Bullet time (also known as frozen time, the big freeze, dead time, flow motion, or time slice) is a special and visual effect that refers to a digitally enhanced simulation of variable-speed (i.e. slow motion, time-lapse, etc.) photography used in films, broadcast advertisements, and video games. It is characterized both by its extreme transformation of time (slow enough to show normally imperceptible and unfilmable events, such as flying bullets) and space (by way of the ability of the camera angle—the audience's point-of-view—to move around the scene at a normal speed while events are slowed). This is almost impossible with conventional slow-motion, as the physical camera would have to move impossibly fast; the concept implies that only a "virtual camera", often illustrated within the confines of a computer-generated environment such as a virtual world or virtual reality, would be capable of "filming" bullet-time types of moments. Technical and historical variations of this effect have been referred to as time slicing, view morphing, slow-mo, ''temps mort'', and virtual cinematography.

Technology

For many years, it has been possible to use computer vision techniques to capture scenes and render images of novel viewpoints sufficient for bullet time type effects. More recently, these have been formalized into what is becoming known as free viewpoint television (FTV). At the time of ''The Matrix'', FTV was not a fully mature technology. FTV is effectively the live action version of bullet time, without the slow motion.

In ''The Matrix'', the camera path was pre-designed using computer-generated visualizations as a guide. Cameras were arranged, behind a green or blue screen, on a track and aligned through a laser targeting system, forming a complex curve through space. The cameras were then triggered at extremely close intervals, so the action continued to unfold, in extreme slow-motion, while the viewpoint moved. Additionally, the individual frames were scanned for computer processing. Using sophisticated interpolation software, extra frames could be inserted to slow down the action further and improve the fluidity of the movement (especially the frame rate of the images); frames could also be dropped to speed up the action. This approach provides greater flexibility than a purely photographic one. The same effect can also be produced using pure CGI, motion capture and universal capture. It is thought that the opening sequence from the late 1960s ''Speed Racer'' cartoons partially inspired The Wachowskis to incorporate the bullet time effect into ''The Matrix''.

History

The technique of using a group of still cameras to freeze motion occurred before the invention of cinema itself. It dates back to the 19th-century experiments by Eadweard Muybridge, who analyzed the motion of a galloping horse by using a line of cameras to photograph the animal as it ran past. Eadweard Muybridge used still cameras placed along a racetrack, and each camera was actuated by a taut string stretched across the track; as the horse galloped past, the camera shutters snapped, taking one frame at a time. (The original intent was to settle a debate the governor of California had engaged in, as to whether all four of the animal's legs would leave the ground when galloping.) Muybridge later assembled the pictures into a rudimentary animation, by placing them on a glass disk which he spun in front of a light source. His zoopraxiscope may have been an inspiration for Thomas Edison to explore the idea of motion pictures.

Muybridge also took photos of actions from many angles at the same instant in time, to study how the human body went up stairs, for example. This is the effect used in ''The Matrix'', and other movies, and is achieved roughly the same way as Muybridge set up his shots. In effect, however, Muybridge had achieved the aesthetic opposite to ''The Matrix'''s bullet-time sequences, since his studies lacked the dimensionality of the later developments. A debt may also be owed to MIT professor Doc Edgerton, who, in the 1940s, captured now-iconic photos of bullets using xenon strobe lights to "freeze" motion.

Long before the emergence of a technology permitting a live-action application, bullet-time as a concept was frequently developed in cel animation. One of the earliest examples is the shot at the end of the title sequence for the 1966 Japanese anime series ''Speed Racer'': as Speed leaps from the Mach Five, he freezes in mid-jump, and then the camera does an arc shot from front to sideways.

In 1980, Tim Macmillan started producing pioneering video work in this field while studying for a BA at the (then named) Bath Academy of Art using 16mm film arranged in a progressing sequence of pinhole cameras.

The first music video to use bullet-time was "Midnight Mover", a 1985 Accept video. A variation on bullet-time came into use in the mid-1990s, first in a series of commercials to sell products for Gap and Lexus, then in feature films such as ''Lost in Space'', and later in ''The Matrix''. Bullet time became popularized when John Gaeta and team expanded it temporally and into the digital arena through the incorporation of frame interpolation and image-based CGI within the film ''The Matrix'' (1999) and through view-morphing techniques pioneered by BUF Compagnie in music videos by Michel Gondry and commercials for, among others, The Gap. Gaeta said of ''The Matrix'''s use of the effect:

For artistic inspiration for bullet time, I would credit Otomo Katsuhiro, who co-wrote and directed ''Akira'', which definitely blew me away, along with director Michel Gondry. His music videos experimented with a different type of technique called view-morphing and it was just part of the beginning of uncovering the creative approaches toward using still cameras for special effects. Our technique was significantly different because we built it to move around objects that were themselves in motion, and we were also able to create slow-motion events that 'virtual cameras' could move around – rather than the static action in Gondry's music videos with limited camera moves.

In popular film culture, ''Blade'' (1998) was the first film to illustrate super-human reflexes dodging bullets in a scene in a park when the character of Blade fires at Stephen Dorff's character, Deacon Frost. Computer generated bullets are also used to illustrate the concept and slow motion camera work.

John Woo is also famous for incorporating slow motion shoot outs in his movies, such as ''A Better Tomorrow'' and ''Hard Boiled''. These films would later influence media such as ''Max Payne'' and ''The Matrix'' series.

In 2003, bullet time evolved further through ''The Matrix Reloaded'' and ''The Matrix Revolutions'' with the introduction of high-definition computer-generated approaches like virtual cinematography and universal capture. Virtual elements within the Matrix Trilogy utilized state-of-the-art image-based computer rendering techniques pioneered in Paul Debevec's 1997 film and custom evolved for the Matrix by George Borshukov, an early collaborator of Debevec.

Following ''The Matrix'', bullet time has featured as a key gameplay mechanic in various video games, which typically involve players having the ability to slow down time during certain actions, allowing them to easily aim weapons. The first video game to use this style of gameplay was Remedy Entertainment's 2001 video game, ''Max Payne''. Bullet time was used for the first time in a live music environment in October 2009 for Creed's live DVD ''Creed Live''.

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Category:Special effects Category:Theatrical combat Category:Visual effects