 Special effects work continued on the film , with Tippett 's unit adjusting to new technology with Dinosaur Input Devices : models which fed information into the computers to allow themselves to animate the characters like stop motion puppets . In addition , they acted out scenes with the raptors and Gallimimus . As well as the computer @-@ generated dinosaurs , ILM also created elements such as water splashing and digital face replacement for Ariana Richards ' stunt double . Compositing the dinosaurs onto the live action scenes took around an hour . Rendering the dinosaurs often took two to four hours per frame , and rendering the T. rex in the rain even took six hours per frame . Spielberg monitored their progress from Poland during the filming of Schindler 's List , having teleconferences four times a week with ILM 's crew . The director described working simultaneously in two vastly different productions as " a bipolar experience " , where he used " every ounce of intuition on Schindler 's List and every ounce of craft in Jurassic Park " . 
