org.jeospace.navigation
Class Alpha

java.lang.Object
  org.jeospace.navigation.Alpha

public class Alpha

extends java.lang.Object

Generator of alpha values (ranging 0.0 to 1.0) for interpolators. This object is designed for synchronous operation; the fraction value is update in response to an external object calling it's tick() method. The alpha may run forward or backward depending on the direction constant value. The alpha's primary (fraction) value is incremented or decremented by the increment value for each tick(). The fraction value may be modified by a behavior function specified by the behavior constant.

Version:

$Revision: 1.1.1.1 $

Author:

Rex Melton

Field Summary

static int	ACCELERATE Behavior constant indicating that the alpha value accelerates or ramps up from it's beginning to end.
static int	ACCELERATE_DECELERATE Behavior constant indicating that the alpha value accelerates for the first half of it's operation then decelerates for the second half.
protected int	behaviour Modifier of the fraction.
static int	CONTINUOUS Loop count value indicating that the Alpha should run continuously
static int	DECELERATE Behavior constant indicating that the alpha value decelerates or ramps down from it's beginning to end.
static boolean	DECREMENT Direction constant indicating that the alpha will decrement
protected double	fraction The base value of the alpha which determines it's begin and end points.
protected double	increment The value to increment (or decrement) the fraction by.
static boolean	INCREMENT Direction constant indicating that the alpha will increment
static int	LINEAR Behavior constant indicating that the alpha value is a linear function of the fraction value.
protected int	loopCount The number of iterations to perform
static int	STOP Loop count value indicating that the Alpha should stop

Constructor Summary

Alpha()
Default Constructor.

Alpha(double fraction, double increment, int behaviour, int loopCount)
Constructor

Method Summary

int	getBehaviour() Return the behavior constant
double	getFraction() Return the fraction value
int	getLoopCount() Return the loop count
double	getValue() Return the alpha value.
void	set(double fraction, double increment, int behaviour, int loopCount) Set the alpha parameters
void	setBehaviour(int behaviour) Set the alpha behavior
void	setFraction(double fraction) Set the fraction value
void	setIncrement(double increment) Set the increment value
void	setLoopCount(int loopCount) Set the loop count to the argument value
boolean	tick(boolean up_or_down) Update the fraction value by the increment, in the direction of the argument

Methods inherited from class java.lang.Object

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

Field Detail

INCREMENT

public static final boolean INCREMENT

Direction constant indicating that the alpha will increment

See Also:

Constant Field Values

DECREMENT

public static final boolean DECREMENT

Direction constant indicating that the alpha will decrement

See Also:

Constant Field Values

LINEAR

public static final int LINEAR

Behavior constant indicating that the alpha value is a linear function of the fraction value.

See Also:

Constant Field Values

ACCELERATE

public static final int ACCELERATE

Behavior constant indicating that the alpha value accelerates or ramps up from it's beginning to end. The function is:
( 1.0 - Math.cos( fraction * Math.PI/2 ) )

See Also:

Constant Field Values

DECELERATE

public static final int DECELERATE

Behavior constant indicating that the alpha value decelerates or ramps down from it's beginning to end. The function is:
( Math.sin( fraction * Math.PI/2 ) )

See Also:

Constant Field Values

ACCELERATE_DECELERATE

public static final int ACCELERATE_DECELERATE

Behavior constant indicating that the alpha value accelerates for the first half of it's operation then decelerates for the second half. The function is:
( 0.5 * ( 1.0 - Math.cos( fraction * Math.PI ) ) )

See Also:

Constant Field Values

CONTINUOUS

public static final int CONTINUOUS

Loop count value indicating that the Alpha should run continuously

See Also:

Constant Field Values

STOP

public static final int STOP

Loop count value indicating that the Alpha should stop

See Also:

Constant Field Values

fraction

protected double fraction

The base value of the alpha which determines it's begin and end points.

increment

protected double increment

The value to increment (or decrement) the fraction by.

behaviour

protected int behaviour

Modifier of the fraction. Must be one of the defined behavior constants.

loopCount

protected int loopCount

The number of iterations to perform

Constructor Detail

Alpha

public Alpha()

Default Constructor. Instantiates an Alpha with the default values of:
fraction = 0.0
increment = 0.01
behavior = ACCELERATE_DECELERATE
loopCount = 1

Alpha

public Alpha(double fraction,
             double increment,
             int behaviour,
             int loopCount)

Constructor

Parameters:

fraction - The fraction value

increment - The increment value

behaviour - A behavior constant

loopCount - The number of cycles to perform

Method Detail

set

public void set(double fraction,
                double increment,
                int behaviour,
                int loopCount)

Set the alpha parameters

Parameters:

fraction - The fraction value

increment - The increment value

behaviour - A behavior constant

loopCount - The number of cycles to perform

setFraction

public void setFraction(double fraction)

Set the fraction value

Parameters:

fraction - The fraction value

setIncrement

public void setIncrement(double increment)

Set the increment value

Parameters:

increment - The increment value

setBehaviour

public void setBehaviour(int behaviour)

Set the alpha behavior

Parameters:

behaviour - A behavior constant

setLoopCount

public void setLoopCount(int loopCount)

Set the loop count to the argument value

Parameters:

loopCount - The number of cycles to perform

tick

public boolean tick(boolean up_or_down)

Update the fraction value by the increment, in the direction of the argument

Parameters:

up_or_down - Flag indicating whether the fraction should be incremented or decremented by the increment value. true for increment, false for decrement.

Returns:

true if the alpha has reached it's final value, false if not.

getFraction

public double getFraction()

Return the fraction value

Returns:

the fraction value

getBehaviour

public int getBehaviour()

Return the behavior constant

Returns:

the behavior constant

getLoopCount

public int getLoopCount()

Return the loop count

Returns:

the loop count

getValue

public double getValue()

Return the alpha value. This is the fraction value, modified by the behavior.

Returns:

the alpha value