Initial Commit - Copy from Altus Metrum AltOS

altoslib/AltosRotation.java

@@ -0,0 +1,108 @@
+/*
+ * 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_14;
+
+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;
+	}
+
+	/* Compute azimuth angle from a reference line pointing out the side
+	 * of the airframe
+	 *
+	 * rot = ao_rotation * x_axis * ao_rotation°
+	 * rot = ao_rotation * (0,1,0,0) * ao_rotation°
+	 *     = (-a.x, a.r, a.z, -a.y) * (a.r, -a.x, -a.y, -a.z) . x
+	 *     = (-a.x * -a.x) + (a.r * a.r) + (a.z * -a.z) - (-a.y * -a.y)
+	 *     = a.x² + a.r² - a.z² - a.y²
+	 *
+	 *     = (-a.x, a.r, a.z, -a.y) * (a.r, -a.x, -a.y, -a.z) . y
+	 *     = (-a.x * -a.y) - (a.r * -a.z) + (a.z * a.r) + (-a.y * -a.x)
+	 *     = a.x * a.y + a.r * a.z + a.z * a.r + a.y * a.x
+	 *
+	 * The X value will be the cosine of the rotation. The Y value will be the
+	 * sine of the rotation; use the sign of that to figure out which direction from
+	 * zero we've headed
+	 */
+
+	public double azimuth() {
+		double rotx = rotation.x * rotation.x + rotation.r * rotation.r - rotation.z * rotation.z - rotation.y * rotation.y;
+		double roty = rotation.x * rotation.y + rotation.r * rotation.z + rotation.z * rotation.r + rotation.y * rotation.x;
+
+		double az = Math.acos(rotx) * 180.0 / Math.PI;
+		if (roty < 0)
+			return -az;
+		return az;
+	}
+
+	/* 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 & 1) == 0 ? 1 : -1;
+		AltosQuaternion	up = new AltosQuaternion(0, 0, 0, sky);
+		rotation = up.vectors_to_rotation(orient);
+	}
+
+	public AltosRotation() {
+		rotation = new AltosQuaternion();
+	}
+}