{"id":240,"date":"2011-02-21T12:28:58","date_gmt":"2011-02-21T19:28:58","guid":{"rendered":"http:\/\/www.hd4pc.com\/techblog\/?p=240"},"modified":"2011-02-21T12:28:58","modified_gmt":"2011-02-21T19:28:58","slug":"3d-display-technology","status":"publish","type":"post","link":"https:\/\/www.hd4pc.com\/techblog\/2011\/02\/21\/3d-display-technology\/","title":{"rendered":"3D Display Technology"},"content":{"rendered":"

It seems like just about every week there is a new 3D technology <\/a>being announced or released.\u00c2\u00a0 This is due to the fact that there are so many\u00c2\u00a0possible ways to present stereoscopic media to a viewer,\u00c2\u00a0but none of the existing solutions are perfect, so there is\u00c2\u00a0clear room for improvement.\u00c2\u00a0 There has been a lot of creative innovation in this regard over the last few years, which is one of\u00c2\u00a0the reasons I am\u00c2\u00a0so interested in this subject, but the variety of competing solutions can be quite confusing, especially to someone unfamiliar with any of the options.\u00c2\u00a0
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\nThere are a number of strategies that can be employed to present separate images to the viewers’ eyes.\u00c2\u00a0 The first is to mount separate displays in front of each eye, but this limits size and\u00c2\u00a0resolution, and only serves a single viewer.\u00c2\u00a0 All other options involve displaying both images on the same screen, and filtering what each eye sees.<\/p>\n

Shutter glasses <\/a>can be used with displays that have high refresh rates, to filter alternating frames from one eye or the other.\u00c2\u00a0 A 120hz display can provide 60 frames to each eye, which is enough to create smooth motion and make the blinking shutter imperceivable.\u00c2\u00a0 The disadvantage is that each viewer requires a pair of expensive active shutter glasses<\/a>, which all require charged batteries or some other source of power.<\/p>\n

Polarization<\/a> has been used in many different variations of 3D display solution.\u00c2\u00a0 The\u00c2\u00a0most straightforward\u00c2\u00a0is to use\u00c2\u00a0dual projectors, each projecting onto the same silver matte screen, with opposite polarizing filters in front of the lenses.\u00c2\u00a0 Complementary filters are used in cheap passive 3D glasses that each viewer wears, filtering out light from one projector or the other, from each eye.\u00c2\u00a0 One issue with this method is that perfectly aligning two projectors\u00c2\u00a0on a large screen\u00c2\u00a0can be\u00c2\u00a0very challenging.\u00c2\u00a0 To solve this,\u00c2\u00a0RealD<\/a>\u00c2\u00a0took this process\u00c2\u00a0a step further, and created a polarizer for a single projector that alternates the\u00c2\u00a0polarization angle at the same rate that shutter glasses usually blink.\u00c2\u00a0 The result is that the “active” part of the filtering for a 120hz projection\u00c2\u00a0is done once, and each viewer can use cheap\u00c2\u00a0passive 3D\u00c2\u00a0glasses <\/a>to separate the views for each eye, while experiencing the full resolution results offered by shutter glasses.<\/p>\n

Polarization can also be used within passive 3D LCD displays<\/a>, but currently with these solutions, any pixel is permanently polarized either right or left.\u00c2\u00a0 As long as the\u00c2\u00a0image\u00c2\u00a0sent to the screen conforms to\u00c2\u00a0the pattern, usually horizontal interlaced, it can\u00c2\u00a0send imagery from the correct angle to each individual pixel.\u00c2\u00a0 This requires a 1:1 image to pixel ratio, in order\u00c2\u00a0to ensure that\u00c2\u00a0the\u00c2\u00a0display places pixels from the correct angle in the\u00c2\u00a0correct locations.\u00c2\u00a0 The disadvantage is that usually\u00c2\u00a0half of the image resolution to each eye is lost to the filtering process.\u00c2\u00a0 Displays that have this type of built in polarization can be viewed with cheaper passive 3D glasses.\u00c2\u00a0 In my opinion, any\u00c2\u00a0passive 3D is also easier on the viewer’s\u00c2\u00a0eyes, especially over periods of extended use, since there is no alternating flicker.<\/p>\n

