42 ITNOW September 2013 The BBC’s recent decision to put its 3D TV venture on hold is yet another indication that all is not well with television’s foray into the third dimension. A number of factors have contributed to its current demise and these include a failure to properly accommodate the ways people behave when ‘watching’ TV - from the child who regularly switches attention between toys and screen, to the adult who multitasks. In every case those glasses get in the way and all too often gravitate to that dark space beneath the sofa. Cinema audiences are more single- minded and are generally intent on a truly immersive experience. They are therefore more willing to tolerate viewing glasses as an interim solution but look forward to the development of alternative technologies that will support the convenience of glasses-free (autostereoscopic) 3D. In fact, glasses-free 3D cinema is not a futuristic vision – in Moscow back in 1941 it was reality playing on a 5x3m screen: ‘The auditorium is plunged in darkness, except for a little lamp suspended from the ceiling by a long cord. But wait – an actor suddenly reaches out from the screen and draws the lamp towards him. How did he do it? As a matter of fact, there was no lamp left burning in the auditorium. It was simply an effect produced by the stereocinema… A juggler flings a ball straight at the audience, and those who happen to come within his line of vision blink and duck involuntarily…’ Ivanov [1941] On show was the 40 minute 3D film, ‘Konsert’ (Fig. 1) and during a four month period some 500,000 people took the opportunity to enjoy autostereoscopic 3D. Unfortunately the venture could not have been more ill-timed, and it came to an abrupt halt in June when Germany and Russia became embroiled in total warfare. On 20 February 1947 glasses-free 3D re-opened in Moscow. Significant developments in display technology were complemented by advances in the art and science of stereo photography. The 3D differences in the images presented to the two eyes. These arise because each eye sees the world from a slightly different vantage point and this is used by the visual system to give a vivid impression of depth. In the case of stereo photography, a scene is photographed from two locations approximately separated by the distance between our eyes. If we then present these photos to the eyes in such a way that the left-hand photo can only be seen by the left eye and the right-hand photo only by the right eye, then the visual system fuses content and we perceive 3D. In the case of glasses-based cinema and TV, the left and right views are encoded in some way and are simultaneously presented to all members of the audience. Viewing glasses serve a decoding function and ensure that the left and right stereo images are mapped to the intended eye. This is a simple and cost-effective method of delivering 3D – provided that viewing glasses are deemed acceptable. Glasses-free 3D cinema poses some interesting challenges. Back in 1940, Dennis Gabor (inventor of holography) doi:10.1093/itnow/bwt052 ©2013 The British Computer Society Fig. 3: The parallax barrier with a light-diffusing screen. Three exemplar viewing locations shown. Fig. 1: Stereo frames from ‘Konsert’ – black and white with the occasional inclusion of colour. This stereopair may be easily fused by slightly crossing the eyes. feature film ‘Robinson Crusoe’ (Fig. 2) was a sterling success: ‘…It was only when Crusoe in his shipwreck throws a rope to a drowning sailor that you get the first shock. The rope comes hurtling and curling right out of the screen into the darkness…. You duck. We all did. After that we were ready for anything… this luminous effect resembles the unearthly atmosphere of the Insect or Tropical Bird Houses in London Zoo. As if light were liquid. As if the heat were tangible… The depth is used cleverly to increase our sense of Crusoe’s loneliness…When he [Crusoe] goes down with fever, therefore, though little dialogue has been possible, he is a real person to us. Sensation in place of speech has placed us inside his head. We fight every inch of the way with him towards survival and recovery…A strikingly beautiful shot of a ship in full sail close inshore - the effect of stereoscopic photography on the canvas, rope and wood of a sailing ship cannot be described except in terms of goldsmith’s work….’ Macleod [1947] Our everyday perception of the 3D world is strongly influenced by small Barry G Blundell FBCS looks at 3D, referring back to glasses-free 3D Cinema 70 years ago in Russia. Fig. 2: Stereo frames from Robinson Crusoe (1947). GLASSES-FREE 3D