Mechanical design in filmmaking makes it possible to acquire real-time footage of the special effects the movie needs. This allows faster turnover from the shoot to the editing because there is no need for animation and computer effects to be done during post-production. This saves the movie studio time and resources as optical effects require hiring a number of animation and special effects experts. They typically work long hours for a period of a few months or even a few years.
Testing and experimenting with mechanical designs are crucial to the success of the film shoot. Often, widely used mechanical effects such as smoke machines and rain cranes don't require test shoots nowadays. However, for more specialized equipment -- for instance, when using an animatronic wolf -- testing should be done ahead of time to make sure it looks realistic on camera. Doing a test shoot for a complicated setup avoids the risk of losing thousands of dollars because of having to reshoot mechanical effects that didn't work the first time.
A mechanical design may require a simple mattress or a sophisticated robot. Depending on the needs of the movie, the studio will provide specific financing to create special effects that look convincing on camera. Typical props and sets used for mechanical effects include a miniature building, guns that fire blanks, exploding cars and window glass that an actor or stuntman will break on camera. In very complicated and dangerous setups, like shooting an exploding car scene, the production typically uses a multiple camera setup. This allows the director to shoot the scene from various angles without having to repeat the setup again and again.
In view of the extensive resources required in making mechanical designs, the typical production will need to hire various makeup and prosthetics experts for the movie. In the film, when an actor suffers a gunshot or a stab wound, it should look realistic on screen. When the movie features a monstrous character, or uses a young actor who should look very old in the movie, makeup and prosthetics artists will create masks and other prosthetic effects ahead of time to ensure that the needed effects are available by the time the actual shooting starts.