• 平視顯示器（HUD）
  
  • 上述的HUD和集成信息融入環(huán)境將是理想的。
  • 在目標上直接描繪十字，比一個固定的深度平面更佳。
  • 特寫武器和工具可能會導致視疲勞；當不使用他們時，可讓他們成為視野外替身的一部分。
• 替身有他們的優(yōu)點和缺點；他們可以讓用戶置身在虛擬環(huán)境中，但當你在現(xiàn)實世界中的身體運動與虛擬的有差異時，會感覺到異常。

平視顯示器（HUD）

一般說來，Oculus不鼓勵使用傳統(tǒng)的HUD。相反，我們鼓勵開發(fā)者嵌入信息到環(huán)境本身。雖然，在立體視覺要求下重新設計，使得有些舊的約定可以起作用（參見：下面十字線的例子），但是簡單的從一個非VR的游戲移植VR的內容到HUD上會引進新的問題，使得傳統(tǒng)方法不切實際，甚至于令人不適。

首先，HUD將（出現(xiàn)在前面的）任何事物都封閉在3D的場景中。這在非立體游戲中不是問題，因為用戶可以容易地假定HUD實際上是在其他事物的前方。不幸的是，增加雙眼視覺差異（圖像投射到每個眼睛的細微差別）作為一個深度線索，如果一個場景元素比起HUD的深度平面更接近用戶，會造成矛盾：基于閉合，HUD被感知比場景元素更近，因為它覆蓋了它后面所有的事物，然而雙眼視覺差異表明，HUD比它所閉合的場景元素更遠。當用戶試圖融合HUD和外界中的圖像時，可能引起困難及（或）不適。

雖然使HUD與用戶更近會避免阻塞和差距上的視覺矛盾，但是為了避免問題，必要條件是使界面比建議的最小舒適距離75cm還要近。設置玩家在HUD的深度剪裁邊界同樣引入了問題，因為用戶會覺得人為地遠離環(huán)境中的對象。盡管他們可能在特定的背景中工作，可以規(guī)避這些問題，但是HUD將很快被認為像VR中一個笨重的遺棄物，常常應被廢棄，轉而采用更加人性化的選擇。

相反，考慮構建信息化設備進入到環(huán)境本身。請記住，用戶可以以自然和直觀的方式移動頭部來收集信息，這在傳統(tǒng)的視頻游戲中是不起作用的。例如，相較于HUD中的迷你地圖和指南針，玩家可能會通過他們替身的手或駕駛艙在實際的地圖和指南針中向下傾斜來獲得他們的方位。這并不是說現(xiàn)實主義是必要的；敵人的健康指標會神奇地漂浮在他們頭的上方。最重要的是以一種清晰、舒適的方式展示信息，當用戶想要獲得的一個清晰，單一的環(huán)境影像或信息時，不妨礙用戶的感知能力。

瞄準十字線是適應舊范例到VR的一個卓越的例證。然而一個十字線對精確的瞄準是決定性的，簡單地粘貼在一個固定的深度平面場景上將不會產出用戶在游戲中期待的十字線行為。如果十字線出現(xiàn)在深度平面上的與眼睛聚焦到的不同，它會被認為是兩個圖形。為了使定位十字線以在傳統(tǒng)視頻游戲中相同的方式工作，它必須直接繪制在屏幕中作為目標的對象上，推測當用戶瞄準時眼睛會聚焦在的地方。十字線本身可以根據距離確定更大或更小的尺寸，或者你可以用編程維持絕對的大小展示給用戶；這對設計師而言，很大程度上是一種審美的決策。這表明，一些舊范例可以移植到VR，但并非為了新媒介的需求就不需要仔細的修飾和設計。

替身

在虛擬世界中，替身是一個用戶主體的可視表示形式，通常與用戶的位置、移動和姿態(tài)一致。用戶可以看到自己的虛擬身體，并觀察其他用戶如何看到他們并與他們進行互動。由于VR往往是第一人稱的體驗，許多VR應用對用戶都沒有任何形體展示，因此用戶在虛擬空間中是無形的。

