javax.media.j3d
Class Sensor

java.lang.Object
  |
  +--javax.media.j3d.Sensor

public class Sensor

extends java.lang.Object

The Sensor Class encapsulates an object that provides real-time data. Examples include six-degree-of-freedom tracking, a joystick, or a data file being read back during a program. A sensor must be used in conjuction with an implementation of the InputDevice interface.

The Sensor object provides an abstract concept of a hardware input device. A Sensor consists of a timestamped sequence of input values and the state of buttons or switches at the time that Java 3D sampled the value. A sensor also contains a hotspot offset specified in the sensor's local coordinate system. If not specified, the hotspot is (0.0, 0.0, 0.0, 0.0).

Since a typical hardware environment may contain multiple sensing elements, Java 3D maintains an array of sensors. Users can access a sensor directly from their Java code or they can assign a sensor to one of Java 3D's predefined 6DOF entities, such as UserHead.

Using a sensor is as easy as accessing an object. Write your Java code to extract the associated sensor value from the array of sensors. You can then directly apply that value to an element in a scene graph or process the sensor values in whatever way necessary.

Java 3D includes three special six-degrees-of-freedom (6DOF) entities. These include UserHead, DominantHand, and NondominantHand. You can assign or change which sensor drives one of these predefined entities. Java 3D uses the specified sensor to drive the 6DOF entity - most visibly the View.

Java 3D does not provide raw tracker or joystick-generated data in a sensor. At a minimum, Java 3D normalizes the raw data using the registration and calibration parameters either provided by or provided for the end user. It additionally may filter and process the data to remove noise and improve latency. The application programmer can suppress this latter effect on a sensor-by-sensor basis.

Unfortunately, tracker or sensor hardware may not always be available or be operational. Thus, Java 3D provides both an available and an enable flag on a per-sensor basis.

See Also:

SensorRead

Field Summary

static int	DEFAULT_SENSOR_READ_COUNT Default SensorRead object count (30); the number of SensorRead objects constructed if no count is specified.
static int	HAND_PREDICTOR Set the predictor policy to assume the sensor is predicting hand position/orientation.
static int	HEAD_PREDICTOR Set the predictor policy to assume the sensor is predicting head position/orientation.
static int	NO_PREDICTOR Use no prediction policy; this is the default.
static int	PREDICT_NEXT_FRAME_TIME Set predictor type to generate the SensorRead to correspond with the next frame time.
static int	PREDICT_NONE Set predictor type to do no prediction; this is the default.

Constructor Summary

Sensor(InputDevice device)
Constructs a Sensor object for the specified input device using default parameters.

Sensor(InputDevice device, int sensorReadCount)
Constructs a Sensor object for the specified input device using the specified number of SensorRead objects.

Sensor(InputDevice device, int sensorReadCount, int sensorButtonCount)
Constructs a Sensor object for the specified input device using the specified number of SensorRead objects and number of buttons.

Sensor(InputDevice device, int sensorReadCount, int sensorButtonCount, Point3d hotspot)
Constructs a Sensor object for the specified input device using the specified number of SensorRead objects, number of buttons, and hotspot.

Sensor(InputDevice device, int sensorReadCount, Point3d hotspot)
Constructs a Sensor object for the specified input device using the specified number of SensorRead objects and hotspot.

Sensor(InputDevice device, Point3d hotspot)
Constructs a Sensor object for the specified input device using the specified hotspot.

Method Summary

SensorRead	getCurrentSensorRead() Gets the current sensor read.
InputDevice	getDevice() Retrieves the sensor's associated input device.
void	getHotspot(Point3d hotspot) Get the sensor's hotspot offset in this sensor's coordinate system.
int	getPredictionPolicy() This function returns the prediction policy used by this sensor.
int	getPredictor() This function returns the type of predictor used by this sensor.
void	getRead(Transform3D read) Computes the sensor reading consistent with the prediction policy and copies that value into the specified argument; calling this method with a prediction policy of NO_PREDICTOR will return the last sensor reading; calling this method with a prediction policy of HAND_PREDICTOR, or HEAD_PREDICTOR will extrapolate previous sensor readings to the current time.
void	getRead(Transform3D read, long deltaT) Computes the sensor reading consistent as of time deltaT in the future and copies that value into the specified argument; the reading is computed using the current prediction policy; a prediction policy of NO_PREDICTOR will yield the most recent sensor reading for any deltaT argument (i.e., this method is the same as getRead for a prediction policy of NO_PREDICTOR).
int	getSensorButtonCount() Returns the number of buttons associated with this sensor.
int	getSensorReadCount() Returns the number of SensorRead objects associated with this sensor.
void	lastButtons(int[] values) Places the most recent sensor reading value for each button into the array parameter; will throw an ArrayIndexOutOfBoundsException if values.length is less than the number of buttons.
void	lastButtons(int k, int[] values) Places the kth-most recent sensor reading value for each button into the array parameter; where k=0 is the most recent sensor reading, k=1 is the next most recent sensor reading, etc.; will throw an ArrayIndexOutOfBoundsException if values.length is less than the number of buttons.
void	lastRead(Transform3D read) Extracts the most recent sensor reading and copies that value into the specified argument.
void	lastRead(Transform3D read, int kth) Extracts the kth-most recent sensor reading and copies that value into the specified argument; where 0 is the most recent sensor reading, 1 is the next most recent sensor reading, etc.
long	lastTime() Returns the time associated with the most recent sensor reading.
long	lastTime(int k) Returns the time associated with the kth-most recent sensor reading; where 0 is the most recent sensor reading, 1 is the next most recent sensor reading, etc.
void	setDevice(InputDevice device) Set the sensor's associated input device.
void	setHotspot(Point3d hotspot) Set the sensor's hotspot offset in this sensor's coordinate system; this value will be subtracted from the translation component of each transform sent to the Sensor object via the setNextSensorRead call.
void	setNextSensorRead(long time, Transform3D transform, int[] values) Sets the next sensor read to the specified values; once these values are set via this method they become the current values returned by methods such as lastRead(), lastTime(), and lastButtons(); note that if there are no buttons associated with this sensor, values can just be an empty array.
void	setNextSensorRead(SensorRead read) Sets the next sensor read to the specified values; once these values are set via this method they become the current values returned by methods such as lastRead(), lastTime(), and lastButtons().
void	setPredictionPolicy(int policy) This function sets the prediction policy use by this sensor.
void	setPredictor(int predictor) This function sets the type of predictor to use with this sensor.
void	setSensorReadCount(int count) Set the number of sensor read objects per Sensor.

