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# MFnNurbsCurve Class Reference
OpenMaya - API module for common classes | FunctionSet classes

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 C: 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:
[legend]

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

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Forms that a curve may take.

Enumerator:

  kInvalid | Search for all occurrences
  kOpen | Ends are independent. Search for all occurrences
  kClosed | Endpoints are coincident. Search for all occurrences
  kPeriodic | Ends overlap such that there is no break in tangency. Search for all occurrences
  kLast | Search for all occurrences

## 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] | object | The MObject to attach the function set to
  [out] | ReturnStatus | the return status

Status Codes:
  - MS::kSuccess if the function set is successfully attached
  - MS::kInvalidParameter if the MObject does not represent a valid Maya object or if the function set is not allowed to attach to this MObject

MFnNurbsCurve | ( | const MDagPath & | object,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  |

Constructor.

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

Parameters:

  [in] | object | The const MDagPath to attach the function set to
  [out] | ReturnStatus | The return status

Status Codes:
  - MS::kSuccess if the function set is successfully attached
  - MS::kInvalidParameter if the MObject does not represent a valid Maya object or if the function set is not allowed to attach to this MObject

MFnNurbsCurve | ( | const MObject & | object,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  |

Constructor.

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

Parameters:

  [in] | object | The MObject to attach the function set to
  [out] | ReturnStatus | the return status

Status Codes:
  - MS::kSuccess if the function set is successfully attached
  - MS::kInvalidParameter if the MObject does not represent a valid Maya object or if the function set is not allowed to attach to this MObject

## Member Function Documentation

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

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Function set type.

Return the class type : MFn::kNurbsCurve.

Reimplemented from MFnDagNode.

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

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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`
| ) |  |

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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] | controlVertices | an array of control vertices
  [in] | knots | an array of knots
  [in] | degree | the degree to create the curve with
  [in] | form | either kOpen, kClosed, kPeriodic
  [in] | create2D | indictates whether to create 2D or 3D curve
  [in] | createRational | true means curve being created will be rational
  [in] | parentOrOwner | the DAG parent or kNurbsCurveData the new curve will belong to
  [out] | ReturnStatus | Status 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:
  - MS::kSuccess Curve was successfully created
  - MS::kInvalidParameter Invalid parameter specified
  - MS::kLicenseFailure Application not licensed for attempted operation
  - MS::kFailure Error creating curve

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`
| ) |  |

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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] | editPoints | an array of edit points
  [in] | degree | the degree to create the curve with
  [in] | form | either kOpen, kClosed, kPeriodic
  [in] | create2D | indictates whether to create 2D or 3D curve
  [in] | createRational | true means curve being created will be rational
  [in] | uniformParam | true means curve being created will have uniform parameterization, false means chord length
  [in] | parentOrOwner | the DAG parent or kNurbsCurveData the new curve will belong to
  [out] | ReturnStatus | Status 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:
  - MS::kSuccess Curve was successfully created
  - MS::kInvalidParameter Invalid parameter specified
  - MS::kLicenseFailure Application not licensed for attempted operation
  - MS::kFailure Error creating curve

MObject create | ( | const MObjectArray & | sources,
|  | MObject & | parentOrOwner = `MObject::kNullObj`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  |

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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] | sources | Input array of souce curves.
  [in] | parentOrOwner | the DAG parent or kNurbsCurveData the new curve will belong to
  [out] | ReturnStatus | Status 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:
  - MS::kSuccess Curve was successfully created
  - MS::kInvalidParameter Invalid parameter specified
  - MS::kFailure Error creating curve

MObject copy | ( | const MObject & | source,
|  | MObject & | parentOrOwner = `MObject::kNullObj`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  |

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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] | source | the curve to be copied
  [in] | parentOrOwner | the DAG parent or kNurbsCurveData the new curve will belong to
  [out] | ReturnStatus | Status 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:
  - MS::kSuccess Curve was successfully created
  - MS::kInvalidParameter Invalid parameter specified
  - MS::kLicenseFailure Application not licensed for attempted operation
  - MS::kFailure Error creating curve

MStatus reverse | ( | bool | constructionHistory = `false` | ) |

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This method reverse the curve direction.

