Update Camera.html

docs/api/zh/cameras/Camera.html

@@ -70,13 +70,13 @@
 
 		<h3>[method:Vector3 getWorldDirection]( [param:Vector3 target] )</h3>
 		<p>
-		[page:Vector3 target] — the result will be copied into this Vector3. <br /><br />
+		[page:Vector3 target] — 调用该函数的结果将复制给的Vector3对象。<br /><br />
 
-		Returns a [page:Vector3] representing the world space direction in which the camera is looking.
-		(Note: A camera looks down its local, negative z-axis).<br /><br />
+		返回一个能够表示当前摄像机所正视的世界空间方向的[page:Vector3]对象。
+		（注意：摄像机俯视时，其Z轴坐标为负。）<br /><br />
 		</p>
 
-		<h2>Source</h2>
+		<h2>源代码</h2>
 
 		[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]
 	</body>