FbxNurbsCurve Class Reference

This reference page is linked to from the following overview topics: Supported Scene Elements, FBX Node Attributes, List of Python Fbx classes.

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Detailed Description

A Non-Uniform Rational B-Spline (NURBS) curve is a type of parametric geometry.

A NURBS curve is defined by the order, form, knot vector and control points.

Let M be the order of the curve. Let N be the number of control points of the curve.

The form of the curve can be open, closed or periodic. A curve with end points that do not meet is defined as an open curve. The number of knots in an open curve is defined as N+(M+1).

A closed curve simply has its last control point equal to its first control point. Note that this does not imply tangent continuity at the end point. The curve may have a kink at this point. In FBX the last control point is not specified by the user in the InitControlPoints() method. For example, if there are to be 10 control points in total, and the curve is to be closed, than only 9 control points need to be passed into the InitControlPoints() method. The last control point is implied to be equal to the first control point. Thus N represents the number of unique CVs.

A periodic curve has its last M control points equal to its first M control points. A periodic curve is tangent continuous at the ends. Similar to a closed curve, when creating a periodic curve, only the unique control points need to be set. For example a periodic curve of order 3 with 10 control points requires only 7 CVs to be specified in the InitControlPoints() method. The last 3 CVs, which are the same as the first 3, are not included.

The calculation of the number of knots in closed and periodic curves is more complex. Since we have excluded one CV in N in a closed curve, the number of knots is N+(M+1)+1. Similarly, we excluded M CVs in periodic curves so the number of knots is N+(M+1)+M.

Note that FBX stores one extra knot at the beginning and and end of the knot vector, compared to some other graphics applications such as Maya. The two knots are not used in calculation, but they are included so that no data is lost when converting from file formats that do store the extra knots.

Definition at line 60 of file fbxnurbscurve.h.

#include <fbxnurbscurve.h>

Inheritance diagram for FbxNurbsCurve:

List of all members.

Public Types
enum	EDimension { e2D = 2, e3D }
	The dimension of the CVs. More...
enum	EType { eOpen, eClosed, ePeriodic }
	The curve's form. More...
enum	EErrorCode {   eNurbsCurveTypeUnknown, eWeightTooSmall, eKnotVectorError, eWrongNumberOfControlPoint,   eErrorCount }
Public Member Functions
virtual FbxNodeAttribute::EType	GetAttributeType () const
	Returns the EType::eNurbsCurve node attribute type.
void	InitControlPoints (int pCount, EType pVType)
	Allocates memory space for the control points array as well as for the knot vector.
double *	GetKnotVector () const
	Returns the knot vector.
int	GetKnotCount () const
	Returns the number of elements in the knot vector.
void	SetOrder (int pOrder)
	Sets the order of the curve.
int	GetOrder () const
	Returns the NURBS curve order.
void	SetStep (int pStep)
	Sets the step of the curve.
int	GetStep () const
	Returns the NURBS curve step.
void	SetDimension (EDimension pDimension)
	Sets the dimension of the CVs.
EDimension	GetDimension () const
	Returns the control points dimension.
bool	IsRational ()
	Determines if the curve is rational or not.
int	GetSpanCount () const
	Calculates the number of curve spans with the following: Where S = Number of spans N = Number of CVs M = Order of the curve.
EType	GetType () const
	Returns NURBS type.
bool	IsPolyline () const
	Checks if the curve is a poly line.
bool	IsBezier () const
	This function determines if this NURBS curve is a Bezier curve.
int	TessellateCurve (FbxArray< FbxVector4 > &pPointArray, int pStep=16)
	Evaluate the point on the curve.
FbxLine *	TessellateCurve (int pStep=16)
	Evaluate the point on the curve.
virtual FbxObject &	Copy (const FbxObject &pObject)
	Copy an object content into this object.
bool	FullMultiplicity () const
Public Attributes
bool	mIsRational
Protected Member Functions
virtual void	Construct (const FbxNurbsCurve *pFrom)
virtual void	Destruct (bool pRecursive)
	Optional destructor override, automatically called by default destructor.
void	Reset ()

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Member Enumeration Documentation

enum EDimension

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The dimension of the CVs.

• e2D The CVs are two dimensional points.
• e3D The CVs are three dimensional points.

Enumerator:

e2D	Search for all occurrences
e3D	Search for all occurrences

Definition at line 72 of file fbxnurbscurve.h.

    {
        e2D = 2,
        e3D
    };

enum EType

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The curve's form.

• eOpen
• eClosed
• ePeriodic

Enumerator:

eOpen	Search for all occurrences
eClosed	Search for all occurrences
ePeriodic	Search for all occurrences

Reimplemented from FbxNodeAttribute.

Definition at line 83 of file fbxnurbscurve.h.

    {
        eOpen,
        eClosed,
        ePeriodic
    }; 

enum EErrorCode

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Enumerator:

eNurbsCurveTypeUnknown	Search for all occurrences
eWeightTooSmall	Search for all occurrences
eKnotVectorError	Search for all occurrences
eWrongNumberOfControlPoint	Search for all occurrences
eErrorCount	Search for all occurrences

Definition at line 202 of file fbxnurbscurve.h.

    {
        eNurbsCurveTypeUnknown,
        eWeightTooSmall,
        eKnotVectorError,
        eWrongNumberOfControlPoint,
        eErrorCount
    };

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Member Function Documentation

virtual FbxNodeAttribute::EType GetAttributeType

(

)

const [virtual]

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Returns the EType::eNurbsCurve node attribute type.