Parameters:

  [in] | constructionHistory | This 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:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MStatus makeMultipleEndKnots | ( |  | ) |

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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:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MObject cv | ( | unsigned int | index,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

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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] | index | Index of the CV
  [out] | ReturnStatus | Status code

Returns:
  A handle to the CVs requested

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter CV index out of range
  - MS::kFailure An object error has occurred

MStatus getCV | ( | unsigned int | index,
|  | MPoint & | pt,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  | const

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Get the CV at the given index.

Parameters:

  [in] | index | The index of the CV that will be retrieved
  [out] | pt | Storage for the CV
  [in] | space | Specifies the coordinate system for this operation

Returns:
  Status code

Status Codes:
  - MS::kSuccess The CV was successfully set
  - MS::kInvalidParameter CV index out of range
  - MS::kFailure Object error

MStatus setCV | ( | unsigned int | index,
|  | const MPoint & | pt,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  |

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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] | index | The index of the CV that will be changed
  [in] | pt | The new value that the CV will take
  [in] | space | Specifies the coordinate system for this operation

Returns:
  Status code

Status Codes:
  - MS::kSuccess The CV was successfully set
  - MS::kInvalidParameter CV index out of range
  - MS::kFailure Object error

MFnNurbsCurve::Form form | ( | MStatus * | ReturnStatus = `NULL` | ) | const

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This method returns the form of the curve.

The curve can be open, closed, or periodic.

Parameters:

  [out] | ReturnStatus | Status code

Returns:
  - MFnNurbsCurve::kOpen
  - MFnNurbsCurve::kClosed
  - MFnNurbsCurve::kPeriodic

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

int degree | ( | MStatus * | ReturnStatus = `NULL` | ) | const

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Return the degree of this curve.

If the degree cannot be determined then 0 is returned.

Parameters:

  [out] | ReturnStatus | Status code

Returns:
  The degree of this curve.

Status Codes:
  - MS::kSuccess The degree was successfully returned.
  - MS::kFailure An object error has occurred.

int numCVs | ( | MStatus * | ReturnStatus = `NULL` | ) | const

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Return the number of CVs for this curve.

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

Parameters:

  [out] | ReturnStatus | Status code

Returns:
  The number of CVs for this curve.

Status Codes:
  - MS::kSuccess The number of CVs was successfully returned.
  - MS::kFailure An object error has occurred.

int numSpans | ( | MStatus * | ReturnStatus = `NULL` | ) | const

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Return the number of spans for this curve.

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

Parameters:

  [out] | ReturnStatus | Status code

Returns:
  The number of spans for this curve.

Status Codes:
  - MS::kSuccess The number of spans was successfully returned.
  - MS::kFailure An object error has occurred.

int numKnots | ( | MStatus * | ReturnStatus = `NULL` | ) | const

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Return the number of knots for this curve.

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

Parameters:

  [out] | ReturnStatus | Status code

Returns:
  The number of knots for this curve.

Status Codes:
  - MS::kSuccess The number of knots was successfully returned.
  - MS::kFailure An object error has occurred.

MStatus getKnotDomain | ( | double & | start,
|  | double & | end
| ) |  | const

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

Parameters:

  [out] | start | storage for the max parameter value
  [out] | end | storage for the min parameter value

Returns:
  Status code

Status Codes:
  - MS::kSuccess The range was successfully returned
  - MS::kFailure Object error

MStatus getKnots | ( | MDoubleArray & | array | ) | const

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

Parameters:

  [out] | array | storage where the parameter values of the knots for this curve will be copied

Returns:
  Status code

Status Codes:
  - MS::kSuccess The knots were successfully copied
  - MS::kFailure Object error

MStatus setKnots | ( | const MDoubleArray & | array,
|  | unsigned int | startIndex,
|  | unsigned int | endIndex
| ) |  |

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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] | array | a double array of knot points
  [in] | startIndex | the starting index of the knots to be altered.
  [in] | endIndex | the 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
| ) |  |

