From 7badd2c402f9e8e9fd13f6915ad2e32301f9f305 Mon Sep 17 00:00:00 2001 From: Mathias Agopian Date: Mon, 22 Nov 2010 15:48:10 -0800 Subject: allow rotation-vector to have 4 components - upadte documentation for rotation vector - update method dealing with rotation vector to deal with 4 components - virtual rotation-vector sensor reports all four components - improve SensorManager documentation layout Whent he 4-th component of the rotation-vector is present, we can save a square-root when computing the quaternion or rotation matrix from it. Change-Id: Ia84d278dd5f0909fab1c5ba050f8df2679e2c7c8 --- core/java/android/hardware/SensorEvent.java | 48 ++++++++++++++++++------- core/java/android/hardware/SensorManager.java | 21 +++++++---- services/sensorservice/RotationVectorSensor.cpp | 1 + 3 files changed, 50 insertions(+), 20 deletions(-) diff --git a/core/java/android/hardware/SensorEvent.java b/core/java/android/hardware/SensorEvent.java index 32ff3b3d9791..8c55bf33788b 100644 --- a/core/java/android/hardware/SensorEvent.java +++ b/core/java/android/hardware/SensorEvent.java @@ -220,25 +220,47 @@ public class SensorEvent { *

* *

{@link android.hardware.Sensor#TYPE_GRAVITY Sensor.TYPE_GRAVITY}:

- * A three dimensional vector indicating the direction and magnitude of gravity. Units - * are m/s^2. The coordinate system is the same as is used by the acceleration sensor. + *

A three dimensional vector indicating the direction and magnitude of gravity. Units + * are m/s^2. The coordinate system is the same as is used by the acceleration sensor.

+ *

Note: When the device is at rest, the output of the gravity sensor should be identical + * to that of the accelerometer.

* *

{@link android.hardware.Sensor#TYPE_LINEAR_ACCELERATION Sensor.TYPE_LINEAR_ACCELERATION}:

* A three dimensional vector indicating acceleration along each device axis, not including * gravity. All values have units of m/s^2. The coordinate system is the same as is used by the - * acceleration sensor. + * acceleration sensor. + *

The output of the accelerometer, gravity and linear-acceleration sensors must obey the + * following relation:

+ *

* *

{@link android.hardware.Sensor#TYPE_ROTATION_VECTOR Sensor.TYPE_ROTATION_VECTOR}:

- * The rotation vector represents the orientation of the device as a combination of an angle - * and an axis, in which the device has rotated through an angle theta around an axis - * <x, y, z>. The three elements of the rotation vector are - * <x*sin(theta/2), y*sin(theta/2), z*sin(theta/2)>, such that the magnitude of the rotation - * vector is equal to sin(theta/2), and the direction of the rotation vector is equal to the - * direction of the axis of rotation. The three elements of the rotation vector are equal to - * the last three components of a unit quaternion - * <cos(theta/2), x*sin(theta/2), y*sin(theta/2), z*sin(theta/2)>. Elements of the rotation - * vector are unitless. The x,y, and z axis are defined in the same way as the acceleration - * sensor. + *

The rotation vector represents the orientation of the device as a combination of an angle + * and an axis, in which the device has rotated through an angle θ around an axis + * <x, y, z>.

+ *

The three elements of the rotation vector are + * <x*sin(θ/2), y*sin(θ/2), z*sin(θ/2)>, such that the magnitude of the rotation + * vector is equal to sin(θ/2), and the direction of the rotation vector is equal to the + * direction of the axis of rotation.

+ *

The three elements of the rotation vector are equal to + * the last three components of a unit quaternion + * <cos(θ/2), x*sin(θ/2), y*sin(θ/2), z*sin(θ/2)>.

+ *

Elements of the rotation vector are unitless. + * The x,y, and z axis are defined in the same way as the acceleration + * sensor.

+ * * *

{@link android.hardware.Sensor#TYPE_ORIENTATION * Sensor.TYPE_ORIENTATION}:

All values are angles in degrees. diff --git a/core/java/android/hardware/SensorManager.java b/core/java/android/hardware/SensorManager.java index c178aee3d548..1b799aed857f 100644 --- a/core/java/android/hardware/SensorManager.java +++ b/core/java/android/hardware/SensorManager.java @@ -1938,13 +1938,18 @@ public class SensorManager * @param R an array of floats in which to store the rotation matrix */ public static void getRotationMatrixFromVector(float[] R, float[] rotationVector) { - float q0 = (float)Math.sqrt(1 - rotationVector[0]*rotationVector[0] - - rotationVector[1]*rotationVector[1] - - rotationVector[2]*rotationVector[2]); + + float q0; float q1 = rotationVector[0]; float q2 = rotationVector[1]; float q3 = rotationVector[2]; + if (rotationVector.length == 4) { + q0 = rotationVector[3]; + } else { + q0 = (float)Math.sqrt(1 - q1*q1 - q2*q2 - q3*q3); + } + float sq_q1 = 2 * q1 * q1; float sq_q2 = 2 * q2 * q2; float sq_q3 = 2 * q3 * q3; @@ -1995,10 +2000,12 @@ public class SensorManager * @param Q an array of floats in which to store the computed quaternion */ public static void getQuaternionFromVector(float[] Q, float[] rv) { - float w = (float)Math.sqrt(1 - rv[0]*rv[0] - rv[1]*rv[1] - rv[2]*rv[2]); - //In this case, the w component of the quaternion is known to be a positive number - - Q[0] = w; + if (rv.length == 4) { + Q[0] = rv[3]; + } else { + //In this case, the w component of the quaternion is known to be a positive number + Q[0] = (float)Math.sqrt(1 - rv[0]*rv[0] - rv[1]*rv[1] - rv[2]*rv[2]); + } Q[1] = rv[0]; Q[2] = rv[1]; Q[3] = rv[2]; diff --git a/services/sensorservice/RotationVectorSensor.cpp b/services/sensorservice/RotationVectorSensor.cpp index eecf260a7724..50cd6beac37b 100644 --- a/services/sensorservice/RotationVectorSensor.cpp +++ b/services/sensorservice/RotationVectorSensor.cpp @@ -125,6 +125,7 @@ bool RotationVectorSensor::process(sensors_event_t* outEvent, outEvent->data[0] = qx; outEvent->data[1] = qy; outEvent->data[2] = qz; + outEvent->data[3] = qw; outEvent->sensor = '_rov'; outEvent->type = SENSOR_TYPE_ROTATION_VECTOR; return true; -- cgit v1.2.3-59-g8ed1b