Quaternion.setFromUnitVectors(): Fixed edge case

src/math/Quaternion.js

@@ -258,19 +258,41 @@ THREE.Quaternion.prototype = {
 
 	setFromUnitVectors: function () {
 
-		// http://lolengine.net/blog/2013/09/18/beautiful-maths-quaternion-from-vectors
+		// http://lolengine.net/blog/2014/02/24/quaternion-from-two-vectors-final
 
 		// assumes direction vectors vFrom and vTo are normalized
 
-		var v1;
+		var v1, r;
+
+		var EPS = 0.000001;
 
 		return function( vFrom, vTo ) {
 
 			if ( v1 === undefined ) v1 = new THREE.Vector3();
 
-			v1.crossVectors( vFrom, vTo );
+			r = vFrom.dot( vTo ) + 1;
+
+			if ( r < EPS ) {
+
+				r = 0;
+
+				if ( Math.abs( vFrom.x ) > Math.abs( vFrom.z ) ) {
+
+					v1.set( - vFrom.y, vFrom.x, 0 );
+
+				} else {
+
+					v1.set( 0, - vFrom.z, vFrom.y );
+
+				}
+
+			} else {
+
+				v1.crossVectors( vFrom, vTo );
+
+			}
 
-			this.set( v1.x, v1.y, v1.z, vFrom.dot( vTo ) + 1 ).normalize();
+			this.set( v1.x, v1.y, v1.z, r ).normalize();
 
 			this._updateEuler();