An open and shut case [computer graphics]

摘要

You press the button on your camera, the shutter opens, the film is exposed, the shutter closes, and you have a picture. If anything moved, including you, the image will show motion blur. When we create synthetic images with computer graphics, we have to account for motion blur for three reasons. First, we're used to it from physical motion pictures. Second, without motion blur a film can suffer from strobing, a psychophysical phenomenon. Third, without motion blur an object can alias in time. In a real camera, a mechanical device called the shutter controls the exposure of the film. The computer graphics literature includes many camera models, lenses, and even discussions of film and its simulation. Surprisingly, there is little discussion of simulating how a moving shutter actually exposes the film. The author finds it surprising because modeling the shutter mechanism is easy, and as shown in the article, very important to the rendered image. The following shutter types are modelled via computer graphics: instantaneous shutter; uniform shutter; focal plane shutter; interlaced shutter; leaf shutter; inverse leaf shutter; and clock shutter.