+/**
+ * Get the angle between two 3D vectors
+ * @param {vec3} a The first operand
+ * @param {vec3} b The second operand
+ * @returns {Number} The angle in radians
+ */
+vec3.angle = function(a, b) {
+
+ var tempA = vec3.fromValues(a[0], a[1], a[2]);
+ var tempB = vec3.fromValues(b[0], b[1], b[2]);
+
+ vec3.normalize(tempA, tempA);
+ vec3.normalize(tempB, tempB);
+
+ var cosine = vec3.dot(tempA, tempB);
+
+ if(cosine > 1.0){
+ return 0;
+ } else {
+ return Math.acos(cosine);
+ }
+};
+