Aside from The Abyss the year before, computer graphics hadn't been used very much in movies to create creatures at the time of Terminator 2. The liquid being from The Abyss was a major breakthrough for the industry, but most computer work was still confined to rod removals and some bluescreen shots. Until 1991 anyway.
In 1991, Arnold Schwarzenegger was slated to star in a large budget sequel to The Terminator. That was well known throughout Hollywood. What was not well known, was the revolution it would spark in the field of special effects. The 3D rendered T-1000 was created by Industrial Light and Magic using SGI computers. To make the model for the creature, animators took actor Robert Patrick and scanned his body into the computer. Using that as a basis to construct a wireframe, the animators needed only to mesh the model with the footage obtained of the actor.
A technique called morphing was used to blend from the computer model to actor Robert Patrick. With this technique, the first image is slowly given the characteristics of the second and it's own features are removed. This creates the illusion that one is changing into the other. The result of this work was the liquid metal android changing it's features to form into numerous characters played by several actors.
Morphing was also used in the final scene of the movie where the T-1000 is melted down in a large melting vat. The animators took several of the models used previously in the film and morphed from one to the other as the creature attempted to find a form that would help him to survive. Of course it doesn't work, and the T-1000 dissolves in the vat in a nice CG rendering of the face turning inside out several times and then melting so that a thin layer of silver metal in the shape of the android's face is left on the surface.
The model of the T-1000 was fairly simple to render. A simple metallic texture was used for the exterior in most cases, and the interior didn't require anything special. Unlike the water creature of The Abyss and the living creatures of Jurassic Park and Jumanji, a liquid android doesn't have any muscles or rippling surfaces for the animators to worry about. The largest concern for the ILM team was getting the metal surface to accurately reflect the surroundings. Considering the talents of the people at Industrial Light and Magic, this wasn't particularly a challenge.
While not really difficult by today's standards, Terminator 2: Judgement Day was a breakthrough film when it was released. It spawned the new generation of special effects films, and ushered in an era to be controlled by computers. ILM had moved the bar a little bit higher, and it was going to be that much more difficult to reach it.
Computer Effects: Extras Last Updated August 19, 1996
Computer Effects: Effects using Humans, Bluescreens
Visual Effects HQ: ILM
Computer Effects: Effects using Humans, Morphing
Computer Effects: Creatures, Jurassic Park
Computer Effects: Creatures, Jumanji
Visual Effects HQ: Jumanji
Computer Effects: Extras
Last Updated August 19, 1996