The various techniques used are:
1) Graphics monitors for the display of three-dimensional scenes have been devised using a technique that reflects a CRT image from a vibrating, flexible mirror. In this system, as the mirror vibrates, it changes focal length.
These vibrations are synchronized with the display of an object on a CRT so that each point on the object is reflecting from the mirror into a spatial position corresponding to the distance of that point from a specified viewing position. This allows us to walk around an object or scene and view it from different sides.
2) Another technique for representing three-dimensional objects is displaying stereoscopic views. This method does not produce true three-dimensional images, but it does provide a three dimensional effect by presenting a different view to each eye of an observer so that scenes do appear to have depth. To obtain a stereoscopic projection, we first need to obtain two views of a scene generated from a viewing direction corresponding to each eye.
We can construct the two views as computer-generated scenes with different viewing positions, or we can use a stereo camera pair to photograph some object or scene. When we simultaneously look at the left view withy the left eye and the right view with the right eye, the two images merge into a single image and we perceive a scene with depth. Stereoscopic viewing is also a component in virtual reality systems, where users can step into a scene and interact with the environment.
A headset containing an optical system to generate the stereoscopic view is commonly used in conjunction withy interactive input devices to locate and manipulate objects in the scene. A sensing system in the headset keeps track of the viewer?s position, so that the front and back of objects can be seen as the viewer walks through and interacts with the display.