circle the subject almost completely in most of the sequences, computer technology was used to edit out the cameras that appeared in the background on the other side. To create backgrounds, Gaeta hired George Borshukov, who created 3D models based on the geometry of buildings and used the photographs of the buildings themselves as texture. The photo-realistic surroundings generated by this method were incorporated into the bullet time scene, and algorithms based on optical flow were used to interpolate between the still images to produce a fluent dynamic motion; the computer-generated "lead in" and "lead out" slides were filled in between frames in sequence to get an illusion of orbiting the scene. Manex Visual Effects used a cluster farm running the Unix-like operating system FreeBSD to render many of the film's visual effects. Manex also handled creature effects, such as Sentinels and machines in real world scenes; Animal Logic created the code hallway and the exploding Agent at the end of the film. DFilm managed scenes that required heavy use of digital compositing, such as Neo's jump off a skyscraper and the helicopter crash into a building. The ripple effect in the latter scene was created digitally, but the shot also included practical elements, and months of extensive research were needed to find the correct kind of glass and explosives to use. The scene was shot by colliding a quarter-scale helicopter mock-up into a glass wall wired to concentric rings of explosives; the explosives were then triggered in sequence from the center outward, to create a wave of exploding glass. The photogrammetric and image-based computer-generated background approaches in The Matrixs bullet time evolved into innovations unveiled in the sequels The Matrix Reloaded and The Matrix Revolutions. The method of using real photographs of buildings as texture for 3D models eventually led the visual effect team to digitize all data, such as scenes, characters' motions and expressions. It also led to the development of "Universal Capture", a process which samples and stores facial details and expressions at high resolution. With these highly detailed collected data, the team were able to create virtual cinematography in which characters, locations, and events can all be created digitally and viewed through virtual cameras, eliminating the restrictions of real cameras. Release Home media The Matrix was released on DVD and Laserdisc in its original aspect ratio of 2.35:1 on September 21, 1999, in the US from