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Merge "update rotation-vector documentation." into gingerbread

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Mathias Agopian
2010-11-30 14:05:02 -08:00
committed by Android (Google) Code Review
parent 2ec2193365 42b743c855
commit 3cceaceeca
1 changed files with 15 additions and 0 deletions
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15
include/hardware/sensors.h
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@@ -233,12 +233,19 @@ __BEGIN_DECLS
* A gravity output indicates the direction of and magnitude of gravity in the devices's * A gravity output indicates the direction of and magnitude of gravity in the devices's
* coordinates. On Earth, the magnitude is 9.8. Units are m/s^2. The coordinate system * coordinates. On Earth, the magnitude is 9.8. Units are m/s^2. The coordinate system
* is the same as is used for the acceleration sensor. * is the same as is used for the acceleration sensor.
* When the device is at rest, the output of the gravity sensor should be identical
* to that of the accelerometer.
* *
* Linear Acceleration * Linear Acceleration
* ------------------- * -------------------
* Indicates the linear acceleration of the device in device coordinates, not including gravity. * Indicates the linear acceleration of the device in device coordinates, not including gravity.
* This output is essentially Acceleration - Gravity. Units are m/s^2. The coordinate system is * This output is essentially Acceleration - Gravity. Units are m/s^2. The coordinate system is
* the same as is used for the acceleration sensor. * the same as is used for the acceleration sensor.
* The output of the accelerometer, gravity and linear-acceleration sensors must obey the
* following relation:
*
* acceleration = gravity + linear-acceleration
*
* *
* Rotation Vector * Rotation Vector
* --------------- * ---------------
@@ -252,6 +259,14 @@ __BEGIN_DECLS
* unit quaternion <cos(theta/2), x*sin(theta/2), y*sin(theta/2), z*sin(theta/2)>. * 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 * Elements of the rotation vector are unitless. The x, y, and z axis are defined
* in the same was as for the acceleration sensor. * in the same was as for the acceleration sensor.
*
* The rotation-vector is stored as:
*
* sensors_event_t.data[0] = x*sin(theta/2)
* sensors_event_t.data[1] = y*sin(theta/2)
* sensors_event_t.data[2] = z*sin(theta/2)
* sensors_event_t.data[3] = cos(theta/2)
*
*/ */
typedef struct { typedef struct {