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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] | index | Index of the knot to be set
  [in] | param | The parameter value that the knot will take

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter Knot index out of range or new knot value breaks the non-decreasing requirement for the knot array.
  - MS::kFailure An object error has occurred

MObject cvs | ( | unsigned int | startIndex,
|  | unsigned int | endIndex,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

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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] | startIndex | the start index for the CVs to return
  [in] | endIndex | the end index for the CVs to return
  [out] | ReturnStatus | Status code

Returns:
  An MObject providing direct-access to the specified CVs

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kInvalidParameter CV index out of range
  - MS::kFailure An object error has occurred.

MStatus getCVs | ( | MPointArray & | array,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  | const

Search for all occurrences

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] | array | The array of point values for the CVs
  [in] | space | Specifies the coordinate system for this operation

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter Cannot do world space transform
  - MS::kFailure An object error has occurred

MStatus setCVs | ( | const MPointArray & | array,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  |

Search for all occurrences

Set the CVs for this curve to the given points.

Parameters:

  [in] | array | The array of point values for the CVs
  [in] | space | Specifies the coordinate system for this operation

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kInvalidParameter Cannot do world space transform.
  - MS::kFailure An object error has occurred.

double knot | ( | unsigned int | index,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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

Knot indices range from 0 to numKnots() - 1

Parameters:

  [in] | index | The knot index
  [out] | ReturnStatus | Status code

Returns:
  The parameter value for the knot at index.

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter Knot index out of range
  - MS::kFailure An object error has occurred

MStatus removeKnot | ( | double | atThisParam,
|  | bool | removeAll = `false`
| ) |  |

Search for all occurrences

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] | atThisParam | Status code
  [in] | removeAll | Determines whether we remove all knots, or all but one

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter Parameter value is out of range
  - MS::kFailure An object error has occurred

bool isPointOnCurve | ( | const MPoint & | point,
|  | double | tolerance = `kMFnNurbsEpsilon`,
|  | MSpace::Space | space = `MSpace::kObject`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

Determines whether the given point is on this curve.

Parameters:

  [in] | point | The point to test
  [in] | tolerance | The amount of error (epsilon value) in the calculation
  [in] | space | Specifies the coordinate system for this operation
  [out] | ReturnStatus | Status code

Returns:
  true if the given point is on the curve, false otherwise.

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MStatus getPointAtParam | ( | double | param,
|  | MPoint & | point,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  | const

Search for all occurrences

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] | param | The parameter value that we are examining
  [out] | point | Storage for the point being returned
  [in] | space | Specifies the coordinate system for this operation

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kInvalidParameter Invalid parameter specified.
  - MS::kFailure An object error has occurred.

MStatus getParamAtPoint | ( | const MPoint & | atThisPoint,
|  | double & | param,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  | const

Search for all occurrences

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

Parameters:

  [in] | atThisPoint | Point to check
  [out] | param | storage for the parameter value
  [in] | space | Specifies the coordinate system for this operation

Returns:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MStatus getParamAtPoint | ( | const MPoint & | atThisPoint,
|  | double & | param,
|  | double | tolerance,
|  | MSpace::Space | space = `MSpace::kObject`
| ) |  | const

Search for all occurrences

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

Parameters:

  [in] | atThisPoint | Point to check
  [out] | param | storage for the parameter value
  [in] | tolerance | tolerance used for operation
  [in] | space | Specifies the coordinate system for this operation

Returns:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

bool isParamOnCurve | ( | double | param,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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

Parameters:

  [in] | param | The parameter value to check
  [out] | ReturnStatus | Status code

Returns:
  - true The parameter is on this curve.
  - false Parameter is NOT on this curve.

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MVector normal | ( | double | param,
|  | MSpace::Space | space = `MSpace::kObject`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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] | param | The parameter of the point on the curve from which to get the normal
  [in] | space | Specifies the coordinate system for this operation
  [out] | ReturnStatus | Status code

Returns:
  The normal vector for the given parameter

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter Normal cannot be found for the given parameter value
  - MS::kFailure An object error has occurred

Examples:
  closestTangentUAndDistance.cpp.

