MFnNurbsCurve Class Reference
[OpenMaya - API module for common classes, FunctionSet classes]

#include <MFnNurbsCurve.h>
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List of all members.

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.


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)
MObject  createWithEditPoints (const MPointArray &editPoints, unsigned int degree, Form agForm, bool create2D, bool createRational, bool uniformParam, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
MObject  create (const MObjectArray &sources, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
MObject  copy (const MObject &source, MObject &parentOrOwner=MObject::kNullObj, MStatus *ReturnStatus=NULL)
MStatus  reverse (bool constructionHistory=false)
MStatus  makeMultipleEndKnots ()
MObject  cv (unsigned int index, MStatus *ReturnStatus=NULL) const
MStatus  getCV (unsigned int index, MPoint &pt, MSpace::Space space=MSpace::kObject) const
MStatus  setCV (unsigned int index, const MPoint &pt, MSpace::Space space=MSpace::kObject)
Form  form (MStatus *ReturnStatus=NULL) const
int  degree (MStatus *ReturnStatus=NULL) const
int  numCVs (MStatus *ReturnStatus=NULL) const
int  numSpans (MStatus *ReturnStatus=NULL) const
int  numKnots (MStatus *ReturnStatus=NULL) const
MStatus  getKnotDomain (double &start, double &end) const
MStatus  getKnots (MDoubleArray &array) const
MStatus  setKnots (const MDoubleArray &array, unsigned int startIndex, unsigned int endIndex)
MStatus  setKnot (unsigned int index, double param)
MObject  cvs (unsigned int startIndex, unsigned int endIndex, MStatus *ReturnStatus=NULL) const
MStatus  getCVs (MPointArray &array, MSpace::Space space=MSpace::kObject) const
MStatus  setCVs (const MPointArray &array, MSpace::Space space=MSpace::kObject)
double  knot (unsigned int index, MStatus *ReturnStatus=NULL) const
MStatus  removeKnot (double atThisParam, bool removeAll=false)
bool  isPointOnCurve (const MPoint &point, double tolerance=1.0e-3, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
MStatus  getPointAtParam (double param, MPoint &point, MSpace::Space space=MSpace::kObject) const
MStatus  getParamAtPoint (const MPoint &atThisPoint, double &param, MSpace::Space space=MSpace::kObject) const
MStatus  getParamAtPoint (const MPoint &atThisPoint, double &param, double tolerance, MSpace::Space space=MSpace::kObject) const
bool  isParamOnCurve (double param, MStatus *ReturnStatus=NULL) const
MVector  normal (double param, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
MVector  tangent (double param, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
MStatus  getDerivativesAtParm (double param, MPoint &pos, MVector &dU, MSpace::Space space, MVector *dUU=NULL) const
bool  isPlanar (MVector *planeNormal=NULL, MStatus *ReturnStatus=NULL) const
MPoint  closestPoint (const MPoint &toThisPoint, double *param=NULL, double tolerance=1.0e-3, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
MPoint  closestPoint (const MPoint &toThisPoint, bool paramAsStart, double *param=NULL, double tolerance=1.0e-3, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
double  distanceToPoint (const MPoint &pt, MSpace::Space space=MSpace::kObject, MStatus *ReturnStatus=NULL) const
double  area (double tolerance=1.0e-3, MStatus *ReturnStatus=NULL) const
double  length (double tolerance=1.0e-3, MStatus *ReturnStatus=NULL) const
double  findParamFromLength (double partLength, MStatus *ReturnStatus=NULL) const
bool  hasHistoryOnCreate (MStatus *ReturnStatus=NULL)
MStatus  updateCurve ()
  MFnNurbsCurve (const MObject &object, MStatus *ret=NULL)
  Constructor.

Protected Member Functions
virtual const char *  className () const
  Class name.

Member Enumeration Documentation

enum MFnNurbsCurve::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::~MFnNurbsCurve (  )  [virtual]

Destructor.

Class desctructor.

MFnNurbsCurve::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:

MFnNurbsCurve::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:

MFnNurbsCurve::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:

Member Function Documentation

MFn::Type MFnNurbsCurve::type (  )  const [virtual]

Function set type.

Return the class type : MFn::kNurbsCurve

Reimplemented from MFnDagNode.

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

Class name.

Return the class name : "MFnNurbsCurve"

Reimplemented from MFnDagNode.

