Source : Free On-Line Dictionary of Computing

ray tracing
     
         A technique used in {computer graphics} to create
        realistic {images} by calculating the paths taken by rays of
        light entering the observer's eye at different angles.  The
        paths are traced backward from the viewpoint, through a point
        (a {pixel}) in the image plane until they hit some object in
        the scene or go off to infinity.  Objects are modelled as
        collections of abutting surfaces which may be rectangles,
        triangles, or more complicated shapes such as 3D {splines}.
        The optical properties of different surfaces (colour,
        reflectance, transmitance, refraction, texture) also affect
        how it will contribute to the colour and brightness of the
        ray.  The position, colour, and brightness of light sources,
        including ambient lighting, is also taken into account.
     
        Ray tracing is an ideal application for {parallel processing}
        since there are many pixels, each of whose values is
        independent and can thus be calculated in parallel.
     
        Compare: {radiosity}.
     
        {Usenet} newsgroup: {news:comp.graphics.raytracing}.
     
       
     {(http://directory.google.com/Top/Computers/Software/Graphics/3D/Ray_Tracing/)}.
     
        (2003-09-11)