Reimplemented from FbxGeometry.

void InitControlPoints	(	int	pCount,
		EType	pVType
	)

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Allocates memory space for the control points array as well as for the knot vector.

Parameters:

pCount	Number of control points.
pVType	NURBS type.

Remarks:

This function should always be called after FbxNurbsCurve::SetOrder().

double* GetKnotVector

(

)

const [inline]

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Returns the knot vector.

Returns:

Pointer to the knots array.

Definition at line 101 of file fbxnurbscurve.h.

{ return mKnotVector; }

int GetKnotCount

(

)

const

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Returns the number of elements in the knot vector.

Returns:

The number of knots.

void SetOrder

(

int

pOrder

)

[inline]

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Sets the order of the curve.

Parameters:

pOrder

The curve order.

Remarks:

The curve order must be set before InitControlPoints() is called.

Definition at line 112 of file fbxnurbscurve.h.

{ mOrder = pOrder; }

int GetOrder

(

)

const [inline]

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Returns the NURBS curve order.

Returns:

The NURBS curve order.

Definition at line 117 of file fbxnurbscurve.h.

{ return mOrder; }

void SetStep

(

int

pStep

)

[inline]

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Sets the step of the curve.

Parameters:

pOrder

The curve step.

Remarks:

To tessellate curve, it denotes the evaluation frequency between two neighbor knots.

Definition at line 123 of file fbxnurbscurve.h.

{ mStep = pStep; }

int GetStep

(

)

const [inline]

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Returns the NURBS curve step.

Returns:

The NURBS curve step.

Remarks:

To tessellate curve, it denotes the evaluation frequency between two neighbor knots.

Definition at line 129 of file fbxnurbscurve.h.

{ return mStep; }

void SetDimension

(

EDimension

pDimension

)

[inline]

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Sets the dimension of the CVs.

For 3D curves: control point = ( x, y, z, w ), where w is the weight. For 2D curves: control point = ( x, y, 0, w ), where the z component is unused, and w is the weight.

Parameters:

pDimension

The control points dimension(3D or 2D).

Definition at line 136 of file fbxnurbscurve.h.

{ mDimension = pDimension; }

EDimension GetDimension

(

)

const [inline]

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Returns the control points dimension.

Returns:

The curve dimension.

Definition at line 141 of file fbxnurbscurve.h.

{ return mDimension; }

bool IsRational

(

)

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Determines if the curve is rational or not.

Returns:

True if the curve is rational, return false if not.

int GetSpanCount

(

)

const

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Calculates the number of curve spans with the following: Where S = Number of spans N = Number of CVs M = Order of the curve.

S = N - M + 1;

In this calculation N includes the duplicate CVs for closed and periodic curves.

Returns:

The number of curve spans if the curve has been initialized, returns -1 if the curve has not been initialized.

EType GetType

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)

const [inline]

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Returns NURBS type.

Returns:

NURBS type identifier.

Definition at line 165 of file fbxnurbscurve.h.

{ return mNurbsType; }

bool IsPolyline

(

)

const [inline]

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Checks if the curve is a poly line.

(A poly line is a linear NURBS curve )

Returns:

True if curve is a poly line, return false if it is not a poly line.

Definition at line 172 of file fbxnurbscurve.h.

{ return ( GetOrder() == 2 ); }

bool IsBezier

(

)

const

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This function determines if this NURBS curve is a Bezier curve.

Bezier curves are a special case of NURBS curve.

Returns:

True if curve is a Bezier curve. If it is not a Bezier curve return false.

int TessellateCurve	(	FbxArray< FbxVector4 > &	pPointArray,
		int	pStep = 16
	)

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Evaluate the point on the curve.

Save the result as a point array. Meanwhile, return the length of the point array.

Parameters:

pPointArray	Save the evaluate result as a point array.
pStep	The evaluation frequency between two neighbor knots. Its default value is 16, which is same as Maya.

Returns:

The length of the point array.

FbxLine* TessellateCurve

(

int

pStep = 16

)

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Evaluate the point on the curve.

Per the evaluation result, create a FbxLine and return the pointer to the line.

Parameters:

pStep

The evaluation frequency between two neighbor knots. Its default value is 16, which is same as Maya.

Returns:

A line to hold the tessellate points.

virtual FbxObject& Copy

(

const FbxObject &

pObject

)

[virtual]

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Copy an object content into this object.

Parameters:

pObject

The source object to copy data from.

Returns:

Returns the destination object being modified by the source.

Remarks:

This function replace the assignment operator (operator=). It will copy all property values and the name. Connections are NOT copied.

Reimplemented from FbxGeometry.

bool FullMultiplicity

(

)

const

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virtual void Construct

(

const FbxNurbsCurve *

pFrom

)

[protected, virtual]

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virtual void Destruct

(

bool

pRecursive

)

[protected, virtual]

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Optional destructor override, automatically called by default destructor.

Parameters:

pRecursive

If true, children objects should be destroyed as well.

Remarks:

In case it is decided to override this function, do not forget to call ParentClass::Destruct(pResursive) at the end.

Reimplemented from FbxGeometry.

void Reset

(

)

[protected]

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Member Data Documentation

bool mIsRational

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Definition at line 211 of file fbxnurbscurve.h.

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The documentation for this class was generated from the following file:

• fbxsdk/scene/geometry/fbxnurbscurve.h