com.graphbuilder.curve

Class NURBSpline

java.lang.Object

com.graphbuilder.curve.Curve

com.graphbuilder.curve.ParametricCurve

com.graphbuilder.curve.BSpline

com.graphbuilder.curve.NURBSpline

public class NURBSpline
extends BSpline

General implementation of the Non-Uniform Rational B-spline or NURB-Spline. The main advantage of the NURB-Spline over the B-Spline is the ability to represent conic sections. To do this, a curve with degree of 2 is used. Figure 1 contains examples of conic arcs.

NURB-Splines can also be used to generate circles as shown in figure 2.

As seen in the figures, every control-point has an associated weight value. The weight-values control how much relative pull each control-point has on the curve. If the weight-value is 0, then the associated point will have no affect on the curve. If a point has an associated weight of 0, but the curve is expected to pass through that point, then it is likely that the result of evaluation will be the origin. All weights must be >= 0.

Field Summary

Fields

Modifier and Type	Field and Description
private static double[]	nw
private boolean	useWeightVector
private static double[]	weight
private ValueVector	weightVector

Fields inherited from class com.graphbuilder.curve.BSpline

NON_UNIFORM, UNIFORM_CLAMPED, UNIFORM_UNCLAMPED

Fields inherited from class com.graphbuilder.curve.Curve

connect, cp, gi

Constructor Summary

Constructors

Constructor and Description
NURBSpline(ControlPath cp, GroupIterator gi)

Method Summary

Modifier and Type	Method and Description
void	appendTo(MultiPath mp) The requirements of the appendTo method include the requirements of the BSpline appendTo method, plus a couple more.
protected void	eval(double[] p) The eval method evaluates a point on a curve given a parametric value "t".
boolean	getUseWeightVector() Returns the value of the useWeightVector flag.
ValueVector	getWeightVector() Returns the weight-vector.
void	resetMemory() Resets the shared memory to the initial state.
void	setUseWeightVector(boolean b) Sets the value of the useWeightVector flag.
void	setWeightVector(ValueVector v) Sets the weight-vector.

Methods inherited from class com.graphbuilder.curve.BSpline

getDegree, getKnotVector, getKnotVectorType, getSampleLimit, getUseDefaultInterval, N, setDegree, setInterval, setKnotVector, setKnotVectorType, setSampleLimit, setUseDefaultInterval, t_max, t_min

Methods inherited from class com.graphbuilder.curve.Curve

getConnect, getControlPath, getGroupIterator, setConnect, setControlPath, setGroupIterator

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

nw

private static double[] nw

weight

private static double[] weight

weightVector

private ValueVector weightVector

useWeightVector

private boolean useWeightVector

Constructor Detail

NURBSpline

public NURBSpline(ControlPath cp,
                  GroupIterator gi)

Method Detail

eval

protected void eval(double[] p)

Description copied from class: ParametricCurve

The eval method evaluates a point on a curve given a parametric value "t". The parametric value "t" is stored in the last index location of the specified double array. This value should not be changed. The dimension of the point to evaluate is p.length - 1. The result of the evaluation is placed in index locations 0 .. p.length - 2 (inclusive). The eval method should remain protected except for those curves that do no need any preparation to be done in the appendTo method.

Overrides:

eval in class BSpline

getWeightVector

public ValueVector getWeightVector()

Returns the weight-vector.

See Also:

setWeightVector(ValueVector)

setWeightVector

public void setWeightVector(ValueVector v)

Sets the weight-vector.

Throws:

java.lang.IllegalArgumentException - If the value-vector is null.

See Also:

getWeightVector()

getUseWeightVector

public boolean getUseWeightVector()

Returns the value of the useWeightVector flag. The default value is true.

See Also:

setUseWeightVector(boolean)

setUseWeightVector

public void setUseWeightVector(boolean b)

Sets the value of the useWeightVector flag. If the flag is true, then the internal weightVector will be used. If the flag is false, then all weights will be assumed to be 1.

See Also:

getUseWeightVector()

appendTo

public void appendTo(MultiPath mp)

The requirements of the appendTo method include the requirements of the BSpline appendTo method, plus a couple more. The additional requirements only apply if the useWeightVector flag is true. If so, then the weight-vector must have size equal to the group-size of the GroupIterator and all weights must have a value >= 0. This method returns quietly if these requirements are not met.

Overrides:

appendTo in class BSpline

See Also:

BSpline.appendTo(MultiPath)

resetMemory

public void resetMemory()

Description copied from class: Curve

Resets the shared memory to the initial state.

Overrides:

resetMemory in class BSpline