedly. The resetRandomState() method uses this value (see its documentation for details on how to implement repeatable randomized behaviour in emitters). This value is obtained by evaluating an element of the emitter's "seed" array attribute.

Parameters:

[in]	plugIndex	identifies which emitter target's random seed is to be evaluated.
[in]	block	data block containing storage for the node's attributes

Returns:

The random seed value for the specified target.

void MPxEmitterNode::getRandomState	(	int	plugIndex,
		MDataBlock &	block
	)

Intended to be called from within the emitter's compute() method, this method copies the emitter node attribute representing the current random state for a particular emitter target into a local variable on the emitter object, to facilitate efficient random number generation using the randgen() method. See the documentation for resetRandomState() for a description of how to use this method in conjunction with the other random stream methods of this class.

There is only one local random state data member, so care should be taken not to inadvertently overwrite this member by calling getRandomState() on one target before setRandomState() has been called on a previously-evaluated target.

Parameters:

[in]	plugIndex	identifies which emitter target's random state is to be copied to the local random state data member.
[in]	block	data block containing storage for the node's attributes

void MPxEmitterNode::setRandomState	(	int	plugIndex,
		MDataBlock &	block
	)

Intended to be called from within the emitter's compute() method, this method copies the emitter node class random state data member onto the emitter node's random state attribute. See the documentation for resetRandomState() for a description of how to use this method in conjunction with the other random stream methods of this class.

There is only one local random state data member, so care should be taken not to inadvertently write the wrong random state value to the attribute by calling setRandomState() on a target before getRandomState() has been called for that target.

Parameters:

[in]	plugIndex	identifies which emitter target's random state is to be written from the local random state data member.
[in]	block	data block containing storage for the node's attributes

void MPxEmitterNode::resetRandomState	(	int	plugIndex,
		MDataBlock &	block
	)

Intended to be called from within the emitter's compute() method, this method resets the emitter's random state data member. To implement repeatable randomized emitter behavior, the following steps should be followed:

• When the current time is less than the start time, call resetRandomState(). This sets the emitter's random state to an initial value determined by the random seed for the given target. This initializes both the emitter's randomState attribute and a random state data member on the emitter class.
• When the emitter needs to emit either particles or fluid in a compute() call, first call the getRandomState() method. This copies the emitter's current random state from its randomState attribute into the data member on the emitter class.
• Over the course of the compute() method, when a random value is required, call randgen(). This generates a random value using the random state data member value, which is then incremented.
• When the emitter is finished emitting, call the setRandomState() method to set the random state data member's value back onto the random state attribute for the node. This way, the next evaluation of the emitter will pick up where the previous one left off in the random sequence.

This way, the emitter gets a repeatable stream of random numbers that is independent of the order of evaluation of the various emitter targets. Persistence is achieved by storing the random state on emitter attributes between evaluations, and efficiency is achieved by using a local random state variable during evaluations.

Parameters:

[in]	plugIndex	identifies which emitter target's random state is to be reset.
[in]	block	data block containing storage for the node's attributes

double MPxEmitterNode::randgen

(

)

Intended to be called from within the emitter's compute() method, this method generates a double-precision random number in the rand [0,1]. The emitter object's random state data member is used to generate the random number, and will be updated after the number is generated. To generate a stream of random numbers for a particular target, ensure that getRandomState() is called before calling randgen(), and that setRandomState() is called after all the random numbers have been generated. See the documentation for resetRandomState() for a description of how to use this method in conjunction with the other random stream methods of this class.

Returns:

A double-precision random number between 0 and 1.

double MPxEmitterNode::getRate

(

MDataBlock &

block

)

Intended to be called from within the emitter's compute() method, this method retrieves the "rate" attribute value common to all particle and fluid emitters. For particle emitters, this indicates the number of particles to be emitted per second. For fluid emitters, this value is usually used as a multiplier applied to the emission rates for various fluid grids such as density, temperature, etc.

Parameters:

[in]

block

data block containing storage for the node's attributes

Returns:

The emission rate for the emitter.

double MPxEmitterNode::getMinDistance

(

MDataBlock &

block

)

Intended to be called from within the emitter's compute() method, this method retrieves the "minDistance" attribute value common to all particle and fluid emitters. This value indicates the minimum distance from the emitter center at which fluid or particles will be emitted.

Parameters:

[in]

block

data block containing storage for the node's attributes

Returns:

The minimum emission distance for the emitter.

double MPxEmitterNode::getMaxDistance

(

MDataBlock &

block

)

Intended to be called from within the emitter's compute() method, this method retrieves the "maxDistance" attribute value common to all particle and fluid emitters. This value indicates the maximum distance from the emitter center at which fluid or particles will be emitted.

