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MFnNurbsCurve Class Reference

This reference page is linked to from the following overview topics: Objects and Function Sets, A more complex example, Threading and Maya, Example C++ plug-in descriptions, Appendix A: NURBS Geometry, Appendix D: Frequently asked questions.


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Detailed Description

NURBS curve function set.

This is the function set for NURBS (Non-Uniform Rational B-Spline) curves.

The shape of a NURBS curve is defined by an array of CVs (control vertices), an array of knot values, a degree, and a form. There are 3 possible "forms" for the curve: open, closed and periodic.

The open and closed forms are quite similar, and in fact a closed curve will become an open curve if either the first or last CV is moved so that they are no longer coincident. To create an open or closed curve of degree N with M spans, you must provide M+N CVs. This implies that for a degree N curve, you must specify at least N+1 CVs to get a curve with a single span.

The number of knots required for a curve is M + 2N - 1. If you want the curve to start exactly at the first CV and end exactly at the last CV, then the knot vector must be structured to have degree N "multiplicity" at the beginning and end. This means that the first N knots must be identical, and the last N knots must be identical.

A periodic curve is a special case of a closed curve. Instead of having just the first and last CVs coincident, the last N CVs in the curve must overlap the first N CVs. This results in a curve with no tangent break at the seam where the ends meet. The last N CVs in a periodic curve are permanently bound to the first N CVs, and Maya will not allow those last N CVs to be repositioned. If one or more of the first N CVs of the curve are repositioned, the overlapping CV's will remain bound, and will also be moved.

In order to create a periodic curve, you must specify at least 2N+1 CVs, so that that last N can overlap the first N and you still have 1 non-overlapping CV left. The number of CVs required to create a periodic curve is still N+M (with a lower limit of 2N+1), but you must ensure that the positions of the last N CVs are identical to the positions of the first N.

You still need M + 2N - 1 knots for a periodic curve, but the knot values required are more restrictive than for open or closed curves because of the overlap at the ends, The difference between the first N pairs of knots values should be equal to the difference between the last N pairs. Additionally there can be no knot multiplicity at the ends of the curve, because that would compromise the tangent continuity property. So an example knot sequence could begin with knots at { -(N-2), -(N-1), ... , 0}.

Managing different knot representations in external applications

Note that some third party applications use a different format for knots, where the number of knots required for a curve is M+2N+1 rather than M+2N-1 as used in Maya. Both knot representations are equivalent mathematically. To convert from one of these external representations into the Maya representation, simply omit the first and last knots from the external representation when creating the Maya representation. To convert from the Maya representation into the external representation, add two new knots at the beginning and end of the Maya knot sequence. The value of these new knots depends on the existing knot sequence. For a knot sequence with multiple end knots, simply duplicate the existing first and last knots once more, for example:

Maya representation: {0,0,0,...,N,N,N}
External representation: {0,0,0,0,...,N,N,N,N}

For a knot sequence with uniform end knots, create the new knots offset at an interval equal to the existing first and last knot intervals, for example:

Maya representation: {0,1,2,...,N,N+1,N+2}
External representation: {-1,0,1,2,...,N,N+1,N+2,N+3}

Examples:

arcLenNode.cpp, closestTangentUAndDistance.cpp, fullLoftNode.cpp, helix2Cmd.cpp, helixCmd.cpp, helixTool.cpp, instanceCallbackCmd.cpp, motionTraceCmd.cpp, multiCurveNode.cpp, particlePathsCmd.cpp, and simpleLoftNode.cpp.

#include <MFnNurbsCurve.h>

Inheritance diagram for MFnNurbsCurve:
Inheritance graph
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List of all members.

Public Types

enum  Form {
  kInvalid = 0, kOpen, kClosed, kPeriodic,
  kLast
}
 

Forms that a curve may take.

More...