The cheapest, but lowest quality option for viewing stereoscopic depth information on regular displays, involves using color information to separate the\u00c2\u00a0images for each eye.\u00c2\u00a0 This is called anaglyphic<\/a>\u00c2\u00a0processing, and the benefit is that nearly any standard full color display device can be used, but it comes at the cost of most or all of the original color information being discarded.\u00c2\u00a0 Anaglyphic video can either be generated on the fly during playback from two separate streams, or rendered out into a single stream to be edited, usually as an offline version.\u00c2\u00a0 Viewing anaglyphic imagery, or even just wearing anaglyphic glasses for any significant period of time is usually not comfortable.<\/p>\n

On the other end of the spectrum, there are certain displays<\/a> available that use lenticular filters<\/a> to isolate the separate views, and\u00c2\u00a0focus them\u00c2\u00a0on each\u00c2\u00a0eye.\u00c2\u00a0 This is similar to the process used\u00c2\u00a0to create\u00c2\u00a0depth and motion effects\u00c2\u00a0on static 2D surfaces,\u00c2\u00a0called\u00c2\u00a0lenticular printing<\/a>,\u00c2\u00a0but using this method for video requires\u00c2\u00a0the underlying display to be\u00c2\u00a0extremely high resolution.\u00c2\u00a0\u00c2\u00a0With stereoscopic source, this\u00c2\u00a0results in certain areas where the effect is null or reversed, and requires the viewer to be in just the right spot for maximum effectiveness.<\/p>\n

The next step to solve that issue is to replace the alternating left and right views projected from the lenticular screen, with a series of progressively different views.\u00c2\u00a0 That way any viewing angle within reason can be accommodated for,\u00c2\u00a0without gaps where the illusion breaks down.\u00c2\u00a0\u00c2\u00a0Instead of recording every variation of viewing angle, these perspectives are usually generated on the fly from a single recorded perspective, usually with the help of a Z-depth map<\/a>.\u00c2\u00a0 The Z-depth channel is like an alpha channel<\/a>, but instead of storing values of transparency info, it records how far an object on screen is from the camera.\u00c2\u00a0 This information can either be captured at record time with specialized hardware, or be generated from an image analysis process,\u00c2\u00a0with a bit of interpolation.<\/p>\n

At the end of the day, each option has certain pros and cons, and multiple display types could be used\u00c2\u00a0at different stages of\u00c2\u00a0a single project.\u00c2\u00a0 As long as you have both full streams of data available, you can adapt your content for any display.\u00c2\u00a0 Once you render it into a display specific\u00c2\u00a0format, like interlaced or anaglyphic, certain image content may be lost that cannot be recovered for use on other\u00c2\u00a0 display types, without going back to your original source.\u00c2\u00a0 Because of this, it is highly preferable to have a system that allows you to display stereoscopic content in 3D without having to pre-render into a dedicated display format.\u00c2\u00a0 As computers become more powerful, and better software is developed, that capability is becoming much more common, greatly aiding the stereoscopic post process.<\/p>\n","protected":false},"excerpt":{"rendered":"

It seems like just about every week there is a new 3D technology being announced or released.\u00c2\u00a0 This is due to the fact that there are so many\u00c2\u00a0possible ways to present stereoscopic media to a viewer,\u00c2\u00a0but none of the existing solutions are perfect, so there is\u00c2\u00a0clear room for improvement.\u00c2\u00a0 There has been a lot of […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,17],"tags":[42],"_links":{"self":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts\/240"}],"collection":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/comments?post=240"}],"version-history":[{"count":13,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts\/240\/revisions"}],"predecessor-version":[{"id":253,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/posts\/240\/revisions\/253"}],"wp:attachment":[{"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/media?parent=240"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/categories?post=240"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.hd4pc.com\/techblog\/wp-json\/wp\/v2\/tags?post=240"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}