From 72eac64d07af484314745fd0e9466e0f94915684 Mon Sep 17 00:00:00 2001
From: Scott Worley <ScottWorley@ScottWorley.com>
Date: Sun, 30 Dec 2012 22:56:34 -0800
Subject: [PATCH 1/1] Explicitly bounds-check in angle_between()

This avoids introducing NaNs due to numerical error while measuring
extreme angles -- angles near 0 or pi radians.
---
 nt3d.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/nt3d.js b/nt3d.js
index 9eee504..0389946 100644
--- a/nt3d.js
+++ b/nt3d.js
@@ -259,7 +259,14 @@ nt3d = {
 		        point[2] + offset[2]];
 	},
 	angle_between: function(a, b) { // a and b must be unit vectors
-		return Math.acos(this.dot(a, b));
+		var the_dot = this.dot(a, b);
+		if (the_dot <= -1) {
+			return Math.PI;
+		}
+		if (the_dot >= 1) {
+			return 0;
+		}
+		return Math.acos(the_dot);
 	},
 	rotate_about_origin: function(points, axis, angle) { // axis must be a unit vector
 		// From http://inside.mines.edu/~gmurray/ArbitraryAxisRotation/
-- 
2.44.1