/* * Copyright © 2014 Keith Packard * * 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(); } }