X-Git-Url: http://git.scottworley.com/nt3d/blobdiff_plain/34592f10eb3e47c8f6738aceb5ff5ea48acb089c..08b46dbddc6defd45926a69631e3a09ea2273e45:/nt3d.js

diff --git a/nt3d.js b/nt3d.js
index 9eee504..7198e22 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/
@@ -281,8 +288,8 @@ nt3d = {
 		// by crossing a and b to get a rotation axis and using
 		// angle_between to get a rotation angle.
 		var angle = this.angle_between(this.unit(a), this.unit(b));
-		if (Math.abs(angle) < 1e-15) {
-			// No siginificant rotation to perform.  Bail to avoid
+		if (Math.abs(angle) < 1e-7) {
+			// No significant rotation to perform.  Bail to avoid
 			// NaNs and numerical error
 			return points;
 		}