替身可以有它的優(yōu)點和缺點。一方面，替身可以讓用戶在虛擬世界中，對他們身體的比例和體積有較強的感覺。另一方面，呈現(xiàn)出逼真的替身身體時，與用戶的本體感受矛盾（例如，替身正在走路而用戶是坐著的），而讓用戶覺得怪異。用Rift在公共區(qū)域演示，對于能夠看到自己的虛擬身體，用戶普遍反應積極，至少可以作為引發(fā)審美響應的手段。像其他初期的媒介一樣，用戶的測試和評估對看看有什么最適合你的體驗是必要的。

注：由于到目前為止我們只能彎曲我們的脖子，所有替身的身體只出現(xiàn)在圖像邊緣（圖4）。任何武器或工具應與替身結合在一起，因此，用戶看到替身實際持有它們。使用輸入設備進行人體運動跟蹤的開發(fā)者，應當跟蹤用戶的手或身體的其他部分，并更新替身以盡可能地減少匹配延遲。

武器和工具

在第一人稱的射擊游戲中，武器通常出現(xiàn)在屏幕的底部，放置位置仿佛用戶正在持有和瞄準他們。在空間上，這意味著該武器在該場景中比任何東西都更接近。在一個典型的非立體游戲中，這不會產生任何特殊的問題，并且我們可以接受正在看一個大的、在一個正常距離內疊加在場景上的特寫物體。

然而，當這被轉變成一個立體的實現(xiàn)，事情會變得更加復雜。渲染的武器和工具如此靠近相機，要求用戶在武器和場景內其他內容之間進行觀察時，視野有很大的變化。同樣，因為武器是如此接近觀眾，左右視野會變得明顯不同，難以形成單一的三維視圖。

我們覺得最舒服的方法是僅僅在一個無頭的、全身替身的脖子上放置相機，如上文所述。武器和工具都作為替身的一部分呈現(xiàn)，可以在使用過程中舉起他們，不使用時退出視野范圍。

在玩家看來有一些可行的“障眼法”來渲染武器和工具，雖然我們不認同他們，但是你的內容可能需要或者適合于它們的某些變化。一種可能性是，如果你有2D的武器，可在你的HUD后渲染它。這需要兼顧一些收斂性和費用的融合問題，以使得武器看起來扁平化和人工化。

另一種可能的方法是采用多操縱，以使特寫對象（例如：駕駛艙、頭盔、槍）從主世界分開，并獨立地使用環(huán)境中隔離的不同攝像機。這種方法有產生視覺缺陷的風險，諸如前景物體立體地展現(xiàn)在遠與它們背景物體的地方，因此不建議使用這種方法。

你的內容區(qū)別于這里的任何內容，那么迭代試驗和用戶測試可能會為你的內容揭示最佳的解決方案。但是目前我們的建議是將武器和工具作為用戶替身的一個組成部分來實現(xiàn)。

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原文如下

• Heads-Up Display (HUD)
  
  • Foregoing the HUD and integrating information into the environment would be ideal.
  • Paint reticles directly onto targets rather than a fixed depth plane.
  • Close-up weapons and tools can lead to eyestrain; make them a part of the avatar that drops out of view when not in use.
• Avatars have their pros and cons; they can ground the user in the virtual environment, but also feel unusual when discrepant from what your real world body is doing.

Heads-Up Display (HUD)

In general, Oculus discourages the use of traditional HUDs. Instead, we encourage developers to embed that information into the environment itself. Although certain old conventions can work with thoughtful re-design that is mindful of the demands of stereoscopic vision (see: reticle example below), simply porting over the HUD from a non-VR game into VR content introduces new issues that make them impractical or even discomforting.

First, HUDs occlude (appear in front of) everything in the 3D scene. This isn’t a problem in non-stereoscopic games, because the user can easily assume that the HUD actually is in front of everything else. Unfortunately, adding binocular disparity (the slight differences between the images projected to each eye) as a depth cue can create a contradiction if a scene element comes closer to the user than the depth plane of the HUD: based on occlusion, the HUD is perceived as closer than the scene element because it covers everything behind it, yet binocular disparity indicates that the HUD is farther away than the scene element it occludes. This can lead to difficulty and/or discomfort when trying to fuse the images for either the HUD or the environment.

