X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=altoslib%2FAltosRotation.java;h=85e213b25f5a0ef0700c3151b6723ee8ff34b925;hb=3ed101d634968666cd3ee2d8c49737970caf406b;hp=eec8c5296fd8956ba4f89f35b382c8bdc832cd2f;hpb=13abb6739ae9be5a8733724c5d9b3f714f32bea4;p=fw%2Faltos

diff --git a/altoslib/AltosRotation.java b/altoslib/AltosRotation.java
index eec8c529..85e213b2 100644
--- a/altoslib/AltosRotation.java
+++ b/altoslib/AltosRotation.java
@@ -16,7 +16,7 @@
  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
  */
 
-package org.altusmetrum.altoslib_12;
+package org.altusmetrum.altoslib_14;
 
 public class AltosRotation extends AltosQuaternion {
 	private AltosQuaternion		rotation;
@@ -29,7 +29,7 @@ public class AltosRotation extends AltosQuaternion {
 	 *
 	 * 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.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
@@ -50,6 +50,34 @@ public class AltosRotation extends AltosQuaternion {
 		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
 	 */
@@ -69,7 +97,7 @@ public class AltosRotation extends AltosQuaternion {
 			     double z,
 			     int pad_orientation) {
 		AltosQuaternion	orient = AltosQuaternion.vector(x, y, z).normalize();
-		double sky = pad_orientation == 0 ? 1 : -1;
+		double sky = (pad_orientation & 1) == 0 ? 1 : -1;
 		AltosQuaternion	up = new AltosQuaternion(0, 0, 0, sky);
 		rotation = up.vectors_to_rotation(orient);
 	}