With the box office popularity of James Cameron’s Avatar assuring a stereoscopic 3D rerelease of the six-part Star Wars saga, 3D itself is proving a bankable element. Savvy editors, camera technicians, animators and, hopefully, scriptwriters will now learn how to use stereoscopic 3D to greenlight their projects. Panasonic thinks so, with its release of an integrated twin-lens stereoscopic 3D camcorder. Sony Creative certainly thinks so, as evidenced by the new stereoscopic 3D editing tools in Sony Vegas Pro 10. So here’s a short primer on the physiology and technology of 3D moviemaking to get you competitively up to speed.
Most people assume patch-eyed Long John Silver wouldn’t appreciate a stereoscopic version of even Pirates of the Caribbean, but what is it that makes a stereoscopic projection cinematically successful or, more importantly, not successful? The illusion of cinematic 3D is based on tricking human physiology by using a flat plane (the screen) to produce many of the cues that our brains employ to create a 3D sensation from the real world. Surprisingly, most of these cues are monocular, so Long John might buy a ticket after all.
Monocular cues that may be employed by creatives include:
• Paralax Effects—The relative movement between objects when the camera moves
• Motion Depth—An object’s change in size as it moves closer and farther from the camera
• Vanishing Point Conformity—The horizontal lines of an object converging at the same vanishing point as other objects
• Texture Resolution—Where detail is more refined the closer a surface is to the camera
• Atmospheric Resolution—The propensity of farther objects to be fuzzier than closer objects
• Familiarization Effects—Manipulating the size of objects that the audience knows to be a certain size, such as a toothbrush, in relation to the scene
• Occlusion—Blocking the view of one object by another, closer object
• Peripheral Warping—Making a scene appear to bend slightly, like a fisheye lens at the edges
Another monocular cue, Light & Shadow, uses the way an object casts a shadow on, or reflects light of, other objects, and light to create depth. When employed stereoscopically, with slightly different lighting and shadow effects being projected to each eye, the brain greatly enhances the depth effect. Creative use of these cues can create a powerful 3D effect even when wearing a patch on one eye.
The most obvious requirement of stereoscopic 3D cinema is that it create stereopsis—an effect of depth derived from projecting a slightly different film channel for each eye. By filming these two channels through lenses that are separated about the same distance as our eyes, stereopsis depth is created. In real life, our brains create depth from the difference between each eye’s angular view of objects. This difference varies based on distance. When both eyes perceive no difference between the views of an object, the brain assumes the object is distant. As the difference increases, the brain interprets the object coming nearer.