question: Why would it be possible to see a ball inside a closed box in a 4d world but not a 3d world?
comment: Let's reduce the dimensionality of it, and consider the case of a 2D circle inside a 2D square, as viewed by yourself and Mr. Stick Figure, a flatlander. As a flatlander, Mr. Figure can only see forwards/backwards and up/down. He sees everything as lines that are closer or further away from him, or higher up/lower down than he is. He can also rotate objects only so that they roll towards him or away from him. Left and right do not exist for him, and so if he puts a circle in a square, there is no "other" direction for him to move in to go "around" the walls of his square safe. Except, as a 3D creature observing Mr. Figure sliding around on your wall, you can clearly see the alternate direction. Mr. Figure is thinner than a piece of paper and can't even conceptualize something that is off his wall, but you could just reach out and poke the ball inside the safe, since there's no wall blocking your access from the third dimension. You could also poke inside of his brains if you wanted, because his skull is just a 2D oval, not a 3D ovoid. If you've got some time, look at URL_0 . I've put in a timestamp near the good part of the explanation, but it's a full movie on the subject if you're interested.
passages: Recent developments of consumer virtual reality headsets such as for example Oculus Rift, HTC Vive, PlayStation VR, Fove, and Open Source Virtual Reality also include stereoscopic support as one of their features. The entire development trend of games and other software for such head-mounted displays remains to be seen.
  
  Section::::Rendering techniques.
  
  There are two primary rendering techniques employed in stereoscopic video games: 2D + depth rendering, and dual rendered 3D.
  
  Section::::Rendering techniques.:2D + depth rendering.
   Section::::History.:2010s.
   Although no longer considered a key feature for successful game development by as many as during the stereoscopic 3D hype in 2010, stereoscopic support for video games is still considered a minor enhancement to video games. One of the reasons for the technology's lack of success was that the surprise effect quickly wears off.
   Even simple shading and size of an image could be considered pseudo-3D, as shading makes it look more realistic. If the light in a 2D game were 2D, it would only be visible on the outline, and because outlines are often dark, they would not be very clearly visible. However, any visible shading would indicate the usage of pseudo-3D lighting and that the image uses pseudo-3D graphics. Changing the size of an image can cause the image to appear to be moving closer or further away, which could be considered simulating a third dimension.
   On a larger scale, the 2018 movie "In Saturn's Rings" used over 7.5 million separate two-dimensional images, captured in space or by telescopes, which were composited and moved using multi-plane animation techniques.
  
  Section::::Graphic design.
   Basic binocularity is already developed when the child is from 6 to 12 months old. Vision is well formed when reaching the age of 3 years, by this moment children can watch three-dimensional graphics without involving risks to their eye health.
  
  In case of presenting PSE (Photosensitive epilepsy), precautions should be taken. The risk of an episode is present with 3D viewing as with 2D viewing. Although the risks are present in both cases there is no evidence, whatsoever that points out that 3D factors in visual effects have a greater influence on inducing PSE.
   Film critic Mark Kermode, a noted detractor of 3D, has surmised that there is an emerging policy of distributors to limit the availability of 2D versions, thus "railroading" the 3D format into cinemas whether the paying filmgoer likes it or not. This was especially prevalent during the release of "Prometheus" in 2012, where only 30% of prints for theatrical exhibition (at least in the UK) were in 2D. His suspicions were later reinforced by a substantial number of complaints about "Dredd" from those who wished to see it in 2D but were denied the opportunity. In July 2017, IMAX announced that they will begin to focus on screening more Hollywood tentpole movies in 2D (even if there's a 3D version) and have fewer 3D screenings of movies in North America, citing that moviegoers in North America prefer 2D films over 3D films.
   Production studios are developing an increasing number of 3D titles for the cinema and as many as a dozen companies are actively working on the core technology behind the product. Many have technologies available to demonstrate, but no clear road forward for a mainstream offering has emerged.
   Nintendo has stated that a parental control involving a PIN would allow parents to disable autostereoscopic effects. Playing games in 3D has been suspected of causing headaches among some gamers. The dizziness experienced by some users may be explained similarly to the headaches that watchers of 3D movies have similarly experienced, which is believed to be due to confusion caused by a lack of visual cues that humans use to perceive depth in their everyday environment.
   Though 3D movies were generally well received by the public, 3D television did not become popular until after the CES 2010 trade show, when major manufacturers began selling a full lineup of 3D televisions. According to DisplaySearch, 3D television shipments totaled 41.45 million units in 2012, compared with 24.14 in 2011 and 2.26 in 2010. In late 2013, the number of 3D TV viewers started to decline, and in 2016, development of 3D TV is limited to a few premium models.
  
  Section::::Technologies.
   Stereoscopic video games have been available for several years for PCs through the Nvidia 3D Vision and other platforms including AMD HD3D, DDD TriDef that use compatible hardware and active shutter 3D glasses. For video game consoles, however, stereoscopic 3D support must be specifically built into each game. Potential stereoscopic game support is available, for instance, on Xbox 360, PlayStation 3, Xbox One, Wii U and PlayStation 4. Nintendo 3DS is fully designed for autostereoscopic games.
   Director Christopher Nolan has criticised the notion that traditional film does not allow depth perception, saying "I think it's a misnomer to call it 3D versus 2D. The whole point of cinematic imagery is it's three dimensional... You know 95% of our depth cues come from occlusion, resolution, color and so forth, so the idea of calling a 2D movie a '2D movie' is a little misleading." Nolan also criticised that shooting on the required digital video does not offer a high enough quality image and that 3D cameras cannot be equipped with prime (non-zoom) lenses.
   So far, the ability to reconstruct scenes with occlusion and other position-dependent effects have been at the expense of vertical parallax, in that the 3D scene appears distorted if viewed from locations other than those the scene was generated for.
   In February 2012 Telecable de Tricom, a major Dominican cable TV provider, announced the launch of the first 3D TV programming package in Latin America. As of 10 August 2012 the only 3D channels available are Wildearth, 3 Flow 3D, and High TV 3D.
  