Although moving the HUD closer to the user might prevent visual contradictions of occlusion and disparity, the proximity necessary to prevent problems will most likely bring the interface closer than the recommended minimum comfortable distance, 75 cm. Setting the player’s clipping boundary at the depth of the HUD similarly introduces issues, as users will feel artificially distanced from objects in the environment. Although they might work within particular contexts that can circumvent these issues, HUDs can quickly feel like a clunky relic in VR and generally should be deprecated in favor of more user-friendly options.

Instead, consider building informational devices into into the environment itself. Remember that users can move their heads to glean information in a natural and intuitive way that might not work in traditional video games. For instance, rather than a mini map and compass in a HUD, the player might get their bearings by glancing down at an actual map and compass in their avatar’s hands or cockpit. This is not to say realism is necessary; enemy health gauges might float magically over their heads. What’s important is presenting information in a clear and comfortable way that does not interfere with the player’s ability to perceive a clear, single image of the environment or the information they are trying to gather.

Targeting reticles are an excellent illustration of adapting old paradigms to VR. While a reticle is critical for accurate aiming, simply pasting it over the scene at a fixed depth plane will not yield the reticle behavior players expect in a game. If the reticle appears at a depth plane different from where the eyes are converged, it is perceived as a double image. In order for the targeting reticle to work the same way it does in traditional video games, it must be drawn directly onto the object it is targeting on screen, presumably where the user’s eyes are converged when aiming. The reticle itself can be a fixed size that appears bigger or smaller with distance, or you can program it to maintain an absolute size to the user; this is largely an aesthetic decision for the designer. This simply goes to show that some old paradigms can be ported over to VR, but not without careful modification and design for the demands of the new medium.

Avatars

An avatar is a visible representation of a user’s body in a virtual world that typically corresponds to the user’s position, movement and gestures. The user can see their own virtual body and observe how other users see and interact with them. Since VR is often a first person experience, many VR applications dispense with any representation of the user whatsoever, and therefore the user is simply disembodied in virtual space.

An avatar can have its pros and cons. On the one hand, an avatar can give the user a strong sense of scale and of their body’s volume in the virtual world. On the other hand, presenting a realistic avatar body that contradicts the user’s proprioception (e.g., a walking body while they are seated) can feel peculiar. At public demonstrations with the Rift, users generally react positively to being able to see their virtual bodies, and so can at least serve as a means of eliciting an aesthetic response. Like anything else in this young medium, user testing and evaluation are necessary to see what works best for your experience.

Note: Since we can only bend our neck so far, the avatar’s body only appears at the very edge of the image (figure 4). Any weapons or tools should be integrated with the avatar, so the user sees the avatar actually holding them. Developers that use input devices for body tracking should track the user’s hands or other body parts and update the avatar to match with as little latency as possible.

Weapons and Tools

In first person shooters, weapons typically appear towards the bottom of the screen, positioned as though the user is holding and aiming them. Spatially, this means that the weapon is much closer than anything else in the scene. In a typical non-stereoscopic game, this doesn’t create any special problems, and we accept that we are seeing a big, close-up object superimposed over a scene at a normal distance.

However, when this is translated into a stereoscopic implementation, things get a little more complicated. Rendering weapons and tools so close to the camera requires the user to make large changes in eye convergence when looking between the weapon to the rest of the scene. Also, because the weapon is so close to the viewer, the left and right views can be significantly different and difficult to resolve into a single threedimensional view.

The approach we find most comfortable is to position the cameras just above the neck of a headless, full-body avatar, as described above. Weapons and tools are rendered as part of the user avatar, which can hold them up during use, but otherwise drop them out of view.

There are some possible “cheats” to rendering weapons and tools in the player’s view, and although we do not endorse them, your content might require or be suited to some variation on them. One possibility is to render weapons in 2D, behind your HUD if you have one. This takes care of some of the convergence and fusion problems at the expense of making the weapon look flat and artificial.

Another possible approach is to employ multi-rigging, so that close-up objects (e.g., cockpit, helmet, gun) are separate from the main world and independently employ a different camera separation from the environment. This method runs the risk of creating visual flaws, such as foreground objects appearing stereoscopically further away than the background behind them, and are discouraged.

Iterative experimentation and user testing might reveal an optimal solution for your content that differs from anything here, but our current recommendation is to implement weapons and tools as a component of the user’s avatar.