Because of the enormous volume of image capture data contained in the ultra-high resolution, IMAX®/OMNIMAX® film format that 'Welcome to the Max' was photographed in (65mm x 15-perforations per frame, which is ten times larger than 35mm), and the limitations of the computing power available at the time of the movie's production, CGI and green screen VFX were cost-prohibitive. Thus, all scenes are live-action, and all stunts and VFX (even the star field that opens the show) are practical ones.
Marto's fall from outer space is a live-action stunt, filmed at 10,000 feet above Manhattan in Class 'D' air space with special arrangement by the FAA for the re-routing airline aircraft. Though he appears to hurtle at ballistic speed from low Earth orbit, when Marto first appears in frame his stunt double (skydiver David Jacaruso) has fallen only 18 inches - the distance from his release position on the helicopter's skid to the down-looking lens on the aircraft-mounted camera. He then falls at a normal (24 fps) frame rate, but the illusions of altitude, velocity, and the distance Marto covers are created by the combination of fisheye lens and sound design: the lens distortion speeds the action, while panning the fall audio from the IMAX dome's overhead channel, through the rear surrounds and into the theater's massive, front-speaker array completes illusion. Ancient sound lab axiom: "The eye believes what the ear hears."
For the fall-from-outer-space shot, the stuntman double free-falls over New York Harbor for a distance of only a thousand feet before releasing his tear-away 'spacesuit', deploying his parachute, and using his remaining altitude to paraglide across the Hudson River with a chase boat below for a landing in Liberty State Park. (Authorities would not permit a touchdown in Manhattan.) After the jump, the helicopter was used to 'fly cover' for the stuntman on his flight path through uncontrolled (VFR) air space over the river. A play-by-play description of the entire stunt by the helicopter pilot (Al Curello) was broadcast live to New York commuters on morning drive-time radio.
The shot of Marto's crash through the theater's ceiling and fall into his seat is seen in an ImaxDome/OMNIMAX theater as a virtual holographic image; i.e., the illusion of a real person falling top-to-bottom through the theater in real time and space is startling. This is accomplished by a combination of recording frame rate (normal), the camera lens matching that of the projector (reproducing 'normal' perspective), and both the camera's elevation and distance from the stunt action matching those of the average viewing height and distance from the projected image. In other words, the actual stunt's ceiling-to-floor length (same as the dome cinema's height), angle of view, and distance from the camera lens-it place in space-matches the dimensions of the cinema in which the action is being played back and the audience's place in that theater.
Again, because of the CGI limitations that existed at the time of production, Max the talking, giant OMNIMAX® screen is a live-action miniature, accomplished with special-effects makeup: an inverted human chin and mouth, with glass eyes and an inverted teeth prosthetic-creating a 'chin face'-that is then welded to a latex sheet that surrounds the face.