Public Member Functions

virtual MFn::Type type () const
 Function set type.
virtual ~MFnNurbsCurve ()
 Destructor.
 MFnNurbsCurve ()
 Default constructor.
 MFnNurbsCurve (MObject &object, MStatus *ReturnStatus=NULL)
 Constructor.
 MFnNurbsCurve (const MDagPath &object, MStatus *ret=NULL)
 Constructor.
MObject create (const MPointArray &controlVertices, const MDoubleArray &knotSequences, unsigned int degree, Form agForm, bool create2D, bool createRational, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
 This method creates a nurbs curve from the given control vertices and knot vector and sets this function set to operate on the new curve.
MObject createWithEditPoints (const MPointArray &editPoints, unsigned int degree, Form agForm, bool create2D, bool createRational, bool uniformParam, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
 This method creates a nurbs curve from the given edit points and sets this function set to operate on the new curve.
MObject create (const MObjectArray &sources, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
 This method creates a single curve that represents all the curves in the MObjectArray.
MObject copy (const MObject &source, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
 This method creates a copy of a nurbs curve.
MStatus reverse (bool constructionHistory=false)
 This method reverse the curve direction.
MStatus makeMultipleEndKnots ()
 This method gives end knots full multiplicity.
MObject cv (unsigned int index, MStatus *ReturnStatus=NULL) const
 Get a direct access handle to the CV at the specified index.
MStatus getCV (unsigned int index, MPoint &pt, MSpace::Space space=MSpace::kObject) const
 Get the CV at the given index.
MStatus setCV (unsigned int index, const MPoint &pt, MSpace::Space space=MSpace::kObject)
 Set the CV at the given index to the given point.
Form form (MStatus *ReturnStatus=NULL) const
 This method returns the form of the curve.
int degree (MStatus *ReturnStatus=NULL) const
 Return the degree of this curve.
int numCVs (MStatus *ReturnStatus=NULL) const
 Return the number of CVs for this curve.
int numSpans (MStatus *ReturnStatus=NULL) const
 Return the number of spans for this curve.
int numKnots (MStatus *ReturnStatus=NULL) const
 Return the number of knots for this curve.
MStatus getKnotDomain (double &start, double &end) const
 Return the range corresponding to the maximum and minimum parameter values for this curve.
MStatus getKnots (MDoubleArray &array) const
 This method retrieves a copy of the knot array for this curve.
MStatus setKnots (const MDoubleArray &array, unsigned int startIndex, unsigned int endIndex)
 This method is used to set the values of a contiguous group of knots of the curve.
MStatus setKnot (unsigned int index, double param)
 Set the given knot's parameter value.
MObject cvs (unsigned int startIndex, unsigned int endIndex, MStatus *ReturnStatus=NULL) const
 This method is used to directly access a contiguous group of CVs.
MStatus getCVs (MPointArray &array, MSpace::Space space=MSpace::kObject) const
 Get the positions of the CVs of this curve.
MStatus setCVs (const MPointArray &array, MSpace::Space space=MSpace::kObject)
 Set the CVs for this curve to the given points.
double knot (unsigned int index, MStatus *ReturnStatus=NULL) const
 Get the parameter value of the specified knot for this curve.
MStatus removeKnot (double atThisParam, bool removeAll=false)
 Remove knot(s) from this curve.
bool isPointOnCurve (const MPoint &point, double tolerance=kMFnNurbsEpsilon, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
 Determines whether the given point is on this curve.
MStatus getPointAtParam (double param, MPoint &point, MSpace::Space space=MSpace::kObject) const
 Returns the point in space that is at the given parameter value of the curve.
MStatus getParamAtPoint (const MPoint &atThisPoint, double &param, MSpace::Space space=MSpace::kObject) const
 This method retrieves the parameter value corresponding to the given point on the curve.
MStatus getParamAtPoint (const MPoint &atThisPoint, double &param, double tolerance, MSpace::Space space=MSpace::kObject) const
 This method retrieves the parameter value corresponding to the given point on the curve.
bool isParamOnCurve (double param, MStatus *ReturnStatus=NULL) const
 Determines whether the specified parameter value is within the bounds of the knot vector of this curve.
MVector normal (double param, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
 This method returns the normal at the given parameter value on the curve.
MVector tangent (double param, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
 This method returns the tangent at the given parameter value on the curve.
MStatus getDerivativesAtParm (double param, MPoint &pos, MVector &dU, MSpace::Space space, MVector *dUU=NULL) const
 Evaluate the surface at the given parameter returning the position, first derivative and optionally the seecond derivative.
bool isPlanar (MVector *planeNormal=NULL, MStatus *ReturnStatus=NULL) const
 This method determines if this curve is a planar curve.
MPoint closestPoint (const MPoint &toThisPoint, double *param=NULL, double tolerance=kMFnNurbsEpsilon, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
 This method determines the closest point on the curve to the given point.
MPoint closestPoint (const MPoint &toThisPoint, bool paramAsStart, double *param=NULL, double tolerance=kMFnNurbsEpsilon, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
 This method determines the closest point on the curve to the given point.
double distanceToPoint (const MPoint &pt, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
 This method determines the distance from the given point to closest point on the curve.
double area (double tolerance=kMFnNurbsEpsilon, MStatus *ReturnStatus=NULL) const
 This method returns the area bounded by this curve.
double length (double tolerance=kMFnNurbsEpsilon, MStatus *ReturnStatus=NULL) const
 Return the arc length of this curve or 0.0 if it cannot be computed.
double findParamFromLength (double partLength, MStatus *ReturnStatus=NULL) const
 Given the length along the curve, find the parameter value that corresponds to it.
bool hasHistoryOnCreate (MStatus *ReturnStatus=NULL)
 This method determines if the shape was created with history.
MStatus updateCurve ()
 This method signals that this curve has changed and needs to be recalculated.
 MFnNurbsCurve (const MObject &object, MStatus *ret=NULL)
 Constructor.

