From 2ee3f055058d10ec7a50182e102ba0a235878f71 Mon Sep 17 00:00:00 2001
From: "David A. Madore" <david+git@madore.org>
Date: Tue, 27 Mar 2012 16:08:35 +0200
Subject: Simple matrix library + formula for precession.

---
 org/madore/ephem/Frames.java | 85 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 org/madore/ephem/Frames.java

(limited to 'org/madore/ephem/Frames.java')

diff --git a/org/madore/ephem/Frames.java b/org/madore/ephem/Frames.java
new file mode 100644
index 0000000..e85412c
--- /dev/null
+++ b/org/madore/ephem/Frames.java
@@ -0,0 +1,85 @@
+package org.madore.ephem;
+
+public final class Frames {
+
+    private static double[] unboxDoubleArray(Double[] c) {
+	double[] unboxed = new double[c.length];
+	for ( int i=0 ; i<unboxed.length ; i++ )
+	    unboxed[i] = c[i];
+	return unboxed;
+    }
+
+    public static final class Vector {
+	double[] crd;
+	public Vector(double... crd) {
+	    if ( crd.length != 3 )
+		throw new IllegalArgumentException("Vector constructor expects 3 coordinates");
+	    this.crd = crd;
+	}
+	public Vector(Double... crd) {
+	    this(unboxDoubleArray(crd));
+	}
+	public double dotprod(Vector v) {
+	    double res = 0;
+	    for ( int i=0 ; i<3 ; i++ )
+		res += crd[i]*v.crd[i];
+	    return res;
+	}
+	public double sqnorm() {
+	    double res = 0;
+	    for ( int i=0 ; i<3 ; i++ )
+		res += crd[i]*crd[i];
+	    return res;
+	}
+    }
+
+    public static final class RotationMatrix {
+	double[][] mat;
+	public RotationMatrix(double[][] mat) {
+	    if ( mat.length != 3 )
+		throw new IllegalArgumentException("RotationMatrix constructor expects 3 lines");
+	    for ( int i=0 ; i<3 ; i++ )
+		if ( mat[i].length != 3 )
+		    throw new IllegalArgumentException("RotationMatrix constructor expects 3 columns");
+	    this.mat = mat;
+	}
+	private static double[][] matOfVectors(Vector[] vecs) {
+	    double[][] mat = new double[vecs.length][];
+	    for ( int i=0 ; i<mat.length ; i++ )
+		mat[i] = vecs[i].crd;
+	    return mat;
+	}
+	public RotationMatrix(Vector... vecs) {
+	    this(matOfVectors(vecs));
+	}
+	public Vector apply(double[] v) {
+	    double out[] = new double[3];
+	    for ( int i=0 ; i<3 ; i++ )
+		for ( int j=0 ; j<3 ; j++ )
+		    out[i] += v[j]*mat[j][i];
+	    return new Vector(out);
+	}
+	public Vector apply(Vector v) {
+	    return apply(v.crd);
+	}
+	public RotationMatrix apply(RotationMatrix mv) {
+	    return new RotationMatrix(this.apply(mv.mat[0]), this.apply(mv.mat[1]), this.apply(mv.mat[2]));
+	}
+	public static RotationMatrix rotx(double theta) {
+	    return new RotationMatrix(new Vector(1, 0, 0),
+				      new Vector(0, Math.cos(theta), -Math.sin(theta)),
+				      new Vector(0, Math.sin(theta), Math.cos(theta)));
+	}
+	public static RotationMatrix roty(double theta) {
+	    return new RotationMatrix(new Vector(Math.cos(theta), 0, Math.sin(theta)),
+				      new Vector(0, 1, 0),
+				      new Vector(-Math.sin(theta), 0, Math.cos(theta)));
+	}
+	public static RotationMatrix rotz(double theta) {
+	    return new RotationMatrix(new Vector(Math.cos(theta), -Math.sin(theta), 0),
+				      new Vector(Math.sin(theta), Math.cos(theta), 0),
+				      new Vector(0, 0, 1));
+	}
+    }
+
+}
-- 
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