1. Field of the Invention
This invention relates to the field of computer graphics systems. More particularly, this invention relates to real time generation of complex high resolution stereo 3D images in a head tracked stereo display system.
2. Art Background
The human eye can be modeled as an optical system coupled to a retina, with the retina functioning as a light transducer. The human eye is immersed in physical space filled with light rays. A point source of light exists at every point in the physical space that is a boundary between transparent and opaque surfaces, or a boundary between transparent surfaces of different refractive indices. Human stereo vision is achieved by immersing the two eyes at different locations within the physical space.
A typical computer graphics system generates images by producing an image plane of light sources, or an image plane of reflectors of light. Such an image plane is approximated by a two dimensional array of point light sources known as pixels. The light produced by the image plane is the sum of the half spheres of light expanding out from each pixel on the image plane. The color and intensity of each pixel is separately controllable, but the distribution of color and intensity across the half sphere usually is not controllable. The pixels that comprise the image plane appear substantially the same when viewed from any angle.
Nevertheless, a head tracked stereo display system simulates the interaction of human eyes with the light rays of the physical space in order to enable a viewer to perceive 3D images. A head tracked stereo display system senses the location in physical space of the viewer's head and eyes, computes a pair of stereo images of a virtual object based upon the location of the head and eyes, and generates the stereo image on a stereo display device.
A head tracked stereo display system requires that only two images be computed and generated at a time, which results in substantially less computation than holographic systems. Moreover, the pair of stereo images have the same appearance as a hologram. With a head tracked stereo display system, the virtual object appears to remain stationary when the viewer's head tilts, or when the viewer's head moves to look around the side or over the top of the virtual object. For further discussion regarding head tracked stereo display systems, refer to Paley, W. B. Head-tracking Stereo Display, Techniques and Applications, Proceedings of SPIE, Febuary 1992.
In a head tracked stereo display system, the scenery and objects of the stereo images must be rendered in a sufficiently short time span to be physiologically acceptable to the human visual system. Past head tracked stereo display systems used commonly available 3D computer graphics image generation hardware and software to produce stereo images with 3D display primitives. However, the performance of such systems is limited by the speed of the 3D graphics rendering hardware. As the complexity of the stereo images increases, the graphics rendering hardware becomes too slow to generate 3D stereo images at an acceptable rate.
As will be described, the present method and apparatus generates complex 3D stereo images by dynamically accessing pairs of stero images selected from among a precomputed set of images. The precomputed images are selected based upon a prediction of viewer head location for the next frame of the stereo display.
This application is related to application Ser. No. 07/875,042, filed on Apr. 28, 1992, entitled Method and Apparatus for High Resolution Virtual Reality Systems Using Head Tracked Display.