109 lines
3.8 KiB
Java
109 lines
3.8 KiB
Java
/*
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* Copyright © 2014 Keith Packard <keithp@keithp.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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*/
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package org.altusmetrum.altoslib_14;
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public class AltosRotation extends AltosQuaternion {
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private AltosQuaternion rotation;
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/* Compute pitch angle from vertical by taking the pad
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* orientation vector and rotating it by the current total
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* rotation value. That will be a unit vector pointing along
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* the airframe axis. The Z value will be the cosine of the
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* angle from vertical.
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*
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* rot = ao_rotation * vertical * ao_rotation°
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* rot = ao_rotation * (0,0,0,1) * ao_rotation°
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* = ((-a.z, a.y, -a.x, a.r) * (a.r, -a.x, -a.y, -a.z)) .z
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*
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* = (-a.z * -a.z) + (a.y * -a.y) - (-a.x * -a.x) + (a.r * a.r)
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* = a.z² - a.y² - a.x² + a.r²
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*
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* rot = ao_rotation * (0, 0, 0, -1) * ao_rotation°
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* = ((-a.z, -a.y, a.x, -a.r) * (a.r, -a.x, -a.y, -a.z)) .z
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*
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* = (a.z * -a.z) + (-a.y * -a.y) - (a.x * -a.x) + (-a.r * a.r)
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* = -a.z² + a.y² + a.x² - a.r²
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*
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* tilt = acos(rot) (in radians)
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*/
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public double tilt() {
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double rotz = rotation.z * rotation.z - rotation.y * rotation.y - rotation.x * rotation.x + rotation.r * rotation.r;
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double tilt = Math.acos(rotz) * 180.0 / Math.PI;
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return tilt;
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}
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/* Compute azimuth angle from a reference line pointing out the side
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* of the airframe
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*
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* rot = ao_rotation * x_axis * ao_rotation°
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* rot = ao_rotation * (0,1,0,0) * ao_rotation°
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* = (-a.x, a.r, a.z, -a.y) * (a.r, -a.x, -a.y, -a.z) . x
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* = (-a.x * -a.x) + (a.r * a.r) + (a.z * -a.z) - (-a.y * -a.y)
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* = a.x² + a.r² - a.z² - a.y²
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*
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* = (-a.x, a.r, a.z, -a.y) * (a.r, -a.x, -a.y, -a.z) . y
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* = (-a.x * -a.y) - (a.r * -a.z) + (a.z * a.r) + (-a.y * -a.x)
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* = a.x * a.y + a.r * a.z + a.z * a.r + a.y * a.x
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*
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* The X value will be the cosine of the rotation. The Y value will be the
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* sine of the rotation; use the sign of that to figure out which direction from
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* zero we've headed
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*/
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public double azimuth() {
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double rotx = rotation.x * rotation.x + rotation.r * rotation.r - rotation.z * rotation.z - rotation.y * rotation.y;
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double roty = rotation.x * rotation.y + rotation.r * rotation.z + rotation.z * rotation.r + rotation.y * rotation.x;
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double az = Math.acos(rotx) * 180.0 / Math.PI;
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if (roty < 0)
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return -az;
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return az;
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}
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/* Given euler rotations in three axes, perform a combined rotation using
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* quaternions
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*/
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public void rotate(double x, double y, double z) {
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AltosQuaternion rot = AltosQuaternion.euler(x, y, z);
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rotation = rot.multiply(rotation).normalize();
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}
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/* Clone an existing rotation value */
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public AltosRotation (AltosRotation old) {
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this.rotation = new AltosQuaternion(old.rotation);
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}
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/* Create a new rotation value given an acceleration vector pointing down */
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public AltosRotation(double x,
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double y,
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double z,
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int pad_orientation) {
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AltosQuaternion orient = AltosQuaternion.vector(x, y, z).normalize();
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double sky = (pad_orientation & 1) == 0 ? 1 : -1;
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AltosQuaternion up = new AltosQuaternion(0, 0, 0, sky);
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rotation = up.vectors_to_rotation(orient);
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}
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public AltosRotation() {
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rotation = new AltosQuaternion();
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}
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}
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