Protected Member Functions

virtual const char * className () const
 Class name.

Member Enumeration Documentation

enum Form

Forms that a curve may take.

Enumerator:
kInvalid 

 

kOpen 

Ends are independent.

kClosed 

Endpoints are coincident.

kPeriodic 

Ends overlap such that there is no break in tangency.

kLast 

 


Constructor & Destructor Documentation

~MFnNurbsCurve ( ) [virtual]

Destructor.

Class desctructor.

MFnNurbsCurve ( MObject object,
MStatus ReturnStatus = NULL 
)

Constructor.

Class constructor that initializes the function set to the given MObject.

Parameters:
[in]objectThe MObject to attach the function set to
[out]ReturnStatusthe return status
Status Codes:
MFnNurbsCurve ( const MDagPath object,
MStatus ReturnStatus = NULL 
)

Constructor.

Class constructor that initializes the function set to the given constant MDagPath object.

Parameters:
[in]objectThe const MDagPath to attach the function set to
[out]ReturnStatusThe return status
Status Codes:
MFnNurbsCurve ( const MObject object,
MStatus ReturnStatus = NULL 
)

Constructor.

Class constructor that initializes the function set to the given MObject.

Parameters:
[in]objectThe MObject to attach the function set to
[out]ReturnStatusthe return status
Status Codes:

Member Function Documentation

MFn::Type type ( ) const [virtual]

Function set type.

Return the class type : MFn::kNurbsCurve.

Reimplemented from MFnDagNode.

const char * className ( ) const [protected, virtual]

Class name.

Return the class name : "MFnNurbsCurve".

Reimplemented from MFnDagNode.

MObject create ( const MPointArray controlVertices,
const MDoubleArray knots,
unsigned int  degree,
MFnNurbsCurve::Form  form,
bool  create2D,
bool  createRational,
MObject parentOrOwner = MObject::kNullObj,
MStatus ReturnStatus = NULL 
)

This method creates a nurbs curve from the given control vertices and knot vector and sets this function set to operate on the new curve.

The parentOrOwner argument is used to specify the owner of the new curve.