MVector tangent | ( | double | param,
|  | MSpace::Space | space = `MSpace::kObject`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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

The resulting tangent vector is normalized.

Parameters:

  [in] | param | The parameter of the point on the curve from which to get the tangent
  [in] | space | Specifies the coordinate system for this operation
  [out] | ReturnStatus | Status code

Returns:
  The tangent vector for the given parameter

Status Codes:
  - MS::kSuccess The method was successful
  - MS::kInvalidParameter Tangent cannot be found for the given parameter value
  - MS::kFailure An object error has occurred

Examples:
  closestTangentUAndDistance.cpp.

MStatus getDerivativesAtParm | ( | double | param,
|  | MPoint & | pos,
|  | MVector & | dU,
|  | MSpace::Space | space,
|  | MVector * | dUU = `NULL`
| ) |  | const

Search for all occurrences

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

Derivatives are not normalized.

Parameters:

  [in] | param | U parameter value to evaluate
  [out] | pos | Storage for the XYZ position of the curve
  [out] | dU | Storage for the first order partial derivative with respect to u
  [in] | space | Coordinate space for the returned vectors
  [out] | dUU | Pointer to storage for the second order partial derivative with respect to u

Returns:
  Status Code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kInvalidParameter Parameter does not define a point on the curve
  - MS::kFailure An object error has occurred.

bool isPlanar | ( | MVector * | planeNormal = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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] | planeNormal | Normal to the plane containing this curve
  [out] | ReturnStatus | Status code

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MPoint closestPoint | ( | const MPoint & | toThisPoint,
|  | double * | param = `NULL`,
|  | double | tolerance = `kMFnNurbsEpsilon`,
|  | MSpace::Space | space = `MSpace::kObject`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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

Parameters:

  [in] | toThisPoint | The point to test
  [in] | param | pointer to a double. If non-null, on successful returns this will contain the parameter value of the returned point.
  [in] | tolerance | The amount of error (epsilon value) in the calculation
  [in] | space | Specifies the coordinate system for this operation
  [out] | ReturnStatus | Status code

Returns:
  The point on the curve closest to the given point.

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

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

Search for all occurrences

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] | toThisPoint | The point to test
  [in] | paramAsStart | If true use the value pointed to by param as a starting point for the search.
  [in] | param | pointer to a double. If non-null, on successful returns this will contain the parameter value of the returned point.
  [in] | tolerance | The amount of error (epsilon value) in the calculation
  [in] | space | Specifies the coordinate system for this operation
  [out] | ReturnStatus | Status code

Returns:
  The point on the curve closest to the given point.

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

double distanceToPoint | ( | const MPoint & | pt,
|  | MSpace::Space | space = `MSpace::kObject`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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

Parameters:

  [in] | pt | The point to calculate the distance to
  [in] | space | Specifies the coordinate system for this operation
  [out] | ReturnStatus | Status code

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

Examples:
  closestTangentUAndDistance.cpp.

double area | ( | double | tolerance = `kMFnNurbsEpsilon`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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] | tolerance | The amount of error (epsilon value) in the calculation
  [out] | ReturnStatus | Status code

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

double length | ( | double | tolerance = `kMFnNurbsEpsilon`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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

Parameters:

  [in] | tolerance | The amount of error (epsilon value) in the calculation
  [out] | ReturnStatus | Status code

Returns:
  Status code

Status Codes:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

double findParamFromLength | ( | double | partLength,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | const

Search for all occurrences

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] | partLength | Length along the curve to find parameter value at
  [out] | ReturnStatus | Status 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:
  - MS::kSuccess The method was successful.
  - MS::kInvalidParameter Parameter value cannot be found
  - MS::kFailure An object error has occurred.

bool hasHistoryOnCreate | ( | MStatus * | ReturnStatus = `NULL` | ) |

Search for all occurrences

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:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

MStatus updateCurve | ( |  | ) |

Search for all occurrences

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:
  - MS::kSuccess The method was successful.
  - MS::kFailure An object error has occurred.

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