  Avi Arad is currently developing a 3D Pac-Man TV show.
  
  The Xbox Live broadcasts of the 2012 Miss Universe and Miss USA beauty pageants were available in RealD 3D.
  
  In 2013, in Brazil, NET HD pay-per-view broadcastes of the thirteenth season of "Big Brother Brasil" were available in 3D.
   Ever since "Monsters vs. Aliens" was made, all feature films released by DreamWorks Animation were produced in a stereoscopic 3-D format, using Intel's InTru3D technology. IMAX 3D, RealD and 2D versions were released.
  
  Section::::Release.
  
  Section::::Release.:Marketing.
   As a viewer moves through a 3D scene, it is common for the skybox or skydome to remain stationary with respect to the viewer. This technique gives the skybox the illusion of being very far away since other objects in the scene appear to move, while the skybox does not. This imitates real life, where distant objects such as clouds, stars and even mountains appear to be stationary when the viewpoint is displaced by relatively small distances. Effectively, everything in a skybox will always appear to be infinitely distant from the viewer. This consequence of skyboxes dictates that designers should be careful not to carelessly include images of discrete objects in the textures of a skybox since the viewer may be able to perceive the inconsistencies of those objects' sizes as the scene is traversed.
   Discounting 3D television and cinema (which generally require more than one digital projector whose moving images are mechanically coupled, in the case of IMAX 3D cinema), several stereoscopic LCDs are going to be offered by Sharp, which has already started shipping a notebook with a built in stereoscopic LCD. Although older technology required the user to don goggles or visors for viewing computer-generated images, or CGI, newer technology tends to employ Fresnel lenses or plates over the liquid crystal displays, freeing the user from the need to put on special glasses or goggles.
  
  Section::::Stereopsis tests.
   As volumetric video developed into a commercially applicable approach to environment and performance capture, the ability to move about the results with six degrees of freedom and true stereoscopy necessitated a new type of display device. With the rise of consumer-facing VR in 2016 through devices such as the Oculus Rift and HTC Vive, this was suddenly possible. Stereoscopic viewing and the ability to rotate and move the head as well as move in a small space allows immersion into environments well beyond what was possible in the past. The photographic nature of the captures combined with this immersion and the resulting interactivity is one giant step closer to being the holy grail of true virtual reality. With the rise of 360º video content, the demand for 6-DOF capture is rising, and VR in particular drives the applications for this technology, slowly fusing cinema, games and art with the field of volumetric capture research.
   On 28 September 2010, Virgin Media launched a 3D TV on Demand service.
   There is also an extension on the 2D-plus-Depth format called the WOWvx Declipse format. It is described in the same Philips' white paper "3D Interface Specifications". In this advanced format, two more planes are added to the original 2D image and its depth map for each frame: the background areas covered by foreground objects and their respective depth map. So, each frame in the Declipse format is described with an image containing four parts, or quadrants. This extension improves potential visual quality by providing data for more correct and precise filling of the uncovered occlusion areas created by shifting foreground objects during the multiview generation process.
   Section::::The fall of 3D television.
  
  As early as 2013, 3D televisions were being seen as a fad. DirecTV had stopped broadcasting 3D programs in 2012, while ESPN stopped in 2013. In the UK, Sky moved its content to on demand.
  
  Fewer and fewer 3D TVs were sold and soon TV manufactures stopped making them. Vizio stopped production in 2014 and was followed by others. In January 2017, the last two major television manufacturers still producing 3D televisions, Sony and LG, announced they would stop all 3D support.
  
  Section::::World record.
   Section::::Home media.
  
  Section::::Home media.:Television.
   There have been several notable examples in television where 3D episodes have been produced, typically as one-hour specials or special events.
  
  Section::::Broadcasts.:3D episodes and shows.:1980s.
   2d-plus-Depth cannot handle* transparency (semi-transparent objects in the scene) and occlusion (an object blocking the view of another). The 2d plus DOT format takes these factors into account. Additionally, it cannot handle reflection, refraction (beyond simple transparency) and other optical phenomena.
  
  Creation of accurate 2D-plus-Depth can be costly and difficult, though recent advances in range imaging have made this process more accessible.
  
  2d-plus-Depth lacks the potential increase in resolution of using two complete images.
   After capture, stereo or multi-view image data can be processed to extract 2D plus depth information for each view, effectively creating a device-independent representation of the original 3D scene. These data can be used to aid inter-view image compression or to generate stereoscopic pairs for multiple different view angles and screen sizes.
  
  2D plus depth processing can be used to recreate 3D scenes even from a single view and convert legacy film and video material to a 3D look, though a convincing effect is harder to achieve and the resulting image will likely look like a cardboard miniature.
  
  Section::::Technologies.:3D production.
  