If the parentOrOwner is kNurbsCurveData then the created curve will be of type kNurbsCurveGeom and will be returned. The parentOrOwner will become the owner of the new curve.

If parentOrOwner is NULL then a new transform will be created and returned which will be the parent for the curve. The new transform will be added to the DAG.

If parentOrOwner is a DAG node then the new curve will be returned and the parentOrOwner will become its parent.

The knot vector is valid if it is non-decreasing and of length spans + 2 * degree - 1. The cvs are assumed to be in rational form (as opposed to homogeneous)

If the form specified is kClosed and the endpoints are not close then a new span will be created inorder to close the curve.

Parameters:
[in]controlVerticesan array of control vertices
[in]knotsan array of knots
[in]degreethe degree to create the curve with
[in]formeither kOpen, kClosed, kPeriodic
[in]create2Dindictates whether to create 2D or 3D curve
[in]createRationaltrue means curve being created will be rational
[in]parentOrOwnerthe DAG parent or kNurbsCurveData the new curve will belong to
[out]ReturnStatusStatus code
Returns:
  • If parentOrOwner is NULL then the transform for this curve is returned
  • If parentOrOwner is a DAG object then the curve shape is returned
  • The curve geometry is returned if parentOrOwner is of type kNurbsCurveData
Status Codes:
Examples:
helixCmd.cpp, helixTool.cpp, motionTraceCmd.cpp, and particlePathsCmd.cpp.
MObject createWithEditPoints ( const MPointArray editPoints,
unsigned int  degree,
MFnNurbsCurve::Form  form,
bool  create2D,
bool  createRational,
bool  uniformParam,
MObject parentOrOwner = MObject::kNullObj,
MStatus ReturnStatus = NULL 
)

This method creates a nurbs curve from the given edit points and sets this function set to operate on the new curve.

The parentOrOwner argument is used to specify the owner of the new curve.

If the parentOrOwner is kNurbsCurveData then the created curve will be of type kNurbsCurveGeom and will be returned. The parentOrOwner will become the owner of the new curve.

If parentOrOwner is NULL then a new transform will be created and returned which will be the parent for the curve. The new transform will be added to the DAG.

If parentOrOwner is a DAG node then the new curve will be returned and the parentOrOwner will become its parent.

If the form specified is kClosed and the endpoints are not close then a new span will be created inorder to close the curve.

Parameters:
[in]editPointsan array of edit points
[in]degreethe degree to create the curve with
[in]formeither kOpen, kClosed, kPeriodic
[in]create2Dindictates whether to create 2D or 3D curve
[in]createRationaltrue means curve being created will be rational
[in]uniformParamtrue means curve being created will have uniform parameterization, false means chord length
[in]parentOrOwnerthe DAG parent or kNurbsCurveData the new curve will belong to
[out]ReturnStatusStatus code
Returns:
  • If parentOrOwner is NULL then the transform for this curve is returned
  • If parentOrOwner is a DAG object then the curve shape is returned
  • The curve geometry is returned if parentOrOwner is of type kNurbsCurveData
Status Codes:
MObject create ( const MObjectArray sources,
MObject parentOrOwner = MObject::kNullObj,
MStatus ReturnStatus = NULL 
)

This method creates a single curve that represents all the curves in the MObjectArray.

The method assumes the curves in the sources are good for building a single curve:

  • they are in the same direction,
  • they are not intersective to themselvies or eath other,
  • there are no gaps between the points at the ends.
  • the order of the curves in the array are followed, i.e. the result curve starts from sources[0].

It is good enough to be C0 continouns (tangent breaks are okay).

Parameters:
[in]sourcesInput array of souce curves.
[in]parentOrOwnerthe DAG parent or kNurbsCurveData the new curve will belong to
[out]ReturnStatusStatus code
Returns:
  • If parentOrOwner is NULL then the transform for this curve is returned
  • If parentOrOwner is a DAG object then the curve shape is returned
  • The curve geometry is returned if parentOrOwner is of type kNurbsCurveData
Status Codes:
MObject copy ( const MObject source,
MObject parentOrOwner = MObject::kNullObj,
MStatus ReturnStatus = NULL 
)

This method creates a copy of a nurbs curve.

