Add 3D directional statistic

render-app/src/main/java/org/janelia/alignment/inpainting/RandomDirection3D.java

@@ -0,0 +1,38 @@
+package org.janelia.alignment.inpainting;
+
+import java.util.Random;
+
+/**
+ * A statistic that yields a completely random 3D direction for each sample.
+ */
+public class RandomDirection3D implements DirectionalStatistic {
+
+	private final Random random;
+
+	/**
+	 * Creates a new statistic with a random seed.
+	 */
+	public RandomDirection3D() {
+		this(new Random());
+	}
+
+	/**
+	 * Creates a new statistic with the given random number generator.
+	 *
+	 * @param random the random number generator to use
+	 */
+	public RandomDirection3D(final Random random) {
+		this.random = random;
+	}
+
+	@Override
+	public void sample(final double[] direction) {
+		final double x = random.nextGaussian();
+		final double y = random.nextGaussian();
+		final double z = random.nextGaussian();
+		final double norm = Math.sqrt(x * x + y * y + z * z);
+		direction[0] = x / norm;
+		direction[1] = y / norm;
+		direction[2] = z / norm;
+	}
+}