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Alternative approaches to real-time image manipulation


It is useful to compare the GUI with an alternative method of real-time image generation used by video synthesisers and analogue computers for TV production. Machines such as the Scanimate were derived from the experimental video processors developed by video art pioneers such as Nam June Paik. Until the early 1980s, these analogue graphics machines were the only way of performing live interaction with images because digital computers were limited in memory and processing power. Billy Klüver explained this was the reason he had not used digital computers for EAT’s “9 Evenings” show in 1966: they were not yet realtime devices.[1]

The field of video art impinges on Computer Art, yet there is not sufficient space to cover it here. Suffice it to say it led to machines such as Dan Sandin’s “Image Processor” at the University of Illinois in Chicago, which performed darkroom-type effects on video material, such as dodging and colorization; and by combining the video feeds they could superimpose images and use oscilloscopes to generate graphics. [2] These effects were later incorporated into digital video workstations and then into painting software. Even though the video processor was something of an evolutionary dead-end, its visual legacy lives on.

Video processors were the visual equivalents of contemporary music synthesisers, such as the Moog; indeed, that was why Sandin wanted to build his machine.[3] Like the Moog, these analogue devices utilised hardware controllers to modify waveforms and produce effects. I asked Dave Sieg, long associated with the widely-used Scanimate system, about the efficacy of the hardware-based knobs-and-switches interface against the mouse and keyboard. He replied that the Scanimate is an open-ended instrument – unfortunately “It is so flexible that almost nobody can be very good at operating it.” [4]

Animators would spend three months training, and even then take almost two years to do jobs entirely unaided. Sieg declared that it was an awful User Interface. However, he added, “I always liked Jim Blinn’s […] comment that a piano has an awful UI but it doesn’t stop a virtuoso from practising to become perfect.” [5]

Sieg recalled that it was difficult to get them to reproduce the same image on two separate occasions, because all the work was done “live”. The Scanimate had so many patch cords and knobs that even a small adjustment to an existing piece of work required it to be redone from scratch. [6] The control interface was quite different to the standardised mouse/windows system: as the picture below illustrates, video synths offered a daunting array of knobs and switaches that modified the various inputs and outputs.

Thus there was a wide range of controls at the operator’s fingertips. The advantage of such a system was that it allowed very fine tuning and changes to live video images, without any digital intermediary. Because of the complexity, operators used their non-quantifiable knowledge and skills to perform image transformations.

Sieg said that controlling the Scanimate was more like playing a musical instrument; far greater precision was available from later digital graphics workstations, not to mention a lack of annoying analogue-specific colour variations such as scanlines and colour drift. [7] The digital precision derives from the image’s discrete structure and the exactitude with which changes can be specified, and undone.

Thus a user interface based on specialised hardware is not necessarily more effective than the generalised windows-mouse environment, but it draws on different strengths. It may allow for an element of “performance” because it can be “played” by virtuosi. Sieg pointed out that at least one software maker [see Houdini] is using MIDI controllers (developed for music programs) to create 3D images. The sliders control various parameters and can be altered in real time, allowing for more interaction with the developing image. (Ref to them) By contrast, a standardised interface of mouse and keyboard may have an underlying flexibility through the use of different commands and options within a standardised GUI.

[1] In discussion with Malcolm Le Grice and David Whitman, Leeds film festival, 11th October 2002.

[2] Christine Tamblyn, “Image Processing in Chicago Video Art, 1970-1980” Leonardo Vol.21 No.3, pp303-310, 1991

[3] Christine Tamblyn, “Image Processing in Chicago Video Art, 1970-1980” Leonardo Vol.21 No.3, pp303-310, 1991

[4] Email correspondence with Dave Sieg, <> Tue, 23 Oct 2001 11:11:52 -0400

[5] Email correspondence with Dave Sieg, <> Tue, 23 Oct 2001 11:11:52 -0400

[6] “Scanimation in the Analog Days” By Dave Sieg [check URL] ScanimationintheAnalog Days.htm

[7] Personal correspondence with Dave Sieg.