The parentOrOwner argument is used to specify the owner of the new curve.

If the parentOrOwner is kNurbsCurveData then the created curve will be of type kNurbsCurveGeom and will be returned. The parentOrOwner will become the owner of the new curve.

If parentOrOwner is NULL then a new transform will be created and returned which will be the parent for the curve. The new transform will be added to the DAG.

If parentOrOwner is a DAG node then the new curve will be returned and the parentOrOwner will become its parent.

Parameters:
[in]sourcethe curve to be copied
[in]parentOrOwnerthe DAG parent or kNurbsCurveData the new curve will belong to
[out]ReturnStatusStatus code
Returns:
  • If parentOrOwner is NULL then the transform for this curve is returned
  • If parentOrOwner is a DAG object then the curve shape is returned
  • The curve geometry is returned if parentOrOwner is of type kNurbsCurveData
Status Codes:
MStatus reverse ( bool  constructionHistory = false)

This method reverse the curve direction.

Parameters:
[in]constructionHistoryThis parameter has no effect. Regardless of how it is set, if the function set was initialized with the DAG path of a curve node which already has history, then the reverse operation will be added into that history, otherwise the reverse operation will be applied directly to the curve's data and no history will be left behind.
Returns:
Status code
Status Codes:
MStatus makeMultipleEndKnots ( )

This method gives end knots full multiplicity.

This ensures the end points of the curve interpolate the first and last CVs. It can also be used to convert a periodic curve to a closed curve.

Returns:
Status code
Status Codes:
MObject cv ( unsigned int  index,
MStatus ReturnStatus = NULL 
) const

Get a direct access handle to the CV at the specified index.

The CV iterator class MItCurveCV must be used to access the returned CV.

Parameters:
[out]indexIndex of the CV
[out]ReturnStatusStatus code
Returns:
A handle to the CVs requested
Status Codes:
MStatus getCV ( unsigned int  index,
MPoint pt,
MSpace::Space  space = MSpace::kObject 
) const

Get the CV at the given index.

Parameters:
[in]indexThe index of the CV that will be retrieved
[out]ptStorage for the CV
[in]spaceSpecifies the coordinate system for this operation
Returns:
Status code
Status Codes:
MStatus setCV ( unsigned int  index,
const MPoint pt,
MSpace::Space  space = MSpace::kObject 
)

Set the CV at the given index to the given point.

The method updateCurve should be called to trigger changes in the curve.

Parameters:
[in]indexThe index of the CV that will be changed
[in]ptThe new value that the CV will take
[in]spaceSpecifies the coordinate system for this operation
Returns:
Status code
Status Codes:
MFnNurbsCurve::Form form ( MStatus ReturnStatus = NULL) const

This method returns the form of the curve.

The curve can be open, closed, or periodic.

Parameters:
[out]ReturnStatusStatus code
Returns:
Status Codes:
int degree ( MStatus ReturnStatus = NULL) const

Return the degree of this curve.

If the degree cannot be determined then 0 is returned.

Parameters:
[out]ReturnStatusStatus code
Returns:
The degree of this curve.
Status Codes:
int numCVs ( MStatus ReturnStatus = NULL) const

Return the number of CVs for this curve.

If the number of CVs cannot be determined then 0 is returned.

Parameters:
[out]ReturnStatusStatus code
Returns:
The number of CVs for this curve.
Status Codes:
int numSpans ( MStatus ReturnStatus = NULL) const

Return the number of spans for this curve.

If the number of spans cannot be determined then 0 is returned.

Parameters:
[out]ReturnStatusStatus code
Returns:
The number of spans for this curve.
Status Codes:
int numKnots ( MStatus ReturnStatus = NULL) const

Return the number of knots for this curve.

If the number of knots cannot be determined then 0 is returned.

