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/*
* Copyright © 2014 Keith Packard <keithp@keithp.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
package org.altusmetrum.altoslib_12;
public class AltosRotation extends AltosQuaternion {
private AltosQuaternion rotation;
/* Compute pitch angle from vertical by taking the pad
* orientation vector and rotating it by the current total
* rotation value. That will be a unit vector pointing along
* the airframe axis. The Z value will be the cosine of the
* angle from vertical.
*
* rot = ao_rotation * vertical * ao_rotation°
* rot = ao_rotation * (0,0,0,1) * ao_rotation°
* = ((a.z, a.y, -a.x, a.r) * (a.r, -a.x, -a.y, -a.z)) .z
*
* = (-a.z * -a.z) + (a.y * -a.y) - (-a.x * -a.x) + (a.r * a.r)
* = a.z² - a.y² - a.x² + a.r²
*
* rot = ao_rotation * (0, 0, 0, -1) * ao_rotation°
* = ((-a.z, -a.y, a.x, -a.r) * (a.r, -a.x, -a.y, -a.z)) .z
*
* = (a.z * -a.z) + (-a.y * -a.y) - (a.x * -a.x) + (-a.r * a.r)
* = -a.z² + a.y² + a.x² - a.r²
*
* tilt = acos(rot) (in radians)
*/
public double tilt() {
double rotz = rotation.z * rotation.z - rotation.y * rotation.y - rotation.x * rotation.x + rotation.r * rotation.r;
double tilt = Math.acos(rotz) * 180.0 / Math.PI;
return tilt;
}
/* Given euler rotations in three axes, perform a combined rotation using
* quaternions
*/
public void rotate(double x, double y, double z) {
AltosQuaternion rot = AltosQuaternion.euler(x, y, z);
rotation = rot.multiply(rotation).normalize();
}
/* Clone an existing rotation value */
public AltosRotation (AltosRotation old) {
this.rotation = new AltosQuaternion(old.rotation);
}
/* Create a new rotation value given an acceleration vector pointing down */
public AltosRotation(double x,
double y,
double z,
int pad_orientation) {
AltosQuaternion orient = AltosQuaternion.vector(x, y, z).normalize();
double sky = pad_orientation == 0 ? 1 : -1;
AltosQuaternion up = new AltosQuaternion(0, 0, 0, sky);
rotation = up.vectors_to_rotation(orient);
}
public AltosRotation() {
rotation = new AltosQuaternion();
}
}
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