Methods inherited from class java.lang.Object

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

Field Detail

PREDICT_NONE

public static final int PREDICT_NONE

Set predictor type to do no prediction; this is the default.

PREDICT_NEXT_FRAME_TIME

public static final int PREDICT_NEXT_FRAME_TIME

Set predictor type to generate the SensorRead to correspond with the next frame time.

NO_PREDICTOR

public static final int NO_PREDICTOR

Use no prediction policy; this is the default.

HEAD_PREDICTOR

public static final int HEAD_PREDICTOR

Set the predictor policy to assume the sensor is predicting head position/orientation.

HAND_PREDICTOR

public static final int HAND_PREDICTOR

Set the predictor policy to assume the sensor is predicting hand position/orientation.

DEFAULT_SENSOR_READ_COUNT

public static final int DEFAULT_SENSOR_READ_COUNT

Default SensorRead object count (30); the number of SensorRead objects constructed if no count is specified.

Constructor Detail

Sensor

public Sensor(InputDevice device)

Constructs a Sensor object for the specified input device using default parameters. The default values are as follows:

sensor read count : 30
sensor button count : 0
hot spot : (0,0,0)
predictor : PREDICT_NONE
prediction policy : NO_PREDICTOR

Parameters:

device - the Sensor's associated device.

Sensor

public Sensor(InputDevice device,
              int sensorReadCount)

Constructs a Sensor object for the specified input device using the specified number of SensorRead objects. Default values are used for all other parameters.

Parameters:

device - the Sensor's associated device

sensorReadCount - the number of SensorReads to associate with this sensor

Sensor

public Sensor(InputDevice device,
              int sensorReadCount,
              int sensorButtonCount)

Constructs a Sensor object for the specified input device using the specified number of SensorRead objects and number of buttons. Default values are used for all other parameters.

Parameters:

device - the Sensor's associated device

sensorReadCount - the number of SensorReads to associate with this sensor

sensorButtonCount - the number of buttons associated with each sensor read

Sensor

public Sensor(InputDevice device,
              Point3d hotspot)

Constructs a Sensor object for the specified input device using the specified hotspot. Default values are used for all other parameters.

Parameters:

device - the Sensor's associated device

hotspot - the Sensor's hotspot defined in its local coordinate system

Sensor

public Sensor(InputDevice device,
              int sensorReadCount,
              Point3d hotspot)

Constructs a Sensor object for the specified input device using the specified number of SensorRead objects and hotspot. Default values are used for all other parameters.

Parameters:

device - the Sensor's associated device

sensorReadCount - the number of SensorReads to associate with this sensor

hotspot - the Sensor's hotspot defined in its local coordinate system

Sensor

public Sensor(InputDevice device,
              int sensorReadCount,
              int sensorButtonCount,
              Point3d hotspot)

Constructs a Sensor object for the specified input device using the specified number of SensorRead objects, number of buttons, and hotspot. Default values are used for all other parameters.

Parameters:

device - the Sensor's associated device

sensorReadCount - the number of SensorReads to associate with this sensor

sensorButtonCount - the number of buttons associated with each sensor read

hotspot - the Sensor's hotspot defined in its local coordinate system

Method Detail

setPredictor

public void setPredictor(int predictor)

This function sets the type of predictor to use with this sensor.

Parameters:

predictor - predictor type one of PREDICT_NONE or PREDICT_NEXT_FRAME_TIME

Throws:

java.lang.IllegalArgumentException - if an invalid predictor type is specified.

getPredictor

public int getPredictor()

This function returns the type of predictor used by this sensor.