Parameters:
[out]ReturnStatusStatus code
Returns:
The number of knots for this curve.
Status Codes:
MStatus getKnotDomain ( double &  start,
double &  end 
) const

Return the range corresponding to the maximum and minimum parameter values for this curve.

Parameters:
[out]startstorage for the max parameter value
[out]endstorage for the min parameter value
Returns:
Status code
Status Codes:
MStatus getKnots ( MDoubleArray array) const

This method retrieves a copy of the knot array for this curve.

Parameters:
[out]arraystorage where the parameter values of the knots for this curve will be copied
Returns:
Status code
Status Codes:
MStatus setKnots ( const MDoubleArray array,
unsigned int  startIndex,
unsigned int  endIndex 
)

This method is used to set the values of a contiguous group of knots of the curve.

The range of knots to set is specified using the start and end index. The knots of index startIndex to endIndex inclusive will be set using the value in the double array.

Knot indices range from 0 to numKnots() - 1

Parameters:
[in]arraya double array of knot points
[in]startIndexthe starting index of the knots to be altered.
[in]endIndexthe ending index of the knots to be altered.
Returns:
Status code
Status Codes:
  • MS::kSuccess The method was successful
  • MS::kInvalidParameter Invalid start or end indices, or the length of the array is not sufficient to fill the range given, or the knots are in decreasing order.
  • MS::kFailure An object error has occurred
MStatus setKnot ( unsigned int  index,
double  param 
)

Set the given knot's parameter value.

Knot indices range from 0 to numKnots() - 1.

If a knot value is set that breaks the non-decreasing requirement for the knot array, the knot value will be changed and a kInvalidParameter error will be returned.

Parameters:
[in]indexIndex of the knot to be set
[in]paramThe parameter value that the knot will take
Returns:
Status code
Status Codes:
MObject cvs ( unsigned int  startIndex,
unsigned int  endIndex,
MStatus ReturnStatus = NULL 
) const

This method is used to directly access a contiguous group of CVs.

The returned group can be accessed via the MItCurveCV class. Any modifications to these CVs will affect this curve. updateCurve should be called to cause the curve to redraw itself.

Parameters:
[in]startIndexthe start index for the CVs to return
[in]endIndexthe end index for the CVs to return
[out]ReturnStatusStatus code
Returns:
An MObject providing direct-access to the specified CVs
Status Codes:
MStatus getCVs ( MPointArray array,
MSpace::Space  space = MSpace::kObject 
) const

Get the positions of the CVs of this curve.

The returned group can be accessed via the MPointArray class. Any modifications to these CVs will not affect this curve. setCVs should be called to modify the original curve. updateCurve should be called to cause the curve to redraw itself.

Parameters:
[out]arrayThe array of point values for the CVs
[in]spaceSpecifies the coordinate system for this operation
Returns:
Status code
Status Codes:
MStatus setCVs ( const MPointArray array,
MSpace::Space  space = MSpace::kObject 
)

Set the CVs for this curve to the given points.

Parameters:
[in]arrayThe array of point values for the CVs
[in]spaceSpecifies the coordinate system for this operation
Returns:
Status code
Status Codes:
double knot ( unsigned int  index,
MStatus ReturnStatus = NULL 
) const

Get the parameter value of the specified knot for this curve.

Knot indices range from 0 to numKnots() - 1

Parameters:
[in]indexThe knot index
[out]ReturnStatusStatus code
Returns:
The parameter value for the knot at index.
Status Codes:
MStatus removeKnot ( double  atThisParam,
bool  removeAll = false 
)

Remove knot(s) from this curve.

If removeAll is true then all of the knots except for the knot at the given parameter value will be removed. If removeAll is false then only the knot at the given parameter value will be removed.

Parameters:
[in]atThisParamStatus code
[in]removeAllDetermines whether we remove all knots, or all but one
Returns:
Status code
Status Codes:
bool isPointOnCurve ( const MPoint point,
double  tolerance = kMFnNurbsEpsilon,
MSpace::Space  space = MSpace::kObject,
MStatus ReturnStatus = NULL 
) const

Determines whether the given point is on this curve.

