KFbxNurbsCurve Class Reference
#include
<kfbxnurbscurve.h>
Detailed Description
A Non-Uniform Rational B-Spline (NURBS) curve is a type of parametric geometry.A NURBS curve is defined by the degree, form, knot vector and control points.
Let M be the degree 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 degree 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 84 of file kfbxnurbscurve.h.
Public Types |
|
| enum | EDimension
{ e2D = 2, e3D, eDIMENSIONS_COUNT = 2 } |
| The dimension of the CVs. More... |
|
| enum | EType { eOPEN, eCLOSED, ePERIODIC, eTYPE_COUNT } |
| The curve's form. More... |
|
Public Member Functions |
|
|
virtual KFbxNodeAttribute::EAttributeType |
GetAttributeType () const |
| Returns the EAttributeType::eNURBS_CURVE
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 | 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. |
|
Member Enumeration Documentation
| enum EDimension |
The dimension of the CVs.
- e2D The CVs are two dimensional points.
- e3D The CVs are three dimensional points.
Definition at line 95 of file kfbxnurbscurve.h.
| enum EType |
Member Function Documentation
| virtual KFbxNodeAttribute::EAttributeType GetAttributeType | ( | ) | const [virtual] |
Returns the EAttributeType::eNURBS_CURVE node attribute type.
Reimplemented from KFbxGeometry.
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 KFbxNurb::SetOrder().
| double* GetKnotVector | ( | ) | const [inline] |
Returns the knot vector.
- Returns:
- Pointer to the knots array.
Definition at line 126 of file kfbxnurbscurve.h.
| int GetKnotCount | ( | ) | const |
Returns the number of elements in the knot vector.
- Returns:
- The number of knots.
| void SetOrder | ( | int | pOrder | ) | [inline] |
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 137 of file kfbxnurbscurve.h.
| int GetOrder | ( | ) | const [inline] |
Returns the NURBS curve order.
- Returns:
- The NURBS curve order.
Definition at line 142 of file kfbxnurbscurve.h.
| void SetDimension | ( | EDimension | pDimension | ) | [inline] |
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 149 of file kfbxnurbscurve.h.
| EDimension GetDimension | ( | ) | const [inline] |
Returns the control points dimension.
- Returns:
- The curve dimension.
Definition at line 154 of file kfbxnurbscurve.h.
| bool IsRational | ( | ) |
Determines if the curve is rational or not.
- Returns:
Trueif the curve is rational, returnfalseif 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.
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 | ( | ) | const [inline] |
Returns NURBS type.
- Returns:
- NURBS type identifier.
Definition at line 178 of file kfbxnurbscurve.h.
| bool IsPolyline | ( | ) | const [inline] |
Checks if the curve is a poly line.
(A poly line is a linear NURBS curve )
- Returns:
Trueif curve is a poly line, returnfalseif it is not a poly line.
Definition at line 185 of file kfbxnurbscurve.h.
| bool IsBezier | ( | ) | const |
This function determines if this NURBS curve is a Bezier curve.
Bezier curves are a special case of NURBS curve.
- Returns:
Trueif curve is a Bezier curve. If it is not a Bezier curve returnfalse.