Parameters:

[in]

block

data block containing storage for the node's attributes

Returns:

The maximum emission distance for the emitter.

MPoint MPxEmitterNode::getWorldPosition

(

)

Returns the worldspace coordinates of the emitter. For curve, surface, and volume emitters, this returns the worldspace coordinates of the center of the emitter's local space. For point emitters, this value usually corresponds to the position of the emitter object itself.

Returns:

The worldspace coordinates of the center of the emitter's local space.

Examples:

ownerEmitter.h, and simpleEmitter.h.

MMatrix MPxEmitterNode::getWorldMatrix

(

)

Returns the matrix that maps from the emitter's local space coordinates to worldspace.

Returns:

Emitter's object to world space transformation matrix.

bool MPxEmitterNode::volumePrimitiveBoundingBox

(

MBoundingBox &

box

)

For volume emitters, this method returns the object-space bounding box of the volume primitive associated with the emitter.

Parameters:

[out]

box

receives the object space bounding box for the emission volume primitive.

Returns:

true if the emitter has an associated volume primitive, false otherwise.

bool MPxEmitterNode::volumePrimitivePointInside	(	const MPoint &	worldPoint,
		const MMatrix &	emitterWorldMatrix
	)

For volume emitters, this method determines whether a particular point in space lies within the volume defined by the emitter's volume primitive.

Parameters:

[in]	worldPoint	worldspace coordinates of the point to be tested.
[in]	emitterWorldMatrix	object to worldspace matrix for the emitter, which can be obtained using the MPxEmitterNode::getWorldMatrix() method.

Returns:

true if the point lies inside the emitter's volume primitive, false otherwise.

double MPxEmitterNode::volumePrimitiveDistanceFromAxis	(	const MPoint &	worldPoint,
		const MMatrix &	emitterWorldMatrix
	)

For volume emitters, this method determines the distance from a particular point to the major axis of the volumetric primitive associated with the emitter. For fluid emitters, this distance can be used to implement simple emission dropoff behavior.

Parameters:

[in]	worldPoint	worldspace coordinates of the point to be tested.
[in]	emitterWorldMatrix	object to worldspace matrix for the emitter, which can be obtained using the MPxEmitterNode::getWorldMatrix() method.

Returns:

The distance from the point to the major axis of the emitter's volume primitive.

bool MPxEmitterNode::hasValidEmission2dTexture	(	const MObject &	texAttr,
		MStatus *	status = NULL
	)

Certain aspects of Maya's particle and fluid emitters can be textured using 2d textures. For example, surface particle emitters can use a 2d texture to modulate the emission rate over the surface. For these purposes, only a subset of Maya's textures are supported, namely the default 2d textures (bulge, checker, cloth, file, fluid texture 2d, fractal, grid, mountain, movie, noise, ocean, ramp, water). No other nodes are supported. This method takes an attribute on an emitter, and determines if there is a supported texture connected to it. If the texture is supported, then the evalEmission2dTexture() method can be called to evaluate the texture at various (u,v) coordinate values.

Parameters:

[in]	texAttr	attribute to be tested for a valid texture connection.
[out]	status	status code.

Status Codes:

• MS::kSuccess The connected texture was successfully examined.
• MS::kUnknownParameter There was no node connected to the specified attribute.

Returns:

true if the node connected to the specified emitter attribute is a texture that can be evaluated using the evalEmission2dTexture() method, false otherwise.

MStatus MPxEmitterNode::evalEmission2dTexture	(	const MObject &	texAttr,
		MDoubleArray &	uCoords,
		MDoubleArray &	vCoords,
		MVectorArray *	resultColors,
		MDoubleArray *	resultAlphas
	)

If a supported 2d texture (see hasValidEmission2dTexture() method documentation) is connected to the given emitter attribute, this method can be called to evaluate that texture at a number of (u,v) texture coordinate values.

Parameters:

[in]	texAttr	attribute whose connected texture is to be evaluated.
[in]	uCoords	array of u coordinate values
[in]	vCoords	array of v coordinate values
[out]	resultColors	if non-NULL, receives the result of the connected texture's outColor attribute, evaluated at all the (u,v) coordinates given by the uCoords and vCoords arrays.
[out]	resultAlphas	if non-NULL, receives the outAlpha values evaluated from the texture at these same points.

Status Codes:

• MS::kSuccess The connected texture was successfully evaluated
• MS::kUnknownParameter There was no texture, or an unsupported texture connected to the specified attribute, so textured values could not be evaluated.