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.

在科技行業(yè)，最新的流行詞是AR（增強(qiáng)現(xiàn)實(shí)）和VR（虛擬現(xiàn)實(shí)）。VR方面最突出的代表是臉書的Oculus Rift頭戴式顯示器，而AR在智能手機(jī)應(yīng)用中更為常見，如Snapchat和Pokémon Go等。上周，蘋果發(fā)布了專為開發(fā)人員設(shè)計(jì)的ARKit，這一工具包能讓前述應(yīng)用的開發(fā)變得簡單，此舉讓AR再次成為新聞焦點(diǎn)。不過，普通人很難說出兩者的區(qū)別。其實(shí)，區(qū)分VR和AR的最簡單的方法就是看虛擬Pokémon的背后能否看到真實(shí)的世界（很多業(yè)內(nèi)人更愿意稱之為RR，即“真實(shí)的現(xiàn)實(shí)”）。如果能，那就是AR;戴上護(hù)目鏡以后，如果眼前的一切都是數(shù)字化的——包括你自己的手，那么你就是沉浸于VR中。

增強(qiáng)現(xiàn)實(shí)

臉書的首席執(zhí)行官扎克伯格曾談及AR的三大用途：展現(xiàn)相機(jī)捕捉到的信息，如指示和消息等;添加數(shù)字物體;以及美化真實(shí)物體，如房間或臉部等。在臉書的“相機(jī)特效平臺”，開發(fā)和設(shè)計(jì)人員可以把三維數(shù)字物體添加到臉書的圖片和視頻中，如Snapchat風(fēng)格的自拍面具以及能在真實(shí)墻壁上顯現(xiàn)的虛擬涂鴉等。蘋果對AR的展望完全不同，開發(fā)人員有權(quán)利用其相機(jī)技術(shù)并可把開發(fā)成果應(yīng)用到他們自己的應(yīng)用軟件中。有了ARKit，設(shè)計(jì)人員或應(yīng)用開發(fā)商就能輕松地把數(shù)字物體放在真實(shí)場景中，比如可以把一個虛擬的咖啡杯放到廚桌上。VR是對我們自身之外的虛擬世界的呈現(xiàn)，而AR則把數(shù)字元素嵌入我們的視野，以此增強(qiáng)現(xiàn)實(shí)世界。

虛擬現(xiàn)實(shí)

如果說AR主要使用的是我們早已具備的設(shè)備——智能手機(jī)，那么VR需要一些其他的工具?？梢园阉胂蟪梢环N要戴在臉上的電子游戲，只是這種電子游戲能夠模擬從出行（谷歌地球已有VR版）到教育（如廣受歡迎的手術(shù)模擬器）的任何事物。以O(shè)culus Rift和HTC Vive為代表的VR頭顯，屏幕與智能手機(jī)的屏幕并無二致，它們把屏幕固定在距離眼睛只有幾英寸的地方。借助頭顯內(nèi)部以及有時會安置在房間內(nèi)的諸多傳感器，屏幕內(nèi)的虛擬世界可以隨著頭部的移動而真實(shí)地變換。

當(dāng)前質(zhì)量最好的VR頭顯必須基于高配電腦或PlayStation游戲機(jī)進(jìn)行使用。從本周起，部分蘋果Mac筆記本也可以支持HTV Vive了。

關(guān)于視頻要注意：不管多逼真，VR涉及的應(yīng)用和體驗(yàn)都完全是由計(jì)算機(jī)圖形學(xué)創(chuàng)造出來的。如果頭顯中的世界是360度相機(jī)拍攝的真實(shí)世界鏡頭，一般稱為“全景視頻”而不是VR。

混合現(xiàn)實(shí)

除了AR和VR，另一個流行的縮略詞是MR——混合現(xiàn)實(shí)，以此來稱呼以微軟的HoloLens為代表的一類頭顯。還有更讓人困惑的，近來筆者發(fā)現(xiàn)有些技術(shù)人員開始用另一個超級縮略詞——XR——來囊括上述三類，其中X似乎就代表“上述所有”。某種程度上，混合現(xiàn)實(shí)最難定義，因?yàn)闃I(yè)界對該術(shù)語的含義似乎少有一致意見。其中一種理解思路是，MR把AR效果融于VR頭顯中，讓人通過鏡片看到真實(shí)的世界。

微軟的HoloLens頭顯是一種把數(shù)字物體直接置于視野之中的眼鏡，并且終有一天這種視野會與現(xiàn)實(shí)難分真假。

（譯者單位：北京航空航天大學(xué)）