Parameters:
[in]pointThe point to test
[in]toleranceThe amount of error (epsilon value) in the calculation
[in]spaceSpecifies the coordinate system for this operation
[out]ReturnStatusStatus code
Returns:
true if the given point is on the curve, false otherwise.
Status Codes:
MStatus getPointAtParam ( double  param,
MPoint point,
MSpace::Space  space = MSpace::kObject 
) const

Returns the point in space that is at the given parameter value of the curve.

If the parameter value does not give a valid point on the curve, then MS::kInvalidParameter is returned.

Parameters:
[in]paramThe parameter value that we are examining
[out]pointStorage for the point being returned
[in]spaceSpecifies the coordinate system for this operation
Returns:
Status code
Status Codes:
MStatus getParamAtPoint ( const MPoint atThisPoint,
double &  param,
MSpace::Space  space = MSpace::kObject 
) const

This method retrieves the parameter value corresponding to the given point on the curve.

Parameters:
[in]atThisPointPoint to check
[out]paramstorage for the parameter value
[in]spaceSpecifies the coordinate system for this operation
Returns:
MStatus getParamAtPoint ( const MPoint atThisPoint,
double &  param,
double  tolerance,
MSpace::Space  space = MSpace::kObject 
) const

This method retrieves the parameter value corresponding to the given point on the curve.

Parameters:
[in]atThisPointPoint to check
[out]paramstorage for the parameter value
[in]tolerancetolerance used for operation
[in]spaceSpecifies the coordinate system for this operation
Returns:
bool isParamOnCurve ( double  param,
MStatus ReturnStatus = NULL 
) const

Determines whether the specified parameter value is within the bounds of the knot vector of this curve.

Parameters:
[in]paramThe parameter value to check
[out]ReturnStatusStatus code
Returns:
  • true The parameter is on this curve.
  • false Parameter is NOT on this curve.
Status Codes:
MVector normal ( double  param,
MSpace::Space  space = MSpace::kObject,
MStatus ReturnStatus = NULL 
) const

This method returns the normal at the given parameter value on the curve.

For degree 1 curves the normal is the vector at right angles to the curve that lies in the average plane of the curve. For higher degrees the normal is defined by the local curvature at param.

Parameters:
[in]paramThe parameter of the point on the curve from which to get the normal
[in]spaceSpecifies the coordinate system for this operation
[out]ReturnStatusStatus code
Returns:
The normal vector for the given parameter
Status Codes:
Examples:
closestTangentUAndDistance.cpp.
MVector tangent ( double  param,
MSpace::Space  space = MSpace::kObject,
MStatus ReturnStatus = NULL 
) const

This method returns the tangent at the given parameter value on the curve.

The resulting tangent vector is normalized.

Parameters:
[in]paramThe parameter of the point on the curve from which to get the tangent
[in]spaceSpecifies the coordinate system for this operation
[out]ReturnStatusStatus code
Returns:
The tangent vector for the given parameter
Status Codes:
Examples:
closestTangentUAndDistance.cpp.
MStatus getDerivativesAtParm ( double  param,
MPoint pos,
MVector dU,
MSpace::Space  space,
MVector dUU = NULL 
) const

Evaluate the surface at the given parameter returning the position, first derivative and optionally the seecond derivative.

Derivatives are not normalized.

Parameters:
[in]paramU parameter value to evaluate
[out]posStorage for the XYZ position of the curve
[out]dUStorage for the first order partial derivative with respect to u
[in]spaceCoordinate space for the returned vectors
[out]dUUPointer to storage for the second order partial derivative with respect to u
Returns:
Status Code
Status Codes:
bool isPlanar ( MVector planeNormal = NULL,
MStatus ReturnStatus = NULL 
) const

This method determines if this curve is a planar curve.

If planeNormal is non-NULL then the normal to the plane containing this curve is returned in this location.

