Terminator 2: Judgment Day is a 1991 science fiction film directed by James Cameron, and starred Linda Hamilton, Arnold Schwarzenegger, Edward Furlong, and Robert Patrick.
Cameron wanted to do a sequel to his blockbuster film The Terminator (1984), but could never make the technology work to do what he wanted (the liquid metal T-1000). Cameron pioneered the use of CGI in his 1989 film The Abyss -- a full five years before Jurassic Park (which most people associate with the CGI revolution). Cameron then had to spend $5 million to get the rights to the film back from Hemdale Film Corporation, which was in bankruptcy. (Carolco, the company that produced Terminator 2 then went bankrupt itself!)
Robert Patrick was chosen to play the T-1000 because of his agility. Cameron wanted the comparison between the T-800 and T-1000 to be the difference between a Porsche and a tank. Adam Greenberg (who worked on The Terminator) was hired as director of photography. Joseph Nemec III (who worked on The Abyss) was the production designer.
There are just five minutes of CGI material in the 136-minute film.
The biggest challenge for the crew in The Terminator was creating a realistic T-800 robotic skeleton. But this was not a problem by the time T2 went into production seven years later. A full-size T-800 puppet was created, with its arms and limbs attached to a puppeteer walking behind it. The poles controlling it were erased using CGI.
Another major advance was in make-up. The producers worried that they would have to do extensive CGI work on both Schwarzenegger and Patrick's heads in order to make the damage of shotgun blasts and and other attacks look realistc. During the filming of T1, metallic film was applied to Schwarzenegger's face; this, however, looked like it was on top of his skin, not beneath it. But for T2, Stan Winston (the creature and effects genius) and his team discovered a way to make the metal under-skeleton appear BELOW the skin -- thus doing away with a huge amount of CGI work.
A third major advance was in the use of animatronic puppet heads. Both Schwarzenegger and Patrick had their faces scanned by lasers. Foam replicas were then sculpted by lasers. This "cyber scan" foam sculpture was rough, so a mold was made of the foam sculpture, and a clay model created from the mold. The clay model was then cleaned up and details added.