ShadowMapPlugin: Copy instead of reference.

src/extras/renderers/plugins/ShadowMapPlugin.js

@@ -100,7 +100,7 @@ THREE.ShadowMapPlugin = function () {
 						virtualLight.originalCamera = camera;
 
 						var gyro = new THREE.Gyroscope();
-						gyro.position = light.shadowCascadeOffset;
+						gyro.position.copy( light.shadowCascadeOffset );
 
 						gyro.add( virtualLight );
 						gyro.add( virtualLight.target );