Returns:

returns the predictor type. One of PREDICT_NONE or PREDICT_NEXT_FRAME_TIME.

setPredictionPolicy

public void setPredictionPolicy(int policy)

This function sets the prediction policy use by this sensor.

Parameters:

policy - prediction policy one of NO_PREDICTOR, HEAD_PREDICTOR, or HAND_PREDICTOR

Throws:

java.lang.IllegalArgumentException - if an invalid prediction policy is specified.

getPredictionPolicy

public int getPredictionPolicy()

This function returns the prediction policy used by this sensor.

Returns:

returns the prediction policy. one of NO_PREDICTOR, HEAD_PREDICTOR, or HAND_PREDICTOR.

setHotspot

public void setHotspot(Point3d hotspot)

Set the sensor's hotspot offset in this sensor's coordinate system; this value will be subtracted from the translation component of each transform sent to the Sensor object via the setNextSensorRead call.

Parameters:

hotspot - the sensor's new hotspot

getHotspot

public void getHotspot(Point3d hotspot)

Get the sensor's hotspot offset in this sensor's coordinate system.

Parameters:

hotspot - the variable to receive the sensor's hotspot

setDevice

public void setDevice(InputDevice device)

Set the sensor's associated input device.

Parameters:

device - the sensor's new device

getDevice

public InputDevice getDevice()

Retrieves the sensor's associated input device.

Returns:

the sensor's device

getRead

public void getRead(Transform3D read)

Computes the sensor reading consistent with the prediction policy and copies that value into the specified argument; calling this method with a prediction policy of NO_PREDICTOR will return the last sensor reading; calling this method with a prediction policy of HAND_PREDICTOR, or HEAD_PREDICTOR will extrapolate previous sensor readings to the current time.

Parameters:

read - The matrix that will receive the predicted sensor reading

getRead

public void getRead(Transform3D read,
                    long deltaT)

Computes the sensor reading consistent as of time deltaT in the future and copies that value into the specified argument; the reading is computed using the current prediction policy; a prediction policy of NO_PREDICTOR will yield the most recent sensor reading for any deltaT argument (i.e., this method is the same as getRead for a prediction policy of NO_PREDICTOR). The time argument must be >= 0.

Parameters:

read - the matrix that will receive the predicted sensor reading

deltaT - the time delta into the future for this read

lastRead

public void lastRead(Transform3D read)

Extracts the most recent sensor reading and copies that value into the specified argument.

Parameters:

read - the matrix that will receive the most recent sensor reading

lastRead

public void lastRead(Transform3D read,
                     int kth)

Extracts the kth-most recent sensor reading and copies that value into the specified argument; where 0 is the most recent sensor reading, 1 is the next most recent sensor reading, etc.

Parameters:

read - the matrix that will receive the most recent sensor reading

k - the kth previous sensor reading

lastTime

public long lastTime()

Returns the time associated with the most recent sensor reading.

Returns:

the time associated with the most recent sensor reading.

lastTime

public long lastTime(int k)

Returns the time associated with the kth-most recent sensor reading; where 0 is the most recent sensor reading, 1 is the next most recent sensor reading, etc.

Returns:

the time associated with the kth-most recent sensor reading.

lastButtons

public void lastButtons(int[] values)

Places the most recent sensor reading value for each button into the array parameter; will throw an ArrayIndexOutOfBoundsException if values.length is less than the number of buttons.

Parameters:

values - the array into which the button values will be placed

lastButtons

public void lastButtons(int k,
                        int[] values)

Places the kth-most recent sensor reading value for each button into the array parameter; where k=0 is the most recent sensor reading, k=1 is the next most recent sensor reading, etc.; will throw an ArrayIndexOutOfBoundsException if values.length is less than the number of buttons.

Parameters:

k - the time associated with the most recent sensor reading

values - the array into which the button values will be placed.

getSensorReadCount

public int getSensorReadCount()

Returns the number of SensorRead objects associated with this sensor.

Returns:

the number of SensorReadObjects associated with this sensor

setSensorReadCount

public void setSensorReadCount(int count)

Set the number of sensor read objects per Sensor. This is a calibration parameter that should normally be set in this object's constructor. Calling this method resets all of this sensor's values that are already in the buffer.

Parameters:

count - the new sensor read count

getSensorButtonCount

public int getSensorButtonCount()

Returns the number of buttons associated with this sensor.

Returns:

the number of buttons associated with this sensor.

getCurrentSensorRead

public SensorRead getCurrentSensorRead()

Gets the current sensor read.

setNextSensorRead

public void setNextSensorRead(long time,
                              Transform3D transform,
                              int[] values)

Sets the next sensor read to the specified values; once these values are set via this method they become the current values returned by methods such as lastRead(), lastTime(), and lastButtons(); note that if there are no buttons associated with this sensor, values can just be an empty array.

Parameters:

time - the next SensorRead's associated time

transform - the next SensorRead's transformation

values - the next SensorRead's buttons' states

setNextSensorRead

public void setNextSensorRead(SensorRead read)

Sets the next sensor read to the specified values; once these values are set via this method they become the current values returned by methods such as lastRead(), lastTime(), and lastButtons().

Parameters:

read - the next SensorRead's values