Alton Towers

A Refurbished 3D Cinema Attraction
Staffordshire, UK

Alton Towers, in the middle of England, is the UK's most visited theme park. It is part of the Tussauds Group. One of the attractions in the park was a 3D Cinema, which first opened in 1981. In 2003, Electrosonic converted the system from film to electronic projection.

Alton Towers' original 3D Cinema installation used a split frame technique, whereby a single 70mm film carried both left and right eye images. Tussauds wanted to reduce maintenance costs, and maintain a more consistent image quality by changing over to an all-electronic system.

Electrosonic was originally approached by Attraction Media & Entertainment, a leader in the area of 3D content production and distribution, who had been asked by Alton Towers to develop a solution for their existing 3D film system. The existing venue represented an interesting challenge in that the screen was dome shaped.

While the same format was being taken up elsewhere, the installation was a world first, showing 3D images of UXGA resolution at 24 frames per second. Key to the success of the show was the combination of MediaSonic High Definition players and Sanyo PLC-UF15 projectors. The unfiltered light output of the projector was 7,700 lumens, and on site tests showed that a pair of projectors with polarizing filters could show an 11.5m × 8.6m (38 feet × 28 feet) 3D image. The high resolution was needed to ensure that patrons could not see any image pixelation, even at the very close viewing distances that could be involved (as little as 2.5m or 8 feet).

Alton Towers

The opening show in the new format was "Adventures in 3D", produced in a special 15-minute version for Alton Towers by Attraction Media & Entertainments. The film had originally been produced by nWave Productions in the IMAX® format, which was 4:3 aspect ratio that ran at 24 frames per second.

The playback system was based on a synchronized pair of MediaSonic MP9200 High Definition players. The film was encoded as two 1280 × 960, 24 fps, 25Mb/s MPEG-2 files. The MP9200 had built-in image re-sizing, so in this case it was set to output images at UXGA (1600 × 1200). Sanyo provided special firmware for the projectors to allow the image to be applied directly to the LCD panels, effectively by-passing the image scaler that was in the projector, which might otherwise have introduced undesirable artifacts as a result of duplicated image processing.

The original film had a six-channel sound track that matched IMAX format. For Alton Towers this was encoded as a Dolby® signal that could be carried within the MPEG-2 video file. A Marantz SR8200 AV preamplifer decoded this to the six channels which were then fed to a BSS Soundweb DSP processor for equalization; the outputs of which were fed to the existing amplifier/loudspeaker system.