When making the scene of Forrest Gump meeting and shaking hands with the late president, visual effects director Ken Ralston and his industrial light and magic special effects team applied CGI technology, and Hanks completed the performance with reference to relevant markers in front of the blue screen. Thus it is seamlessly integrated with documentary images. In order to record the voices of historical figures, the crew used voice substitutes. To ensure that the voices matched, the special effects department modified the characters' oral movements.
In a scene from the Vietnam War, Forrest Gump with his wounded comrades on his back had to withdraw from the battlefield before the incendiary bomb hits the ground. The crew first filmed this scene with stuntmen, and then asked Tom Hanks and McCalty Williamson to personally Go into battle and use a wire rope to support Williamson's weight, and finally shoot the explosion scene, and then use digital technology to put the actors on the scene. The jet fighters and incendiary bombs are all added with CGI. After Lieutenant Dan was amputated, the special effects department used CGI technology to remove Gary Sinis’s legs. Sinis covered his legs with blue cloth for this purpose. Sinis could use it when shooting shots of getting up and sitting in a wheelchair. "Invisible" legs to support the body.
The peaceful gathering of 10,000 people in front of the Lincoln Memorial in the film requires the special effects department to create a spectacular crowd. During the two-day shooting, the crew used 1,500 extras. After shooting a sequence, all the extras had to be rearranged. , After computer special effects processing, the number of people on the scene soared to hundreds of thousands.