MObject MFnNurbsCurve::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]  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:
Examples:
helixCmd.cpp, helixTool.cpp, motionTraceCmd.cpp, and particlePathsCmd.cpp.

MObject MFnNurbsCurve::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]  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:

MObject MFnNurbsCurve::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]  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:

MObject MFnNurbsCurve::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]  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:

MStatus MFnNurbsCurve::reverse ( bool  constructionHistory = false  ) 

This method reverse the curve direction.

Returns:
Status code
Status Codes:

MStatus MFnNurbsCurve::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 MFnNurbsCurve::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]  index  Index of the CV
[out]  ReturnStatus  Status code
Returns:
A handle to the CVs requested
Status Codes:

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

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:

MStatus MFnNurbsCurve::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]  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:

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

This method returns the form of the curve. The curve can be open, closed, or periodic.

Parameters:
[out]  ReturnStatus  Status code
Returns:
Status Codes:

int MFnNurbsCurve::degree ( MStatus *  ReturnStatus = NULL  )  const

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:

int MFnNurbsCurve::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]  ReturnStatus  Status code
Returns:
The number of CVs for this curve.
Status Codes:

int MFnNurbsCurve::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]  ReturnStatus  Status code
Returns:
The number of spans for this curve.
Status Codes:

int MFnNurbsCurve::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]  ReturnStatus  Status code
Returns:
The number of knots for this curve.
Status Codes:

MStatus MFnNurbsCurve::getKnotDomain ( double &  start,
double &  end  
) const

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:

MStatus MFnNurbsCurve::getKnots ( MDoubleArray &  array  )  const

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:

MStatus MFnNurbsCurve::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]  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 MFnNurbsCurve::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]  index  Index of the knot to be set
[in]  param  The parameter value that the knot will take
Returns:
Status code
Status Codes:

MObject MFnNurbsCurve::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]  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:

MStatus MFnNurbsCurve::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]  array  The array of point values for the CVs
[in]  space  Specifies the coordinate system for this operation
Returns:
Status code
Status Codes:

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

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:

double MFnNurbsCurve::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]  index  The knot index
[out]  ReturnStatus  Status code
Returns:
The parameter value for the knot at index.
Status Codes:

MStatus MFnNurbsCurve::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]  atThisParam  Status code
[in]  removeAll  Determines whether we remove all knots, or all but one
Returns:
Status code
Status Codes:

bool MFnNurbsCurve::isPointOnCurve ( const MPoint &  point,
double  tolerance = 1.0e-3,
MSpace::Space  space = MSpace::kObject,
MStatus *  ReturnStatus = NULL  
) const

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:

MStatus MFnNurbsCurve::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]  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:

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

MStatus MFnNurbsCurve::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]  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:

bool MFnNurbsCurve::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]  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:

MVector MFnNurbsCurve::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]  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:
Examples:
closestTangentUAndDistance.cpp.

MVector MFnNurbsCurve::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]  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:
Examples:
closestTangentUAndDistance.cpp.

MStatus MFnNurbsCurve::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]  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:

bool MFnNurbsCurve::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]  planeNormal  Normal to the plane containing this curve
[out]  ReturnStatus  Status code
Returns:
Status code
Status Codes:

MPoint MFnNurbsCurve::closestPoint ( const MPoint &  toThisPoint,
double *  param = NULL,
double  tolerance = 1.0e-3,
MSpace::Space  space = MSpace::kObject,
MStatus *  ReturnStatus = NULL  
) const

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:
Examples:
closestTangentUAndDistance.cpp.

MPoint MFnNurbsCurve::closestPoint ( const MPoint &  toThisPoint,
bool  paramAsStart,
double *  param = NULL,
double  tolerance = 1.0e-3,
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]  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:

double MFnNurbsCurve::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]  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:
Examples:
closestTangentUAndDistance.cpp.

double MFnNurbsCurve::area ( double  tolerance = 1.0e-3,
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]  tolerance  The amount of error (epsilon value) in the calculation
[out]  ReturnStatus  Status code
Returns:
Status code
Status Codes:

double MFnNurbsCurve::length ( double  tolerance = 1.0e-3,
MStatus *  ReturnStatus = NULL  
) const

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:

double MFnNurbsCurve::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]  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:

bool MFnNurbsCurve::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 MFnNurbsCurve::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:
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