javax.media.j3d
Class PathInterpolator

java.lang.Object
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  +--javax.media.j3d.SceneGraphObject
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        +--javax.media.j3d.Node
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              +--javax.media.j3d.Leaf
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                    +--javax.media.j3d.Behavior
                          |
                          +--javax.media.j3d.Interpolator
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                                +--javax.media.j3d.PathInterpolator

Direct Known Subclasses:

PositionPathInterpolator, RotationPathInterpolator, RotPosPathInterpolator, RotPosScalePathInterpolator

public abstract class PathInterpolator

extends Interpolator

PathInterpolator behavior. This class defines the base class for all Path Interpolators. Subclasses have access to the computePathInterpolation() method, which computes the currentInterpolationValue given the current time and alpha. The method also computes the currentKnotIndex, which is based on the currentInterpolationValue. The currentInterpolationValue is calculated by linearly interpolating among a series of predefined knots (using the value generated by the specified Alpha object). The first knot must have a value of 0.0 and the last knot must have a value of 1.0. An intermediate knot with index k must have a value strictly greater than any knot with index less than k.

Field Summary

protected float	currentInterpolationValue This value is the ratio between knot values indicated by the currentKnotIndex variable.
protected int	currentKnotIndex This value is the index of the current base knot value, as determined by the alpha function.

Fields inherited from class javax.media.j3d.Interpolator

defaultWakeupCriterion

Fields inherited from class javax.media.j3d.Node

ALLOW_AUTO_COMPUTE_BOUNDS_READ, ALLOW_AUTO_COMPUTE_BOUNDS_WRITE, ALLOW_BOUNDS_READ, ALLOW_BOUNDS_WRITE, ALLOW_COLLIDABLE_READ, ALLOW_COLLIDABLE_WRITE, ALLOW_LOCAL_TO_VWORLD_READ, ALLOW_PICKABLE_READ, ALLOW_PICKABLE_WRITE, ENABLE_COLLISION_REPORTING, ENABLE_PICK_REPORTING

Constructor Summary

PathInterpolator(Alpha alpha, float[] knots)
Constructs a new PathInterpolator object that interpolates between the knot values in the knots array.

Method Summary

protected void	computePathInterpolation() Computes the base knot index and interpolation value given the current value of alpha and the knots[] array.
int	getArrayLengths() Retrieves the length of the knots array.
float	getKnot(int index) Retrieves the knot at the specified index.
void	getKnots(float[] knots) Copies the array of knots from this interpolator into the specified array.
void	setKnot(int index, float knot) Sets the knot at the specified index for this interpolator.
protected void	setKnots(float[] knots) Replaces the existing array of knot values with the specified array.

Methods inherited from class javax.media.j3d.Interpolator

getAlpha, initialize, setAlpha

Methods inherited from class javax.media.j3d.Behavior

getEnable, getSchedulingBoundingLeaf, getSchedulingBounds, getView, postId, processStimulus, setEnable, setSchedulingBoundingLeaf, setSchedulingBounds, updateNodeReferences, wakeupOn

Methods inherited from class javax.media.j3d.Node

cloneNode, cloneTree, cloneTree, cloneTree, cloneTree, cloneTree, cloneTree, duplicateNode, getBounds, getBoundsAutoCompute, getCollidable, getLocalToVworld, getLocalToVworld, getParent, getPickable, setBounds, setBoundsAutoCompute, setCollidable, setPickable

Methods inherited from class javax.media.j3d.SceneGraphObject

clearCapability, duplicateSceneGraphObject, getCapability, getUserData, isCompiled, isLive, setCapability, setUserData

Methods inherited from class java.lang.Object

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

Field Detail

currentInterpolationValue

protected float currentInterpolationValue

This value is the ratio between knot values indicated by the currentKnotIndex variable. So if a subclass wanted to interpolate between knot values, it would use the currentKnotIndex to get the bounding knots for the "real" value, then use the currentInterpolationValue to interpolate between the knots. To calculate this variable, a subclass needs to call the computePathInterpolation() method from the subclass's processStimulus() method. Then this variable will hold a valid value which can be used in further calculations by the subclass.

currentKnotIndex

protected int currentKnotIndex

This value is the index of the current base knot value, as determined by the alpha function. A subclass wishing to interpolate between bounding knots would use this index and the one following it, and would use the currentInterpolationValue variable as the ratio between these indices. To calculate this variable, a subclass needs to call the computePathInterpolation() method from the subclass's processStimulus() method. Then this variable will hold a valid value which can be used in further calculations by the subclass.

Constructor Detail

PathInterpolator

public PathInterpolator(Alpha alpha,
                        float[] knots)

Constructs a new PathInterpolator object that interpolates between the knot values in the knots array. The array of knots is copied into this PathInterpolator object.

Parameters:

alpha - the alpha object for this interpolator.

knots - an array of knot values that specify interpolation points.

Method Detail

getArrayLengths

public int getArrayLengths()

Retrieves the length of the knots array.

Returns:

the array length

setKnot

public void setKnot(int index,
                    float knot)

Sets the knot at the specified index for this interpolator.

Parameters:

index - the index to be changed

knot - the new knot value

getKnot

public float getKnot(int index)

Retrieves the knot at the specified index.

Parameters:

index - the index of the value requested

Returns:

the interpolator's knot value at the associated index

setKnots

protected void setKnots(float[] knots)

Replaces the existing array of knot values with the specified array. The array of knots is copied into this interpolator object. Prior to calling this method, subclasses should verify that the lengths of the new knots array and subclass-specific parameter arrays are the same.

Parameters:

knots - a new array of knot values that specify interpolation points.

Since:

Java 3D 1.2

getKnots

public void getKnots(float[] knots)

Copies the array of knots from this interpolator into the specified array. The array must be large enough to hold all of the knots.

Parameters:

knots - array that will receive the knots.

Since:

Java 3D 1.2

computePathInterpolation

protected void computePathInterpolation()

Computes the base knot index and interpolation value given the current value of alpha and the knots[] array. If the index is 0 and there should be no interpolation, both the index variable and the interpolation variable are set to 0. Otherwise, currentKnotIndex is set to the lower index of the two bounding knot points and the currentInterpolationValue variable is set to the ratio of the alpha value between these two bounding knot points.