Parameters:
[in]planeNormalNormal to the plane containing this curve
[out]ReturnStatusStatus code
Returns:
Status code
Status Codes:
MPoint closestPoint ( const MPoint toThisPoint,
double *  param = NULL,
double  tolerance = kMFnNurbsEpsilon,
MSpace::Space  space = MSpace::kObject,
MStatus ReturnStatus = NULL 
) const

This method determines the closest point on the curve to the given point.

Parameters:
[in]toThisPointThe point to test
[in]parampointer to a double. If non-null, on successful returns this will contain the parameter value of the returned point.
[in]toleranceThe amount of error (epsilon value) in the calculation
[in]spaceSpecifies the coordinate system for this operation
[out]ReturnStatusStatus code
Returns:
The point on the curve closest to the given point.
Status Codes:
Examples:
closestTangentUAndDistance.cpp.
MPoint closestPoint ( const MPoint toThisPoint,
bool  paramAsStart,
double *  param = NULL,
double  tolerance = kMFnNurbsEpsilon,
MSpace::Space  space = MSpace::kObject,
MStatus ReturnStatus = NULL 
) const

This method determines the closest point on the curve to the given point.

Performance can be greatly increased by supplying a starting parameter value that is reasonably close to the final point.

Parameters:
[in]toThisPointThe point to test
[in]paramAsStartIf true use the value pointed to by param as a starting point for the search.
[in]parampointer to a double. If non-null, on successful returns this will contain the parameter value of the returned point.
[in]toleranceThe amount of error (epsilon value) in the calculation
[in]spaceSpecifies the coordinate system for this operation
[out]ReturnStatusStatus code
Returns:
The point on the curve closest to the given point.
Status Codes:
double distanceToPoint ( const MPoint pt,
MSpace::Space  space = MSpace::kObject,
MStatus ReturnStatus = NULL 
) const

This method determines the distance from the given point to closest point on the curve.

Parameters:
[in]ptThe point to calculate the distance to
[in]spaceSpecifies the coordinate system for this operation
[out]ReturnStatusStatus code
Returns:
Status code
Status Codes:
Examples:
closestTangentUAndDistance.cpp.
double area ( double  tolerance = kMFnNurbsEpsilon,
MStatus ReturnStatus = NULL 
) const

This method returns the area bounded by this curve.

The curve must be closed and planar.

A value of 0.0 will be returned if area cannot be determined.

Parameters:
[in]toleranceThe amount of error (epsilon value) in the calculation
[out]ReturnStatusStatus code
Returns:
Status code
Status Codes:
double length ( double  tolerance = kMFnNurbsEpsilon,
MStatus ReturnStatus = NULL 
) const

Return the arc length of this curve or 0.0 if it cannot be computed.

Parameters:
[in]toleranceThe amount of error (epsilon value) in the calculation
[out]ReturnStatusStatus code
Returns:
Status code
Status Codes:
double findParamFromLength ( double  partLength,
MStatus ReturnStatus = NULL 
) const

Given the length along the curve, find the parameter value that corresponds to it.

If the parameter value cannot be found for the given length then ReturnStatus is set to kInvalidParameter and the parameter for the end point of the curve is returned.

Parameters:
[in]partLengthLength along the curve to find parameter value at
[out]ReturnStatusStatus code
Returns:
The parameter value corrisponding to the given length. If a parameter cannot be found for the given length then the parameter for the end point of the curve is returned.
Status Codes:
bool hasHistoryOnCreate ( MStatus ReturnStatus = NULL)

This method determines if the shape was created with history.

If the object that this function set is attached to is not a shape then this method will fail.

Parameters:
[out]ReturnStatus
Returns:
  • true shape has history
  • false shape does not have history
Status Codes:
MStatus updateCurve ( )

This method signals that this curve has changed and needs to be recalculated.

This method is useful when a large number of CVs for the curve are being modified. Instead of updating the curve every time a CV is changed it is more efficient to call this method once after updating all of the CVs.

Returns:
Status code
Status Codes:

MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve
MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve MFnNurbsCurve