虚拟现实还是增强现实？看这里

蒂姆·布拉德肖

The latest tech industry buzzwords are AR （augmented reality） and VR （virtual reality）. The most prominent example of VR is the Facebook-owned Oculus Rift1 headset， while AR is more commonly associated with smartphone apps such as Snapchat and Pokémon Go. Last week， Apple launched ARKit—a toolkit for developers that will make creating apps like those much easier， thrusting AR back into the headlines. To the casual observer， though， it can be hard to tell the difference. The easiest way to distinguish between VR and AR is whether you can still see the real world （or RR， short for “real reality”， as some insiders perversely2 enjoy calling it） behind the virtual Pokémon. If you can， that is AR. If everything around you is digital—even the hand you hold up in front of your begoggled3 face—you know you are immersed in VR.

Augmented reality

Facebook’s chief， Mr. Zuckerberg， talks about three main uses for AR： displaying information depending on what the camera sees， such as directions or messages; adding digital objects; and enhancing real objects， like your home or your face. Facebook’s “camera effects platform” allows developers and designers to put 3D digital objects inside photos or videos in Facebook， ranging from Snapchat-style selfie masks to virtual graffiti that appears on real walls. Apple’s vision for AR turns this inside out， giving developers access to its camera technology and allowing them to bring the results to their own apps. Its ARKit makes it easy for a designer or app maker to position a digital object in a scene， like putting a virtual coffee cup on your kitchen table. Where VR is a virtual representation of a reality outside our own， AR inserts digital elements into our field of view to augment our existing world.

Virtual reality

If AR mostly uses the devices we already have—smartphones—then VR requires some extra kit. Think of it as a video game that you wear on your face， but with the ability to simulate anything from travel （Google Earth is now on VR） to education （surgery simulators are a popular example）. VR headsets such as Oculus Rift and HTC Vive put a screen not dissimilar to a smartphone’s just a few inches away from your eyes. When the head moves， the virtual world moves around realistically， thanks to an array of sensors， both inside the headset and， sometimes， set up around the room.

The highest-quality VR headsets today must be tethered4 to a powerful PC or PlayStation games console5 to function. As of this week， some of Apple’s Macs can also support the HTC Vive， too.

A note about video： VR tends to refer to applications and experiences conjured entirely in computer graphics， however realistic. If the world inside your headset is real-world footage filmed using a 360-degree camera， that is generally described as “spherical video” rather than VR.

Mixed reality

Alongside AR and VR， the next acronym being bandied about6 is MR— mixed reality. This is used to describe headsets such as Microsoft’s HoloLens. To confuse things even more， I am now starting to see some techies use XR， a sort of super-acronym to rule them all， where X just seems to stand for “all of the above”. Mixed reality is in some ways the hardest to define because there seems to be little agreement in the industry about what the term means. One way to think about it is it puts AR effects into something like a VR headset， so you see the real world through its lenses.

Microsoft’s HoloLens headset is a kind of eyewear that places digital objects directly in your field of vision that one day will be indistinguishable from real reality.

在科技行业，最新的流行词是AR（增强现实）和VR（虚拟现实）。VR方面最突出的代表是脸书的Oculus Rift头戴式显示器，而AR在智能手机应用中更为常见，如Snapchat和Pokémon Go等。上周，苹果发布了专为开发人员设计的ARKit，这一工具包能让前述应用的开发变得简单，此举让AR再次成为新闻焦点。不过，普通人很难说出两者的区别。其实，区分VR和AR的最简单的方法就是看虚拟Pokémon的背后能否看到真实的世界（很多业内人更愿意称之为RR，即“真实的现实”）。如果能，那就是AR;戴上护目镜以后，如果眼前的一切都是数字化的——包括你自己的手，那么你就是沉浸于VR中。

增强现实

脸书的首席执行官扎克伯格曾谈及AR的三大用途：展现相机捕捉到的信息，如指示和消息等;添加数字物体;以及美化真实物体，如房间或脸部等。在脸书的“相机特效平台”，开发和设计人员可以把三维数字物体添加到脸书的图片和视频中，如Snapchat风格的自拍面具以及能在真实墙壁上显现的虚拟涂鸦等。苹果对AR的展望完全不同，开发人员有权利用其相机技术并可把开发成果应用到他们自己的应用软件中。有了ARKit，设计人员或应用开发商就能轻松地把数字物体放在真实场景中，比如可以把一个虛拟的咖啡杯放到厨桌上。VR是对我们自身之外的虚拟世界的呈现，而AR则把数字元素嵌入我们的视野，以此增强现实世界。

虚拟现实

如果说AR主要使用的是我们早已具备的设备——智能手机，那么VR需要一些其他的工具。可以把它想象成一种要戴在脸上的电子游戏，只是这种电子游戏能够模拟从出行（谷歌地球已有VR版）到教育（如广受欢迎的手术模拟器）的任何事物。以Oculus Rift和HTC Vive为代表的VR头显，屏幕与智能手机的屏幕并无二致，它们把屏幕固定在距离眼睛只有几英寸的地方。借助头显内部以及有时会安置在房间内的诸多传感器，屏幕内的虚拟世界可以随着头部的移动而真实地变换。

当前质量最好的VR头显必须基于高配电脑或PlayStation游戏机进行使用。从本周起，部分苹果Mac笔记本也可以支持HTV Vive了。

关于视频要注意：不管多逼真，VR涉及的应用和体验都完全是由计算机图形学创造出来的。如果头显中的世界是360度相机拍摄的真实世界镜头，一般称为“全景视频”而不是VR。

混合现实

除了AR和VR，另一个流行的缩略词是MR——混合现实，以此来称呼以微软的HoloLens为代表的一类头显。还有更让人困惑的，近来笔者发现有些技术人员开始用另一个超级缩略词——XR——来囊括上述三类，其中X似乎就代表“上述所有”。某种程度上，混合现实最难定义，因为业界对该术语的含义似乎少有一致意见。其中一种理解思路是，MR把AR效果融于VR头显中，让人通过镜片看到真实的世界。

微软的HoloLens头显是一种把数字物体直接置于视野之中的眼镜，并且终有一天这种视野会与现实难分真假。

（译者单位：北京航空航天大学）